
==== Front
Nat Commun
Nat Commun
Nature Communications
2041-1723
Nature Publishing Group UK London

39231937
51715
10.1038/s41467-024-51715-w
Article
Modulation of triplet quantum coherence by guest-induced structural changes in a flexible metal-organic framework
Yamauchi Akio 1
http://orcid.org/0000-0002-4147-6713
Fujiwara Saiya 1
Kimizuka Nobuo 12
Asada Mizue 3
Fujiwara Motoyasu 3
http://orcid.org/0000-0001-8672-0946
Nakamura Toshikazu 3
http://orcid.org/0000-0002-8866-4279
Pirillo Jenny 4
http://orcid.org/0000-0003-4883-5085
Hijikata Yuh 5
http://orcid.org/0000-0003-0297-6544
Yanai Nobuhiro yanai@mail.cstm.kyushu-u.ac.jp

1267
1 https://ror.org/00p4k0j84 grid.177174.3 0000 0001 2242 4849 Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka, Japan
2 https://ror.org/00p4k0j84 grid.177174.3 0000 0001 2242 4849 Center for Molecular Systems (CMS), Kyushu University, Fukuoka, Japan
3 https://ror.org/04wqh5h97 grid.467196.b 0000 0001 2285 6123 Institute for Molecular Science, Okazaki, Japan
4 https://ror.org/04chrp450 grid.27476.30 0000 0001 0943 978X Department of Chemistry and Biotechnology, School of Engineering, and Department of Materials Chemistry, Graduate School of Engineering, Nagoya University, Nagoya, Japan
5 https://ror.org/04chrp450 grid.27476.30 0000 0001 0943 978X Research Center for Net Zero Carbon Society, Institute of Innovation for Future Society, Nagoya university, Nagoya, Japan
6 grid.419082.6 0000 0004 1754 9200 FOREST, CREST, JST, Saitama, Japan
7 https://ror.org/057zh3y96 grid.26999.3d 0000 0001 2169 1048 Department of Chemistry, Graduate School of Science, The University of Tokyo, 113-0033 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
2 9 2024
2 9 2024
2024
15 762214 12 2023
13 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Quantum sensing has the potential to improve the sensitivity of chemical sensing by exploiting the characteristics of qubits, which are sensitive to the external environment. Modulation of quantum coherence by target analytes can be a useful tool for quantum sensing. Using molecular qubits is expected to provide excellent sensitivity due to the proximity of the sensor to the target analyte. However, many molecular qubits are used at cryogenic temperatures, and how to make molecular qubits respond to specific analytes remains unclear. Here, we propose a material design in which the coherence time changes in response to a variety of analytes at room temperature. We used the photoexcited triplet, which can be initialized at room temperature, as qubits and introduce them to a metal–organic framework that can flexibly change its pore structure in response to guest adsorption. By changing the local molecular density around the triplet qubits by adsorption of a specific analyte, the mobility of the triplet qubit can be changed, and the coherence time can be made responsive.

Molecular qubits have great potential as quantum sensors due to their ability to be in close proximity to target analytes, but design guidelines on how to make them respond to specific analytes remain unclear. Here authors show that hybrids of triplet qubits and flexible MOFs can change the coherence time of electron spins of photo-excited triplet state upon adsorption of guest.

Subject terms

Metal-organic frameworks
Excited states
501100002241 MEXT | Japan Science and Technology Agency (JST) JPMJFR201Y 501100003382 MEXT | JST | Core Research for Evolutional Science and Technology (CREST) JPMJCR23I6 501100001691 MEXT | Japan Society for the Promotion of Science (JSPS) JP20H02713, JP22K19051, JP23H00304 Innovation inspired by Nature Program of Sekisui Chemical Co. Ltd Advanced Research Infrastructure for Materials and Nanotechnology (JPMXP1222MS0010) Nanotechnology Platform Program <Molecule and Material Synthesis> (JPMXP09S21MS0038)issue-copyright-statement© Springer Nature Limited 2024
==== Body
pmcIntroduction

In the second quantum revolution, quantum information science (QIS) comprises the application of quantum mechanics to fields such as quantum computing1,2, quantum communication3,4, and quantum sensing5–10. Quantum bits (qubits) are its building blocks, and manipulating these superposition states creates new properties that cannot be achieved by classical bits11,12. Among the quantum technologies, quantum sensing will have an impact on a wide range of fields, including chemistry9 and biology10. An important parameter for quantum sensing is the time over which the coherence of spin correlations is preserved13. Since the sensitivity of quantum sensing depends on coherence time, a long coherence time is highly desirable5. Defect centers, such as the nitrogen-vacancy (NV) centers in diamond, have long coherence times of more than microseconds at room temperature, enabling sensing of a variety of small molecules and biomolecules8,10. However, defect centers are difficult to place in a specific position, and it is also difficult to selectively address different centers14.

Unlike defect-based systems, molecular qubits14–31 are uniform in structure and can be precisely controlled. Furthermore, their small size allows them to closely approach the target analyte. For electron spin-based systems, the coherence time can be determined as the spin-spin relaxation time (T2). Paramagnetic metal complexes15–18, radical pairs22, and metal complex-radical conjugates24–26 are typical examples of molecular qubits. Although some radical is known to show long T2 over several microseconds32, it is still not easy to achieve microsecond-scale T2 at room temperature for many molecular qubits. Furthermore, it remains unclear how to make molecular qubits responsive and selective to specific analytes.

One strategy to gain responsivity to analytes is employing porous materials such as metal-organic frameworks (MOFs) or covalent–organic frameworks (COFs). There are a few examples of quantum sensing using MOFs containing paramagnetic species33,34. In these reports, the hyperfine interaction between electron spins and nuclear spins was used to sense analytes, but this method left a major challenge in that it could not distinguish compounds composed of the same nuclear species, such as benzene and toluene, for example.

Another way to sense analytes is by using the modulation of the coherence time, known as relaxometry. In general, T2 depends on several factors, such as the motion of the qubit itself and surrounding spins11,35. The motion of the qubit changes the orientation of the molecule relative to the external magnetic field, and since the g factor is usually anisotropic, the interaction with the magnetic field is perturbed, causing relaxation. Other sources of relaxation are the surrounding electron and nuclear spins. In particular, nuclear motion in the surrounding molecules causes fluctuation in the local magnetic field, leading to relaxation. Relaxometry can be a powerful method to detect target analytes based on these mechanisms. However, since qubits exposed in the nanopores of MOFs and COFs can undergo significant relaxation from the motion of the qubit itself, it is necessary to design the environment around the qubit appropriately to have a sufficiently long T2.

The photoexcited triplet state of organic dyes is an excellent candidate for qubits. Photoexcited triplet states have the advantage that anisotropic spin-orbit coupling allows temperature-independent sublevel selective intersystem crossing (ISC) from photoexcited singlet states, creating highly polarized electronic states, even at room temperature36–39 (Fig. 1a). This is a major difference from the spins of metal complexes and radicals in thermal equilibrium33,34, and triplets can offer higher spin polarization than those systems at room temperature and low magnetic fields. This means that more spins are available as qubits in the triplet state, which is an advantage in multi-qubit systems. Furthermore, it has long been known that the triplet state of pentacene doped in dense p-terphenyl crystals exhibits a long T2 on the microsecond scale even at room temperature37. However, except for a few pioneering examples27–30, photoexcited triplets are largely unexplored in the context of qubits and have never been used for quantum sensing because they are buried in dense matrix crystals and cannot approach the target analyte. As with other paramagnetic qubits, the response of triplet qubits to target analytes based on hyperfine spectroscopy and relaxometry is expected34. A characteristic of triplets is that they have an anisotropic and large (~ GHz) zero-field splitting (ZFS) interaction so that the molecular motion of the qubit causes a pronounced relaxation based on orientation change with respect to the magnetic field40. Therefore, when target analytes are incorporated into the nanopores and the environment around the qubit changes, it is expected that the changes can be sensitively captured through relaxometry.Fig. 1 Strategy for quantum sensing using triplet qubits and a flexible MOF.

a Initialization of the triplet qubit. Spin polarization between two of the three triplet sublevels generated by photoexcitation and following spin-selective intersystem crossing (ISC) can be used as qubits. b Response of triplet qubits to the guest-induced structural change of a flexible MOF. DAT and D-MIL-53 are employed as triplet qubits and the flexible MOF, respectively. c Guest analyte molecules used in this research. H2O, 2-propanol (PrOH), pyridine (Py), 5-fluorouracil (FU), p-benzoquinone (BQ), THF, chloroform (CHCl3), ethyl acetate (EtAc), toluene (h-Tol), ethanol (EtOH), and acetonitrile (AcNt) are introduced to D-MIL-53⊃DAT.

