[NH3(CH2)4NH3]SnX4 (X = Br, I): Dion-Jacobson type 2-D perovskites with short interlayer spacing

Two-dimensional tin(II) halide perovskites stand as an environmentally benign alternative to Pb(II) halide perovskites. However, they are often challenging to make due to the oxidation of Sn(II) ion to more stable Sn(IV) ion. Here we report hybrid tin bromide and iodide perovskites: (1,4-BDA)Sn(IV)Br6 and (1,4-BDA)Sn(II)X4 (where X = Br, I; 1,4-BDA = 1,4-diammoniumbutane) with 0D and 2D structures, respectively. Their synthesis, structural characterization and photophysical properties are reported. They show bandgaps in the 1.94-2.70 eV range.

Antimony Bromide Organic-Inorganic Hybrid Compound with a Long-Chain Diamine Showing Switchable Phase Transition and Second-Harmonic Generation Properties

Organic-inorganic hybrid metal halides have attracted significant attention in recent years due to their excellent optoelectronic properties and potential applications in solar cells. Herein, the organic-inorganic hybrid molecule [N,N-dimethyl-1,3-propanediamine]SbBr5 (1) was synthesized by reacting a long-chain organic diamine N,N-dimethyl-1,3-propanediamine with SbBr3 as a metal halide precursor in HBr aqueous solution. Compound 1 possesses a one-dimensional chainlike structure with the second-harmonic generation switch and two continuous phase transitions above room temperature. The band gap of compound 1 is about 2.62 eV, exhibiting a semiconductive property, which may have important implications for the development of new optoelectronic devices.

Integrated Reversible Thermochromism, High Tc , Dielectric Switch and Narrow Band Gap in One Multifunctional Ferroic

Organic-inorganic Hybrid (OIH) materials for multifunctional switchable applications have attracted enormous attention in recent years due to their excellent optoelectronic properties and good structural tunability. However, it still remains challenging to fabricate one simple OIH compound with multi-functionals properties, such as dielectric switching, thermochromic properties, semiconductor characteristics and ferroelasticity. Under this context, we successfully synthesized [2-(2-fluorophenyl)ethan-1- ammonium]₂ SnBr₆ (compound 1), which has a higher phase transition temperature of 427.7 K. Additionally, it exhibits a semiconducting property with an indirect band gap of 2.36 eV. Combining ferroelastic, narrow band gap, thermochromic, and dielectric properties, compound 1 can be considered as a rarely reported multi-functional ferroelastic material, which is expected to give inspiration for broadening the applications in the smart devices field.

3D Perovskite (1,5-3.2.2-H2dabcn)CsBr3 with Reverse Symmetry Breaking

Even though hybrid organic-inorganic perovskites (HOIPs) have been studied by many scholars in recent years, there are not many reports on three-dimensional (3D) alkali metal cesium halide perovskites. Here, we report an unprecedented 3D HOIP molecule (1,5-3.2.2-H₂dabcn)CsBr₃ (1), in which the 3D anionic framework is constructed by corner-sharing CsBr₆ octahedra and organic cations [1,5-3.2.2-H₂dabcn]²⁺ are located in the cavities formed by the octahedra. Organic cations interact with an inorganic metal frame via two N-H···Br hydrogen bonds. Compound 1 undergoes a reversible order-disorder phase transition and exhibits switchable dielectric and second-harmonic generation (SHG) properties. Interestingly, product 1 crystallizes in a non-centrosymmetric space group Pmn2₁ at the low-temperature phase (LTP) and transforms into a centrosymmetric space group P2/m at the high-temperature phase (HTP). The space group Pmn2₁ in the LTP has a higher symmetry than P2/m in the HTP. This inverted symmetry breaking is very unusual.

