Two novel phase transition materials based on 1-isopropyl-1,4-diazabicyclo[2.2.2]octan-1-ium

Above-Room-Temperature Ferroelastic Phase Transitions in Two Tetrafluoroborate-Based Hexagonal Molecular Perovskites

ABX₃-type molecular perovskites provide an important platform to tune phase transitions, via judiciously choosing A-, B-, and X-site components, to approach advanced functional materials for applications. Although tetrafluoroborate can act as X-site component to assemble ten instances of ABX₃ molecular perovskites, only two of them possess hexagonal perovskite structures. Herein, we report two tetrafluoroborate-based hexagonal molecular perovskites, A[Na(BF₄)₃], by judiciously choosing two different A-site cations: 1-methyl-1,4-diazabicyclo[2.2.2]octane-1,4-diium (Hmdabco²⁺) for 1 and 1-methylpiperazine-1,4-diium (H₂mpz²⁺) for 2. They have high-temperature phases in the same space group (P6₃/mmc) revealing highly disordered A-site cations. Upon cooling, 1 undergoes two-step P6₃/mmc ↔ P3̅c1 ↔ P2₁/n transitions at 344 and 338 K, respectively, including a ferroelastic one (3̅mF2/m) accompanied by a spontaneous strain of 0.013. In contrast, the smaller H₂mpz²⁺ cation with more adoptable conformations induces a one-step sharp P6₃/mmc ↔ P2₁/c ferroelastic transition (6/mmmF2/m(s)) at 418 K in 2, leading to more significant symmetry breaking and a considerable spontaneous strain of 0.129. This study provides important clues to modulate structural phase transitions by tuning diverse components for the multicomponent dense hybrid crystals.

Band gap modulation of organic–inorganic Sb(iii) halide by molecular design

Four organic–inorganic hybrid materials were designed, and a successful adjustment of the band gap was obtained, from 2.933 eV to as low as 2.788 eV, via replacing the third hydrogen atom of the benzene ring in the organic cation with a halogen.

Crystal structure of tert-butyl 4-[4-(4-fluoro-phen-yl)-2-methyl-but-3-yn-2-yl]piperazine-1-carboxyl-ate

The title sterically congested piperazine derivative, C20H27FN2O2, was prepared using a modified Bruylants approach. A search of the Cambridge Structural Database identified 51 compounds possessing an N-tert-butyl piperazine substructure. Of these only 14 were asymmetrically substituted on the piperazine ring and none with a synthetically useful second nitro-gen. Given the novel chemistry generating a pharmacologically useful core, determination of the crystal structure for this compound was necessary. The piperazine ring is present in a chair conformation with di-equatorial substitution. Of the two N atoms, one is sp 3 hybridized while the other is sp 2 hybridized. Inter-molecular inter-actions resulting from the crystal packing patterns were investigated using Hirshfeld surface analysis and fingerprint analysis. Directional weak hydrogen-bond-like inter-actions (C-H⋯O) and C-H⋯π inter-actions with the dispersion inter-actions as the major source of attraction are present in the crystal packing.

Concomitant polymorphs: an alternative to modulate the oxygen evolution performance of mononuclear nickel complexes

Studying two stable reversible transformations of concomitant polymorphs of NiL2 as heterogeneous catalysts, coplanar NiL2-R exhibits better OER activities than zigzag NiL2-G, dependent on different disparities in crystal packing.

A lead-free perovskite-like hybrid with above-room-temperature switching of quadratic nonlinear optical properties

We report a new lead-free perovskite-like hybrid, composed of hexamethyleneimine and one-dimensional [SbCl5]n2- polyanionic zigzag chains, which shows above-room-temperature switching of quadratic nonlinear optical (NLO) properties induced by the unique order-disorder conformational changes of the organic cation.

[C6H14N]PbI3: a one-dimensional perovskite-like order–disorder phase transition material with semiconducting and switchable dielectric attributes

Here we report a new one-dimensional organic–inorganic hybrid, adopting an ABX₃ perovskite-like architecture, which exhibits semiconducting and switchable dielectric attributes.

A high temperature reversible phase transition in a supramolecular complex of 15-crown-5 with tetraphenylboron sodium

High temperature (391 K) reversible phase transition and large thermal hysteresis (19 K) was observed in 15-crown-5 clathrates: [Na(15-crown-5)][BPh₄] (15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane, NaBPh₄ = sodium tetraphenylboron).

Exceptional bi-step switching of quadratic nonlinear optical properties in a one-dimensional channel compound

A new solid-state channel compound shows exceptional bi-step switching between three distinct nonlinear optical states.