Homochiral Chemistry Strategy To Trigger Dielectric Switching and Second-Harmonic Generation Response on Spirocyclic Derivatives

Abstract

Organic–inorganic hybrid materials with switchable properties have significant potential applications in intelligent devices. There are some conventional ways to obtain optical and/or electric multiple responses, such as asymmetric design, chirality, doping, and structural dimension in hybrid materials. Among them, the homochirality strategy is one of the best ways to regulate the molecular structure and symmetry, thereby ensuring second-harmonic generation (SHG) and dielectric dual response characteristics. Here, we report a homochiral design strategy to obtain noncentrosymmetric [R-(HASD)]­[Cd­(SCN)3] (HASD = 7-hydroxy-5-azaspiro[4.5]­decan) and [S-(HASD)]­[Cd­(SCN)3]; [Rac-(HASD)]­[Cd­(SCN)3] was also synthesized as a comparative experiment to illustrate the relationship between structural chirality and physical properties. With the help of homochiral regulation, the SHG response is excited and dielectric phase transition temperature (T c) is also highly improved. In addition, both the optical SHG and dielectric phase change show an optical/electric switchable response. This work is of great significance for the further exploration of multifunctional molecular switching materials through homochiral chemistry.

Homochiral Chemistry Strategy to Trigger Second-Harmonic Generation and Dual Dielectric Switches

“…Switchable materials are substances that can switch between two different states under external stimuli such as heat, light, external electric field, and magnetic fields; their physical properties change with the change of states. − These materials can be widely used in various fields such as communication transmission, information storage, and photonic carriers. − Dielectric switches are mostly appearing in structural phase transition materials, where the dielectric constant changes abruptly near the phase transition temperature ( T h ) and reversible cycling occurs. − For example, (DMTBA) 3 Bi 2 Br 9 (DMTBA = N , N -dimethyl- tert -butylaminiu) was reported to have a pair of reversible phase transitions at 188 and 425 K and exhibited excellent dielectric switching properties − However, a single dielectric switch also limits the application scenarios for the material. Therefore, ensuring the wide practicality of phase transition materials is necessary and becomes a great challenge in the temperature range.…”

Dielectric/SHG/PL triple-channel properties in chiral spirocyclic organic–inorganic hybrids

“…3,[11][12][13] Organic-inorganic hybrid compounds, with both organic cationic and inorganic anion structural frameworks, are highly flexible and adjustable. [14][15][16] Moreover, under thermal stimulation, the deformation of the inorganic framework and the reorientation of flexible organic components can easily induce the crystal structure changes, accompanied by the sudden change of physical properties. 2,14,[17][18][19] Therefore, they are ideal templates for the preparation of multifunctional switchable materials.…”

“…Chiral molecules behave in inherent non-centrosymmetric structures, which facilitates crystals to crystallize as chiral or even polar structures. 15,[21][22][23] Notably, chiral organic-inorganic hybrid materials offer the possibility of more properties, such as chiral PL activity, second harmonic generation (SHG), and excellent piezoelectric properties. [23][24][25] Therefore, the construction of organic-inorganic hybrid materials through the introduction of appropriate chiral organic amines to achieve multichannel switching response has become a research focus.…”

“…14,26 For example, [R/S-(HASD)][Cd(SCN) 3 ] (HASD = 7-hydroxy-5azaspiro [4.5]decan) reported by our group are two types of switchable organic-inorganic hybrid materials with SHG and dielectric dual response properties. 15 Xiong and colleagues successfully prepared two chiral crystals (S-CTA) 2 CuCl 4 and (R-CTA) 2 CuCl 4 (CTA = 3-chloro-2-hydroxypropyltrimethylammonium), which showed switchable properties in seven physical channels. 12 In addition, Wei and colleagues report a pair of 0D hybrid lead-tin bromides, (RR/SS-C 6 N 2 H 16 ) 2 Pb 0.968 Sn 0.032 Br 6 Á2H 2 O with strong circularly polarized luminescence (CPL) and high photoluminescence quantum yield (PLQY).…”

“…However, it remains challenging to design and obtain chiral compounds containing spirocyclic ammonium that possess with multi-channel switchable characteristics, and excellent PL properties. 15,[27][28][29] Chiral spirocyclic amines have good flexibility and are easy to form low symmetry compounds after hybridization with inorganic metals. [30][31][32][33] In addition, manganese (Mn) is an environmentally friendly metal with low toxicity.…”