A series of dynamic single crystals of [MII(en)3]SO4 (M = Ni, Mn, and Cd) shows tunable dielectric properties and anisotropic thermal expansion

A series of dynamic single crystals with a chemical formula of [M^II(en)₃]SO₄ (en = ethylene and M^II = Ni^II, Mn^II, and Cd^II) was synthesized. As the temperature decreases, these materials exhibit dielectric switching in the vicinity of the phase transition point accompanied by anisotropic thermal expansion in the cell parameters as a consequence of the order-disorder structural change of SO2-4 in a cavity surrounded by five [M^II(en)₃]²⁺ complex cations. Because the variation of metal centers with different ionic radii changes the shape of the complex cation, which affects the distribution of hydrogen-bond interactions around the SO2-4, the dynamic motion of SO2-4 is substantially tuned. Correspondingly, the dielectric properties and anisotropic thermal expansion of materials were largely shifted, especially in the single crystals of [Mn^II(en)₃]SO₄, whose structural change is distinctly different from the crystals of Ni(II) and Cd(II). The detailed structural mechanism accounting for the different physical properties of these materials was discussed.

The Role of Fluorine-Substituted Positions on the Phase Transition in Organic-Inorganic Hybrid Perovskite Compounds

Although research on organic-inorganic hybrid perovskites (OIHPs) has grown exponentially in the past two decades, the high phase transition temperature of OIHP materials is still one of the insurmountable difficulties. Herein, a series of A₂BX₄ type OIHP materials [(2,n-DFBA)₂PbCl₄] (n = 3, for 1; n = 4, for 2; n = 5, for 3; n = 6, for 4) have been prepared by reactions of double-substituted difluorobenzylamine (difluorobenzylamine = DFBA) with lead chloride in concentrated HCl aqueous solution. It was found the OIHP compounds 1-3 proceed a switchable phase transition with phase transition temperatures (T_c) at 449 K (1), 462 K (2) and 500 K (3), higher than that of the parent compound [(BA)₂PbCl₄] (BA = benzylammonium) at 438 K, but compound 4 exhibits no phase transition. A crystal structure analysis elucidated that the organic template ligands DFBA lead in the inorganic part in compounds 1-3 to a two-dimensional (2D) perovskite structure, while that in compound 4 leads to a one-dimensional (1D) chain structure. The different double-substituted positions of fluorine atoms on benzylamine have important influences on the phase transition in compounds 1-4.

Multisequential reversible phase transition materials with semiconducting and fluorescence properties: (C8H18BrN)2SnBr6

A novel organic–inorganic hybrid metal halide has synthesized, namely (C8H18BrN)2SnBr6 (1), which have excellent switchable dielectric properties, narrow band gap and broadband yellow fluorescence characteristics.

Tautomeric and conformational switching in a new versatile N-rich heterocyclic ligand

A new N-rich triazolo-triazole derivative, 4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole (C8H7N7), bearing a pyrazine residue at 7-position of the triazolo-triazole bicycle, was synthesized, and its acid-base and metal coordination properties were evaluated in solution. The results showed amphoteric behavior and the formation of stable complexes with Cu(ii) and Zn(ii) in pH intervals in which the ligand is neutral or deprotonated. Computational studies were performed in order to evaluate the stability of the different tautomers/conformers of the ligand, and the proton position in the neutral and acidic forms. Single crystal X-ray analysis of the free neutral ligand (2H/s-trans tautomer/conformer), and of its singly protonated (2H-3H/s-trans), doubly protonated (2H-3H-7H/s-trans) and deprotonated forms showed that the influence of the pyrazine ring on the triazolo-triazole system is mainly as electron withdrawing and chelating group, and proton acceptor. Different coordination modes have been evidenced for the neutral and deprotonated ligand. Upon metal coordination, the neutral ligand switches from 2H/s-trans to 3H/s-cis tautomer/conformer forming five-membered chelate rings, while the anionic deprotonated ligand forms six-membered chelate rings in the s-trans conformation. Altogether, five different tautomers/conformers of the ligand were isolated and characterized. In vitro tests confirmed the general antiproliferative activity of triazolo-triazole compounds and the importance of substitution in position 7 for their selectivity.

A square-pyramidal coordinated copper(ii) hydrazine dimeric complex showing reversible phase transition, dielectric anomaly and thermochromism

A square-pyramidal coordinated copper(ii) hydrazine dimeric complex was prepared by reaction of CuCl₂ with trimethyl hydrazine showing reversible phase transition, dielectric anomaly and thermochromism.