Exceptional Three-Level Switching Behaviors of Quadratic NonlinearOptical Properties in a Tristable Molecule-Based DielectricChengmin Ji,† Sasa Wang,† Sijie Liu,†,‡ Zhihua Sun,*,† Jing Zhang,† Lina Li,† and Junhua Luo*,†

†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 100049, China

*S Supporting Information

ABSTRACT: Significant progress on a new brilliant scheme for the solid phasetransition has opened up new possibilities of highly efficiently switching the quadraticnonlinear optical (NLO) properties. However, the NLO switching capacities ofpreviously reported solid-state materials were restrictively modulated between theconventional bistable states. Exploring NLO tristability is strongly required for multistepoperations in multilevel memory elements and optoelectronic devices. Here, we firstreport a tristable molecule-based dielectric, dipropylammonium trichloroacetate (DPA-TCA), which shows an exceptional three-level switching of quadratic NLO effects (i.e.,NLO-off, low-NLO, and high-NLO states). This unprecedented three-level switching ofthe NLO effect originates from the stepwise ordering of the dynamic molecularcomponents in DPA-TCA, associated with the tristability of dielectric phase transitionsat 142 and 228 K. It is believed that this finding will shed light on the further design of new multilevel NLO switching materialsand promote their prospective device applications.

■ INTRODUCTION

Nonlinear optical (NLO) switch material, as an exciting newbranch of NLO material science, allows us to convert theintrinsic NLO effects under the influence of external stimuli,such as heat, laser radiation, pressure, electric and magneticfields, etc. These materials are of great interest because of theirpotentials in controllable intelligent devices.1−7 Although greatprogress has been achieved, the switchable NLO activities ofpreviously reported solid-state NLO switches were restrictivelymodulated only between bistable states, such as “NLO-on” and“NLO-off” states (or high-NLO and low-NLO states), whichseverely limits their practical application in multistep operationsfor multilevel memory elements and optoelectronic devices.8−12

For instance, the three-level conversion among distinguishablespin states in tristable spin-crossover systems has long beenestablished as an applicable way to assemble multilevelmagnetic switches.13−17 As a counterpart, however, there isstill a rare report of three-level NLO switches. In thiscircumstance, it is highly desirable to develop new conceptuallytristable materials that allow us to switch the quadratic NLOeffects at three levels.In the past few decades, much of the attention in exploring

NLO switches has been focused on the conventional strategiesof chemical modification (e.g., redox process, protonation, orion capture trapping) and thermochromic/photochromicresponses.18−24 Recently, the solid-state phase transitionrepresents a new brilliant scheme that relies on the structuraltransformation for the development of new NLO switchingcandidates.25−31 It has proven that solid-state phase transitionswith a change in the crystallographic symmetry from the

centrosymmetric (CS) phase to the noncentrosymmetric(NCS) phase can generate drastic variations in NLO effects,which has significantly enhanced the development of high-performance quadratic NLO switches.32−35 Since Mercier et al.first reported the organic−inorganic hybrid NLO switch,[{H3N(CH2)2SS-(CH2)2NH3}PbI5]·H3O, great progress inNLO switch materials has been achieved on the basis of thisprinciple in metal−organic hybrids and multicomponent ionicsalts.36 In particular, a plastic molecular NLO switch shows arecord high “on/off” contrast of ≲150 by extending theprinciple of structural transformation to a plastic materialsystem.37 However, to the best of our knowledge, all NLOswitches mentioned above can allow conversion of NLOactivities between only common bistable states, and studies ofstimulus-responsive NLO tristability are in their infancy. Zhanget al. recently discussed a two-step NLO switch within avariable confined space based on the sequential solid-statephase transitions.38 Unfortunately, it shows an “off−on−off”NLO switching capacity, with the NLO active state merelyexisting in a narrow intermediate temperature range between198 and 240 K. Therefore, further exploration of new phasetransition materials is quite necessary to achieve three-levelswitching of quadratic NLO properties accompanied by thestep-by-step enhancement of NLO effects.Here, we have reported a tristable molecule-based dielectric,

dipropylammonium trichloroacetate (DPA-TCA), which

Received: February 8, 2017Revised: March 11, 2017Published: March 19, 2017

Article

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© 2017 American Chemical Society 3251 DOI: 10.1021/acs.chemmater.7b00524Chem. Mater. 2017, 29, 3251−3256

undergoes tristable dielectric phase transitions at 142 and 228K. Emphatically, it shows an exceptional three-level switching ofquadratic NLO effects, changing from an “NLO-off state” tolow-NLO and high-NLO states. Stepwise ordering of theflexible components dominates such a unique NLO switchingbehavior, as well as the tristable dielectric states in DPA-TCA.To the best of our knowledge, this is the first tristable moleculardielectric with unprecedented three-level NLO switching,which opens up a new strategy for designing the stimulus-responsive multistable materials.

