Rational Design and Syntheses of Molecular ... - ACS Publications

Subscriber access provided by UNIV TORONTO

Perspective

Rational Design and Syntheses of Molecular Phase Transition Crystal Materials Lina Li, Zhihua Sun, Chengmin Ji, Sangen Zhao, and Junhua Luo Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01378 • Publication Date (Web): 14 Nov 2016 Downloaded from http://pubs.acs.org on November 16, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Crystal Growth & Design is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Rational Design and Syntheses of Molecular Phase Transition Crystal Materials Lina Li, Zhihua Sun,* Chengmin Ji, Sangen Zhao and Junhua Luo* Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China.

ABSTRACT: Reversible phase transition materials (PTMs), of which their photoelectric responses can be modulated upon external heat, pressure or light, have attracted great interest because of the potential applications for electronic, optical and energy-based devices. The design strategy of chemical flexible structural components highlights great feasibility to construct new PTMs with outstanding photoelectric activities. Here, this paper presents our efforts on the design and syntheses of phase transition crystalline materials, as well as the related photoelectric effects. These unique physical properties make them potential candidates as the switchable dielectrics, nonlinear optical switches and pyroelectric sensors, etc.

INTRODUCTION Phase transition is defined as the transformation of a thermodynamic system from one phase of matter to another.1 The term “Phase Transition” is usually used to describe the common transitions between gaseous, liquid and solid states of matter. Recently, crystal-to-crystal phase transitions of solid-state materials have evoked much attention because of their significant roles in the exploration of photoelectric functional materials, including ferroelectrics, pyroelectrics, second-order nonlinear optical (NLO) switches, tunable and switchable dielectric materials, etc.2−6 Phase transitions can be realized upon external stimuli, such as heat, pressure, light,

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 27

electric filed and so on.7−10 Particularly, thermal-induced reversible phase transitions in solid-state compounds are not only of great significance for exploring technologically useful materials, but also greatly benefit for the understanding on structure-property relationship. Although various approaches have been developed to construct solid-state PTMs, it is still difficult to predict phase transition in the crystalline materials because of the complicated molecular interactions. Although several classifications of phase transitions are proposed according to different criteria, changes of crystal structures are inseparable from the phase transitions. From the viewpoint of structural changes, the mechanisms of phase transition fall into three major categories known as the order-disorder, displacive and reconstructive types. In this context, the reorientational order-disorder transformation and/or displacement of chemical flexible structural components should be efficient to construct molecular PTMs, and thus considerable efforts have been made by researchers. 11, 12

Recently, we have performed systematic studies on exploring the solid-state PTMs by introducing flexible structural components. Such moieties can easily inspire structural changes upon thermal stimuli, which are essential requirements for phase transitions. This paper presents a short review of our recent advances in this filed, and we envision that such materials will hold potentials for a variety of photoelectric applications, such as switchable dielectrics, quadratic NLO switches, pyroelectric sensors and photoconductors, etc.

SWITCHABLE DIELECTRIC MATERIALS Switchable molecular dielectrics, which undergo transitions between high and low dielectric states, have received extensive research community attention for the potential application in the electrical and electronic industry.13−15 Nevertheless, it still remains a challenge to design novel crystalline materials possessing tunable dielectric properties, owing to a lack of knowledge regarding control of the motions of dipole moments inside the crystal lattice. Fortunately, crystalline molecules undergoing the reversible phase transitions demonstrate specific responses to external magnetic, electric or mechanical stimuli, which provide us with effective platform to explore switchable dielectrics. As one of the most prominent strategies to assemble phasetransition materials, the progress associated with reorientational order-disorder motion of the moiety in the molecules has been developed. A series of simple organic molecules were used as motional moieties to construct phase-transition materials, which show the intentional switching of dielectric properties.16−32 For


2

Page 3 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


instance, the compound of [(C4H9)3NH](fumrate)0.5·(fumaric acid)0.5, containing the chain-like alkylamine, exhibits a reversible molecular phase transition at about 182 K (Tc, phase transition point). This is greatly ascribed to order-disorder transformations of carboxyl oxygen atoms and distinct reorientations among cations and anion-acid infinite sheets, together with the proton-dynamic motions (Figure 1a).16 It is notable that such structural changes lead to distinguishable switchable dielectric responses, and step-like dielectric anomalies are clearly observed in the vicinity of Tc (Figure 1b). For convenience, the structural phase below Tc is called as “low-temperature phase (LTP)”, and the phase above Tc is recognized as “high-temperature phase (HTP)”. Figure 1b shows that dielectric constants of the complex at HTP are approximately 1.6 times larger than those at LTP, revealing switchable feature of dielectric properties. Besides, another phase transition compound, [(C4H9)3NH+]·CCl3COO-, was successfully obtained by the reaction of the same amine with trichloroacetic acid. It is interesting that this compound also exhibits the switchable dielectric responses at about 196 K.17 Variable-temperature structural analysis studies reveal that the phase transition is mainly ascribed to the combined synergetic effects of the order-disorder transformations of the ions and torsion of the flexible n-butyl moieties.

