Photochromism and Photomagnetism Induced by Structural Disorder

Article Cite This: Cryst. Growth Des. 2019, 19, 3688−3693

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Photochromism and Photomagnetism Induced by Structural Disorder of a Crystalline Spin-Crossover FeII Complex Published as part of a Crystal Growth and Design virtual special issue on Crystalline Functional Materials in Honor of Professor Xin-Tao Wu Ai-Ping Jin,†,‡ Xiang-Yi Chen,† Ming-Sheng Wang,*,† and Guo-Cong Guo*,†

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†

State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China ‡ University of Chinese Academy of Sciences, Beijing 100039, P. R. China S Supporting Information *

ABSTRACT: Photochromic and photoswitchable magnetic (photomagnetic) properties of spin-crossover (SCO) metal complexes in the solid state were observed almost at cryogenic temperature. Here we present a new crystalline complex [FeII(TMPT)6](ClO4)8 (TMPT = 1-(1,2,4-triazol-4-yl)-2,4,6trimethyl-pyridinium) showing photochromism and reversible hysteresis shift, with one direction being triggered by thermal annealing and the other by irradiation at room temperature. IR/Raman and single-crystal X-ray diffraction data revealed that these behaviors are very probably induced by thermal disorder of ClO4− anions, which change intermolecular interactions and the ligand field strength of the FeII center. This discovery may inspire the design and synthesis of new photochromic and photomagnetic compounds through controlling structural disorder.

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INTRODUCTION As an electronically labile molecular species, SCO complexes can switch between high-spin (HS, S = 2) and low-spin (LS, S = 0) states under external stimuli such as temperature, pressure, or light at the molecule scale1−4 and thus show potential applications in sensors and memory devices.5−8 Photoswitching of their magnetism has attracted much attention because of the high speed, high selectivity, and low power dissipation of light.9−13 For real application, it is best to realize the photoswitching around room temperature (RT).13−16 Light-induced excited spin state trapping (LIESST) is a well-known method to switch magnetism of SCO complexes.17,18 However, because of the low energy barrier between excited and ground states, it usually occurs at temperatures below 50 K.19−21 To address this issue, two effective approaches have been developed. One is to excite the SCO complex with light in the hysteresis loop that covers the RT region.22,23 For example, single crystals of the [Fe(pyrazine)(Pt(CN)4)] SCO complex exhibit a complete bidirectional photoconversion within the thermal hysteresis region around RT.24 The other is to trigger photoisomerization of organic ligands that show photochromism at RT.25−27 For instance, the ligand-driven light-induced spin change (LDLISC) complex, [Fe(H2B(pz)2)2phen*] (pz = 1-pyrazolyl, phen* = bis(2,5-dimethyl-3-thienyl)-1,10-phenanthroline), was recently found to exhibit significant magnetic change at RT in the solid state by photoisomerization of the diarylethene-based ligand phen*.28 Even so, there are still only a few © 2019 American Chemical Society

SCO complexes that exhibit photoswitchable magnetism (photomagnetism) in the solid state around RT.12,13,23−33 In addition, photochromic materials have appealing applications on smart windows, photomasks, data storage, photocatalysis, solar energy conversion, etc.34 Photochromic phenomena around RT were observed in limited SCO complexes.19 Therefore, it is meaningful to develop new photomagnetic and photochromic SCO complexes that show photoswitching in the solid state at RT. In this work, we found that the new mononuclear FeII−trz (trz = triazole) SCO complex, [FeII(TMPT)6](ClO4)8 (1; Figure 1), exhibited both reversible hysteresis shift and photochromism in the solid state, with one direction being triggered by thermal annealing and the other by irradiation at RT. Complex 1 contains no organic ligands showing isomerization photochromism, and the photoexcitation is not realized in the hysteresis loop. IR/Raman and X-ray diffraction data indicate that these behaviors may be closely related to the structural disorder of ClO4− anions.

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EXPERIMENTAL SECTION

Materials and Instruments. Materials. (TMPT)BF4 was synthesized according to a literature method.35 Other reagents in

Received: December 19, 2018 Revised: April 28, 2019 Published: May 28, 2019 3688

DOI: 10.1021/acs.cgd.8b01885 Cryst. Growth Des. 2019, 19, 3688−3693

Crystal Growth & Design

Article

were generated geometrically and refined isotropically. Crystallographic data are summarized in Table 1. Selected bond distances are listed in Table S1. More details on the crystallographic studies as well as atomic displacement parameters are given as CIFs deposited with the CCDC.