Here, we propose a material design toward quantum sensing in which triplet qubits are supported in nanoporous metal-organic frameworks (MOFs) to make the analyte molecules accessible and the coherence time T2 of the triplet qubits is changed by flexibly changing the MOF structure through adsorption of the guest analyte. Our method can show different T2 responses for a wider variety of organic compounds. In the present system, MOF has molecular recognition ability by interacting with guest analytes, and triplet qubit is a reporter that outputs it as the change in the coherence time T2. In other words, qubit and analyte do not interact directly but are indirectly influencing each other via MOF. By utilizing the change in molecular motion of qubits due to the introduction of guest molecules, we have succeeded in harnessing the molecular motion, which is normally a source of harsh relaxation at room temperature, to change the quantum coherence.

We selected MIL-53 as a flexible MOF that exhibits guest-responsive structural change, termed breathing behavior41–43. Some MOFs can flexibly change their crystal structure by introduction and removal of guest molecules44–46. The N-substituted tetracene, 5,12-diazatetracene (DAT)36, was employed as the triplet qubit. Compared with conventional pentacene, DAT has the advantages of good solubility and superior air stability. Recently, we reported the successful introduction of DAT into MIL-53 nanopores and polarization transfer from the electron spins of the DAT triplet to the 19F nuclear spins of the guest fluorouracil47.

We introduced a variety of additional guest analyte molecules into DAT-accommodated MIL-53 and evaluated T2 of the DAT triplet using pulsed electron paramagnetic resonance (EPR) (Fig. 1b). Analyte molecules have nuclear spins, such as that on protons, which usually work as noise to shorten T2. Interestingly, the T2 of DAT in MIL-53 shows various T2 depending on the type of guest analyte, with the longest T2 being longer than 1 μs at room temperature. This can be mainly attributed to the local molecular density around the DAT and has led to a new concept of quantum sensing by controlling the dynamics of qubits.

Results and discussion

DAT was introduced into partially deuterated MIL-53 [Al(µ2-OH)(BDC-d4)]n (denoted as D-MIL-53⊃DAT; BDC-d4 = perdeuterated terephthalate) by simply soaking D-MIL-53 in a dichloromethane solution of DAT, according to our previous report47. Since the MOF was washed several times with dichloromethane during sample preparation, excess DAT was removed and it is unlikely that DAT remains on the MOF crystal surface. As the concentration of the DAT solution is increased, the structure of the obtained MOF changes gradually (Supplementary Fig. 1), supporting the accommodation of DAT in the MOF nanopores. The loading amount of DAT was estimated to be 0.87 wt% by UV–Vis absorbance after digesting D-MIL-53 (Supplementary Fig. 2), similar to our previous report47. The following 11 guests were additionally introduced to D-MIL-53⊃DAT: H2O, 2-propanol (PrOH), pyridine (Py), 5-fluorouracil (FU), p-benzoquinone (BQ), THF, chloroform (CHCl3), ethyl acetate (EtAc), toluene (h-Tol), ethanol (EtOH), and acetonitrile (AcNt). FU and BQ were introduced by sublimation, and other guests were introduced by exposing D-MIL-53 to each vapor. Guest molecules were selected to cover as wide a range of volumes as possible based on the previous reports41–43. In addition, for liquid guests, we selected those with boiling points high enough not to be evacuated during sample preparation and not too high to be introduced by vapor diffusion. For solid guests, we chose those that could be introduced by sublimation.

Guest-dependent coherence time (T2)

The coherence times (T2) of the photoexcited triplets of DAT in D-MIL-53 were measured by pulsed EPR at room temperature with a spin echo sequence varying the pulse intervals (Fig. 2a). Measurements were taken at the magnetic field of the high-field and low-field peaks of the EPR spectra shown later, respectively, and both decay curves are shown (Fig. 2c). The decay of echo intensity was fitted with a single exponential function and T2 was obtained as the decay constant. While DAT shows electron spin echo envelope modulation (ESEEM) due to hyperfine coupling with 1H nuclei and 14N nuclei at a higher magnetic field, it does not affect the estimation of T2. The T2 values obtained at the higher and lower magnetic fields are similar (Supplementary Table 1). A relatively short T2 of around 0.1 μs is observed for D-MIL-53⊃DAT without any guest analyte (termed empty). No echo signals are detected when h-Tol, EtOH, or AcNt are introduced as guests, probably due to the shortening of T2 (< 0.1 μs). This is not strange, since proton nuclear spins usually work as noise and reduce coherence time13. Meanwhile, interestingly, the introduction of some guest molecules such as Py, FU, BQ, and THF clearly elongated T2 of the DAT triplets, despite the increase in proton and other nuclear spins that could cause spin relaxation. The T2 of DAT in the presence of FU and BQ are over 1 μs, which are notably long as molecular qubits at room temperature48. To confirm the measurements were run in the spin dilute regime, the T2 was measured with different laser powers (Supplementary Fig. 3). As expected from the low concentration of DAT in the sample (0.87 wt%), the change of T2 was small and intermolecular interactions between electron spins of DAT triplets could be ignored.Fig. 2 Guest-dependent T2 of DAT triplets in D-MIL-53.

a Spin echo sequence used for T2 measurement. The intervals of microwave pulses and echo detection were varied. b Plot of T2 and the fit error obtained by the single-exponential fitting of the spin echo decay curves against the unit cell volume of MIL-53. Only the T2 obtained from the low field peaks where the effect of ESEEM was small is plotted. For the empty, FU, and THF samples, the means and the standard errors of three measurements are shown. Errors of the H2O and THF samples were small and buried in the symbol. c Spin echo decay curves after pulsed photoexcitation at 532 nm for empty (D-MIL-53⊃DAT) and guest-filled (D-MIL-53⊃[DAT + guest]) samples for each guest shown in Fig. 1 at room temperature. The decay curves of each sample at the magnetic field corresponding to the higher and lower EPR peaks (Fig. 3a) are shown at the top and bottom, respectively. Single-exponential fitting curves for each sample are also shown. Echo signals were not observed when the guest was h-Tol, EtOH, or AcNt.

The T2 value was plotted against the cell volume of pristine MIL-53 (Fig. 2b). With increasing cell volume, T2 shows a non-monotonic trend, becoming longer and then shorter. Interestingly, triplet qubits and flexible MOF hybrids exhibit different coherence times for various guest molecules at room temperature.

Possible mechanism of guest-dependent T2

To obtain information about the interaction of DAT with guest molecules in the ground and excited triplet states, we obtained UV–Vis absorption and time-resolved EPR spectra, respectively. For D-MIL-53⊃[DAT + H2O] (MIL-53 immediately absorbs water and forms a hydrated structure), DAT shows absorption peaks at 450, 480, and 515 nm derived from π–π* transitions. This is consistent with the absorption peaks of DAT molecularly dispersed in p-terphenyl crystal and is clearly different from the red-shifted peaks of DAT in its aggregated solid state, as we previously reported36 (Supplementary Fig. 4). With the exception of BQ, where the analyte guest itself shows absorption, no significant change in the absorption spectrum is observed when various guest molecules are introduced (Supplementary Fig. 5). A plot of the T2 versus the dielectric constants of guests also showed no correlation (Supplementary Fig. 6). This indicates that the interaction between DAT and the guest molecules is small in the ground state and that DAT is not aggregated by the introduction of guests.

Figure 3a shows the time-resolved EPR spectra of the DAT triplet in D-MIL-53 in the absence and presence of guest molecules. All the samples show similar EPR spectra typical for a polarized DAT triplet, and it is consistent with the echo-detected field-swept spectra obtained from the pulsed EPR measurements (Supplementary Fig. 7). There is no significant motional narrowing as in the EPR spectrum of the triplet state in solution49, indicating that the incorporation of DAT into the MOF nanopores effectively suppresses its rotation. The EPR spectra were simulated using the EasySpin toolbox50 in MATLAB (red lines in Fig. 3a and Supplementary Table 1). The slight changes in the relative zero-field populations (Px: Py: Pz) were observed probably due to the change in vibronic spin-orbit coupling51, but the T2 values were unrelated to the relative populations (Supplementary Fig. 8). There are also no large differences in zero-field splitting parameters (D and E) among the samples, which reflect the electron structure of DAT, indicating the absence of strong electronic interactions between the DAT triplet and guest analytes. In addition, the DAT structure would be kept after guest introductions.Fig. 3 Time-resolved EPR measurements of DAT in D-MIL-53.

a Time-resolved EPR spectra at 0.1–0.5 µs for empty (D-MIL-53⊃DAT) and guest-filled (D-MIL-53⊃[DAT + guest]) samples for each guest shown in Fig. 1 at room temperature (black). The simulated EPR spectra are shown as red lines. b Decays of the EPR peaks at higher and lower magnetic fields after pulsed photoexcitation at 532 nm for empty (D-MIL-53⊃DAT) and guest-filled (D-MIL-53⊃[DAT + guest]) samples at room temperature. Decay curves were fitted by a single exponential function, and the fitting results are shown as red curves.