■ EXPERIMENTAL SECTIONAll the chemical reagents were purchased as high-purity (AR grade)compounds and used without any further purification. Colorless blocksingle crystals of DPA-TCA were obtained by slow evaporation of anaqueous solution containing equimolar dipropylamine (DPA) andtrichloroacetic acid (TCA) at room temperature. Powder X-raydiffraction (PXRD) patterns were recorded by an X-ray diffractometer(Rigaku Corp., SCXmini). The diffraction patterns were collected inthe 2θ range of 5−50° with a step size of 0.02°. The experimentalPXRD patterns obtained at room temperature match well with thecalculated data based on the single-crystal structure, which solidlyconfirm the purity of the as-grown crystals of DPA-TCA.Variable-temperature X-ray single-crystal diffraction experiments

were performed on a SuperNova diffractometer with Cu Kα radiation(λ = 1.5406 Å). Crystal structures were determined by direct methodsand refined by the full-matrix method based on F2 using the SHELXS-97 software package. All non-hydrogen atom positions were locatedusing difference Fourier methods as implemented in SHELXL-97. Allof the non-hydrogen atoms were refined anisotropically. These crystaldata, structural refinements, and selected geometrical parameters canbe found in Tables S1−S7.Thermal properties were measured by a differential thermal analyzer

(Netzsch DSC 200 F3) under a nitrogen atmosphere in aluminumcrucibles with a heating/cooling rate of 10 K/min.For dielectric measurements, the samples of DPA-TCA were made

with single crystals cut into the form of a thin plate perpendicular tothe crystal axis. Silver conduction paste deposited on the plate surfaceswas used as the electrodes. Dielectric experiments were performedwith a TongHhui TH2828 Precision LCR Meter at differentfrequencies in the temperature range of 115−285 K, with a heating/cooling rate of ∼10 K/min. The UV−vis optical transmission spectraof the samples of DPA-TCA were recorded on a Lambda-950 UV/vis/NIR spectrophotometer, which show that DPA-TCA presents goodtransparency from 350 to 800 nm.SHG switching experiments with DPA-TCA were performed on the

powder samples (particle size range of 72−100 μm), using thefundamental laser beam with a low divergence (pulsed Nd:YAG laserat a wavelength of 1064 nm, 5 ns pulse duration, 1.6 MW peak power,and 10 Hz repetition rate). The instrument is model FLS 920 fromEdinburgh Instruments; the temperature range is 100−300 K (DE202), while the laser is a model Vibrant 355 II laser from OPOTEK.

■ RESULTS AND DISCUSSION

Differential scanning calorimetry (DSC) was first performed toprobe the tristable structural phase transitions of DPA-TCA. Itclearly shows two sets of thermal anomalies, indicating twosequential phase transitions at 228 and 142 K (Figure 1a). Thephase above T1 is designated the high-temperature phase(HTP), the phase between T1 and T2 as the intermediate-temperature phase (ITP), and the phase below T2 as the low-temperature phase (LTP). The broad peaks of the observedthermal anomalies and the slight temperature hysteresis at T1and T2 reveal that two transitions are both of typical second-order phase transition with continuous characteristics.39−41

Entropy changes (ΔS) are estimated to be 4.58 and 5.71 J K−1

mol−1 accompanying the transition around T1 and T2,respectively. Given that ΔS = R ln N, it is found that N(T1)= 1.73 and N(T2) = 1.91, revealing the disorder−order featureof phase transitions at T1 and T2.

42−44 This originates fromstepwise ordering of thermal motions, which coincides wellwith the structural analyses mentioned below.It is known that crystal structure transformation should be

associated with the molecular dipole motions, which are closelyrelated to the tunable dielectric permittivity.45−48 The temper-ature dependence of the real part (ε′) of the complex relativedielectric permittivity of DPA-TCA was measured on a single-crystal sample. The results reveal two relatively obviousdielectric anomalies at T1 and T2 upon cooling and heating,being consistent with the DSC results, which is reminiscent ofthe tristable dielectric states in DPA-TCA (Figure 1b andFigure S2). Below T2, the dielectric constants remain stable anddisplay a small change from 4.4 to 4.6 around the phasetransition point, whereas a sharp dielectric anomaly is observedat T1 with a pronounced steplike increase to ∼5.7. Above T1, itthen remains almost constant until room temperature isreached. There is no distinct dielectric relaxation process inthe vicinity of T1 and T2 at different frequencies (Figure S3),indicating a relatively fast dipolar motion associated with thesetwo structural transformations.49