Table 1. Crystallographic Data Measured at 300 K for the Same Crystal of 1 before and after Thermal Annealing formula Mr/g mol−1 crystal system space group a/Å c/Å V/Å3 Z Dcalcd/g cm−1 reflns collected unique reflns F(000) GOF R1a [I > 2σ(I)] wR2b (all data) CCDC no.

Figure 1. TMPT and coordination sphere of FeII in 1. H atoms are omitted for clarity. AR grade were purchased from commercial sources and used without further purification. Physical Measurements. All measurements, except for elemental analyses, magnetic measurements, and thermogravimetric (TG) analysis, were carried out in air at 300 K. The powder X-ray diffraction (PXRD) patterns were recorded on Rigaku MiniFlex II diffractometer powered at 30 kV and 15 mA using Cu Kα radiation (λ = 1.54056 Å). The simulated pattern was achieved using the free Mercury software (http://www.ccdc.cam.ac.uk/products/mercury/). Elemental analyses of C, H, and N were carried out on an Elementar Vario EL III microanalyzer. The TG analysis of 1 was done on a Netzsch STA449C-QMS403C thermal analysis-quadrupole mass spectrometer under N2 atmosphere (20 mL min−1) at a heating rate of 5 K min−1. A PerkinElmer Spectrum One FT−IR spectrophotometer was used to measure the IR data for complex 1 with the pure KCl pellets as the matrixes. The ultraviolet−visible (UV−vis) absorption spectra were measured in the reflectance mode on a PerkinElmer Lambda 900 UV/vis/NIR spectrophotometer with an integrating sphere attachment and BaSO4 as a reference. The absorbance (A) was achieved using the equation: A = −lg(R%). A Labram HR800 Evolution Raman spectrometer was used to measure the Raman data for 1 with a near-IR (785 nm) laser. Magnetic properties of 1 were carried out on a Quantum Design SQUID magnetometer working in the 2−400 K temperature range with a 1.5 K min−1 sweeping rate under a magnetic field of 5000 Oe. An OPOTECK VIBRANT HE 355 LD tunable laser system was used to illuminate samples for decoloration of thermally annealed 1 (YAG laser, λ = 470 nm). The DSC analysis of 1 was done on a using a METTLER TOLEDO apparatus, in which the samples were heated in an Al2O3 crucible with a stream of nitrogen (20 mL min−1) at a heating rate of 2 K min−1. Synthesis of [FeII(TMPT)6](ClO4)8 (1). Excess Fe(ClO4)2·6H2O (36.2 mg, 0.1 mmol) was added to a solution of (TMPT)BF4 (27.8 mg, 0.1 mmol) in MeOH/CH3CN (10 mL, v/v = 1:1). The mixture was stirred for 1 h and filtered. The resulting clear solution was slowly evaporated in air at room temperature for 5 days. Pale purple prismatic single crystals of 1 (35% yield based on TMPT) suitable for X-ray diffraction analysis were mechanically selected with the help of a microscope. The phase purity of the crystals for all tests was confirmed by PXRD (Figure S1, Supporting Information) and elemental analysis. Calcd (%) for C60H78Cl8FeN24O32: C 36.27, H 3.96, N 16.92. Found: C 36.21, H 3.88, N 16.83. TG data and PXRD patterns (Figure S1, Supporting Information) indicate that compound 1 is thermally stable up to at least 423 K. Crystal Structure Determination. X-ray diffraction data of the same single crystal of 1 before and after thermal annealing were recorded on Rigaku Pilatus 200 K diffractometer using graphitemonochromatic Mo Kα (λ = 0.71073 Å) at 300(2) K in air. All absorption corrections were performed using the multiscan program, and the structures were solved by direct method and refined by fullmatrix least-squares techniques on F2 with SHELXTL-97.36,37 Nonhydrogen atoms were refined anisotropically, while hydrogen atoms

a

as-synthesized

annealed at 400 K for 3 h

C60H78Cl8FeN24O32 1986.91 trigonal R3̅ 20.404(5) 18.409(5) 6637(3) 3 1.491 19017 3400 3072 1.034 0.0830 0.2829 1497825

C60H78Cl8FeN24O32 1986.91 trigonal R3̅ 20.428(5) 18.421(5) 6657(3) 3 1.487 19142 3417 3072 1.046 0.0830 0.2847 1449324

R1 = Σ||F0| − |Fc||/Σ|F0|. bwR2 = {Σ[w(F02 − Fc2)2]/Σ[w(F02)2]}1/2.