The spin-lattice relaxation time (T1) was estimated from the decay of the EPR signal after light irradiation (Fig. 3b). Even under continuous microwave irradiation which makes the decay faster, the T1 value for each sample is more than an order of magnitude longer than the corresponding T2 value, indicating that T2 is not dominated by T1 (Supplementary Fig. 9 and Supplementary Table 1). The guest dependence of T1 shows a similar trend to that of T2, with some exceptions (such as H2O). This result suggests that additional relaxation mechanisms exist for spin-spin relaxation.

To gain insight into the local molecular density around DAT in the MOF nanopores, thermogravimetric analysis (TGA) was performed (Supplementary Fig. 10). The MOF cell volume minus the framework volume was approximated as the guest accessible pore volume, and the volume fraction of the pore volume occupied by the guest was estimated. Interestingly, the larger the volume fraction occupied by the guest, the longer the T2 (Fig. 4). h-Tol does not fit this trend, and it is possible that the rotation of the methyl group is responsible for shortening T213. When perdeuterated toluene (d-Tol) is introduced as a guest, T2 for the DAT triplet is extended to ~ 0.3 μs (Supplementary Fig. 11), which matches the trend for the other guest molecules. This suggests that, in the absence of a particularly relaxing substituent such as a methyl group, the higher the volume fraction occupied by guest (or local molecular density), the more the motility of DAT is suppressed and the longer T2 is. We also plotted T2 against other MOF parameters, such as guest-accessible pore volume and accommodated guest volume. The former shows a similar trend to MOF volume (Supplementary Fig. 12) and is considered not to determine the coherence time. The latter show weak positive correlations between the two parameters (Supplementary Fig. 13). This might be because guest molecules with larger volumes can fill larger space and suppress the motional relaxation of DAT. As for the terephthalate ligand of MIL-53, there is no change in T2 for the DAT triplet in the deuterated and protonated forms. There is little change in the T2 of the DAT triplet when H2O and D2O are used as guest molecules. Moreover, the increase of numbers of 1H or 19F nucleus due to the guest introduction should normally shorten the relaxation time, but in many of our systems, T2 was rather lengthened (Supplementary Fig. 14). Therefore, the effect of the change in the nuclear spin bath should not be a primary regulator of T2.Fig. 4 Dependence of T2 on volume fraction occupied by the guest.

T2 and volume fraction occupied by the guest are plotted for empty (D-MIL-53⊃DAT) and guest-filled (D-MIL-53⊃[DAT + guest]) samples. The means and the standard errors of three measurements are shown for the empty, FU, and THF samples, and the fit errors obtained by the single-exponential fitting of the spin echo decay curves are shown for other samples. For the H2O and THF samples, errors were small and buried in the symbols.

Further analysis using experimental techniques such as solid-state nuclear magnetic resonance (NMR) and terahertz spectroscopy may reveal the detailed dynamics of DAT, but it is difficult to get such insights because the amount of DAT incorporated in the MOF is only 0.87 wt% and there are much larger amounts of the host ligands and other guest molecules. Indeed, we synthesized deuterated DAT (95 % D) and introduced it into MIL-53 composed of protonated (non-deuterated) terephthalate, but we could not detect any 2H NMR signal even after integrating 1000 scans with 15 kHz magic angle spinning at 9.4 T.

Instead, we performed a molecular dynamics (MD) simulation to get insights about the DAT dynamics in MIL-53. We selected three representative systems, empty (MIL-53⊃DAT), MIL-53⊃[DAT + H2O], and MIL-53⊃[DAT + BQ], which showed different guest density and either longer or shorter T2. The simulation was conducted at 300 K for 0.2 μs. We attempted to get insight into the rotational and translational motions of DAT based on the distances between the aluminum atom and the four carbon atoms (Supplementary Figs. 15, 16, and Supplementary Table 4). In the empty sample, the distances of all directions changed drastically, indicating the presence of both rotational and translational motions. In the case of MIL-53⊃[DAT + H2O], the displacement in the z (pore) direction was observed, while only fluctuated movements in the x and y directions were observed, which means translational motion in the pore direction is dominant. Importantly, judging from the standard deviation shown in Supplementary Table 4, much fewer displacements were observed for MIL-53⊃[DAT + BQ], which has the longest T2 reported in this paper, implying that DAT mobility is significantly suppressed in this system. These results support that the DAT motions can contribute to spin relaxation processes. Since μ-OH groups bridging aluminum metals were not deuterated, the interaction between the proton and DAT remained and could be modulated by the translational motion of DAT. Moreover, the DAT triplet has anisotropic zero-field splitting parameters, D and E, which can also be altered by the change of molecular orientation by rotational motions known as tumbling. Therefore, the fluctuations of interactions with surrounding proton spins of the OH groups and anisotropic parameters based on the molecular motion of DAT would cause spin-spin relaxation (See Supplementary Discussion for more information)35. Note that the T2 of D-MIL-53⊃[DAT + H2O] was comparable to the empty sample, while the result of MD simulation implies D-MIL-53⊃[DAT + H2O] has less motion than the empty sample. The possible reason is the difference in the dynamics of the Al-OH groups. The root mean square fluctuation (RMSF) value of the OH groups, which indicates how much the OH is dynamic, was found to be larger in MIL-53⊃[DAT + H2O] (Supplementary Fig. 17). This intense motion may bring additional relaxation sources to the D-MIL-53⊃[DAT + H2O] system.

Although the mobility changes in DAT can affect the linewidths of the EPR spectra, almost no change was observed for our system40. Even for the empty sample, which is considered to have the highest mobility of DAT in the present systems, the spectral shape is completely anisotropic and solid-like. This is consistent with the MD simulation result (Supplementary Fig. 16) that the timescale of the rotation is around tens of nanoseconds. Thus, even under an empty situation, the rotational motions of DAT are sufficiently slower than the EPR timescale (~ 100 ps) and might bring no notable changes.

To support the idea that DAT dynamics can be a main factor determining T2, we measured T2 at lower temperatures in the empty, guest-free state (D-MIL-53⊃DAT) (Supplementary Fig. 18). The T2 of the DAT triplet, which is 0.1 μs at room temperature, is longer at 100 and 50 K at 1.0 and 2.8 μs, respectively. Conversely, in p-terphenyl, which is a solid and dense crystal, the DAT triplet shows a long T2 of 2.4 μs, even at room temperature. These results confirm that the dynamics of DAT is important for spin–spin relaxation process.

This study demonstrates the response of quantum coherence to diverse neutral molecules by hybridizing triplet qubits in flexible MOFs. The photoexcited triplet, which is initializable at room temperature and exhibits a long coherence time, was used as qubits, and the MOF, which can flexibly change its structure upon adsorption of various analyte molecules, was used to make the qubits responsive. This proof-of-concept result will stimulate the development of many hybrid quantum sensors using various combinations of MOFs and qubits in the future. For example, if a MOF that strongly interacts with guests having a certain functional group, and a chromophore that can strongly interact with the MOF are used as a qubit, when a molecule that can interact more strongly with the MOF than the qubit is adsorbed as a guest, the qubits may become more mobile and a change in T2 will be observed. Since there are many examples of MOFs selectively adsorbing specific guests or showing abrupt adsorption at a certain pressure, numerous quantum sensors that read the type and concentration of molecules could be realized. This concept can be generalized to create dozens to hundreds of hybrid sensors by combining dozens of MOFs and qubits, and by recognizing the response of each analyte to these sensors as a pattern, it will be possible to selectively sense specific analytes. The current discovery is expected to lead to the creation of a new concept of quantum sensing platform, which could be called a quantum nose. The control of MOF orientation is expected to enable more advanced quantum sensing by sophisticated qubit manipulation. Our system uses photoexcited triplets as qubits, which is highly compatible with optically detected magnetic resonance (ODMR). The implementation of ODMR would lead to highly sensitive sensing and, ultimately, to single molecule quantum sensing27,52–54. The triplet-MOF complex will provide an ultra-sensitive and highly selective quantum sensing platform that will have an impact in a wide range of fields such as analytical chemistry, life sciences, and medicine.

Methods

All reagents were used as received unless otherwise noted. Aluminum chloride hexahydrate (AlCl3• 6H2O) and p-benzoquinone (BQ) were purchased from Sigma-Aldrich. p-Terphenyl was purchased from FUJIFILM Wako Pure Chemical and purified by zone melting. o-Phenylenediamine, potassium dichromate (K2Cr2O7), and ethylenediamine-N,N,N’,N’-tetraacetic acid, tetrasodium tetrahydrate salt (Na4-EDTA) were purchased from FUJIFILM Wako Pure Chemical. 2,3-Dihydroxynaphthalene and 5-fluorouracil (FU) were purchased from TCI. Glacial acetic acid and oxalic acid dihydrate were purchased from Kishida Chemical. Terephthalic acid-d4 (BDC-d4) (ring-d4, 98 atom%) was purchased from Cambridge Isotope Laboratories, Inc. 5,12-Diazatetracene (DAT) and deuterated MIL-53 (D-MIL-53) were prepared following the literature with slight modifications36,47.

