Novel 1D coordination polymers built from acyclic cryptate containing bis(1H-1,2,4-triazole) ligands and featuring coordinated counteranions

Abstract

Two new coordination polymers, namely, ZnL₂(BF₄)₂ (1) and CuL₂(NO₃)₂ (2) were constructed from a new flexible acyclic cryptate-bis(1H-1,2,4-triazole) ligand. Both coordination polymers were characterized by FT-IR, UV-vis, and thermal analysis and the crystal structures were confirmed by single crystal XRD analysis. According to single crystal X-ray diffraction analysis, both polymers are isostructural and crystallize in the monoclinic space group, C2/m, with unit cell dimensions for 1 as a = 14.0391(17) Å, b = 16.899(2) Å, c = 8.8800(14) Å, β = 109.629(5)°, V = 1984.3(5) ų and Z = 2. Interestingly, the counteranions are found to be coordinated to the metal centers. In particular, 1 represents the first example of BF₄⁻ coordination to a Zn coordination polymer. Optimized geometry and vibrational frequencies of the title coordination polymers in the ground state were computed using B3LYP/6-31G(d,p) theory levels for structure optimization and coupling constant calculations. HOMO–LUMO energy gap and NBO analysis of the new complexes were also calculated. All the calculated parameters are in good agreement with the experimental values obtained from single crystal X-ray diffraction, even for the BF₄⁻ coordination polymer. Sacrificial thermal treatment of 1 and 2 afforded ZnO and CuO oxides, respectively.