(a)

(b)

Figure 1. (a) Order-disorder transformation of fumarate anions. (b) Temperature-dependent dielectric constants measured at different frequencies.16 Previous investigations disclose that the simple organic salts of [(Hdabco)+X-] (where dabco = 1,4diazabicyclo[2.2.2] octane; X = ClO4-, BF4- and ReO4-) undergo the above-room-temperature ferroelectric phase transitions in the temperature range of 374–378 K. In these ferroic compounds, the monovalent


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 27

[Hdabco]+ cations are connected linearly through the N−H···N bonds. The dynamic protons can undergo reversibly bistable orientations by a collective proton-transfer process, which undertakes a key role in the appearance of phase transitions. Besides, dabco molecule also enables to behave as a molecular rotator. As a highly-symmetric tertiary diamine with a globular shape, this cation is quite sensitive to external stimuli and usually undergoes dynamic motions or order-disorder transformation. Such a structural feature is greatly favorable for the occurrence of phase transition, along with the appearance of switchable dielectric properties. Therefore, the dabco molecule has been rationally utilized to construct solid-state PTMs. By assembling dabco with the simple organic acids, two solid-state phase transition compounds, dabco·p-nitrophenol18 and [(Hdabco)+ClF2CCOO−]19 have been successfully synthesized in our laboratory. The former undergoes a reversible structural phase transition at about 128 K, and displays switchable dielectric behaviors induced by the ordering of molecular rotational motions in the dabco moieties (Figure 2). As temperature decreases from 293 to 100 K, the anisotropic displacement parameters of the rotator atoms become smaller and the exclusive equilibrium

positions

can

be

determined.

Similarly,

dielectric

measurements

indicate

that

[(Hdabco)+ClF2CCO−] also displays a switchable dielectric response at about 165 K (as shown in Figure 3b). However, the driving force is ascribed to the order-disorder transformation of anions in the molecule (Figure 3a). That is, the origin of the switchable dielectric bistability mainly results from the atomic movements of anions from the equilibrium position, induced by the frozen ordering of twisting motions of chlorodifluoroacetate anions.

(a)


(b)

4

Page 5 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. (a) Order-disordering of dabco moiety in the compound of dabco·p-nitrophenol. (b) Temperaturedependent dielectric constants measured at the frequencies of 100 kHz and 1 MHz along the [100] directions.18

(a)

(b)

Figure 3. (a) Order-disorder transformation of twisting motion in [(Hdabco)+ClF2CCOO−]. (b) The temperature-dependent dielectric constant response.19 Note that the phase transition temperatures of the above-mentioned compounds are below the room temperature. This disadvantage may hinder their potential device application around the ambient temperature.33−35 As the most valuable region, the temperature range between 270 and 365 K endows dielectric materials practical application in the electronic technology fields.36, 37 As a continuation of our research of switchable dielectrics, we have successfully designed two PTMs using an analogous method to above cases, 4N, N-Dimethylamino-4′-N′-methylstilbazolium trifluoromethanesulfonate

20

and dibutylammonium hydrogen

oxalate.21 Interestingly, both compounds exhibit above-room-temperature switchable dielectric behaviors associated

with

the

order-disorder

structure

changes.

In

detail,

4-N,

N-Dimethylamino-4′-N′-

methylstilbazolium trifluoromethanesulfonate exhibits a reversible solid-state phase transition at Tc = 319 K. Upon heating, the anionic moiety transforms from an ordered state to the disordered state (Figure 4a). Such a structural change evokes the phase transition and leads to two distinguishable dielectric states below and above Tc, respectively. Figure 4b shows that the dielectric constants keep almost stable below Tc, but display distinct changes to high dielectric state with step-like anomalies around Tc.


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

Page 6 of 27

(b)

Figure 4. (a) The molecular units in RTP and HTP with the trifluoromethanesulfonate anion disordered in the HTP. (b) Temperature dependence of the dielectric response of 4-N, N-Dimethylamino-4′-N′methylstilbazolium trifluoromethanesulfonate at different frequencies.20 Likewise, the compound of dibutylammonium hydrogen oxalate also undergoes a reversible phase transition at Tc = 321.6 K.21 Dielectric measurement reveals that its dielectric constants display the step-like anomalies in the vicinity of Tc. As shown in Figure 5, the dielectric constants show a gradual enhancement in the heating mode below Tc. In contrast, with the temperature approaching to Tc, the dielectric constants increase sharply and locate into a high plateau. This alteration fulfills the requirement of switchable dielectric materials. From a viewpoint of microscopic structure, it resembles the characteristic of crystals with the “freezing phase” in LTP but transform into a disordered state through the thermally-induced vibration of chainlike cations (Figure 6). Structure analyses solidly confirm the order-disorder changes of the dibutylammonium moieties dominate the dielectric phase transition.


6

Page 7 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. Temperature-dependent dielectric constants measured at 100 KHz and 1 KHz.

Figure 6. Order-disorder change and reorientation of the dibutylammonium cation at HTP and LTP. NONLINEAR OPTICAL SWITCH MATERIALS As one classic type of phase transitions, structural change accompanied by symmetry breaking of inversion center would easily lead to non-centrosymmetric structure in the crystal lattice. The absence of spatialinversion symmetry is essential for considerable physical properties, such as piezoelectricity, pyroelectricity, quadratic nonlinear optical (NLO) effect and ferroelectricity, etc. In particular, the phase transition from one centrosymmetric state to non-centrosymmetric state readily yields switchable second-order NLO (i.e. second harmonic generation, SHG) effects. The NLO switch materials have practical application in the fields of photoswitching, biosensors, environment monitors, and so forth.38 Several metal-organic complexes and


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 27

photochromic molecules were found to show SHG-switching in liquid phase.39−41 However, it is still difficult to design the high-performance molecular NLO switches, owing to the detuning or instability of optical properties induced by susceptible resonances.42 In this context, the solid-state NLO switches that enable to realize excellent SHG-switching behaviors have been the focus of current research. For instance, the chiral organic-inorganic hybrids were previously reported to show temperature-responsive switchable NLO activities. Conformational change in the crystal accounts for acentric-to-centric structural transition, as well as SHGswitching effects. Encouraged by this pioneering work, we have explored a series of solid-state NLO switches on the basis of symmetry breaking, including organic binary salts, inorganic-organic hybrids and plastic crystals.43−48 Herein, we present our systematic work concerning the design of molecular NLO switch materials.