Quadratic NLO switching performances were studied byusing the method of Kurtz and Perry to examine thepolycrystalline sample of DPA-TCA (λ = 1064 nm; Nd:YAGpulsed laser).50 As shown in the inset of Figure 2, it is notablethat there is not any NLO signal at 532 nm above T1. Via in situmeasurement of NLO effects upon cooling, the NLO signalsgradually become active with NLO intensity peaks emerging at532 nm. With a further decrease in temperature, NLOintensities increase significantly. As shown in Figure 2, fromthe integral results of NLO signals, it is clearly shown that NLOeffects are completely obliterative above T1, with the effectivesecond-order NLO susceptibility χ(2) basically being zero,

Figure 1. (a) DSC curves and (b) dielectric constant measurements ofDPA-TCA as a function of temperature, revealing the tristabledielectric phase transitions at T1 and T2.

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corresponding to the NLO-off state. Upon DPA-TCA wasfurther cooled from HTP to ITP, a steplike jump of the NLOsignals was observed, achieving a saturation value andremaining stable. As expected from the tristable dielectricphase transition, the enhanced NLO signals emerge at T2 andreach a new level with the temperature decreasing far below T2.Compared with common bistable NLO switches that rely onthe CS−NCS phase transition,25−37 DPA-TCA shows a three-level “off−low−high” NLO switching behavior with step-by-step enhancements of NLO effects from T1 to T2. To the bestof our knowledge, DPA-TCA is the first example of a tristabledielectric material with a significant three-level NLO switching,which shows great potential in multilevel optoelectronicdevices.To understand the origin of the tristable NLO switching

capacities, variable-temperature crystal structures of DPA-TCAwere determined at 100 K (LTP), 150 K (ITP), and 240 K(HTP) (Table S1).51 As shown in Figure 3, the crystal

structures of DPA-TCA, composed of protonated DPA cationsand TCA counteranions, crystallize in the orthorhombic crystalsystem. However, its crystal symmetry transforms from a CSspace group of Pnma in HTP to a NCS one of P212121 in ITPand LTP. At 240 K, two diverse geometry configurations ofDPA cations and TCA anions were observed in the unit cell(abbreviated as DPA1 and DPA2 and as TCA1 and TCA2,respectively). It is interesting to note that the DPA1 and DPA2cations and the TCA1 anion are highly disordered with N2, C8,and C11 of DPA1 and C5 of DPA2 apparently existing in twopossible equilibrium occupations. Meanwhile, all the Cl atomsin TCA1 also exhibit dynamical disorder, which exhibits sevenpossible equilibrium occupations. The related dynamiccharacteristics of DPA1, DPA2, and TCA1 create a crystallo-

graphic mirror plane parallel to [010]. The mirror symmetry issatisfied by the orientational disorder of DPA1 and DPA2cations and TCA1 anions. In addition, the TCA2 anion shows arelatively ordered state, in which C13, C14, and Cl2 are locatedon the special position with mmm symmetry. This centrosym-metric construction was adopted in HTP for DPA-TCA withmutually canceled dipole moments, corresponding to the NLO-off state in HTP.The crystal structure of DPA-TCA at 150 K was measured to

investigate the phase transition related to the CS−NCSsymmetry transformation. Although the structure of DPA-TCA in ITP remains in the orthorhombic crystal system andthe lattice parameters are almost the same as those in HTP(Table S1), the loss of the mirror symmetry in the (010) planeresults in the structural phase transition from CS space groupPnma to chiral space group P212121. This transformationsignificantly enhances the NLO activity at T1. The thermalvibration parameters of all atoms in ITP are obviously smallerthan those found in HTP (Tables S2 and S3), which suggests adeceleration of the molecular thermal motions. The disorderedDPA1 and DPA2 moieties turn from disorder to ordered states,and all atoms of DPA cations can be exclusively determined inITP. It can be seen that the geometry configuration of DPAcations clearly changes with obvious distortion of the carbonchain because of the inherent flexibility of the chain-typeconfiguration. As shown in Figure 4a, DPA1 adopts a usual

zigzig geometry configuration with normal C−C(N) bonddistances (1.455−1.546 Å) and C−C(N)−C bond angles(108.1−114.3°). The DPA2 cation chain is not a regular zigziggeometry with a torsion angle of 18° (N1−C4−C5−C6) inITP, which is different from the N2−C10−C11−C12 torsionangle for DPA1 (Table S6). In addition, it is worth mentioningthat all cationic atoms lie in approximate plane (1) for DPA1and plane (2) for DPA2 in ITP (Figure 4a).With respect to the crystal structure at 100 K in LTP, all the