General characterization

Solution-state 1H-NMR (400 MHz) spectra were recorded on a JEOL JNM-ECZ400 spectrometer using tetramethylsilane (TMS) as the internal standard. Elemental analysis was carried out using a Yanaco CHN Corder MT-5 at the Elemental Analysis Center, Kyushu University. UV–Vis absorption spectra were obtained on a JASCO V-670 spectrophotometer. Fluorescence spectra were obtained using a JASCO FP-8700 fluorescence spectrometer. Thermogravimetric analysis curves were obtained on a Rigaku Thermo Plus EVO2 under N2.

Sample preparation

The samples were prepared according to a previously reported method with slight modifications36,47.

Synthesis of DAT

A mixture of 2,3-dihydroxynaphthalene (2.00 g, 12.5 mmol) and o-phenylenediamine (1.35 g, 12.5 mmol) was put into a 50 mL flask and heated to 200 °C for 1 h under N2 atmosphere. After filtering and washing the crude product with methanol, 5,12-dihydrodibenzo[b]phenazine was obtained as a yellow solid and used in the next step without further purification.

5,12-Dihydrodibenzo[b]phenazine (2.04 g, 8.69 mmol) was added to 60 mL of glacial acetic acid to produce a suspension. K2Cr2O7 (5.32 g, 18.0 mmol) in 20 mL water was slowly added dropwise, and the mixture was stirred overnight in the dark at room temperature. After neutralization, the organic layer was extracted with CHCl3, dried with anhydrous Na2SO4, and concentrated under reduced pressure. Recrystallization from toluene gave 5,12-diazatetracene (DAT) as a reddish-orange solid (yield: 47%).

1H-NMR (400 MHz, CDCl3, TMS): δ (ppm) = 8.92 (s, 2H), 8.23 (dd, 2H), 8.13 (dd, 2H), 7.81 (dd, 2H), 7.54 (dd, 2H).

Elemental analysis for C16H10N2: calculated (%) H 4.38, C 83.46, N 12.17; found (%) H 4.30, C 83.50, N 12.03.

Synthesis of D-MIL-53

AlCl3• 6H2O (966 mg, 4 mmol), oxalic acid dihydrate (504 mg, 4 mmol), and BDC-d4 were added to 30 mL deionized H2O and put into a 50 mL Teflon-lined autoclave. The mixture was sonicated, heated at 220 °C for 72 h, and cooled to room temperature over 24 h in an oven. After filtering and washing the product with DMF (N,N-dimethylformamide) and methanol, a colorless powder was obtained.

To remove the residual BDC-d4 ligands from D-MIL-53, the obtained powder was added to 15 mL DMF and heated to 120 °C for 16 h in the oven again. The resulting product was filtered and washed with DMF and methanol. These procedures were repeated until the peak from BDC-d4 was no longer observed in thermogravimetric measurements (at least three times). The product was then activated at 150 °C for 3 h.

In ambient air, activated MIL-53 immediately adsorbs water molecules and forms hydrated structures42 (denoted as D-MIL-53⊃ H2O).

Elemental analysis for [C8H1.08D3.92O5Al1]• 1.0(H2O): calculated (%) H 3.06, C 41.75, N 0.00; found (%) H 3.05, C 41.80, N 0.00.

Introduction of DAT into D-MIL-53

D-MIL-53 (50 mg) was put into a 6 mL vial and dried under reduced pressure at room temperature over 3 h. The vial was placed in the dark for 1 h at room temperature after adding 2.5 mL dichloromethane solution of DAT (1 mM). The mixture was centrifuged, washed with fresh dichloromethane (1.0 mL, seven times), and dried under vacuum at 100 °C for 3 h. D-MIL-53⊃DAT was obtained as a yellow powder.

In the ambient air, D-MIL-53⊃DAT quickly absorbs water and forms the hydrated structure (denoted as D-MIL-53⊃[DAT + H2O]).

Quantification of the number of DAT molecules in D-MIL-53⊃DAT

The amount of DAT molecules in D-MIL-53 was calculated by UV–Vis absorbance after digesting D-MIL-53⊃DAT in aqueous Na4-EDTA solution. DAT was extracted from 20.0 mg D-MIL-53⊃DAT using 4.0 mL dichloromethane after adding 4.0 mL aqueous Na4-EDTA solution (125 mM). The absorbance at 475 nm of the dichloromethane solution of DAT was 0.055 in a 1 mm cell for 20.0 mg of D-MIL-53⊃[DAT + H2O]. From the calibration curve, the concentration of the solution was calculated to be 0.175 mM. Therefore, the total amount of DAT in the 4.0 mL dichloromethane solution was found to be 0.70 µmol ( = 0.16 mg). Since 7.8 wt% of water was contained in D-MIL-53⊃[DAT + H2O] (from the TGA curve), the weight of D-MIL-53⊃DAT without water was determined to be 18.44 mg (21.74 µmol). Thus, the number of DAT molecules per unit cell of D-MIL-53 was estimated to be 0.70/21.74 = 0.032, which corresponds to 0.87 wt% of DAT in D-MIL-53⊃DAT.

Introduction of guests into D-MIL-53⊃DAT

Guest analytes (except for FU and BQ) were introduced by exposing D-MIL-53⊃DAT to each guest vapor. D-MIL-53⊃DAT was put into a 6 mL vial and dried under reduced pressure at 80 °C for 3 h. The vial was placed in a Schlenk flask containing a small amount of solvent containing activated 3 A molecular sieves and stored in the dark overnight.

The introduction of FU and BQ into the nanochannels of D-MIL-53⊃DAT was performed by the sublimation method55. D-MIL-53⊃DAT was evacuated at room temperature for 3 h. FU (35 mg) or BQ (60 mg) were added to D-MIL-53⊃DAT, and the mixtures were put into a 30 mL Schlenk flask. After 1 h of evacuation, guests were sublimated and absorbed directly into the nanopores of the MOF at 175 °C for FU and 80 °C for BQ under reduced pressure for 1 h. Residual guests were eliminated at 175 °C or 80 °C under vacuum until the powder X-ray diffraction (PXRD) peaks of bulk FU and BQ were no longer observed. D-MIL-53⊃[DAT + FU] and D-MIL-53⊃[DAT + BQ] were obtained as a pale-yellow powder and a yellow powder, respectively.

Sample preparation for EPR measurements

Samples used in the EPR measurements were prepared as follows: D-MIL-53⊃[DAT + guests] were put into 2 mm capillaries, which were plugged with cotton wool to avoid sample scattering. For liquid guests, a small amount of guest was added to the cotton wool to maintain the vapor pressure. The capillaries were degassed under 77 K for more than 30 min with an oil pump and sealed with a flame.

EPR spectroscopy

EPR measurements were performed on a Bruker E680 operated at X-band (~ 9.6 GHz) using 2 mm glass capillaries placed into 4 mm quartz EPR tubes. A Bruker standard dielectric resonator was used as a microwave resonator (ER4118X-MD5W) using TE011 mode. The samples were excited at a wavelength of 532 nm, excitation light intensity of 2–3 mJ/pulse, pulse width of 5–12 ns, and repetition rate of 30 Hz using a Spectra-Physics Quanta-Ray YAG laser. The microwave intensity was ~ 0.06 mW for time-resolved measurements. For pulsed EPR measurements, ~ 2 μW microwave was amplified by a 1 kW amplifier and then attenuated by an attenuator to π/2 pulses with a pulse width of 16 ns. 16 ns and 24 ns microwave pulses were used as π/2 pulse and π pulse, respectively. Temperature was controlled by flowing liquid helium using an Oxford Mercury iTC. The echo decay measurements were conducted using a two-pulse spin echo sequence. The first π/2 pulse was irradiated 0.3 μs after laser excitation, and the pulse interval τ was varied. T2 was obtained by single exponential fitting of decay curves.

Estimation of guest density

The number of guest molecules per unit cell of D-MIL-53 (nguest) was calculated from the following equation (Supplementary Table 2):1 nguest=wloss(mMOF+nDATmDAT)mguest(1−wloss)

where wloss, nDAT, mMOF, mDAT and mguest are weight loss (weight of guest) as a percentage of total weight, the number of DAT molecules per unit cell of D-MIL-53, the molecular weight of a unit cell of D-MIL-53 (equivalent to 4 times chemical formula), the molecular weight of DAT, and the molecular weight of the guest, respectively. The guest accessible pore volume per MOF unit cell (Vpore) of MIL-53⊃water was obtained as 638 Å3 by Platon software. By subtracting this Vpore from the volume of the MOF unit cell of MIL-53⊃H2O (VMOF, 977 Å3)42, the volume of the framework (Vstructure) was estimated as 339 Å3. This Vstructure was assumed to be same for all the D-MIL-53⊃[DAT + guest]. The percentage of guest occupied volume was estimated by the following equation,2 guestoccupiedvolume(%)=100nguestVguestVMOF−Vstructure=100nguestVguestVpore

where Vguest is the volume of the guest molecule obtained from its steric parameters (ref. 41 and Supplementary Table 5). The MOF unit cell VMOF of some of D-MIL-53⊃[DAT + guest] was estimated by PXRD peak positions using the program DICVOL56 (Supplementary Fig. 19and Supplementary Table 6). For D-MIL-53⊃[DAT + guest] containing THF, CHCl3, EtAc, h-Tol, EtOH, and AcNt as the guest, VMOF was estimated by using the unit cell volume of MIL-53 (Fe)⊃guest43, considering a linear relationship between the unit cell volumes of MIL-53 (Al)⊃guest and MIL-53 (Fe)⊃guest (Supplementary Fig. 20).