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RESULTS AND DISCUSSION Structure Description. As shown in Table 1, complex 1 crystallizes in the trigonal system, R3̅ space group. The asymmetric unit of 1 contains one crystallographically distinguishable FeII atom (occupancy = 0.16667), one TMPT ligand, and two disordered ClO4− anions (one is thermally disordered, occupancy = 1; the other is symmetrically disordered in the trigonal axis, occupancy = 0.33333, Figure S2, Supporting Information). As shown in Figure 1, the FeII atom adopts slightly distorted octahedral coordination geometry surrounded by six coordinated N atoms coming from different TMPT ligands, which bind to one FeII ion in a monodentate fashion in turn. The average Fe−N bond lengths in as-synthesized 1 are 2.146(3) Å (Table S1, Supporting Information), close to the normal HS FeII−N bond lengths of FeII SCO complexes.38 There are C−H···O hydrogen-bonding interactions (H bonds) between disordered ClO4− anions and nearby TMPT ligands (Table S2 and Figure S3, Supporting Information). Photochromic Properties. The as-synthesized crystalline sample of 1 showed clearly a color shift from pale purple to pale yellow after heating at 400 K (below the decomposing temperature) and then cooling to RT (an annealing process; Figure 2 top). As shown in Figure 2 bottom, the UV−vis spectrum of the as-synthesized 1 displays one intense band peaked at 268 nm, one weak band centered at 544 nm, and one weak band above 700 nm. By comparison to other FeII SCO complexes,16,18,39 the former band can be attributed to π → π* transition of TMPT, and the latter two are d−d transitions (1A1g → 1T1g and 5T2g → 5Eg) of FeII atoms. After annealing, a new absorption band centered at 470 nm appeared. A timedependent UV−vis spectroscopy determination using the same sample verified that the thermally induced coloration was saturated after annealing at 400 K for about 3 h (Figure S4, 3689



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Figure 2. Top: photochromic phenomenon of 1 in air. Bottom: UV− vis spectra of 1 before and after thermal annealing. Inset: A cycle test monitored at 470 nm under repeated thermal annealing (400 K, 3 h) and irradiation (470 nm laser, 2 h). All data were measured in air using the same crystalline sample based on the reflectance diffuse technique. The peak marked with an inverted triangle is noise due to the lamp change. The reason why the first irradiated point cannot restore to the as-synthesized point is that the light spot of laser is smaller than the area of the sample.

Figure 3. IR spectra of 1 upon sequential annealing and irradiation using the same KCl pellet (12.90 × 0.45 mm, 0.65 mg 1 in 90 mg of KCl, irradiated and measured at the center of the pellet).

Supporting Information). A differential scanning calorimetry (DSC) study over the temperature range of 300−400 K showed no phase transition peak during the annealing process (Figure S5, Supporting Information). Under YAG laser irradiation (λ = 470 nm) at RT for 2 h, the initial pale purple color was restored (Figure 2 top), and, at the same time, the 470 nm band was weakened (Figure 2 inset). It is worth noting that irradiation with UV light has no effect on the decoloration process of 1. This wavelength dependence shows that the decoloration proceeds through a photon mode instead of the photothermal one.40 Besides, the YAG laser irradiation did not trigger the coloration of the as-synthesized 1 (Figure S6, Supporting Information). As shown in Figure 2 inset, the heatinduced coloration and laser-induced decoloration processes are repeatable, displaying photochromic behavior. IR and Raman spectra are very sensitive to structural variation. The variation of peak positions in IR or Raman spectra was usually used to monitor the structural variation of a material.41−44 Intensity changes and peak shifts observed in IR spectra reveal the thermal effect on the structure of 1. As shown in Figure 3 and Figure S8 (time-dependent IR data in the same KCl matrix upon heating, Supporting Information), the bands between 2900 and 3000 cm−1, related to asymmetric stretching vibration of aryl methyl C−H bond (νas(C−H)) of TMPT, show clearly a red shift. In the fingerprint region below 1000 cm−1, the characteristic bands around 850−1000 cm−1,