DPA cations and TCA anions are frozen to be totally ordered,and the Cl atoms of TCA are definitely distinguishable. Asshown in Figure 4b, it is notable that the geometryconfigurations of DPA1 and DPA2 cations are different fromthose in ITP, the C atoms of DPA deviating from theircommon plane of ITP with the following deviation values:Δd(C1) = 0.5526, Δd(C2) = 0.1251, Δd(C6) = 0.2805, andΔd(C12) = 0.3129 Å. The clear twisting of DPA chainssignificantly increases the molecular dipole moments, whichfavors the enhancement of NLO activities and triggers thesecond-step NLO effects modulated from the low-NLO state inITP to the high-NLO state in LTP.We notice that the role of the hydrogen-bonding interactions

should not be underemphasized. As shown in Figure 5, in HTP,

Figure 2. Variable-temperature second-order NLO coefficients ofDPA-TCA, revealing the three-level NLO switching response. Theinset shows the relative intensity of NLO signals as a function ofwavelength at various temperatures.

Figure 3. Variable-temperature crystal structures of DPA-TCA in (a)HTP, (b) ITP, and (c) LTP.

Figure 4.Molecular geometry configuration of DPA1 and DPA2 at (a)150 and (b) 100 K.

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the sole N−H···O hydrogen-bonding dimer between the cationand anion anchors the N atom of DPA in the crystal lattice welland leaves a large amount of room for the free motion of thedisordered DPA chain. The hydrogen-bonding dimers, whichare antiparallel to each other in the packing structure of DPA-TCA, form a one-dimensional chainlike structure parallel to theb-axis. As the temperature decreases to ITP, the interactions ofhydrogen bond dimers become much stronger, with N−H···Ohydrogen bond lengths of 2.856 and 2.911 Å. The disorderedcations become more ordered, which synergistically supportsthe switchable NLO response at T1. In LTP, further enhancedN−H···O hydrogen-bonding interactions of 2.796 and 2.816 Åbetween the cation and anion efficiently restrict the dynamicmotions of TCA, and the fixed orientation of the ordered DPAand TCA molecules is unambiguously related to the stable andenhanced NLO activity in LTP.

■ CONCLUSIONIn summary, a new tristable molecule-based dielectric has beenreported as the NLO switch candidate, which exhibits theunprecedented switching of quadratic NLO effects at threelevels. Such an exceptional NLO switching closely involves itsdielectric phase transitions, that is, two-step phase transitionsfrom the CS phase to the NCS state. The stepwise ordering ofthe dynamic components in DPA-TCA, accompanied by thedistortion of flexible chain alkylamine, dominates the tristabilityof its dielectric responses and NLO properties. This findingpaves a new pathway for the further design of multilevelmolecular NLO switching materials and encourages their futureapplication to switch bulk optoelectronic properties inmultistable states.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.chemma-ter.7b00524.

XRD powder patterns, dielectric spectra in the heatingand cooling runs, dielectric spectra at various frequencies,and transmission spectra (Figures S1−S4, respectively),crystal data and structural refinement details (Table S1),atomic coordinates and equivalent isotropic displacementparameters (Tables S2−S4), and torsion angles (TablesS5−S7) (PDF)rystallographic data of DPA-TCA (240 K): CCDCdeposition numbers 1540604 (CIF)Crystallographic data of DPA-TCA (150 K): CCDCdeposition numbers 1540605 (CIF)Crystallographic data of DPA-TCA (100 K): CCDCdeposition numbers 1540606 (CIF)

■ AUTHOR INFORMATIONCorresponding Authors*E-mail: sunzhihua@fjirsm.ac.cn.*E-mail: jhluo@fjirsm.ac.cn.ORCIDJunhua Luo: 0000-0002-5355-9006NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis work was financially supported by the National NaturalScience Foundation of China (51502290, 21525104, 91422301,21571178, 51502288, 21373220, 51402296, and 21301172),the National Science Foundation of Fujian Province(2015J05040 and 2016J01082), and the Youth InnovationPromotion of the Chinese Academy of Sciences (2014262,2015240, and 2016274).