The appearance of switchable NLO activities during phase transitions is inseparable from symmetry breaking. From the engineering viewpoint, utilization of rotators with "flexible" molecular motions is effective to design potential quadratic NLO switches.49−52 Herein, the dynamic Hdabco+ cation was incorporated with the disordered moiety of trifluoroacetate anion for assembling NLO switches. It is found that this simple salt, (Hdabco+)(CF3COO−), shows excellent NLO-switching behaviors, including a large “ON/OFF” contrast of ~35 and high NLO coefficient (Figure 7).43 This fantastic performance arises from its structural phase transition. Furthermore, it displays an excellent SHG-switching reversibility without showing any attenuation of SHG activities after 10 cycles, which almost catches up with some other photochromic systems.

Figure 7. Temperature-dependent NLO signals. The inset shows the intensity curves of SHG signals vs. wavelength at different temperatures.43


8

Page 9 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


SHG-OFF

SHG-ON

Figure 8. Schematic diagrams for the appearance of molecular dipole moments during SHG switching process

Variable-temperature structural analysis suggests that (Hdabco+)(CF3COO−) behaves as an active molecular rotor (as shown in Figure 8). In the “SHG-OFF” state, the Hdabco+ part displays the very fast rotation along the N···N axis, while F and O atoms of CF3COO− moieties are split with different atomic occupancies. Symmetry requirement is thus satisfied by the orientational disordering through the mirror plane. With the temperature decreasing below its Tc, the rotatory motions of Hdabco+ part are totally frozen and the whole setup becomes more ordered. The synergic effects arising from structural moieties account for NLO-switching activities. That is, the NLO switching is greatly attributed to ionic displacements, induced by anionic orderings and the reorientational motions of Hdabco+. Such a dynamic coupling has been solidly confirmed by temperature dependent solid-state NMR studies. The result highlights the potential of molecular motions in the design of novel molecular NLO switches.

Symmetry breaking is regarded as one of the most critical characteristics for ferroelectrics. Accompanying the ferroelectric-to-paraelectric phase transition, the quadratic NLO activity emerges in ferroelectric state but vanishes or decreases in paraelectric phase. As far as we are aware, NLO switch materials based on organic ferroelectrics are still rare, although SHG method has been used to probe ferroelectric phase transitions. Here, we reported a hydrogen-bonded organic NLO switch, bis(imidazolium) L-tartrate,44 which shows a superior NLO-switching capacity associated with a ferroelectric-to-paraelectric phase transition at 353 K (Figure 9a). Structure analyses disclose that the shifts or displacements of protons in H-bonds with respect to ferroelectric-


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 27

to-paraelectric phase transition result in the switchable NLO activity. To the best of our knowledge, it should be the first NLO switch based on the chiral L-tartaric acid, a promising candidate for the assembly of acentric crystal architectures. Remarkably, highly-oriented polymer films of bis(imidazolium) L-tartrate also display the prominent SHG-switching behaviors, including large contrast (up to ∼ 68%), highly tunable reversibility and superior switching “ON-to-OFF” time (Figure 9b). Such highly-oriented films not only maintain comparable properties of crystalline samples, but also overcome the reversibility problems arising in the conventional polymer films of photochromic compounds. It is well known that quadratic NLO coefficients are highly-dependent on the crystallographic symmetry. Bis(imidazolium) L-tartrate crystallizes in the monoclinic crystal system with the space group of P21, and thus there are four independent components of its second-order nonlinear coefficients. Here, we measured the SHG effects along the different crystallographic axis of the bulk crystals. In the measured temperature region, SHG intensities along the polar b-axis are much larger that of caxis (Figure 10), confirming the anisotropy of its NLO activities. However, their NLO-switching contrast values exhibit almost equivalent changes along the b- and c-axes (~80%), which agrees well with our previous results.44 It is believed that such an organic compound with the remarkable SHG-switching behaviors will throw light on further research on molecular NLO switches.

(a)

(b)

Figure 9. Tunable and switchable NLO properties. (a) Temperature-dependent NLO signals for the polycrystalline samples and thin films. (b) NLO-switching traces of thin films. 44


10

Page 11 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

Figure 10. (a) Bulk crystal of bis(imidazolium) L-tartrate. (b) Anisotropic SHG effects measured along the caxis and b-axis.

Concerning NLO switch materials, two host-guest inclusion compounds of bis-(imidazolium hydrochlorate) dihydrate 18-crown-645 and [(dipropylamine)(18-crown-6)]ClO446 have been also successfully designed in our group. Second-order NLO experiments indicate that both of them undergo acentric-to-centric structural phase transitions, corresponding well to the “ON-to-OFF” switching of NLO properties. Notably, superior performances of large contrast and excellent reversibility have been achieved in these compounds. These NLO switching responses are the results of phase transition of the assembled complexes. As mentioned above, organic-inorganic hybrids were first reported to show “on/off” switching of NLO effects by Mercier et al.53 Enlightened by this work, another tunable organic-inorganic hybrid SHG switch, [H2dabcoCl2][FeCl3(H2O)3],47 was also constructed in our group. As shown in Figure 11, it exhibits NLOswitching capacity with moderately large NLO response, a superior switching contrast of ~25 and a highlytunable repeatability. Variable-temperature structural analyses reveal that its NLO switching is greatly attributed to the order-disorder transformation of H2dabco2+ dication, together with the reorientational displacement of inorganic [FeCl3(H2O)3] framework (Figure 12). Such a coupling is different from the previously reported phase transition materials containing Hdabco+ monocation. Considering that hybrids benefit from the structural variability and diversity, inorganic-organic hybrids should afford a new approach to the exploration of solid-state NLO switches.