assigned to aryl C−H bond bending vibrations (δ(C−H)), remain at about the same positions, while their relative intensities show obvious changes. And, notably, the characteristic band of isolated ClO4− ions at 645 cm−1 shifts to 639 cm−1. After laser irradiation for 2 h, the shape and positions of the above-mentioned IR peaks almost returned to the original state (Figure 3), which confirms again that the coloration and decoloration of 1 are reversible. Correlative changes were found from the Raman spectra after thermal annealing (Figure S7, Supporting Information). In the Raman low-frequency regions below 300 cm−1, which are closely related to metal−ligand stretching vibrations,45 the bands observed at 172 and 236 cm−1 apparently shift to 164 and 229 cm−1, respectively, while the band at 149 cm−1 shows intensity reduction after heat treatment. It has been documented that a minor change of ligand field strength of a metal center could induce a clear color change.46 On the basis of the changes of metal−ligand Raman stretching vibrations, we speculate that the coloration behavior of 1 is due to the environment change of FeII after annealing, which has a significant influence on the ligand field strength. The emerged absorption band centered at 470 nm may be attributed to 1A1g → 1T2g d−d transitions of FeII with the new coordination environment.18,39 In the Raman fingerprint region between 3690



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700 and 1400 cm−1, which is related to the aryl and aryl methyl C−H bond vibrations of TMPT, slight changes can be found after thermal annealing. For example, the bands at 764 and 1010 cm−1 decrease in intensities.45 Besides, the characteristic band of ClO4− ions at 613 cm−1 splits into two bands at 612 and 624 cm−1.47 Similar to the IR data, the original Raman spectrum could be restored after laser irradiation for 2 h (Figure S7, Supporting Information). Magnetic Behavior. It is well-known that the intermolecular interactions can affect the thermal hysteresis loop of SCO complex.48−50 Since there are intermolecular H bonds between the ClO4− ions and the C−H bonds of the TMPT ligand in 1 (Table S2 and Figure S3, Supporting Information), the changes of Raman and IR spectra for ClO4− ions after thermal annealing indicate the variation of H bonds and thus thermal hysteresis loop. This was confirmed by a magnetic measurement. Magnetic properties of the as-synthesized, annealed, and irradiated samples for 1 were measured within the temperature range of 150−400 K (Figure 4). The start χMT

complex. Upon further irradiation by the YAG laser, the magnetic properties were nearly restored. Photomagnetic and photochromic properties of known FeII complexes usually originate from spin transition or valence tautomerism.19,53,54 For 1, the unchanging of the χMT value at RT after annealing indicated that there was no variation of the spin state and oxidation state of FeII or generation of radicals. The thermal disorder of ClO4− is a common phenomenon in crystallography. Direct structural changes of ClO4− in 1 can be found by the overlap of the same unit before and after annealing (Figure 5). We infer that the thermal disorder of

Figure 5. Overlap of the same thermal disordered ClO4− anion of 1 before and after thermal annealing (as-synthesized, black-white frame; annealed, red-green ellipsoid).

ClO4− triggers the variation of intermolecular interactions and ligand field strength of the FeII center, which accounts for the change of hysteresis and color, respectively.

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CONCLUSIONS In summary, we have prepared a new crystalline FeII SCO complex that shows reversible photoinduced hysteresis shift and photochromism, with the photoswitching being operated at RT. IR, Raman, and single-crystal X-ray diffraction data revealed that the changes of intermolecular interactions and ligand field strength of the FeII center, induced probably by thermal disorder of ClO4−, should be the principal reason for photochromism and the switchable magnetism. Further studies are now under investigation in our group.

Figure 4. Temperature dependence of χMT (per Fe unit) for 1 upon sequential processing (applied field: 5000 Oe, temperature range: 150−400 K). Inset: the enlarged hysteresis loop of 1 in the range of 210−280 K.