MD simulation

1. Models construction for MD simulations

To construct model structures, we referred to the reported experimental crystal structures of MIL-53 in degassed and H2O-solvated phases42, and optimized the infinite crystal structure using the Crystal17 program57,58 under periodic boundary conditions. For the optimization, we employed the pob-TZVP-rev2 basis set59 for all atoms and PBE functional60 together with Grimme D3 type dispersion correction61. The shrinking parameters were set to 2 and 2, and cell parameters were fixed to the experimental ones. Similarly, we optimized the MIL-53 in the BQ-solvated phase using the crystal structure of the desolvated phases after we changed the cell parameters to the estimated one in Supplementary Table 6. After the optimization of all three systems, we constructed each model structure of the 2 × 2 × 4 supercell (16 unit cells), where the 4 cells correspond to the pore direction. One DAT molecule was introduced into each model using the insert-molecule tool in GROMACS62. According to the experimental estimation of the amount of solvent molecules, 64 H2O molecules and 64 BQ molecules are added into each model, respectively, after the introduction of the DAT molecule.

2. Details of MD simulations

The force field parameters for the metal cluster of the MIL-53 were generated by using the Seminario methods63 in the MCPB.py modeling tool64 of AmberTools1865 with the general AMBER force field (GAFF)66. The Lennard-Jones parameters for the Al atoms and the O atoms coordinating to the Al atoms were taken from the universal force field67, and the Mulliken partial charges were taken for the literature68. The topologies files for the H2O, BQ, and DAT molecules were prepared as follows. The geometries of the three molecules were optimized using density functional theory at the B3LYP/6-311 + G(d, p) level of theory. The Mulliken atomic charges were obtained from the single point calculation at HF/6-31 G* level of theory. The optimization and charge evaluation were conducted using Gaussian 16 Rev. C. 0169. Using the obtained geometries and charges, the amber topology files were generated by the antechamber package70 with GAFF force field. The amber topology files were converted into a GROMACS format using the Python script, Acpype71.

For the equilibration of the solvents, first, energy minimization of the systems was performed based on the steepest descent algorithm with the threshold of the maximum force, 10.0 kJ/mol/nm. Second, NVT equilibration for 20 ns at 300 K were carried out for relaxation of the introduced solvent molecules within the pore, fixing the atomic positions of the MIL-53.

The main MD simulations with the canonical ensemble were performed without any restraints for 200 ns, and the snapshots were collected every 5 ps. To keep the temperature at 300 K, the velocity rescale thermostat was used72. Dynamics were propagated with a leapfrog integrator using a time step of 1 fs for the equilibration procedure and of 2 fs for the main MD simulation while preserving bond lengths using a linear constraint solver algorithm73. The geometric mixing rules were applied for cross-interactions. The particle-mesh Ewald scheme74 was used for calculating the long-range electrostatic interactions, while short-range contributions were computed with a cutoff distance of 11 Å. All simulations were carried out under periodic boundary conditions using GROMACS software version 2020.562.

To analyze the mobility of the DAT molecule in the MIL-53, we analyzed specific distances, as shown in Supplementary Figs. 15, 16, and Supplementary Table 4. Furthermore, to provide a comprehensive information about the spin relaxation, we conducted the analysis of dynamics of μ-OH (Supplementary Fig. 17).

Supplementary information

Supplementary Information

Peer Review File

Supplementary information

The online version contains supplementary material available at 10.1038/s41467-024-51715-w.

Acknowledgements

This work was partly supported by the JST-FOREST Program (JPMJFR201Y), the JST-CREST Program (JPMJCR23I6), JSPS KAKENHI (JP20H02713, JP22K19051, JP23H00304, JP23KJ1694 (A.Y.)), JST SPRING (JPMJSP2136) (A.Y.), the Innovation inspired by Nature Program of Sekisui Chemical Co. Ltd. Part of this work was conducted at Institute for Molecular Science, supported by Advanced Research Infrastructure for Materials and Nanotechnology (JPMXP1222MS0010), and by Nanotechnology Platform Program <Molecule and Material Synthesis> (JPMXP09S21MS0038), of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. We would like to thank Dr. Ryo Ohtani and Mr. Yudai Iwai for their help in the structural analysis of MIL-53. We appreciate Dr. Hiroshi Naka and Dr. Asuka Naraoka for the synthesis of deuterated DAT. We would like to thank Dr. Yusuke Nishiyama and Dr. Keiko Ideta for the measurement of solid-state NMR.

Author contributions

N. Y. conceived the project. A. Y. and N. Y. designed the experiments. A. Y. and S. F. prepared and characterized the samples, with the input of N. K. and N. Y. A. Y., M. A., T. F., and T. N. conducted the EPR measurements. J. P. and Y. H. performed MD simulations. A. Y. and N. Y. wrote the manuscript with contributions from all authors.

Peer review

Peer review information

Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.

Data availability

The processed data generated in this study have been deposited in the figshare 10.6084/m9.figshare.20586825 and are available from the corresponding authors upon request75.

Competing interests

All authors declare that they have no competing interests.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
==== Refs
References