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

Page 12 of 27

(b)

Figure 11. (a) Temperature-dependent variation of the SHG signals. (b) The SHG “on/ off” cycles.47

Figure 12. Schematic diagrams for the generation of molecular dipole moments during its SHG switching.47 Plastic crystals are a unique class of substances, which exhibit the coexistence of long-rang crystalline order but short-range orientational disorder.54−56 Under external stimuli, the plastic state and ordered crystalline phase can be reversibly converted to each other. The conversion is closely associated with the rotational and/or orientational motions, which is highly favorable for the exploration of NLO switches. Herein, outstanding NLO-switching behaviors were reported in a single-component plastic molecular crystal, 2-(hydroxymethyl)2-nitro-1, 3-propanediol.48 The temperature-dependent NLO studies reveal that it shows quite strong quadratic NLO activities at room temperature. In contrast, its NLO signals fully vanish in the plastic phase (above 345 K), in which the structure of this plastic crystal becomes isotropic and highly-disordered. Superiorly switchable NLO properties were achieved in this plastic transition; that is, a record-high “on/off” contrast of ∼150 (Figure 13a) together with excellent reversibility (Figure 13b), exceeding all the previously reported switching systems.


12

Page 13 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

Figure 13. (a) Switchable conversion of SHG signals between high-NLO and low-NLO states. (b) Completely reversible and recoverable switching of NLO effects.

(a)

(b)

Figure 14. (a) Globular-like shape of the molecules. (b) Thermal vibrational ellipsoids for the nitro groups.48 Studies of the relationship between NLO-switching behavior and plastic transition reveal that ordering of its highly-isotropic molecular motions is closely associated with switchable NLO effects. In the plastic phase, the molecule acts as a rotator with the rapid overall molecular reorientations (Figure 14a, b). The motions of rotation and reorientation are supposed to be the source of power for its plasticity. The optically-isotropic body-centered cube mode corresponds to its SHG-off state, resulting in the vanished NLO response. Cooling down to its transition point, energy barrier for reorientation of whole molecules becomes large enough to preclude thermal tumbling around their equilibrium positions. As a result, its reorientation is prohibited, and the molecules are restricted into a relatively rigid lattice. Only fast molecular motions of 120° rotation exists, which agrees with the population of preferentially occupied sites within the space group of R3. With


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 27

temperature decreasing far below transition point, all the atoms are frozen into an ordered state, showing large NLO response. It is believed that the utilization of plasticity to switch NLO effects opens up a new strategy for the designing of stimuli responsive materials.57

PYROELECTRIC AND FERROELECTRIC MATERIALS Pyroelectric compounds, a type of polar dielectric materials, possess a spontaneous electrical polarization that appears in the absence of an applied electrical field or stress. Pyroelectric materials have been playing an important role in the field of radiation energy detection, infrared detection, and radiation configuration imaging for continuous-wave signals due to their potential as thermal detectors with fast response and high detecting sensitivity.58, 59 Arising from permanent dipoles in the structure, pyroelectricity is the electrical response of polar materials due to the temperature change. In other words, pyroelectric materials also belong to the temperature-responsive materials. In detail, an electric current will be produced upon external variable radiation of thermal energy.60 In microscopic viewpoint, the pyroelectric effect occurs due to the asymmetric environment experienced by electrically charged species within the crystal structure of the material. According to the phase transition strategy, a new molecular pyroelectric compound, di-n-butylaminium trifluoroacetate, has been constructed by our group.61 It is interesting that this compound displays a distinct bistable dielectric phase transition, as well as intriguing pyroelectric behaviors. Pyroelectric studies for di-n-butylaminium trifluoroacetate show that a sharp pyroelectric current was generated to compensate for the charge displacement with temperature increasing to 212 K (the insert of Figure 15a). Temperature dependence of spontaneous polarization affords a value of ≈1.25 µC cm−2 at 200 K and electric polarization disappears above 212 K. A deeper insight into the origin of polarization and microscopic structural change indicates that the pyroelectricity results from the phase transition induced by order-disorder structural changes (Figure 16). Particularly, its figure-of-merits for the pyroelectric detection exhibit a remarkable enhancement as transition temperature approaches (Figure 15b), which are almost an order of magnitude larger than those of other materials, such as TGS and inorganic PMNT. This finding reveals its potentials to obtain highly-efficient signal-to-noise ratio. The results suggest that phase transition material with bistable dielectric feature would provide promising alternative as pyroelectric detector in potential applications.


14

Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

Figure 15. (a) Polarization determined by integration of pyroelectric current. Insert: a sharp current peak at Tc with respect to the change of temperature. (b) The observed and calculated performance of the figure of merits .61

(a)

(b) Figure 16. Molecular structures at HTP (a) and LTP (b), respectively.61 Ferroelectrics are a type of special dielectrics and a subgroup of pyroelectrics. They distinguish themselves from others by spontaneous electric polarization whose direction can be reversed by external electric field. Since Rochelle salt (potassium sodium tartrate tetrahydrate) was first discovered as ferroelectric,62 ferroelectric materials have attracted great attention for versatile technical applications, such as ferroelectric random-access memories, field-effect transistors and infrared detectors, etc.63–66 As a result, a variety of ferroelectric compounds have been extensively explored.67–72 For most ferroelectrics, symmetry-breaking phase transition is essential, involving from a high-symmetric paraelectric phase to a low-symmetric ferroelectric phase. In the


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 27

vicinity of Curie temperature, physical properties of dielectricity, NLO effect, piezoelectricity, and pyroelectricity will display notable anomalies.73 Most essentially, in ferroelectric phase, it should meet the necessary crystallography of one of the ten polar point groups (C1, C2, Cs, C2v, C4, C4v, C3, C3v, C6, and C6v). All things considered, it still remains a challenge to rational design ferroelectric material.

