Structurally well-characterized new multinuclear Cu(ii) and Zn(ii) clusters: X-ray crystallography, theoretical studies, and applications in catalysis

Abstract

Two new trinuclear Cu(II) and dinuclear Zn(II) clusters are crystallized out by reacting the metal salts with the triethanolamine (H₃tea) ligand in the presence of benzoic acid (Hba). The complexes are characterized by elemental, thermal, magnetic, spectral (FTIR, UV-Visible, EPR, and photoluminescence) and single crystal X-ray studies. Single crystal X-ray crystallography reveals the composition of the complexes to be [Cu₃(H₂tea)₂(ba)₂(NO₃)₂] (1) and [Zn₂(H₂tea)(ba)₃]H₂O (2). FTIR ascertains the binding modes of H₂tea⁻, ba⁻ and NO₃⁻. Triethanolamine binds in both the complexes in the monoanionic (H₂tea⁻) mode. ba⁻ is present as an anchoring auxiliary to generate di- and trinuclear clusters. The Cu(II) ion is present as a distorted octahedral center in the Cu₃ cluster (1), while the two Zn(II) ions in 2 have been reported for the first time to possess distorted octahedral as well as tetrahedral geometry in the same molecule. The intriguing features of the non-covalent supramolecular interactions have been investigated and supported theoretically by using Hirshfeld surface analysis and ab initio methods. The solid state photoluminescence (PL) spectra of 1 and 2 disclose the luminescence property of the complexes. Due to the closed or nearly closed shell configuration (d⁹ or d¹⁰), the present complexes are screened for catalytic properties in the hydrocarboxylation of alkanes and cycloalkanes. The catalytic activity data are indicative of the potential catalytic properties of 1 and 2.