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Ferroelastics, an important type of ferroic material, have significant value in applications such as shape memory, mechanical switches, intelligent sensors, etc. With the aim of developing new technologies, ferroelastics with only single properties have certain limitations that hinder expansion of their applications. Thus, it is still a challenge to find multifunctional ferroelastic materials, especially those with multi-dielectric responses and fluorescence properties. Here, under the guidance of a strategy of alkyl modification, (EMP)PbBr3 (EMP = N-ethyl-N-methyl-3-pyrroline) (compound 2) was successfully obtained by modifying the parent compound (DMP)PbBr3 (DMP = N,N-dimethyl-3-pyrroline) (compound 1). Of note, compound 2 was improved to have a triple dielectric response compared with the double dielectric response of compound 1, and both the ferroelastic phase transition temperature and photoluminescence quantum yield of compound 2 were improved. Such changes make compound 2 potentially applicable in smart electronic devices. This work provides some insights into the search for multifunctional ferroelastic materials. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Molecular ferroelastics with the natural features of mechanical flexibility and switchable spontaneous strain have attracted widespread attention in the scientific community due to their potential applications in tunable gratings, flexible memorizers, strain sensors, and intelligent actuators. However, most designs of molecular ferroelastics remain in the stage of blind exploration, posing a challenge to achieve a functional ferroelastic more effectively. Herein, we have successfully obtained a molecular ferroelastic, [Me2NH(CH2)2NH3](ReO4)2 (Me2NH(CH2)2NH3 = N,N‐dimethylethylenediammonium), under the guidance of the mono‐/double‐protonation strategy. The double‐protonated [Me2NH(CH2)2NH3](ReO4)2 undergoes a paraelastic‐ferroelastic phase transition with the Aizu notation of 2/mF1¯ at 322 K. Meanwhile, the theoretical calculation and experimental measurement simultaneously show that [Me2NH(CH2)2NH3](ReO4)2 possesses good mechanical flexibility, because its elastic modulus (E) of 8.26 GPa and hardness (H) of 0.45 GPa are smaller than the average values of organic crystals (E of 12.05 GPa and H of 0.5 GPa), which makes it promising to apply in wearable pressure sensors, implantable medical sensors, high‐precision tuners, etc. This work further enriches the molecular ferroelastic family and demonstrates that mono‐/double‐protonation is one of the effective molecular modification strategies for designing ferroelastics. [ABSTRACT FROM AUTHOR]

Ferroelastic semiconductor materials have garnered significant research interest due to their promising applications in the fields of shape memory, superelasticity, templated electronic nanostructures, mechanical switching, and optoelectronic transmission. However, the toxicity of lead-based structures and low phase-transition temperature (Tc) greatly constrain the application scenarios of ferroelastic semiconductors. Here, using an H/OH-substitution-induced homochiral strategy, we synthesize a pair of lead-free ferroelastic semiconductors (R/S-CTA)2SbCl5 (CTA = 3-chloro-2-hydroxypropyltrimethyllammonium) having semiconductor properties with an indirect bandgap of 3.41 eV. They crystallized in the chiral space group P212121 at room temperature, and both undergo 422F222 type ferroelastic phase transitions with Tc up to 410 K, accompanied by a large entropy change of 68.75 and 66.09 J mol−1 K−1, respectively. Owing to the introduction of chirality, they exhibited temperature-dependent nonlinear second-harmonic generation (SHG) properties. Relatively, the achiral TMCP (TMCP = N,N,N-trimethylchloropropylamine) makes the phase transition properties of centrosymmetric TMCP2SbCl5 ordinary compared to chiral R/S-pair. This is precisely the main starting point of homochiral strategies in phase transition and optical structure research, while arousing research interest. This work, which provides a new avenue for the design of high-Tc lead-free ferroelastic semiconductor compounds, is a powerful motivation for the realization of multifunctional materials related to chirality. [ABSTRACT FROM AUTHOR]

