Solid-state structural transformation triggered by water in zinc(Ⅱ) coordination polymers based on 3,5-ditertbutyl-2-hydroxybenzoic acid:Structural characterization and dielectric properties

Abstract

Single-crystal-to-single-crystal (SCSC) transformation provides a good platform for obtaining new functional coordination polymers. In this study, we demonstrate a violent and rapid structural transformation between two d10 coordination polymers (CPs). The complex 1 [Zn(3,5-thbzc)2(C2H6O)2] transformed into the complex 2 {[Zn(3,5-thbzc)2(H2O)2]·C3H7NO·2H2O} (where t=tbutyl, hbzc-=2-Hydroxybenzoato) triggered by deionized water under standard temperature and pressure conditions in solid state. The transformation reaction was confirmed using single-crystal XRD, PXRD and SEM. The results showed that complex 1 adopts a bidentate chelate six-coordination mode, and complex 2 adopts a monodentate four-coordination mode. SEM clearly showed that complex 2 was in the form of random nanowire clusters, suggesting that their transformation required degradation of the entire crystal structure. UV-Vis-NIR spectra were used to calculate the band gaps of complexes 1 and 2, which demonstrated wide-bandgap semiconductor-like materials with ∼3.2 eV band gap widths. The results of dielectric studies of complex 1 revealed that it possessed a medium dielectric constant (κ=6.08 at 1 kHz), while complex 2 displayed an even higher dielectric constant (κ=7.97 at 1 kHz) at room temperature. Interestingly, parent complex 1 exhibited a small ladder-like dielectric anomaly at 188°C, while progeny complex 2 did not. This paper describes a new strategy for preparing adjustable functional dielectric materials.