Generally, hydrogen bonds could be considered as the donor-accepter systems with directional but much weaker interactions than covalent bonds. As a result, complexes constructed by H-bonds would easily undergo transformation, induced by the cleavage and formation of other H-bonds, by proton transfers or by disordering. For example, O−H···O H-bonds trigger a ferroelectric phase transition in KH2PO4 crystals;74 proton dynamics together with atom displacements cause ferroelectricity during the phase transitions in Rochelle salt derivatives.

Figure 17. Temperature dependence of the saturated polarization. Insert: Dielectric hysteresis loops measured with E// a-axis.75

(a)


(b)

16

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 18. (a) Packing diagram viewed along the a-axis in the ferroelectric phase. (b) The packing diagram viewed along the b-axis in the paraelectric phase.75 Here, an organic hydrogen-bonded molecular ferroelectric material, bis(imidazolium) L-tartrate was constructed by hydrogen bonding interactions.75 For this compound, the presence of L-tartarte group affords the possible crystallization in the polar point group. At room temperature, it adopts the polar space group of P21. However, its crystallography transforms to the nonpolar space group of P212121 through the second-order phase transition at 353 K. This is a classic type of the ferroelectric-to-paraelectric phase transitions. Below Tc, ferroelectric responses are clearly observed as shown in Figure 17. Measurement of ferroelectric hysteresis loops and pyroelectricity affords the spontaneous polarization of ∼1.1 µC/cm2, which is slightly larger than that of Rochelle salt (~0.25 µC/cm2).76 Structural analysis showed that there are two different types of O−H···O and N−H···O hydrogen bonds in this compound. Comprehensive studies suggest that the origin of the ferroelectric phase transition may be the displacements of N−H···O hydrogen bonds. In paraelectric phase, the components of dipole moments are canceled out, due to the structural instabilities of O−H···O and N−H···O hydrogen bonds. In contrast, spontaneous polarization is created owing to the stability of H-bonds in the ferroelectric phase (Figure 18). Besides, organic-inorganic hybrid compounds are another major source for exploring ferroelectric materials because of their structural flexibility and diversity. Particularly, this broader class of compounds presents the coexistence or coupling of other interesting photoelectric functions, such as magnetic, semiconducting, optical and photovoltaic properties. Therefore, we seek to develop structural concepts and potential applications of the organic-inorganic hybrids. For instance, bis(cyclohexylaminium) tetrabromo lead, a layered perovskite-type photoferroelectric material was reported to show exceptionally anisotropic photoelectric responses, including photoconductivity and photovoltaic effects (PVEs).77 That is, significant photoconductivity is observed in the vertical direction with an on/off current ratio greater than 103 (Figure 19a),


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

Page 18 of 27

(b)

Figure 19. (a) Bulk PVEs measured under different light intensities. Insert: a small zoom around zero field. (b) PVEs of photocurrent and photovoltage by periodical switching of a light source.77

Figure 20. Temperature-dependence of photovoltage. Inset: photovoltage vs light intensities.77 and the values are comparative with that of (CH3NH3)PbI3.78 Notably, the time-resolved repeatable switching of PVEs shows tiny temporal change in photocurrent and photovoltage (Figure 19b). Moreover, PVEs of the crystals exhibit the obvious temperature dependence of photovoltage. As shown in Figure 20, photovoltage presents a gradual decline as temperature increases and disappears completely above its Tc. Such a temperature-dependent change of the photovoltage coincides well with that of ferroelectric polarization, indicating its PVEs might be involved with ferroelectricity. Nevertheless, the potential toxicity of lead should be an environmental concern for widespread application. More recently, we reported a lead-free ferroelectric hybrid, (N-methylpyrrolidinium)3Sb2Br9,79 which exhibits the low-dimensional perovskite-like inorganic framework. Studies of structure-property relationship confirm that order-disorder transformation of organic


18

Page 19 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


moieties makes a great contribution to its ferroelectric phase transition (Figure 21). In addition to superior ferroelectricity, it also shows notable semiconducting properties, such as the positive temperature-dependent conductivity and ultraviolet-sensitive photoconductivity (Figure 22), while inorganic structural components hold promise for semiconducting or photovoltaic effects. Such results enrich the understanding of photoelectric effects in ferroelectrics and provide an opportunity for innovative application of hybrid materials in photoelectric devices.

(a)

(b)

Figure 21. (a) Crystal structures at 335 K (up) and 293 K (down). The organic cations at 335 K are highly disordered with two equivalent occupancies, and inorganic dimers also exhibit orientational disordering. (b) Ferroelectric hysteresis loops measured at 20 Hz.79

Figure 22. The I–V curves performed on single-crystals under dark and UV light illumination (λ = 365 nm). Inset: the current density and voltage curves.79

CONCIUSIONS AND PERSPECTIVE


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 27

In the ongoing research toward the design and development of phase transition functional materials, ferroelectrics, nonlinear optical switches, and switchable dielectric materials, have been investigated. Our findings are important for successful design in switchable photoelectric devices by using flexible organic molecules. In spite of great efforts being made, research and application of photoelectric materials based on phase transition are still restricted owing to the lack of basic understanding of relationship between photoelectric properties and microstructure that need extensive exploration. Further studies will include developing of high-performance photoelectric materials and structure-property relationship. Meanwhile, multifunctional photoelectric materials have attracted much attention. Coexistence and coupling of ferroelectric and other physical property such as photoluminescence and semiconductive properties may afford new types of materials. Photovoltaic materials and photoconductive devices are new frontier and expected to give significant results in our group.