■ REFERENCES(1) Boixel, J.; Guerchais, V.; Le Bozec, H.; Jacquemin, D.; Amar, A.;Boucekkine, A.; Colombo, A.; Dragonetti, C.; Marinotto, D.; Roberto,D.; Righetto, S.; De Angelis, R. Second-order NLO switches frommolecules to polymer films based on photochromic cyclometalatedplatinum (II) complexes. J. Am. Chem. Soc. 2014, 136, 5367−5375.(2) Castet, F.; Rodriguez, V.; Pozzo, J. L.; Ducasse, L.; Plaquet, A.;Champagne, B. Champagne, B. Design and characterization ofmolecular nonlinear optical switches. Acc. Chem. Res. 2013, 46,2656−2665.(3) Green, K. A.; Cifuentes, M. P.; Samoc, M.; Humphrey, M. G.Metal alkynyl complexes as switchable NLO systems. Coord. Chem.Rev. 2011, 255, 2530−2541.(4) Irie, M. Diarylethenes for memories and switches. Chem. Rev.2000, 100, 1685−1716.(5) Delaire, J. A.; Nakatani, K. Linear and nonlinear optical propertiesof photochromic molecules and materials. Chem. Rev. 2000, 100,1817−1846.(6) Berkovic, G.; Krongauz, V.; Weiss, V. Spiropyrans andspirooxazines for memories and switches. Chem. Rev. 2000, 100,1741−1754.(7) Marinotto, D.; Castagna, R.; Righetto, S.; Dragonetti, C.;Colombo, A.; Bertarelli, C.; Garbugli, M.; Lanzani, G. Photoswitchingof the Second Harmonic Generation from Poled Phenyl-SubstitutedDithienylethene Thin Films and EFISH Measurements. J. Phys. Chem.C 2011, 115, 20425−20432.(8) Asselberghs, I.; Clays, K.; Persoons, A.; Ward, M. D.; McCleverty,J. A. Switching of molecular second-order polarisability in solution. J.Mater. Chem. 2004, 14, 2831−2839.(9) Zhang, Y.; Ye, H.-Y.; Cai, H.-L.; Fu, D.-W.; Ye, Q.; Zhang, W.;Zhou, Q. H.; Wang, J. L.; Yuan, G.-L.; Xiong, R.-G. SwitchableDielectric, Piezoelectric, and Second-Harmonic Generation Bistability

Figure 5. N−H···O hydrogen bond configurations of DPA-TCA in (a)HTP, (b) ITP, and (c) LTP.

