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

Two new trinuclear Cu(II) and dinuclear Zn(II) clusters are crystallized out by reacting the metal salts with the triethanolamine (H(3)tea) 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 [Cu-3(H(2)tea)(2)(ba)(2)(NO3)(2)] (1) and [Zn-2(H(2)tea)(ba)(3)]H2O (2). FTIR ascertains the binding modes of H(2)tea(-), ba(-) and NO3-. Triethanolamine binds in both the complexes in the monoanionic (H(2)tea(-)) 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 Cu-3 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 (d(9) or d(10)), 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.