value of the as-synthesized sample at 300 K is 3.04 cm3 K mol−1. It is slightly lower than the theoretical value for one HS FeII ion, which can explain the existence of a 1A1g → 1T1g band in the UV−vis spectrum of 1 at 300 K. Upon cooling, the χMT value exhibits an abrupt decrease to about 200 K, reaching a value of 0.34 cm3 K mol−1, and then remains nearly unchanged. Upon heating, the χMT value increases around 200 K and then shows a small hysteresis before reaching a plateau at about 345 K. Thus, we can conclude that the assynthesized 1 undergoes a one-step complete SCO with T1/2 (cooling) = 255 K, T1/2 (heating) = 263 K and ΔT = 8 K, respectively, which agrees with the literature reports about Fe− trz SCO complexes.51 After annealing, the χMT values in the range of 300−400 K were almost unchanged. Our recent work showed that the TMPT analogue could be reduced to form a radical.52 As for 1, the retainment of the χMT value after thermal annealing indicates that the TMPT ligand was not reduced. However, the transition temperatures show a clear change, with T1/2 (cooling) = 247 K, T1/2 (heating) = 251 K, and ΔT = 4 K, respectively, a little lower than the original

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.8b01885. Additional information regarding the selected bond lengths (Å) for the same crystal before and after thermal annealing at 400 K, bond distances (Å) and angles (deg) for H bonds related to the symmetrically disordered ClO4− ions, the TG curve, PXRD patterns, a perspective view along the [0 0 1] direction, hydrogen-bonding diagrams around symmetrically disordered ClO4− anion, electron absorption spectra after annealing at 400 K for different times, the DSC profile in the range of 300−400 K, electron absorption spectra before and after irradiation with the YAG laser (λ = 470 nm, 30 min), comparison of Raman spectra between as-synthesized 3691



Article

(10) Ordejón, B.; de Graaf, C.; Sousa, C. Light-Induced ExcitedState Spin Trapping in Tetrazole-Based Spin Crossover Systems. J. Am. Chem. Soc. 2008, 130, 13961−13968. (11) Sato, O. Dynamic molecular crystals with switchable physical properties. Nat. Chem. 2016, 8, 644−656. (12) Milek, M.; Heinemann, F. W.; Khusniyarov, M. M. Spin Crossover Meets Diarylethenes: Efficient Photoswitching of Magnetic Properties in Solution at Room Temperature. Inorg. Chem. 2013, 52, 11585−11592. (13) Meng, Y. S.; Sato, O.; Liu, T. Manipulating Metal-to-Metal Charge Transfer for Materials with Switchable Functionality. Angew. Chem., Int. Ed. 2018, 57, 12216−12226. (14) Thies, S.; Sell, H.; Schütt, C.; Bornholdt, C.; Näther, C.; Tuczek, F.; Herges, R. Light-Induced Spin Change by Photodissociable External Ligands: A New Principle for Magnetic Switching of Molecules. J. Am. Chem. Soc. 2011, 133, 16243−16250. (15) Venkataramani, S.; Jana, U.; Dommaschk, M.; Sönnichsen, F. D.; Tuczek, F.; Herges, R. Magnetic Bistability of Molecules in Homogeneous Solution at Room Temperature. Science 2011, 331, 445−448. (16) Schmidt, S. O.; Naggert, H.; Buchholz, A.; Brandenburg, H.; Bannwarth, A.; Plass, W.; Tuczek, F. Thermal and Light-Induced Spin Transitions of FeII Complexes with 4- and 5-(Phenylazo)-2,2’bipyridine Ligands: Intra- vs. Intermolecular Effects. Eur. J. Inorg. Chem. 2016, 2016, 2175−2186. (17) Bertoni, R.; Cammarata, M.; Lorenc, M.; Matar, S. F.; Létard, J. F.; Lemke, H. T.; Collet, E. Ultrafast light-induced spin-state trapping photophysics investigated in Fe (phen)2(NCS)2 spin-crossover crystal. Acc. Chem. Res. 2015, 48, 774−781. (18) Ohkoshi, S. I.; Imoto, K.; Tsunobuchi, Y.; Takano, S.; Tokoro, H. Light-Induced Spin-Crossover Magnet. Nat. Chem. 2011, 3, 564− 569. (19) Sato, O.; Tao, J.; Zhang, Y. Z. Control of Magnetic Properties through External Stimuli. Angew. Chem., Int. Ed. 2007, 46, 2152− 2187. (20) Halder, G. J.; Chapman, K. W.; Neville, S. M.; Moubaraki, B.; Murray, K. S.; Létard, J.-F.; Kepert, C. J. Elucidating the Mechanism of a Two-Step Spin Transition in a Nanoporous Metal−Organic Framework. J. Am. Chem. Soc. 2008, 130, 17552−17562. (21) Liu, T.; Zheng, H.; Kang, S.; Shiota, Y.; Hayami, S.; Mito, M.; Sato, O.; Yoshizawa, K.; Kanegawa, S.; Duan, C. A Light-Induced Spin Crossover Actuated Single-Chain Magnet. Nat. Commun. 2013, 4. DOI: 10.1038/ncomms3826 (22) Freysz, E.; Montant, S.; Létard, S.; Létard, J. F. Single Laser Pulse Induces Spin State Transition Within the Hysteresis Loop of an Iron Compound. Chem. Phys. Lett. 2004, 394, 318−323. (23) Bonhommeau, S.; Molnár, G.; Galet, A.; Zwick, A.; Real, J. A.; McGarvey, J. J.; Bousseksou, A. One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature. Angew. Chem., Int. Ed. 2005, 44, 4069−4073. (24) Cobo, S.; Ostrovskii, D.; Bonhommeau, S.; Vendier, L.; Molnár, G.; Salmon, L.; Tanaka, K.; Bousseksou, A. Single-LaserShot-Induced Complete Bidirectional Spin Transition at Room Temperature in Single Crystals of (FeII(pyrazine)(Pt(CN)4)). J. Am. Chem. Soc. 2008, 130, 9019−9024. (25) Boillot, M. L.; Zarembowitch, J.; Sour, A. In Spin Crossover in Transition Metal Compounds II; Springer: Berlin, 2004; Vol. 234, Chapter 10, pp 261−276. (26) Tissot, A.; Boillot, M. L.; Pillet, S.; Codjovi, E.; Boukheddaden, K.; Lawson Daku, L. M. Unidirectional Photoisomerization of Styrylpyridine for Switching the Magnetic Behavior of an Iron(II) Complex: A MLCT Pathway in Crystalline Solids. J. Phys. Chem. C 2010, 114, 21715−21722. (27) Hasegawa, Y.; Takahashi, K.; Kume, S.; Nishihara, H. Complete Solid State Photoisomerization of Bis(Dipyrazolylstyrylpyridine)Iron(II) To Change Magnetic Properties. Chem. Commun. 2011, 47, 6846−6848.