1. Ladd TD Quantum computers Nature 2010 464 45 53 10.1038/nature08812 20203602
Ladd, T. D. et al. Quantum computers. Nature 464, 45–53 (2010).20203602 10.1038/nature08812
2. Arute F Quantum supremacy using a programmable superconducting processor Nature 2019 574 505 510 10.1038/s41586-019-1666-5 31645734
Arute, F. et al. Quantum supremacy using a programmable superconducting processor. Nature 574, 505–510 (2019).31645734 10.1038/s41586-019-1666-5
3. Muralidharan S Optimal architectures for long distance quantum communication Sci. Rep. 2016 6 20463 10.1038/srep20463 26876670
Muralidharan, S. et al. Optimal architectures for long distance quantum communication. Sci. Rep. 6, 20463 (2016).26876670 10.1038/srep20463
4. Bhaskar MK Experimental demonstration of memory-enhanced quantum communication Nature 2020 580 60 64 10.1038/s41586-020-2103-5 32238931
Bhaskar, M. K. et al. Experimental demonstration of memory-enhanced quantum communication. Nature 580, 60–64 (2020).32238931 10.1038/s41586-020-2103-5
5. Degen, C. L., Reinhard, F. & Cappellaro, P. Quantum sensing. Rev. Mod. Phys. 89, 035002 (2017).
6. Guo X Distributed quantum sensing in a continuous-variable entangled network Nat. Phys. 2019 16 281 284 10.1038/s41567-019-0743-x
Guo, X. et al. Distributed quantum sensing in a continuous-variable entangled network. Nat. Phys. 16, 281–284 (2019).10.1038/s41567-019-0743-x
7. Jing M Atomic superheterodyne receiver based on microwave-dressed Rydberg spectroscopy Nat. Phys. 2020 16 911 915 10.1038/s41567-020-0918-5
Jing, M. et al. Atomic superheterodyne receiver based on microwave-dressed Rydberg spectroscopy. Nat. Phys. 16, 911–915 (2020).10.1038/s41567-020-0918-5
8. Maze JR Nanoscale magnetic sensing with an individual electronic spin in diamond Nature 2008 455 644 647 10.1038/nature07279 18833275
Maze, J. R. et al. Nanoscale magnetic sensing with an individual electronic spin in diamond. Nature 455, 644–647 (2008).18833275 10.1038/nature07279
9. Üngör O Ozvat TM Ni Z Zadrozny JM Record chemical-shift temperature sensitivity in a series of trinuclear cobalt complexes J. Am. Chem. Soc. 2022 144 9132 9137 10.1021/jacs.2c03115 35549174
Üngör, O., Ozvat, T. M., Ni, Z. & Zadrozny, J. M. Record chemical-shift temperature sensitivity in a series of trinuclear cobalt complexes. J. Am. Chem. Soc. 144, 9132–9137 (2022).35549174 10.1021/jacs.2c03115
10. Zhang T Toward quantitative bio-sensing with nitrogen-vacancy center in diamond ACS Sens. 2021 6 2077 2107 10.1021/acssensors.1c00415 34038091
Zhang, T. et al. Toward quantitative bio-sensing with nitrogen-vacancy center in diamond. ACS Sens. 6, 2077–2107 (2021).34038091 10.1021/acssensors.1c00415
11. Hendrickx NW A single-hole spin qubit Nat. Commun. 2020 11 3478 10.1038/s41467-020-17211-7 32651363
Hendrickx, N. W. et al. A single-hole spin qubit. Nat. Commun. 11, 3478 (2020).32651363 10.1038/s41467-020-17211-7
12. Gertler JM Protecting a bosonic qubit with autonomous quantum error correction Nature 2021 590 243 248 10.1038/s41586-021-03257-0 33568826
Gertler, J. M. et al. Protecting a bosonic qubit with autonomous quantum error correction. Nature 590, 243–248 (2021).33568826 10.1038/s41586-021-03257-0
13. Jackson CE Moseley IP Martinez R Sung S Zadrozny JM A reaction-coordinate perspective of magnetic relaxation Chem. Soc. Rev. 2021 50 6684 6699 10.1039/D1CS00001B 33949521
Jackson, C. E., Moseley, I. P., Martinez, R., Sung, S. & Zadrozny, J. M. A reaction-coordinate perspective of magnetic relaxation. Chem. Soc. Rev. 50, 6684–6699 (2021).33949521 10.1039/D1CS00001B
14. Wasielewski MR Exploiting chemistry and molecular systems for quantum information science Nat. Rev. Chem. 2020 4 490 504 10.1038/s41570-020-0200-5 37127960
Wasielewski, M. R. et al. Exploiting chemistry and molecular systems for quantum information science. Nat. Rev. Chem. 4, 490–504 (2020).37127960 10.1038/s41570-020-0200-5
15. Bader K Winkler M van Slageren J Tuning of molecular qubits: very long coherence and spin-lattice relaxation times Chem. Commun. 2016 52 3623 3626 10.1039/C6CC00300A
Bader, K., Winkler, M. & van Slageren, J. Tuning of molecular qubits: very long coherence and spin-lattice relaxation times. Chem. Commun. 52, 3623–3626 (2016).10.1039/C6CC00300A
16. Giménez-Santamarina S Cardona-Serra S Clemente-Juan JM Gaita-Arino A Coronado E Exploiting clock transitions for the chemical design of resilient molecular spin qubits Chem. Sci. 2020 11 10718 10728 10.1039/D0SC01187H 34094324
Giménez-Santamarina, S., Cardona-Serra, S., Clemente-Juan, J. M., Gaita-Arino, A. & Coronado, E. Exploiting clock transitions for the chemical design of resilient molecular spin qubits. Chem. Sci. 11, 10718–10728 (2020).34094324 10.1039/D0SC01187H
17. Yamashita M Next generation multifunctional nano-science of advanced metal complexes with quantum effect and nonlinearity Bull. Chem. Soc. Jpn. 2021 94 209 264 10.1246/bcsj.20200257
Yamashita, M. Next generation multifunctional nano-science of advanced metal complexes with quantum effect and nonlinearity. Bull. Chem. Soc. Jpn. 94, 209–264 (2021).10.1246/bcsj.20200257
18. von Kugelgen S Spectral addressability in a modular two qubit system J. Am. Chem. Soc. 2021 143 8069 8077 10.1021/jacs.1c02417 34014650
von Kugelgen, S. et al. Spectral addressability in a modular two qubit system. J. Am. Chem. Soc. 143, 8069–8077 (2021).34014650 10.1021/jacs.1c02417
19. Jellen MJ Ayodele MJ Cantu A Forbes MDE Garcia-Garibay MA 2D Arrays of organic qubit candidates embedded into a pillared-paddlewheel metal-organic framework J. Am. Chem. Soc. 2020 142 18513 18521 10.1021/jacs.0c07251 32976712
Jellen, M. J., Ayodele, M. J., Cantu, A., Forbes, M. D. E. & Garcia-Garibay, M. A. 2D Arrays of organic qubit candidates embedded into a pillared-paddlewheel metal-organic framework. J. Am. Chem. Soc. 142, 18513–18521 (2020).32976712 10.1021/jacs.0c07251
20. Yu CJ von Kugelgen S Laorenza DW Freedman DE A molecular approach to quantum sensing ACS Cent. Sci. 2021 7 712 723 10.1021/acscentsci.0c00737 34079892
Yu, C. J., von Kugelgen, S., Laorenza, D. W. & Freedman, D. E. A molecular approach to quantum sensing. ACS Cent. Sci. 7, 712–723 (2021).34079892 10.1021/acscentsci.0c00737
21. Zadrozny JM Gallagher AT Harris TD Freedman DE A porous array of clock qubits J. Am. Chem. Soc. 2017 139 7089 7094 10.1021/jacs.7b03123 28453274
Zadrozny, J. M., Gallagher, A. T., Harris, T. D. & Freedman, D. E. A porous array of clock qubits. J. Am. Chem. Soc. 139, 7089–7094 (2017).28453274 10.1021/jacs.7b03123
22. Harvey SM Wasielewski MR Photogenerated spin-correlated radical pairs: From photosynthetic energy transduction to quantum information science J. Am. Chem. Soc. 2021 143 15508 15529 10.1021/jacs.1c07706 34533930
Harvey, S. M. & Wasielewski, M. R. Photogenerated spin-correlated radical pairs: From photosynthetic energy transduction to quantum information science. J. Am. Chem. Soc. 143, 15508–15529 (2021).34533930 10.1021/jacs.1c07706
23. Bayliss SL Optically addressable molecular spins for quantum information processing Science 2020 370 1309 1312 10.1126/science.abb9352 33184235
Bayliss, S. L. et al. Optically addressable molecular spins for quantum information processing. Science 370, 1309–1312 (2020).33184235 10.1126/science.abb9352
24. Kirk ML Shultz DA Hewitt P Chen J van der Est A Excited state magneto-structural correlations related to photoinduced electron spin polarization J. Am. Chem. Soc. 2022 144 12781 12788 10.1021/jacs.2c03490 35802385
Kirk, M. L., Shultz, D. A., Hewitt, P., Chen, J. & van der Est, A. Excited state magneto-structural correlations related to photoinduced electron spin polarization. J. Am. Chem. Soc. 144, 12781–12788 (2022).35802385 10.1021/jacs.2c03490
25. Paquette MM Plaul D Kurimoto A Patrick BO Frank NL Opto-spintronics: photoisomerization-induced spin state switching at 300 K in photochrome cobalt-dioxolene thin films J. Am. Chem. Soc. 2018 140 14990 15000 10.1021/jacs.8b09190 30351017
Paquette, M. M., Plaul, D., Kurimoto, A., Patrick, B. O. & Frank, N. L. Opto-spintronics: photoisomerization-induced spin state switching at 300 K in photochrome cobalt-dioxolene thin films. J. Am. Chem. Soc. 140, 14990–15000 (2018).30351017 10.1021/jacs.8b09190
26. McGuire J Miras HN Donahue JP Richards E Sproules S Ligand radicals as modular organic electron spin qubits Chem. Eur. J. 2018 24 17598 17605 10.1002/chem.201804165 30291646