AUTHOR INFORMATION Corresponding Author E-mail: [email protected]; [email protected]; Tel: (+86) 591-63173126. Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was supported by NSFC (21525104, 21622108, 21601188, 91422301 and 51502290), the NSF for Distinguished Young Scholars of Fujian Province (2014J06015), the NSF of Fujian Province (2015J05040), and the Youth Innovation Promotion of CAS (2014262, 2015240, 2016274). Z. S. thanks the support from State Key Laboratory of Luminescence and Applications (SKLA-2016-09).

REFERENCES (1) Zhang, W.; Xiong, R.-G. Chem. Rev. 2012, 112, 1163–1195.


20

Page 21 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(2) Liao, W.-Q.; Zhang, Y.; Hu, C.-L.; Mao, J.-G.; Ye, H.-Y.; Li, P.-F.; Huang, S. D.; Xiong, R.-G. Nat. Commun. 2015, 6, 8338. (3) Champagne, B.; Plaquet, A.; Pozzo, J. L.; Rodriguez, V.; Castet, F. J. Am. Chem. Soc. 2012, 134, 8101−8103. (4) Zheng, H. M.; Rivest, J. B.; Miller, T. A.; Sadtler, B.; Lindenberg, A.; Toney, M. F.; Wang, L.-W.; Kisielowski, C.; Alivisatos, A. P. Science 2011, 333, 206−209. (5) Xu, G. C.; Ma, X. M.; Zhang, L.; Wang, Z. M.; Gao, S. J. Am. Chem. Soc. 2010, 132, 9588–9590. (6) Nagarajan, V.; Roytburd, A.; Stanishevsky, A.; Prasertchoung, S.; Zhao, T.; Chen, L.; Melngailis, J.; Auciello, O.; Ramesh, R. Nat. Mater. 2002, 2, 43–47. (7) Horiuchi, S.; Kumai, R.; Tokura, Y. J. Am. Chem. Soc. 2013, 135, 4492−4500. (8) Yu, Y.; Nakano, M.; Ikeda, T. Nature 2003, 425, 145. (9) Mączka, M.; Gągor, A.; Macalik, B.; Pikul, A.; Ptak, M.; Hanuza, J. Inorg. Chem. 2014, 53, 457–467. (10) Jaffe, A.; Lin, Y.; Mao, W. L.; Karunadasa, H, I. J. Am. Chem. Soc. 2015, 137, 1673–1678. (11) Fu, D. W.; Zhang, W.; Cai, H. L.; Ge, J. Z.; Zhang, Y.; Xiong, R.-G. Adv. Mater. 2011, 23, 5658–5662. (12) Akutagawa, T.; Koshinaka, H.; Sato, D.; Takeda, S.; Noro, S.; Takahashi, H.; Kumai, R.; Tokura, Y.; Nakamura, T. Nat. Mater. 2009, 8, 342–347. (13) Zhang, W.; Cai, Y.; Xiong, R.-G.; Yoshikawa, H.; Awaga, K. Angew. Chem., Int. Ed. 2010, 49, 6608– 6610. (14) Shao, X.-D.; Zhang, X.; Shi, C.; Yao, Y.-F.; Zhang, Wen. Adv. Sci. 2015, 1500029. (15) Zhang, W.; Ye, H.-Y.; Graf, R.; Spiess, H. W.; Yao, Y.-F.; Zhu, R.-Q.; Xiong, R.-G. J. Am. Chem. Soc. 2013, 135, 5230–5233.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

(16) Asghar, M. A.; Sun, Z. H.; Khan, T.; Ji, C. M.; Zhang, S. Q.; Liu, S. J.; Li, L. N.; Zhao, S. G.; Luo, J. H. Cryst. Growth Des. 2016, 16, 895–899. (17) Asghar, M. A.; Ji, C. M.; Zhou, Y.; Sun, Z. H.; Khan, T.; Zhang, S. Q.; Zhao, S. G.; Luo, J. H. J. Mater. Chem. C 2015, 3, 6053–6057. (18) Sun, Z. H.; Wang, X.; Luo, J.; Zhang, S.; Yuan, D.; Hong, M. C. J. Mater. Chem. C 2013, 1, 2561–2567. (19) Shi, X. J.; Luo, J. H.; Sun, Z. H.; Li, S. G.; Ji, C. M.; Li, L. N.; Han, L.; Zhang, S. Q.; Yuan, D. Q.; Hong, M. C. Cryst. Growth Des. 2013, 13, 2081–2086.

(20) Sun, Z. H.; Luo, J. H.; Chen, T. L.; Li, L. N.; Xiong, R.-G.; Tong, M. L.; Hong, M. C. Adv. Funct. Mater. 2012, 22, 4855–4861. (21) Khan, T.; Tang, Y. Y.; Sun, Z. H.; Zhang, S. Q.; Asghar, M. A.; Chen, T. L.; Sangen Zhao, Zhao, S. G.; Luo, J. H. Cryst. Growth Des. 2015, 15, 5263–5268. (22) Li, S. G.; Luo, J. H.; Sun, Z. H.; Zhang, S. Q.; Li, L. N.; Shi, X. J.; Hong, M. C. Cryst. Growth Des. 2013, 13, 2675–2679.