The ability to generate and manipulate photoluminescence (PL) behavior has been of primary importance for applications in information security. Excavating novel optical effects to create more possibilities for information encoding has become a continuous challenge. Herein, we present an unprecedented PL temporary quenching that highly couples with thermodynamic phase transition in a hybrid crystal (DMML)2MnBr4 (DMML=N,N‐dimethylmorpholinium). Such unusual PL behavior originates from the anomalous variation of [MnBr4]2− tetrahedrons that leads to non‐radiation recombination near the phase transition temperature of 340 K. Remarkably, the suitable detectable temperature, narrow response window, high sensitivity, and good cyclability of this PL temporary quenching will endow encryption applications with high concealment, operational flexibility, durability, and commercial popularization. Profited from these attributes, a fire‐new optical encryption model is devised to demonstrate high confidential information security. This unprecedented optical effect would provide new insights and paradigms for the development of luminescent materials to enlighten future information encryption. [ABSTRACT FROM AUTHOR]

A new ferroelastic organic salt nicotinic acid bromide (N–Br) was connected by hydrogen bonding with nicotinic acid cations via a halogen substitution strategy. It exhibits a ferroelastic phase transition from P21/m to P1¯ with 2/mF1¯ Aizu notation with a high Curie temperature (Tc) of 402 K. Moreover, optical regulation from blue light to white light was achieved by halogen substitution. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid phase transition materials with switchable properties have important potential applications in smart devices such as dielectric switches and storage. Nevertheless, it remains challenging to modify molecular structures efficiently to obtain materials simultaneously possessing multiple responsive properties. Herein, different from ordinary halogen substitutions in Metal Halide, we report a halogen regulation design of organic molecular strategy: (ASD)2MnBr4 (ASD=5‐azonia‐spiro [4.5] decane) to (CASD)2MnBr4 (CASD=8‐chloro‐5‐azonia‐spiro [4.5] decane). After organic molecular halogen regulation, the SHG response was excited and the dielectric phase transition temperature (Tc) has also been greatly improved. Furthermore, under the irradiation of UV lamp, both showed green light with quantum yields above 50%. This work is of great significance for further exploration of multifunctional molecular switch materials through halogen modification strategies. [ABSTRACT FROM AUTHOR]

A new ferroelastic organic salt nicotinic acid bromide (N–Br) was connected by hydrogen bonding with nicotinic acid cations via a halogen substitution strategy. It exhibits a ferroelastic phase transition from P21/m to P1¯ with 2/mF1¯ Aizu notation with a high Curie temperature (Tc) of 402 K. Moreover, optical regulation from blue light to white light was achieved by halogen substitution. [ABSTRACT FROM AUTHOR]

The ability to generate and manipulate photoluminescence (PL) behavior has been of primary importance for applications in information security. Excavating novel optical effects to create more possibilities for information encoding has become a continuous challenge. Herein, we present an unprecedented PL temporary quenching that highly couples with thermodynamic phase transition in a hybrid crystal (DMML) 2 MnBr 4 (DMML=N,N-dimethylmorpholinium). Such unusual PL behavior originates from the anomalous variation of [MnBr 4 ] 2- tetrahedrons that leads to non-radiation recombination near the phase transition temperature of 340 K. Remarkably, the suitable detectable temperature, narrow response window, high sensitivity, and good cyclability of this PL temporary quenching will endow encryption applications with high concealment, operational flexibility, durability, and commercial popularization. Profited from these attributes, a fire-new optical encryption model is devised to demonstrate high confidential information security. This unprecedented optical effect would provide new insights and paradigms for the development of luminescent materials to enlighten future information encryption., (© 2023 Wiley-VCH GmbH.)

Organic-inorganic hybrid phase transition materials with switchable properties have important potential applications in smart devices such as dielectric switches and storage. Nevertheless, it remains challenging to modify molecular structures efficiently to obtain materials simultaneously possessing multiple responsive properties. Herein, different from ordinary halogen substitutions in Metal Halide, we report a halogen regulation design of organic molecular strategy: (ASD) 2 MnBr 4 (ASD=5-azonia-spiro [4.5] decane) to (CASD) 2 MnBr 4 (CASD=8-chloro-5-azonia-spiro [4.5] decane). After organic molecular halogen regulation, the SHG response was excited and the dielectric phase transition temperature (T c ) has also been greatly improved. Furthermore, under the irradiation of UV lamp, both showed green light with quantum yields above 50%. This work is of great significance for further exploration of multifunctional molecular switch materials through halogen modification strategies., (© 2022 Wiley-VCH GmbH.)