Chemistry of Materials Article

DOI: 10.1021/acs.chemmater.7b00524Chem. Mater. 2017, 29, 3251−3256

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in a New Improper Ferroelectric above Room Temperature. Adv.Mater. 2014, 26, 4515−4520.(10) Serra-Crespo, P.; van der Veen, M. A.; Gobechiya, E.;Houthoofd, K.; Filinchuk, Y.; Kirschhock, C. E. A.; Martens, J. A.;Sels, B. F.; De Vos, D. E.; Kapteijn, F.; Gascon, J. NH2-MIL-53 (Al): ahigh-contrast reversible solid-state nonlinear optical switch. J. Am.Chem. Soc. 2012, 134, 8314−8317.(11) Beaujean, P.; Bondu, F.; Plaquet, A.; Garcia-Amoros, J.; Cusido,J.; Raymo, F. M.; Castet, F.; Rodriguez, V.; Champagne, B. Oxazines:A New Class of Second-Order Nonlinear Optical Switches. J. Am.Chem. Soc. 2016, 138, 5052−5058.(12) Priimagi, A.; Ogawa, K.; Virkki, M.; Mamiya, J.-i.; Kauranen, M.;Shishido, A. High-Contrast Photoswitching of Nonlinear OpticalResponse in Crosslinked Ferroelectric Liquid-Crystalline Polymers.Adv. Mater. 2012, 24, 6410−6415.(13) Schneider, B.; Demeshko, S.; Dechert, S.; Meyer, F. A Double-Switching Multistable Fe4 Grid Complex with Stepwise Spin-Crossover and Redox Transitions. Angew. Chem., Int. Ed. 2010, 49,9274−9277.(14) Nihei, M.; Tahira, H.; Takahashi, N.; Otake, Y.; Yamamura, Y.;Saito, K.; Oshio, H. Multiple Bistability and Tristability with DualSpin-State Conversions in [Fe(dpp)2][Ni (mnt)2]2·MeNO2. J. Am.Chem. Soc. 2010, 132, 3553−3560.(15) Chernyshov, D.; Hostettler, M.; Tornroos, K. W.; Burgi, H.-B.Ordering Phenomena and Phase Transitions in a Spin-CrossoverCompound-Uncovering the Nature of the Intermediate Phase of[Fe(2-pic)3]Cl2·EtOH. Angew. Chem., Int. Ed. 2003, 42, 3825−2830.(16) Wei, R.-J.; Huo, Q.; Tao, J.; Huang, R.-B.; Zheng, L.-S. Spin-Crossover FeII4 Squares: Two-Step Complete Spin Transition andReversible Single-Crystal-to-Single-Crystal Transformation. Angew.Chem., Int. Ed. 2011, 50, 8940−8943.(17) Feng, X.; Mathoniere, C.; Jeon, I.-R.; Rouzieres, M.; Ozarowski,A.; Aubrey, M. L.; Gonzalez, M. I.; Clerac, R.; Long, J. R. Tristability ina Light-Actuated Single-Molecule Magnet. J. Am. Chem. Soc. 2013,135, 15880−15884.(18) Li, P. X.; Wang, M. S.; Zhang, M. J.; Lin, C. S.; Cai, L. Z.; Guo,S. P.; Guo, G. C. Electron-Transfer Photochromism To Switch BulkSecond-Order Nonlinear Optical Properties with High Contrast.Angew. Chem., Int. Ed. 2014, 53, 11529−11531.(19) Segerie, A.; Castet, F.; Kanoun, M. B.; Plaquet, A.; Liegeois, V.;Champagne, B. Nonlinear Optical Switching Behavior in the SolidState: A Theoretical Investigation on Anils. Chem. Mater. 2011, 23,3993−4001.(20) Sliwa, M.; Letard, S.; Malfant, I.; Nierlich, M.; Lacroix, P. G.;Asahi, T.; Masuhara, H.; Yu, P.; Nakatani, K. Design, Synthesis,Structural and Nonlinear Optical Properties of Photochromic Crystals:Toward Reversible Molecular Switches. Chem. Mater. 2005, 17, 4727−4735.(21) Aubert, V.; Guerchais, V.; Ishow, E.; Hoang-Thi, K.; Ledoux, I.;Nakatani, K.; Le Bozec, H. Efficient photoswitching of the nonlinearoptical properties of dipolar photochromic zinc (II) complexes. Angew.Chem. 2008, 120, 587−590.(22) Yamada, S.; Song, B.-S.; Asano, T.; Noda, S. Experimentalinvestigation of thermo-optic effects in SiC and Si photonic crystalnanocavities. Opt. Lett. 2011, 36, 3981−3983.(23) Boixel, J.; Guerchais, V.; Le Bozec, H.; Chantzis, A.; Jacquemin,D.; Colombo, A.; Dragonetti, C.; Marinotto, D.; Roberto, D.Sequential double second-order nonlinear optical switch by anacido-triggered photochromic cyclometallated platinum(II) complex.Chem. Commun. 2015, 51, 7805−7808.(24) Coe, B.; Houbrechts, S.; Asselberghs, I.; Persoons, A. Efficient,Reversible Redox-Switching of Molecular First Hyperpolarizabilities inRuthenium(II) Complexes Possessing Large Quadratic OpticalNonlinearities. Angew. Chem., Int. Ed. 1999, 38, 366−369.(25) Bi, W. H.; Louvain, N.; Mercier, N.; Luc, J.; Rau, I.; Kajzar, F.;Sahraoui, B. A Switchable NLO Organic-Inorganic Compound Basedon Conformationally Chiral Disulfide Molecules and Bi(III)I5Iodobismuthate Networks. Adv. Mater. 2008, 20, 1013−1017.

(26) Liao, W.-Q.; Ye, H.-Y.; Fu, D.-W.; Li, P.-F.; Chen, L.-Z.; Zhang,Y. Temperature-Triggered Reversible Dielectric and Nonlinear OpticalSwitch Based on the One-Dimensional Organic−Inorganic HybridPhase Transition Compound [C6H11NH3]2CdCl4. Inorg. Chem. 2014,53, 11146−11151.(27) Chen, T. L.; Sun, Z. H.; Zhao, S. G.; Ji, C. M.; Luo, J. H. Anorganic−inorganic hybrid co-crystal complex as a high-performancesolid-state nonlinear optical switch. J. Mater. Chem. C 2016, 4, 266−271.(28) Jain, P.; Ramachandran, V.; Clark, R. J.; Zhou, H. D.; Toby, B.H.; Dalal, N. S.; Kroto, H. W.; Cheetham, A. K. Multiferroic behaviorassociated with an order−disorder hydrogen bonding transition inmetal−organic frameworks (MOFs) with the perovskite ABX3