McGuire, J., Miras, H. N., Donahue, J. P., Richards, E. & Sproules, S. Ligand radicals as modular organic electron spin qubits. Chem. Eur. J. 24, 17598–17605 (2018).30291646 10.1002/chem.201804165
27. Christensen JA Zhou J Tcyrulnikov NA Krzyaniak MD Wasielewski MR Spin-polarized molecular triplet states as qubits: Phosphorus hyperfine coupling in the triplet state of benzoisophosphinoline J. Phys. Chem. Lett. 2020 11 7569 7574 10.1021/acs.jpclett.0c01912 32812766
Christensen, J. A., Zhou, J., Tcyrulnikov, N. A., Krzyaniak, M. D. & Wasielewski, M. R. Spin-polarized molecular triplet states as qubits: Phosphorus hyperfine coupling in the triplet state of benzoisophosphinoline. J. Phys. Chem. Lett. 11, 7569–7574 (2020).32812766 10.1021/acs.jpclett.0c01912
28. Mayländer M Chen S Lorenzo ER Wasielewski MR Richert S Exploring photogenerated molecular quartet states as spin qubits and qudits J. Am. Chem. Soc. 2021 143 7050 7058 10.1021/jacs.1c01620 33929834
Mayländer, M., Chen, S., Lorenzo, E. R., Wasielewski, M. R. & Richert, S. Exploring photogenerated molecular quartet states as spin qubits and qudits. J. Am. Chem. Soc. 143, 7050–7058 (2021).33929834 10.1021/jacs.1c01620
29. Kothe G Initializing 214 pure 14-qubit entangled nuclear spin states in a hyperpolarized molecular solid J. Phys. Chem. Lett. 2021 12 3647 3654 10.1021/acs.jpclett.1c00726 33826347
Kothe, G. et al. Initializing 214 pure 14-qubit entangled nuclear spin states in a hyperpolarized molecular solid. J. Phys. Chem. Lett. 12, 3647–3654 (2021).33826347 10.1021/acs.jpclett.1c00726
30. Jacobberger RM Qiu Y Williams ML Krzyaniak MD Wasielewski MR Using molecular design to enhance the coherence time of quintet multiexcitons generated by singlet fission in single crystals J. Am. Chem. Soc. 2022 144 2276 2283 10.1021/jacs.1c12414 35099963
Jacobberger, R. M., Qiu, Y., Williams, M. L., Krzyaniak, M. D. & Wasielewski, M. R. Using molecular design to enhance the coherence time of quintet multiexcitons generated by singlet fission in single crystals. J. Am. Chem. Soc. 144, 2276–2283 (2022).35099963 10.1021/jacs.1c12414
31. Kirner SV On-off switch of charge-separated states of pyridine-vinylene-linked porphyrin-C60 conjugates detected by EPR Chem. Sci. 2015 6 5994 6007 10.1039/C5SC02051D 29449913
Kirner, S. V. et al. On-off switch of charge-separated states of pyridine-vinylene-linked porphyrin-C60 conjugates detected by EPR. Chem. Sci. 6, 5994–6007 (2015).29449913 10.1039/C5SC02051D
32. Yong L Electron spin relaxation of triarylmethyl radicals in fluid solution J. Magn. Reson. 2001 152 156 161 10.1006/jmre.2001.2379 11531374
Yong, L. et al. Electron spin relaxation of triarylmethyl radicals in fluid solution. J. Magn. Reson. 152, 156–161 (2001).11531374 10.1006/jmre.2001.2379
33. Zhang J Embedded nano spin sensor for in situ probing of gas adsorption inside porous organic frameworks Nat. Commun. 2023 14 4922 10.1038/s41467-023-40683-2 37582960
Zhang, J. et al. Embedded nano spin sensor for in situ probing of gas adsorption inside porous organic frameworks. Nat. Commun. 14, 4922 (2023).37582960 10.1038/s41467-023-40683-2
34. Sun L Room-temperature quantitative quantum sensing of lithium ions with a radical-embedded metal-organic framework J. Am. Chem. Soc. 2022 144 19008 19016 10.1021/jacs.2c07692 36201712
Sun, L. et al. Room-temperature quantitative quantum sensing of lithium ions with a radical-embedded metal-organic framework. J. Am. Chem. Soc. 144, 19008–19016 (2022).36201712 10.1021/jacs.2c07692
35. Mirzoyan R Kazmierczak NP Hadt RG Deconvolving contributions to decoherence in molecular electron spin qubits: A dynamic ligand field approach Chem. Eur. J. 2021 27 9482 9494 10.1002/chem.202100845 33855760
Mirzoyan, R., Kazmierczak, N. P. & Hadt, R. G. Deconvolving contributions to decoherence in molecular electron spin qubits: A dynamic ligand field approach. Chem. Eur. J. 27, 9482–9494 (2021).33855760 10.1002/chem.202100845
36. Kouno H Nonpentacene polarizing agents with improved air stability for triplet dynamic nuclear polarization at room temperature J. Phys. Chem. Lett. 2019 10 2208 2213 10.1021/acs.jpclett.9b00480 30933529
Kouno, H. et al. Nonpentacene polarizing agents with improved air stability for triplet dynamic nuclear polarization at room temperature. J. Phys. Chem. Lett. 10, 2208–2213 (2019).30933529 10.1021/acs.jpclett.9b00480
37. Sloop DJ Yu HL Lin TS Weissman SI Electron spin echoes of a photoexcited triplet: Pentacene in p-terphenyl crystals J. Chem. Phys. 1981 75 3746 3757 10.1063/1.442520
Sloop, D. J., Yu, H. L., Lin, T. S. & Weissman, S. I. Electron spin echoes of a photoexcited triplet: Pentacene in p-terphenyl crystals. J. Chem. Phys. 75, 3746–3757 (1981).10.1063/1.442520
38. Yamauchi S Recent developments in studies of electronic excited states by means of electron paramagnetic resonance spectroscopy Bull. Chem. Soc. Jpn. 2004 77 1255 1268 10.1246/bcsj.77.1255
Yamauchi, S. Recent developments in studies of electronic excited states by means of electron paramagnetic resonance spectroscopy. Bull. Chem. Soc. Jpn. 77, 1255–1268 (2004).10.1246/bcsj.77.1255
39. Oxborrow M Breeze JD Alford NM Room-temperature solid-state maser Nature 2012 488 353 356 10.1038/nature11339 22895341
Oxborrow, M., Breeze, J. D. & Alford, N. M. Room-temperature solid-state maser. Nature 488, 353–356 (2012).22895341 10.1038/nature11339
40. Yamauchi S The lowest photoexcited triplet state of subphthalocyanine in solid and fluid environments. Time-resolved electron paramagnetic resonance studies J. Phys. Chem. A 2003 107 1478 1485 10.1021/jp0258210
Yamauchi, S. et al. The lowest photoexcited triplet state of subphthalocyanine in solid and fluid environments. Time-resolved electron paramagnetic resonance studies. J. Phys. Chem. A 107, 1478–1485 (2003).10.1021/jp0258210
41. Férey G Serre C Large breathing effects in three-dimensional porous hybrid matter: facts, analyses, rules and consequences Chem. Soc. Rev. 2009 38 1380 1399 10.1039/b804302g 19384443
Férey, G. & Serre, C. Large breathing effects in three-dimensional porous hybrid matter: facts, analyses, rules and consequences. Chem. Soc. Rev. 38, 1380–1399 (2009).19384443 10.1039/b804302g
42. Loiseau T A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration Chem. Eur. J. 2004 10 1373 1382 10.1002/chem.200305413 15034882
Loiseau, T. et al. A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration. Chem. Eur. J. 10, 1373–1382 (2004).15034882 10.1002/chem.200305413
43. Millange F Serre C Guillou N Férey G Walton RI Structural effects of solvents on the breathing of metal-organic frameworks: an in situ diffraction study Angew. Chem. Int. Ed. Engl. 2008 47 4100 4105 10.1002/anie.200705607 18425735
Millange, F., Serre, C., Guillou, N., Férey, G. & Walton, R. I. Structural effects of solvents on the breathing of metal-organic frameworks: an in situ diffraction study. Angew. Chem. Int. Ed. Engl. 47, 4100–4105 (2008).18425735 10.1002/anie.200705607
44. Chandler BD Mechanical gas capture and release in a network solid via multiple single-crystalline transformations Nat. Mater. 2008 7 229 235 10.1038/nmat2101 18204452
Chandler, B. D. et al. Mechanical gas capture and release in a network solid via multiple single-crystalline transformations. Nat. Mater. 7, 229–235 (2008).18204452 10.1038/nmat2101
45. Horike S Shimomura S Kitagawa S Soft porous crystals Nat. Chem. 2009 1 695 704 10.1038/nchem.444 21124356
Horike, S., Shimomura, S. & Kitagawa, S. Soft porous crystals. Nat. Chem. 1, 695–704 (2009).21124356 10.1038/nchem.444
46. Schneemann A Flexible metal-organic frameworks Chem. Soc. Rev. 2014 43 6062 6096 10.1039/C4CS00101J 24875583
Schneemann, A. et al. Flexible metal-organic frameworks. Chem. Soc. Rev. 43, 6062–6096 (2014).24875583 10.1039/C4CS00101J
47. Fujiwara S Triplet dynamic nuclear polarization of guest molecules through induced fit in a flexible metal–organic framework Angew. Chem. Int. Ed. Engl. 2022 61 e202115792 10.1002/anie.202115792 34935275
Fujiwara, S. et al. Triplet dynamic nuclear polarization of guest molecules through induced fit in a flexible metal–organic framework. Angew. Chem. Int. Ed. Engl. 61, e202115792 (2022).34935275 10.1002/anie.202115792
48. Dai YZ Chemical modification toward long spin lifetimes in organic conjugated radicals Chemphyschem 2018 19 2972 2977 10.1002/cphc.201800742 30085398
