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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]

Chiral organic–inorganic hybrid materials with multi-channel switchable characteristics play an important role in the fields of sensors, intelligent switches, and information memorizers. The introduction of chiral organic amine into materials with photoluminescent properties is expected to achieve multi-channel switchable characteristics. Here, we report a pair of chiral organic–inorganic hybrids (R-HASD)2MnBr4 and (S-HASD)2MnBr4 (HASD = 2-hydroxy-5-azaspiro[4.5]decan) containing spirocyclic cations and having dielectric/second harmonic generation (SHG)/photoluminescence (PL) triple-channel switchable properties. Both compounds undergo a reversible plastic phase transition around 380 K. Under ultraviolet (UV) irradiation, both of them show intense green emission and their photoluminescence quantum yields (PLQYs) are above 70%. Therefore, multifunctional hybrid compounds with triple-channel dielectric/SHG/PL switches and excellent PL properties have been successfully prepared. This work is of great significance for further exploration of chiral multifunctional switchable materials. [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]

There has been broad exploration of organic–inorganic hybrid perovskite (OIHP) materials in the scientific community because they have shown vigorous vitality and compatibility in the fields of photovoltaics, light-emitting diodes, and intelligent switches. Based on the relationship between structure and property, the internal structure of a material often directly affects its physical and chemical properties, such as electrical and optical performances. OIHPs with one solid–solid phase transition behavior have been widely studied and reported. However, multi-functional OIHPs possessing a two-step dielectric response coupled with photoluminescence properties are rarely reported. Herein, we report two multi-functional hybrid materials, [(BTA)2MnCl2.4Br1.6] (compound 1) and [(BTA)2MnCl4] (compound 2)(BTA = 3-bromopropyltrimethylamonium). Both compounds undergo two sequential structural transitions accompanying remarkably bistable dielectric responses. Moreover, compounds 1 and 2 can emit bright green light under 365 nm with photoluminescence decay lifetimes of 0.153 ms and 0.198 ms, respectively. Notably, the photoluminescence quantum yield of compound 1 is further increased compared with that of compound 2. These two-step reversible dielectric switching materials with photoluminescence properties will provide a new case and guidance for further research and exploration of multifunctional materials that undergo multi-step dielectric switching in the application of sensors. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid materials have received extensive interest due to their easily adjustable structures, environmentally friendly features and excellent properties. Recently, plenty of organic–inorganic hybrids have been reported. However, low phase transition temperature and limited properties restrict their applications. Therefore, improving the phase transition temperature and enriching optoelectronics properties have become the top priorities. Herein, we have successfully synthesized two bilayer (2D/3D) perovskites, (MACH)2·CsPb2Br7 (Prv-2) and (BMACH)·CsPb2Br7 (Prv-3), based on a single layer perovskite, (MACH)2·PbBr4 (Prv-1), (MACH = cyclohexanemethylaminium and BMACH = 1,3-cyclohexanedimethanaminium). The experimental results show that the phase transition temperature (385–415 K) of bilayer perovskites has been significantly improved by increasing the thickness of the inorganic framework. Meanwhile, the offset of the mineralizer (Cs+, (0.5, 0.5, 0.5) → (0.5, 0.76, 0.47)) in the Prv-3 makes it crystallize in the polar space group (Pmc21). Therefore, the SHG (second harmonic generation) measurement indicates that it possesses 0.5 times the signal intensity compared to KDP. Finally, optical characterization and theoretical calculation synergistically verify that all three perovskites belong to direct bandgap semiconductors. Consequentially, the strategies in this work might pave the way for the design and construction of multifunctional materials with a narrow band gap, non-linear optics and ferroelectricity. [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]

Multi-functional switching materials, possessing a high transition temperature, can work in a relatively wide temperature range, particularly for practical applications under extreme thermal conditions such as automotive, aerospace and power generating industries. The halogen substitution strategy, known as an effective molecular modification method, can introduce halogen atoms into cations to increase the energy barrier of cationic motion for obtaining compounds with high transition temperature. Herein, by halogenating organic cations of the prototype (N,N-dimethylmorpholinium)PbBr3 (compound 1), we report two triple-channel dielectric/SHG/PL switching materials (N-ClCH2-N-methylmorpholinium)PbBr3 and (N-BrCH2-N-methylmorpholinium) PbBr3 (2 and 3). These compounds adopt a one-dimensional perovskite structure constituted by face-sharing octahedral [PbBr6]− chains and organic cations, and could emit orange-red light under ultraviolet light excitation. The phase transition temperatures of 2 and 3 achieve a very high value: ca. 380 K. Meanwhile, good nonlinear optical properties (SHG) and optimized PL properties were obtained. Thus, multi-functional hybrid perovskites simultaneously with triple-channel switches and optical properties were successfully fabricated. This work might provide a new impetus for designing new organic hybrid perovskites with multi-channel switching behavior and prominent optical properties. [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]

Since the concept of "multiferroic" was first proposed in 1968, the coupling effect between different ferroic orders has attracted great interest in energy, information, and biomedical fields. However, the fully ferroelectric-fully ferroelastic effect has never been experimentally observed in hybrid perovskites, even though this effect was predicted to exist half a century ago. Realizing such cross-linking effects of polarization vectors and strain tensors has always been a huge challenge because of the complex difference in these two ferroic origins. Here, we report a multiferroic with full ferroelectricity and full ferroelasticity in two-dimensional (2D) hybrid perovskites based on ferroelectrochemistry. The dynamic molecular reorientations endow (cyclohexanemethylaminium) 2 PbCl 4 with a desired symmetry change of 4̅2 m F mm 2 at a Curie temperature of 411.8 K. More strikingly, the switchable evolution of ferroelastic domains was directly observed under the control of either electric or mechanical fields, which is the first experimental observation of a fully ferroelectric-fully ferroelastic effect in hybrid perovskites. This work would provide new insights into understanding the intrinsic cross-linking mechanism between ferroelectricity and ferroelasticity toward the development of multichannel interactive microelectronic devices.

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.)

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 P 2 1 / m to P 1̄ with 2/ mF 1̄ Aizu notation with a high Curie temperature ( T c ) of 402 K. Moreover, optical regulation from blue light to white light was achieved by halogen substitution.

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.)