3D zinc(II) coordination polymers built up by triazole and benzene-polycarboxylate anions: Synthesis, crystal structure, thermal and photoluminescence characterization

Abstract

Two coordination polymers of the formula [Zn 5(tmaH) 4(trz) 2(H 2O) 4] ( 1) and [Zn 3(bta)(trz) 2(H 2O) 4]·2H 2O ( 2) [tmaH 3 = benzene-1,3,5-tricarboxylic acid/trimesic acid, trzH = 1,2,4-triazole, btaH 4 = benzene-1,2,4,5-tetracarboxylic acid] have been synthesized and structurally characterized by X-ray single crystal diffraction analysis. Both complexes are 3D coordination polymers containing [Zn 4(trz) 2] units connected by benzene-carboxylate anions. In particular, an undulated layer containing 6- and 18-membered rings is outlined in the network of 1. Hydrogen bonds, involving the coordinated and lattice water molecules with carboxylate oxygen atoms, contribute to the stabilization of the networks. Their thermal stability was investigated by thermogravimetric analysis. The fluorescence spectrum of 1 features two peaks at 419 and 323 nm, originating from a π–π∗ intraligand transition and LMCT, respectively. For 2 a broad band at 410 nm is assigned solely as a π–π∗ intraligand transition.