architecture. J. Am. Chem. Soc. 2009, 131, 13625−13627.(29) Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Zhao, S. G.; Chen, T. L.;Tang, Y. Y.; Luo, J. H. A host−guest inclusion compound forreversible switching of quadratic nonlinear optical properties. Chem.Commun. 2015, 51, 2298−2300.(30) Xu, J. L.; Semin, S.; Rasing, T.; Rowan, A. E. Organizedchromophoric assemblies for nonlinear optical materials: towards(Sub) wavelength scale architectures. Small 2015, 11, 1113−1129.(31) Zhang, W.-Y.; Ye, Q.; Fu, D.-W.; Xiong, R.-G. OptoelectronicDuple Bistable Switches: A Bulk Molecular Single Crystal andUnidirectional Ultraflexible Thin Film Based on ImidazoliumFluorochromate. Adv. Funct. Mater. 2017, 27, 1603945.(32) Sun, Z. H.; Luo, J. H.; Zhang, S. Q.; Ji, C. M.; Zhou, L.; Li, S. H.;Deng, F.; Hong, M. C. Solid-State Reversible Quadratic NonlinearOptical Molecular Switch with an Exceptionally Large Contrast. Adv.Mater. 2013, 25, 4159−4163.(33) Sun, Z. H.; Chen, T. L.; Ji, C. M.; Zhang, S. Q.; Zhao, S. G.;Hong, M. C.; Luo, J. H. High-Performance Switching of BulkQuadratic Nonlinear Optical Properties with Large Contrast inPolymer Films Based on Organic Hydrogen-Bonded Ferroelectrics.Chem. Mater. 2015, 27, 4493−4498.(34) Ji, C. M.; Li, S. H.; Deng, F.; Sun, Z. H.; Li, L. N.; Zhao, S. G.;Luo, J. H. Polarization Switching Induced by Slowing the DynamicSwinglike Motion in a Flexible Organic Dielectric. J. Phys. Chem. C2016, 120, 27571−27576.(35) Mao, C.-Y.; Liao, W.-Q.; Wang, Z.-X.; Zafar, Z.; Li, P.-F.; Lv, X.-H.; Fu, D.-W. Temperature-Triggered Dielectric-Optical Duple SwitchBased on an Organic−Inorganic Hybrid Phase Transition Crystal:[C5N2H16]2SbBr5. Inorg. Chem. 2016, 55, 7661−7666.(36) Mercier, N.; Barres, A.-L.; Giffard, M.; Rau, I.; Kajzar, F.;Sahraoui, B. Conglomerate-to-True-Racemate Reversible Solid-StateTransition in Crystals of an Organic Disulfide-Based Iodoplumbate.Angew. Chem., Int. Ed. 2006, 45, 2100−2103.(37) Sun, Z. H.; Chen, T. L.; Liu, X. T.; Hong, M. C.; Luo, J. H.Plastic Transition to Switch Nonlinear Optical Properties Showing theRecord High Contrast in a Single-Component Molecular Crystal. J.Am. Chem. Soc. 2015, 137, 15660−15663.(38) Xu, W.-J.; He, C.-T.; Ji, C.-M.; Chen, S.-L.; Huang, R.-K.; Lin,R.-B.; Xue, W.; Luo, J.-H.; Zhang, W.-X.; Chen, X.-M. MolecularDynamics of Flexible Polar Cations in a Variable Confined Space:Toward Exceptional Two-Step Nonlinear Optical Switches. Adv.Mater. 2016, 28, 5886−5890.(39) Sun, Z. H.; Li, S. H.; Zhang, S. Q.; Deng, F.; Hong, M. C.; Luo,J. H. Second-Order Nonlinear Optical Switch of a New Hydrogen-Bonded Supramolecular Crystal with a High Laser-Induced DamageThreshold. Adv. Opt. Mater. 2014, 2, 1199−1205.(40) Zhang, Y.; Zhang, W.; Li, S. H.; Ye, Q.; Cai, H.-L.; Deng, F.;Xiong, R.-G.; Huang, S. D. Ferroelectricity induced by ordering oftwisting motion in a molecular rotor. J. Am. Chem. Soc. 2012, 134,11044−11049.(41) Ji, C. M.; Li, S. H.; Deng, F.; Liu, S. J.; Asghar, M. A.; Sun, Z. H.;Hong, M. C.; Luo, J. H. Bistable N−H N hydrogen bonds forreversibly modulating the dynamic motion in an organic co-crystal.Phys. Chem. Chem. Phys. 2016, 18, 10868−10872.