and thermally annealed samples and time-dependent IR spectra in the same KCl matrix upon heating of 1 (PDF) Accession Codes

CCDC 1449324 and 1497825 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (G.C.G.). *E-mail: [email protected] (M.S.W.). ORCID

Ming-Sheng Wang: 0000-0002-2400-719X Guo-Cong Guo: 0000-0002-7450-9702 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (91545201, 21601185), the Key Research Program of Frontier Sciences, CAS (XDB20010000, QYZDB-SSW-SLH020), the Youth Innovation Promotion Association of CAS, and the Natural Science Foundation of Fujian Province (2017J01033, 2018J01028).

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DEDICATION Dedicated to Professor Xin-Tao Wu on the occasion of his 80th birthday.

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REFERENCES

(1) Gütlich, P.; Hauser, A. Thermal and Light-Induced Spin Crossover in Iron(II) Complexes. Coord. Chem. Rev. 1990, 97, 1−22. (2) Miller, J. S.; Drillon, M. Magnetism II: Molecules to Materials; Wiley-VCH: Weinheim, Germany, 2002. (3) Gütlich, P.; Goodwin, H. In In Spin Crossover Transition Metal Compounds I; Gütlich, P., Goodwin, H. A., Eds.; Springer: Berlin, 2004; Vol. 233, Chapter 1, pp 1−47. (4) Schaefer, A. W.; Ehudin, M. A.; Quist, D. A.; Tang, J. A.; Karlin, K. D.; Solomon, E. I. Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions. J. Am. Chem. Soc. 2019, 141, 4936−4951. (5) Kahn, O.; Martinez, C. J. Spin-Transition Polymers: From Molecular Materials Toward Memory Devices. Science 1998, 279, 44− 48. (6) Gaspar, A. B.; Ksenofontov, V.; Seredyuk, M.; Gütlich, P. Multifunctionality in Spin Crossover Materials. Coord. Chem. Rev. 2005, 249, 2661−2676. (7) Li, B.; Wang, X. N.; Kirchon, A.; Qin, J. S.; Pang, J. D.; Zhuang, G. L.; Zhou, H. C. Sophisticated Construction of Electronically Labile Materials: A Neutral, Radical-Rich, Cobalt Valence Tautomeric Triangle. J. Am. Chem. Soc. 2018, 140, 14581−14585. (8) Š alitroš, I.; Madhu, N. T.; Boča, R.; Pavlik, J.; Ruben, M. RoomTemperature Spin-Transition Iron Compounds. Monatsh. Chem. 2009, 140, 695−733. (9) Delgado, T.; Tissot, A.; Guénée, L.; Hauser, A.; ValverdeMuñoz, F. J.; Seredyuk, M.; Real, J. A.; Pillet, S.; Bendeif, E. E.; Besnard, C. Very Long-Lived Photogenerated High-Spin Phase of a Multistable Spin-Crossover Molecular Material. J. Am. Chem. Soc. 2018, 140, 12870−12876. 3692



