New Zn2+ coordination polymers with mixed triazolate/tetrazolate and acylhydrazidate as linkers

Abstract

Under hydrothermal conditions, at different pH levels adjusted by H₂ox (ox = oxalate, C₂O₄²⁻) or N₂H₄, the reactions of Zn(CH₃COO)₂·2H₂O, phthalic/3-nitrophthalic acid, N₂H₄·H₂O and triazole/tetrazole afforded four new Zn²⁺ coordination polymers as [Zn₅(OH)₂(Hpth)₂(pth)₂(trz)₂] (pth = phthalhydrazidate, trz = 1,2,4-triazolate) 1, [Zn₃(OH)₂(Hpth)₂(datrz)₂] (datrz = 3,5-diamino-1,2,4-triazolate) 2, [Zn₂(pth)(atez)₂] (atez = 5-aminotetrazolate) 3 and [Zn₅(OH)₂(ox)(apth)₂(datrz)₂] (apth = 3-aminophthalhydrazidate) 4. The acylhydrazide molecules H₂pth and H₂apth in compounds 1–4 originated from the hydrothermal in situ acylation of N₂H₄ with phthalic/3-nitrophthalic acid. When preparing compound 4, the reduction of –NO₂ into –NH₂ also occurred besides the acylation, creating finally a new acylhydrazide molecule H₂apth. The X-ray single-crystal diffraction analysis revealed that (i) in compounds 1, 3 and 4, Zn²⁺ and pth/apth aggregate into the 1D endless chains. The triazolate/tetrazolate molecules extend the Zn²⁺-pth/apth chains into the different layer networks of compounds 1 and 4, and a 3D network of compound 3; (ii) in compound 2, the datrz molecules link the Zn²⁺ ions into a 2D layer network. Pth acts as the ancillary ligand; (iii) ox from H₂ox was introduced into the final framework of compound 4; (iv) the acylhydrazide molecules exhibit three types of existing forms in compounds 1–4: the diketo form, the keto-hydroxyl form, and the dihydroxyl form. Of those, the dihydroxyl form was observed for the first time. The solid-state photoluminescence analysis indicated that only compound 4 emits green light, and the others do not emit light.