(23) Tang, Y. Y.; Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Chen, T. L.; Luo, J. H. Chem. - Asian J. 2014, 9, 1771– 1776. (24) Zhou, Y.; Chen, T.; Sun, Z.; Zhang, S.; Ji, C. M.; Song, C.; Luo, J. Chem. - Asian J. 2015, 10, 247–251. (25) Tang, Y. Y.; Sun, Z. H.; Ji, C. M.; Li, L.; Zhang, S. Q.; Chen, T. L.; Luo, J. H. Cryst. Growth Des. 2015, 15, 457–464. (26) Zhou, P.; Sun, Z. H.; Zhang, S. Q.; Ji, C. M.; Zhao, S. G.; Xiong, R. G.; Luo, J. H. J. Mater. Chem. C 2014, 2, 2341–2345. (27) Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Chen, T. L.; Zhou, P.; Luo, J. H. J. Mater. Chem. C 2014, 2, 567–572.


22

Page 23 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(28) Zhou, P.; Sun, Z. H.; Zhang, S. Q.; Chen, T. L.; Ji, C. M.; Zhao, S. G.; Luo, J. H. Chem. - Asian J. 2014, 9, 996–1000. (29) Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Chen, T. L.; Zhou, P.; Tang, Y. Y.; Zhao, S. G.; Luo, J. H. J. Mater. Chem. C 2014, 2, 6134–6139. (30) Asghar, M. A.; Zhang, S. Q.; Khan, T.; Sun, Z. H.; Zeb, A.; Ji, C. M.; Li, L. N.; Zhao, S. G.; Luo, J. H. J. Mater. Chem. C 2016, 4, 7537–7540. (31) Ji, C. M.; Li, S. H.; Deng, F.; Liu, S. J.; Asghar, M. A.; Sun, Z. H.; Hong, M. C.; Luo, J. H. Phys. Chem. Chem. Phys. 2016, 18, 10868-10872. (32) Khan, T.; Asghar, M. A.; Sun, Z. H.; Ji, C. M.; Li, L. N.; Zhao, S. G.; Luo, J. H. RSC Adv. 2016, 6, 69546-69550. (33) Besara, T.; Jain, P.; Dalal, N. S.; Kuhns, P. L.; Reyes, A. P.; Kroto, H. W.; Cheetham, A. K. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 6828−6832. (34) Braga, D.; Gandolfi, M.; Lusi, M.; Polito, M.; Rubini, K.; Grepioni, F. Cryst. Growth Des. 2007, 7, 919−924. (35) Stroppa, A.; Barone, P.; Jain, P.; Perez-Mato, J. M.; Picozzi, S. Adv. Mater. 2013, 25, 2284−2290. (36) Pielichowska, K.; Pielichowski, K. Prog. Mater. Sci. 2014, 65, 67–123. (37) Benita, S. Microencapsulation: methods and industrial applications; Marcel Dekker: New York, 1996. (38) Irie, M.; Fukaminato, T.; Matsuda, K.; Kobatake, S. Chem. Rev. 2014, 114, 12174–12177.

(39) Aubert, V.; Guerchais, V.; Ishow, E.; Hoang-Thi, K.; Ledoux, I.; Nakatani, K.; Bozec, H. L. Angew. Chem., Int. Ed. 2008, 47, 577–580.

(40) Roberts, M. N.; Carling, C.-J.; Nagle, J. K.; Branda, N. R.; Wolf, M. O. J. Am. Chem. Soc. 2009, 131, 16644–16645.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 27

(41) Chan, J. C.-H.; Lam, W. H.; Wong, H.-L.; Zhu, N.; Wong, W.-T.; Yam, V. W.-W. J. Am. Chem. Soc. 2011, 133, 12690–12705.

(42) Yamada, S.; Song, B.-S.; Asano, T.; Noda, S. Opt. Lett. 2011, 36, 3981–3983.

(43) Sun, Z. H.; Luo, J. H.; Zhang, S. Q.; Ji, C. M.; Zhou, L.; Li, S. H.; Deng, F.; Hong, M. C. Adv. Mater. 2013, 25, 4159–4160.

(44) Sun, Z. H.; Chen, T. L.; Ji, C. M.; Zhang, S. Q.; Zhao, S. G.; Hong, M. C.; Luo, J. H. Chem. Mater. 2015, 27, 4493–4498. (45) Sun, Z. H.; Li, S. G.; Zhang, S. Q.; Deng, F.; Hong, M. C.; Luo, J. H Adv. Opt. Mater. 2014, 2, 1199– 1205.

(46) Ji, C. M.; Sun, Z. H.; Zhang, S. Q.; Zhao, S. G.; Chen, T. L.; Tang, Y. Y.; Luo, J. H. Chem. Commun. 2015, 51, 2298–2300.

(47) Chen, T. L.; Sun, Z. H.; Zhao, S. G.; Ji, C. M.; Luo, J. H. J. Mater. Chem. C 2016, 4, 266–271.

(48) Sun, Z. H.; Chen, T. L.; Liu, X. T.; Luo, J. H.; Hong, M. C. J. Am. Chem. Soc. 2015, 137, 15660–15663. (49) Katrusiak, A.; Szafran´ski, M. Phys. Rev. Lett. 1999, 82, 576–579.

(50) Szafran´ski, M.; Katrusiak, A.; McIntyre, G. Phys. Rev. Lett. 2002, 89, 215507.