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DOI: 10.1021/acs.chemmater.7b00524Chem. Mater. 2017, 29, 3251−3256

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(42) Fu, D.-W.; Zhang, W.; Cai, H.-L.; Zhang, Y.; Ge, J.-Z.; Xiong,R.-G.; Huang, S. D.; Nakamura, T. A multiferroic perdeutero metal−organic framework. Angew. Chem., Int. Ed. 2011, 50, 11947−11951.(43) Ye, H.-Y.; Li, S. H.; Zhang, Y.; Zhou, L.; Deng, F.; Xiong, R.-G.Solid State Molecular Dynamic Investigation of An InclusionFerroelectric: [(2,6-Diisopropylanilinium)([18]crown-6)]BF4. J. Am.Chem. Soc. 2014, 136, 10033−10040.(44) Zhang, Y.; Ye, H.-Y.; Fu, D.-W.; Xiong, R.-G. An order−disorderferroelectric host−guest inclusion compound. Angew. Chem. 2014,126, 2146−2150.(45) Zhang, W.; Ye, H.-Y.; Graf, R.; Spiess, H. W.; Yao, Y.-F.; Zhu,R.-Q.; Xiong, R.-G. Tunable and switchable dielectric constant in anamphidynamic crystal. J. Am. Chem. Soc. 2013, 135, 5230−5233.(46) Sun, Z. H.; Luo, J. H.; Chen, T. L.; Li, L. N.; Xiong, R.-G.;Tong, M.-L.; Hong, M. C. Distinct Molecular Motions in a SwitchableChromophore Dielectric 4-N, N-Dimethylamino-4′-N′-methylstilba-zolium Trifluoromethanesulfonate. Adv. Funct. Mater. 2012, 22, 4855−4861.(47) Du, Z.-Y.; Xu, T.-T.; Huang, B.; Su, Y.-J.; Xue, W.; He, C.-T.;Zhang, W.-X.; Chen, X.-M. Switchable Guest Molecular Dynamics in aPerovskite-Like Coordination Polymer toward Sensitive Thermores-ponsive Dielectric Materials. Angew. Chem., Int. Ed. 2015, 54, 914−918.(48) Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Chen, T. L.; Zhou, P.; Tang,Y. Y.; Zhao, S. G.; Luo, J. H. Switchable dielectric behaviour associatedwith above room-temperature phase transition in N-isopropylbenzy-lammonium dichloroacetate (N-IPBADC). J. Mater. Chem. C 2014, 2,6134−6139.(49) Zhang, W.; Cai, Y.; Xiong, R.-G.; Yoshikawa, H.; Awaga, K.Exceptional Dielectric Phase Transitions in a Perovskite-Type CageCompound. Angew. Chem. 2010, 122, 6758−6760.(50) Kurtz, S. K.; Perry, T. T. A powder technique for the evaluationof nonlinear optical materials. J. Appl. Phys. 1968, 39, 3798−3813.(51) Crystal data for DPA-TCA. In LTP (100 K): C8H16Cl3NO2, Mr= 264.57, orthorhombic, P212121, a = 8.6082(10) Å, b = 16.5540(3) Å,c = 17.9068(3) Å, V = 2551.72(7) Å3, Z = 8, Dc = 1.377 mg/Å3, R1 [I >2σ(I)] = 0.0449, wR2 (all data) = 0.1180, S = 1.04. In ITP (150 K):C8H16Cl3NO2, Mr = 264.57, orthorhombic, P212121, a = 8.5305(10) Å,b = 17.1390(3) Å, c = 17.9709(3) Å, V = 2627.42(7) Å3, Z = 8, Dc =1.338 mg/Å3, R1 [I > 2σ(I)] = 0.0659, wR2 (all data) = 0.1825, S =1.066. In HTP (240 K): C8H16Cl3NO2, Mr = 264.57, orthorhombic,Pnma, a = 17.925(7) Å, b = 8.584(2) Å, c = 17.704(6) Å, V =2724.50(15) Å3, Z = 8, Dc = 1.226 mg/Å3, R1 [I > 2σ(I)] = 0.1037,wR2 (all data) = 0.3676, S = 1.081.

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