Article

Transitions in Solid Copper(II) Diiminate Cu[CF3−C(NH)−CF = C(NH)CF3]2. Inorg. Chem. 2012, 51, 10590−10602. (47) Smit, E.; Manoun, B.; Waal, D. d. Low-Wavenumber Raman Spectra of the Spin-Transition Complexes [Fe(NH2 trz)3](ClO4)2 and [Fe(Htrz)3](ClO4)2. J. Raman Spectrosc. 2001, 32, 339−344. (48) Hauser, A. In Spin Crossover in Transition Metal Compounds I; Gütlich, P., Goodwin, H. A., Ed.; Springer: Berlin, Heidelberg, 2004; pp 49−58. (49) Weber, B.; Bauer, W.; Pfaffeneder, T.; Dîrtu, M. M.; Naik, A. D.; Rotaru, A.; Garcia, Y. Influence of Hydrogen Bonding on the Hysteresis Width in Iron(II) Spin-Crossover Complexes. Eur. J. Inorg. Chem. 2011, 2011, 3193−3206. (50) Sciortino, N. F.; Scherl-Gruenwald, K. R.; Chastanet, G.; Halder, G. J.; Chapman, K. W.; Létard, J. F.; Kepert, C. J. Hysteretic Three-Step Spin Crossover in a Thermo- and Photochromic 3D Pillared Hofmann-type Metal−Organic Framework. Angew. Chem., Int. Ed. 2012, 51, 10154−10158. (51) Krober, J.; Codjovi, E.; Kahn, O.; Groliere, F.; Jay, C. A Spin Transition System with A Thermal Hysteresis at Room Temperature. J. Am. Chem. Soc. 1993, 115, 9810−9811. (52) Chen, X. Y.; Zhang, N. N.; Cai, L. Z.; Li, P. X.; Wang, M. S.; Guo, G. C. N-Methyl-4-pyridinium Tetrazolate Zwitterion-Based Photochromic Materials. Chem. - Eur. J. 2017, 23, 7414−7417. (53) Sheu, C. F.; Shih, C. H.; Sugimoto, K.; Cheng, B. M.; Takata, M.; Wang, Y. A Long-Lived Photo-Induced Metastable State of Linkage Isomerization Accompanied with A Spin Transition. Chem. Commun. 2012, 48, 5715−5717. (54) Marino, A.; Chakraborty, P.; Servol, M.; Lorenc, M.; Collet, E.; Hauser, A. The Role of Ligand-Field States in the Ultrafast Photophysical Cycle of the Prototypical Iron(II) Spin-Crossover Compound [Fe(ptz)6](BF4)2. Angew. Chem., Int. Ed. 2014, 53, 3863− 3867.

