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Chiral organic–inorganic hybrid lead halides have recently attracted great attention due to their unique chirality and diverse functional properties. However, they suffer from highly toxic lead, while lead‐free chiral hybrid metal halides especially those with phase transitions remain sparse. Here, we report a new lead‐free chiral metal halide crystal [R‐3‐fluoropiperidinium]2SbCl5 ([R‐3‐FPP]2SbCl5), which crystalizes in chiral P212121 space group at 293 K and consists of chiral [3‐FPP]+ cations and one‐dimensional [SbCl5]n2− zigzag chains of corner‐sharing SbCl6 octahedrons. Notably, [R‐3‐FPP]2SbCl5 undergoes an above room temperature phase transition at 313 K, which can be attributed to the order‐disorder transition of both the organic [R‐3‐FPP]+ cation and inorganic [SbCl5]2− anions. In addition, [R‐3‐FPP]2SbCl5 also shows a broad band gap of 3.21 eV. This work promotes the exploration of chiral lead‐free hybrid lead halides with phase transitions. [ABSTRACT FROM AUTHOR]

Piezoelectricity, one of the most desirable properties of non-centrosymmetric crystalline materials, has long been blooming in academic research, industrial manufacturing, and daily applications owing to its unique electromechanical transformation capability. Compared with inorganic piezoelectric ceramics dominating the market, molecule-based piezoelectric materials exhibit advantages of light weight, mechanical flexibility, and environment friendliness and have attracted widespread interest recently. However, investigations on molecular materials with large piezoelectric coefficients are mainly focused on organic–inorganic hybrids, while pure organic homochiral piezoelectrics holding large piezoelectric coefficients remain scarce. Herein, by precise molecular modification on (S)-2-methylpiperazin-1-ium perchlorate ([(S)-MPP][ClO4]) with polar cyanomethyl groups, a homochiral pure organic compound (3S)-3-methyl-1,4-di(cyanomethyl)piperazin-1-ium perchlorate [DCM-(S)-MPP][ClO4] with large d22 of 18 pC/N was achieved, along with changes in the space group from nonpolar to polar, giving rise to second harmonic generation and phase transition behaviors. The modification strategy proposed here will benefit piezoelectricity enhancement in more chiral compounds, promoting their application potential in biological medicine, flexible devices, and green chemistry. [ABSTRACT FROM AUTHOR]

What is the most favorite and original chemistry developed in your research group? We originally proposed the design principle for molecular ferroelectrics: ferroelectrochemistry, including quasi‐spherical theory, the introduction of homochirality, and H/F substitution. Ferroelectrochemistry changed the blind search for molecular ferroelectrics into targeted chemical design, which will develop into a new discipline. How do you get into this specific field? Could you please share some experiences with our readers? I have been devoted to the field of molecular ferroelectrics for more than 20 years. In the early stage, I worked on non‐centrosymmetric metal‐organic complexes, which are potential molecular ferroelectrics. This laid a foundation for my further study of molecular ferroelectrics. Non‐centrosymmetric crystal symmetry is only one of the necessary requirements for ferroelectrics, which must adopt one of the 10 polar crystallographic point groups and should also generally undergo symmetry‐breaking phase transitions. Due to the lack of a feasible method, the discovery of molecular ferroelectrics has long depended on blindly searching. This process is like finding a needle in a haystack. After years of exploration in this field, I fully understood the Landau phase transition phenomenological theory, Curie symmetry, and Neumann principle from a chemical perspective, and proposed the design principle for molecular ferroelectrics: ferroelectrochemistry, transforming the discovery of molecular ferroelectrics from blind search to targeted chemical design. Never give up no matter how much difficulty you have met, because maybe there is an opportunity the next second. What is the most important personality for scientific research? Curiosity, divergent thinking, perseverance, team spirit, and gratitude. How do you supervise your students? Emphasis on independent problem‐solving abilities. Encourage students to read professional books frequently while doing research. What are your hobbies? What's your favorite book(s)? Jogging, reading, and swimming. My favorite book is The Journey to the West. Comprehensive Summary: Molecular ferroelectrics have attracted tremendous attention in the past decades due to their excellent ferroelectric performance and superiorities of easy processability, mechanical flexibility, and good biocompatibility. However, the discovery of molecular ferroelectrics is a great challenge and has long relied on blind search. This situation changed recently, with the development of ferroelectrochemistry proposed by our group. As a major design approach in ferroelectrochemistry, introducing homochirality, which facilitates the crystallization of materials in polar crystallographic point groups, greatly improves the probability of being ferroelectrics. Various new molecular ferroelectrics with splendid properties have been precisely synthesized by using this efficient and universal strategy. In this review, we summarize the advances in the chemical design of molecular ferroelectrics through the strategy of introducing homochirality. Key Scientists: [ABSTRACT FROM AUTHOR]

Here, we synthesized a series of cholesteryl-based compounds, whose phases and their transformation can be modulated by temperature and the chain length of the fluoroalkyl moieties. To our knowledge, this is the first time that the phase transition could be modulated with perfluoroalkyl tail engineering in organic single-component ferroelectric crystals. [ABSTRACT FROM AUTHOR]

Organic–inorganic metal halides (OIMHs) have attracted immense attention in recent decades due to their diverse physical properties, such as optoelectronic properties, photoluminescence, magnetism, and ferroelectricity. Besides these fascinating physical properties, OIMHs have also received much interest for their phase transitions. Muconic acid has captured extensive interest owing to the presence of cis,cis-form (Z,Z) and trans,trans-form (E,E) isomers. However, there have been no reports on muconic acid derivative OIMHs with phase transitions. In this work, we successfully synthesized the first muconic acid derivative OIMHs (Z,Z)- and (E,E)-[BPHD]ZnCl4 (BPHD = N1,N6-bis(piperidine-1-yl) hexa-2,4-diene diamide). Both of them crystallized in the monoclinic space group P21/c at room temperature. Notably, (Z,Z)-[BPHD]ZnCl4 does not exhibit phase transition behavior, while (E,E)-[BPHD]ZnCl4 has a high-temperature phase transition of up to 449.4 K, which is higher than that of the majority of OIMH phase transition compounds. Furthermore, the high-temperature structural analysis of (E,E)-[BPHD]ZnCl4 discloses that its high-temperature phase transition originates from the order–disorder transition of the piperidine groups of one (E,E)-[BPHD]2+ cation and the swing motion of the piperidine groups of another (E,E)-[BPHD]2+ cation. This work expands the family of OIMHs and provides a new platform for designing high-temperature phase transition OIMHs. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites (OIHPs) have gained tremendous interest for their rich functional properties. However, the coexistence of more than one of ferroelectricity, ferromagnetism and ferroelasticity has been rarely found in OIHPs. Herein, we report a two‐dimensional Cr2+‐based OIHP, [3,3‐difluorocyclobutylammonium]2CrCl4 ([DFCBA]2CrCl4), which shows both ferroelectricity and ferromagnetism. It undergoes a 4/mmmFm type ferroelectric phase transition at a temperature as high as 387 K and shows multiaxial ferroelectricity with a saturate polarization of 2.1 μC cm−2. It acts as a soft ferromagnet with a Curie temperature of 32.6 K. This work throws light on the exploration of OIHPs with the coexistence of ferroelectricity and ferromagnetism for applications in future multifunctional smart devices. [ABSTRACT FROM AUTHOR]