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The lone pair electrons in the electronic structure of molecules have been a prominent research focus in chemistry for more than a century. Stable s2 lone pair electrons significantly influence material properties, including thermoelectric properties, nonlinear optical properties, ferroelectricity, and electro(photo)catalysis. While major advances have been achieved in understanding the influence of lone pair electrons on material characteristics, research on this effect in organic‐inorganic hybrid materials is in its initial stage. In this work, we successfully obtained a novel organic‐inorganic hybrid multifunctional material incorporating Ge with 4s2 lone pair electrons, (MeHDabco)2[GeBr3]4‐H2O (MeHDabco=N‐methyl‐1,4‐diazabicyclo[2.2.2]octane) (1). Driven by the stereochemically active lone pair electrons on the Ge2+, 1 crystallizes in the noncentrosymmetric space group P21 at room temperature and exhibits good second harmonic generation (SHG) responses. Interestingly, 1 also shows electrocatalytic activity for the hydrogen evolution reaction (HER) due to the existence of lone pair electrons on Ge2+ cations. The electrochemical experiment combined with the density functional theory (DFT) calculations revealed that the lone pair electrons act as both an active site for proton adsorption and facilitate the ionization of water. This work not only emphasizes the important role of lone pair electrons in material properties and functions but also provides new insight for designing novel Ge‐based multifunctional hybrid materials. [ABSTRACT FROM AUTHOR]

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]

Organic–inorganic hybrid perovskites (OIHPs) with dielectric switching functions have aroused comprehensive scientific interest, benefitting from their promising applications in sensors and information storage. However, to date, most of these materials discovered thus far possess a single function and are limited in their applicability, failing to meet the requirements of diverse applications. Moreover, the discovery of these materials has been largely serendipitous. Building multifunctional OIHPs with dielectric switching and semiconductors remains a daunting task. In this context, by introducing [C7H16N]+ as cations and in combination with lead halide with semiconducting properties, two OIHPs [C7H16N]PbI3 (1) and [C7H16N]PbBr3 (2) ([C7H16N]+ = (cyclopropylmethyl) trimethylammonium) have been successfully designed. They have dielectric switching properties close to 253 and 279 K and semiconducting behavior with band gaps of 2.67 and 3.22 eV. The phase transition temperature increased by 26 K through halogen substitution. In summary, our findings in this study provide insights into the application of the halogen substitution regulation strategy and open up new possibilities for designing perovskite semiconductors with dielectric switching functionality. [ABSTRACT FROM AUTHOR]

Dion–Jacobson (DJ) hybrid perovskites are considered to be of profound research interest as promising semiconductors in the photovoltaic field. However, it is still a great challenge to construct polar DJ perovskites, and research on the influence of the configuration of diammonium cations on the photophysical properties is also lacking. Herein, starting from the NNPD (N,N-dimethylpropane-1,3-diaminium) cation, the molecule (NNPD)PbBr42 with P21/c space group is obtained. Further molecular modification from NNPD to NMPD (N-methylpropane-1,3-diaminium), a polar semiconductor (NMPD)PbBr41, which crystallizes in the Pn space group is successfully synthesized. Due to the synergic effects of the reorientation of NMPD cations and the deviation of the inorganic layer from the symmetry plane, the positive and negative charge centers in the structure separated. Especially, benefiting from the bulk photovoltaic effect (BPVE) in 1, large polarization ratios at 377 nm (∼5.26) and 405 nm (∼5.46) under zero bias have been achieved, which are much larger than the values obtained by relying on the intrinsic structure anisotropy of 1 (377 nm, ∼2.10, 405 nm, and ∼2.13). This study expands the application of polar DJ hybrid perovskites (HPs) in the field of self-driven polarization detection. [ABSTRACT FROM AUTHOR]