(51) Andrzejewski, M.; Olejniczak, A.; Katrusiak, A. Cryst. Growth Des. 2011, 11, 4892–4899.

(52) Cai, H.-L.; Fu, D.-W.; Zhang, Y.; Zhang, W.; Xiong, R.-G. Phys. Rev. Lett. 2012, 109, 169601.

(53) Bi, W.; Louvain, N.; Mercier, N.; Luc, J.; Rau, I.; Kajzar, F.; Sahraoui, B. Adv. Mater. 2008, 20, 1013– 1017.

(54) Howlett, P. C.; Shekibi, Y.; MacFarlane, D. R.; Forsyth, M. Adv. Eng. Mater. 2009, 11, 1044–1048.


24

Page 25 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(55) Wang, P.; Dai, Q.; Zakeeruddin, S. M.; Forsyth, M.; MacFarlane, D. R.; Grätzel, M. J. Am. Chem. Soc. 2004, 126, 13590–13591.

(56) Jin, L.; Nairn, K. M.; Forsyth, C. M.; Seeber, A. J.; MacFarlane, D. R. J. Am. Chem. Soc. 2012, 134, 9688–9697.

(57) Liu, B.; Besseling, T. H.; Hermes, M.; Demirörs, A. F.; Imhof, A.; Blaaderen, A. Nat. Commun. 2014, 5, 3092.

(58) Whatmore, R. W. Rep. Prog. Phys. 1986, 49, 1335–1386.

(59) Tien, N. T.; Seol, Y. G.; Dao, L. H. A.; Noh, H. Y.; Lee, N.-E. Adv. Mater. 2009, 21, 910–915.

(60) Tang, S. B. Sourcebook of Pyroelectricity, Gordon & Breach Science, London 1974.

(61) Sun, Z. H.; Tang, Y. Y.; Zhang, S. Q.; Ji, C. M.; Chen, T. L.; Hong, M. C.; Luo, J. H. Adv. Mater. 2015, 27, 4795–4801.

(62) Valasek, J. Phys. Rev. 1921, 17, 475–481.

(63) Scott, J. F. Ferroelectric Memories; Springer: Berlin, 2000.

(64) Waser, R., Ed. Nanoelectronics and information technology; Wiley-VCH: Weinheim, Germany, 2003.

(65) Scott, J. F. Science 2007, 315, 954–959.

(66) Lines, M. E.; Glass, A. M. Principles and Applications of Ferroelectrics and Related Materials, Oxford University Press, New York, 1977.

(67) Fu, D. W.; Cai, H. L.; Liu, Y. M.; Ye, Q.; Zhang, W.; Zhang, Y.; Chen, X. Y.; Giovannetti, G.; Capone, M.; Li, J.; Y.; Xiong, R.-G. Science 2013, 339, 425–428.


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 27

(68) Ye, H. Y.; Zhou, Q-.H.; Niu, X. H.; Liao, W. Q.; Fu, D. W.; Zhang, Y.; You, Y.-M.; Wang, J.-L.; Chen, Z.-N.; Xiong, R.-G. J. Am. Chem. Soc. 2015, 137, 13148–13154.

(69) Akutagawa, T.; Koshinaka, H.; Sato, D.; Takeda, S.; Noro, S.-I.; Takahashi, H.; Kumai, R.; Tokura, Y.; Nakamura, T. Nat. Mater. 2009, 8, 342–347.

(70) Zhou, B.; Kobayashi, A.; Cui, H. B.; Long, L.-S.; Fujimori, H.; Kobayashi, H. J. Am. Chem. Soc. 2011, 133, 5736–5739.

(71) Cui, H.; Takahashi, K.; Okano, Y.; Kobayashi, H.; Wang, Z.; Kobayashi, A. Angew. Chem., Int. Ed. 2005, 44, 6508–6512.

(72) Zhang, Y.; Liao, W. Q.; Fu, D. W.; Ye, H. Y.; Chen, Z.-N.; Xiong, R.-G. J. Am. Chem. Soc. 2015, 137, 4928–4931.

(73) H. Schmid, Ferroelectrics, 2001, 252, 41–50.

(74) Katrusiak, A. Phys. Rev. B 1993, 48, 2992–3002.

(75) Sun, Z. H.; Chen, T. L.; Luo, J. H.; Hong, M. C. Angew. Chem., Int. Ed. 2012, 51, 3871–3876.

(76) Jona, F.; Shirance, G. Ferroelectric Crystals; Dover Publications, Inc.: New York, 1962.

(77) Sun, Z. H.; Liu, X. T.; Khan, T,; Ji, C. M.; Asghar, M. A.; Zhao, S. G.; Li, L. N.; Hong, M. C.; Luo, J. H. Angew. Chem., Int. Ed. 2016, 55, 6445–6550.

(78) Xiao, Z.; Yuan, Y.; Shao,Y.; Wang, Q.; Dong, Q.; Bi, C.; Sharma, P.; Gruverman, A.; Huang, J. Nature Mater. 2015, 11, 193–198.

(79) Sun, Z. H.; Zeb, A.; Liu, S. J.; Ji, C. M.; Khan, T.; Li, L. N.; Hong, M. C.; Luo, J. H. Angew. Chem., Int. Ed. 2016, 55, 11854–11858.


26

Page 27 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

Rational Design and Syntheses of Molecular Phase Transition Crystal Materials

A short review of our recent advances in the design and syntheses of molecular phase transition materials and their potential applications in switchable dielectrics, nonlinear optical switches, ferroelectrics, pyroelectrics and photoconductive materials as well as a perspective on this field are provided.


27

Rational Design and Syntheses of Molecular ... - ACS Publications

Recommend Documents