Dai, Y. Z. et al. Chemical modification toward long spin lifetimes in organic conjugated radicals. Chemphyschem 19, 2972–2977 (2018).30085398 10.1002/cphc.201800742
49. Fujisawa J-I Ohba Y Yamauchi S A time-resolved electron paramagnetic resonance study of excited triplet porphyrins in fluid solution J. Am. Chem. Soc. 1997 119 8736 8737 10.1021/ja970507i
Fujisawa, J.-I., Ohba, Y. & Yamauchi, S. A time-resolved electron paramagnetic resonance study of excited triplet porphyrins in fluid solution. J. Am. Chem. Soc. 119, 8736–8737 (1997).10.1021/ja970507i
50. Stoll S Schweiger A EasySpin, a comprehensive software package for spectral simulation and analysis in EPR J. Magn. Reson. 2006 178 42 55 10.1016/j.jmr.2005.08.013 16188474
Stoll, S. & Schweiger, A. EasySpin, a comprehensive software package for spectral simulation and analysis in EPR. J. Magn. Reson. 178, 42–55 (2006).16188474 10.1016/j.jmr.2005.08.013
51. Sakamoto K Polarizing agents beyond pentacene for efficient triplet dynamic nuclear polarization in glass matrices Proc. Natl. Acad. Sci. USA 2023 120 e2307926120 10.1073/pnas.2307926120 37871226
Sakamoto, K. et al. Polarizing agents beyond pentacene for efficient triplet dynamic nuclear polarization in glass matrices. Proc. Natl. Acad. Sci. USA 120, e2307926120 (2023).37871226 10.1073/pnas.2307926120
52. Wrachtrup J Borczyskowski CV Bernard J Orrit M Brown R Optical detection of magnetic resonance in a single molecule Nature 1993 363 244 245 10.1038/363244a0
Wrachtrup, J., Borczyskowski, C. V., Bernard, J., Orrit, M. & Brown, R. Optical detection of magnetic resonance in a single molecule. Nature 363, 244–245 (1993).10.1038/363244a0
53. Mena, A. et al. Room-temperature optically detected coherent control of molecular spins. Preprint at arXiv10.48550/arXiv.2402.07572 (2024).
54. Singh, H. et al. Room-temperature quantum sensing with photoexcited triplet electrons in organic crystals. Preprint at arXiv10.48550/arXiv.2402.13898 (2024).
55. Yanai N Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer Nat. Mater. 2011 10 787 793 10.1038/nmat3104 21892178
Yanai, N. et al. Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer. Nat. Mater. 10, 787–793 (2011).21892178 10.1038/nmat3104
56. Boultif A Louër D Indexing of powder diffraction patterns for low-symmetry lattices by the successive dichotomy method J. Appl. Cryst. 1991 24 987 993 10.1107/S0021889891006441
Boultif, A. & Louër, D. Indexing of powder diffraction patterns for low-symmetry lattices by the successive dichotomy method. J. Appl. Cryst. 24, 987–993 (1991).10.1107/S0021889891006441
57. R. Dovesi et al. CRYSTAL17 User’s Manual (University of Torino, Torino, 2017).
58. Dovesi R Quantum-mechanical condensed matter simulations with CRYSTAL WIREs Comput. Mol. Sci. 2018 8 e1360 10.1002/wcms.1360
Dovesi, R. et al. Quantum-mechanical condensed matter simulations with CRYSTAL. WIREs Comput. Mol. Sci. 8, e1360 (2018).10.1002/wcms.1360
59. Vilela Oliveira D Laun J Peintinger MF Bredow T BSSE-correction scheme for consistent gaussian basis sets of double- and triple-zeta valence with polarization quality for solid-state calculations J. Comput. Chem. 2019 40 2364 2376 10.1002/jcc.26013 31260123
Vilela Oliveira, D., Laun, J., Peintinger, M. F. & Bredow, T. BSSE-correction scheme for consistent gaussian basis sets of double- and triple-zeta valence with polarization quality for solid-state calculations. J. Comput. Chem. 40, 2364–2376 (2019).31260123 10.1002/jcc.26013
60. Perdew JP Burke K Ernzerhof M Generalized gradient approximation made simple Phys. Rev. Lett. 1996 77 3865 3868 10.1103/PhysRevLett.77.3865 10062328
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).10062328 10.1103/PhysRevLett.77.3865
61. Grimme S Semiempirical GGA-type density functional constructed with a long-range dispersion correction J. Comput. Chem. 2006 27 1787 1799 10.1002/jcc.20495 16955487
Grimme, S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27, 1787–1799 (2006).16955487 10.1002/jcc.20495
62. Abraham MJ GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers SoftwareX 2015 1-2 19 25 10.1016/j.softx.2015.06.001
Abraham, M. J. et al. GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers. SoftwareX 1-2, 19–25 (2015).10.1016/j.softx.2015.06.001
63. Seminario JM Calculation of intramolecular force fields from second-derivative tensors Int. J. Quantum Chem. 1996 60 1271 1277 10.1002/(SICI)1097-461X(1996)60:7<1271::AID-QUA8>3.0.CO;2-W
Seminario, J. M. Calculation of intramolecular force fields from second-derivative tensors. Int. J. Quantum Chem. 60, 1271–1277 (1996).10.1002/(SICI)1097-461X(1996)60:7<1271::AID-QUA8>3.0.CO;2-W
64. Li P Merz KM Jr. MCPB.py: A Python based metal center parameter builder J. Chem. Inf. Model. 2016 56 599 604 10.1021/acs.jcim.5b00674 26913476
Li, P. & Merz, K. M. Jr. MCPB.py: A Python based metal center parameter builder. J. Chem. Inf. Model. 56, 599–604 (2016).26913476 10.1021/acs.jcim.5b00674
65. D. A. Case et al. AMBER 2018 (University of California, San Francisco, 2018).
66. Wang J Wolf RM Caldwell JW Kollman PA Case DA Development and testing of a general amber force field J. Comput. Chem. 2004 25 1157 1174 10.1002/jcc.20035 15116359
Wang, J., Wolf, R. M., Caldwell, J. W., Kollman, P. A. & Case, D. A. Development and testing of a general amber force field. J. Comput. Chem. 25, 1157–1174 (2004).15116359 10.1002/jcc.20035
67. Rappe AK Casewit CJ Colwell KS Goddard WA III Skiff WM UFF, a Full periodic table force field for molecular mechanics and molecular dynamics simulations J. Am. Chem. Soc. 1992 114 10024 10035 10.1021/ja00051a040
Rappe, A. K., Casewit, C. J., Colwell, K. S., Goddard, W. A. III & Skiff, W. M. UFF, a Full periodic table force field for molecular mechanics and molecular dynamics simulations. J. Am. Chem. Soc. 114, 10024–10035 (1992).10.1021/ja00051a040
68. Ramsahye NA Charge distribution in metal organic framework materials: transferability to a preliminary molecular simulation study of the CO2 adsorption in the MIL-53 (Al) system Phys. Chem. Chem. Phys. 2007 9 1059 1063 10.1039/B613378A 17311147
Ramsahye, N. A. et al. Charge distribution in metal organic framework materials: transferability to a preliminary molecular simulation study of the CO2 adsorption in the MIL-53 (Al) system. Phys. Chem. Chem. Phys. 9, 1059–1063 (2007).17311147 10.1039/B613378A
69. M. J. Frisch et al. Gaussian 16, Revision C.01 (Gaussian, Inc., Wallingford CT, 2016).
70. Wang J Wang W Kollman PA Case DA Automatic atom type and bond type perception in molecular mechanical calculations J. Mol. Graph. Model. 2006 25 247 260 10.1016/j.jmgm.2005.12.005 16458552
Wang, J., Wang, W., Kollman, P. A. & Case, D. A. Automatic atom type and bond type perception in molecular mechanical calculations. J. Mol. Graph. Model. 25, 247–260 (2006).16458552 10.1016/j.jmgm.2005.12.005
71. Silva AWSD Vranken WF ACPYPE - Antechamber PYthon parser interfacE BMC Res. Notes 2012 5 367 10.1186/1756-0500-5-367 22824207
Silva, A. W. S. D. & Vranken, W. F. ACPYPE - Antechamber PYthon parser interfacE. BMC Res. Notes 5, 367 (2012).22824207 10.1186/1756-0500-5-367
72. Bussi G Donadio D Parrinello M Canonical sampling through velocity rescaling J. Chem. Phys. 2007 126 014101 10.1063/1.2408420 17212484
Bussi, G., Donadio, D. & Parrinello, M. Canonical sampling through velocity rescaling. J. Chem. Phys. 126, 014101 (2007).17212484 10.1063/1.2408420
73. Hess B Bekker H Berendsen HJC Fraaije JGEM LINCS: A linear constraint solver for molecular simulations J. Comput. Chem. 1997 18 1463 1472 10.1002/(SICI)1096-987X(199709)18:12<1463::AID-JCC4>3.0.CO;2-H
Hess, B., Bekker, H., Berendsen, H. J. C. & Fraaije, J. G. E. M. LINCS: A linear constraint solver for molecular simulations. J. Comput. Chem. 18, 1463–1472 (1997).10.1002/(SICI)1096-987X(199709)18:12<1463::AID-JCC4>3.0.CO;2-H
74. Darden T York D Pedersen L Particle mesh Ewald: An N⋅log(N) method for Ewald sums in large systems J. Chem. Phys. 1993 98 10089 10092 10.1063/1.464397
Darden, T., York, D. & Pedersen, L. Particle mesh Ewald: An N⋅log(N) method for Ewald sums in large systems. J. Chem. Phys. 98, 10089–10092 (1993).10.1063/1.464397
75. Yamauchi, A. Modulation of triplet quantum coherence by guest-induced structural changes in a flexible metal-organic framework. Data sets. figshare 10.6084/m9.figshare.20586825 (2024).