(28) Rösner, B.; Milek, M.; Witt, A.; Gobaut, B.; Torelli, P.; Fink, R. H.; Khusniyarov, M. M. Reversible Photoswitching of a SpinCrossover Molecular Complex in the Solid State at Room Temperature. Angew. Chem., Int. Ed. 2015, 54, 12976−12980. (29) Boillot, M. L.; Chantraine, S.; Zarembowitch, J.; Lallemand, J. Y.; Prunet, J. First Ligand-Driven Light-Induced Spin Change Atroomtemperature in a Transition-Metal Molecular Compound. New J. Chem. 1999, 23, 179−184. (30) Sour, A.; Boillot, M. L.; Rivière, E.; Lesot, P. First Evidence of a Photoinduced Spin Change in an FeIII Complex Using Visible Light at Room Temperature. Eur. J. Inorg. Chem. 1999, 1999, 2117−2119. (31) Senechal-David, K.; Zaman, N.; Walko, M.; Halza, E.; Riviere, E.; Guillot, R.; Feringa, B. L.; Boillot, M. L. Combining Organic Photochromism With Inorganic Paramagnetism-Optical Tuning of the Iron(II) Electronic Structure. Dalton Trans 2008, 1932−1936. (32) Hasegawa, Y.; Kume, S.; Nishihara, H. Reversible LightInduced Magnetization Change in an Azobenzene-Attached Pyridylbenzimidazole Complex of Iron(II) at Room Temperature. Dalton Trans 2009, 280−284. (33) Takahashi, K.; Hasegawa, Y.; Sakamoto, R.; Nishikawa, M.; Kume, S.; Nishibori, E.; Nishihara, H. Solid-State Ligand-Driven Light-Induced Spin Change at Ambient Temperatures in Bis(dipyrazolylstyrylpyridine)iron(II) Complexes. Inorg. Chem. 2012, 51, 5188−5198. (34) Zhang, J.; Zou, Q.; Tian, H. Photochromic Materials: More Than Meets the Eye. Adv. Mater. 2013, 25, 378−399. (35) Abramovitch, R. A.; Beckert, J. M.; Gibson, H. H.; Belcher, A.; Hundt, G.; Sierra, T.; Olivella, S.; Pennington, W. T.; Solé, A. The 1,2,4-Triazolyl Cation: Thermolytic and Photolytic Studies. J. Org. Chem. 2001, 66, 1242−1251. (36) Sheldrick, G. M. SHELXL-97; Program for Refinement of Crystal Structures; University of Göttingen: Göttingen, Germany, 1997. (37) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. SIR97: A New Tool for Crystal Structure Determination and Refinement. J. Appl. Crystallogr. 1999, 32, 115−119. (38) Olguín, J.; Brooker, S. Spin Crossover Active Iron(II) Complexes of Selected Pyrazole-Pyridine/Pyrazine Ligands. Coord. Chem. Rev. 2011, 255, 203−240. (39) Dîrtu, M. M.; Naik, A. D.; Rotaru, A.; Spinu, L.; Poelman, D.; Garcia, Y. FeII Spin Transition Materials Including an Amino−Ester 1,2,4-Triazole Derivative, Operating at, below, and above Room Temperature. Inorg. Chem. 2016, 55, 4278−4295. (40) Takahashi, K.; Nakajima, R.; Gu, Z. Z.; Yoshiki, H.; Fujishima, A.; Sato, O. Unusually Long-Lived Light-Induced Metastable State in A Thermochromic Copper(II) Complex. Chem. Commun. 2002, 38, 1578−1579. (41) Smit, E.; Manoun, B.; Waal, D. d. Low-wavenumber Raman spectra of the Spin-Transition Complexes [Fe(NH2 trz)3](ClO4)2 and [Fe(Htrz)3](ClO4)2. J. Raman Spectrosc. 2001, 32, 339−344. (42) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, Part B, 6th ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2009. (43) Cooper, T. E.; Carl, D. R.; Oomens, J.; Steill, J. D.; Armentrout, P. B. Infrared Spectroscopy of Divalent Zinc and Cadmium Crown Ether Systems. J. Phys. Chem. A 2011, 115, 5408−5422. (44) Cai, L. Z.; Chen, Q. S.; Zhang, C. J.; Li, P. X.; Wang, M. S.; Guo, G. C. Photochromism and Photomagnetism of a 3d−4f Hexacyanoferrate at Room Temperature. J. Am. Chem. Soc. 2015, 137, 10882−10885. (45) Urakawa, A.; Van Beek, W.; Monrabal-Capilla, M.; GalánMascarós, J. R.; Palin, L.; Milanesio, M. Combined, Modulation Enhanced X-ray Powder Diffraction and Raman Spectroscopic Study of Structural Transitions in the Spin Crossover Material [Fe(Htrz)2(trz)](BF4). J. Phys. Chem. C 2011, 115, 1323−1329. (46) Khrustalev, V. N.; Kostenko, S. O.; Buzin, M. I.; Korlyukov, A. A.; Zubavichus, Y. V.; Kurykin, M. A.; Antipin, M. Y. Highly Flexible Molecule “Chameleon”: Reversible Thermochromism and Phase 3693


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