Syntheses, structures, electrochemical and optical properties of four transition metal complexes based on the 1-triazolyl-3-benzimidazolyltriazene ligand

Four transition metal complexes based on the 1-triazolyl-3-benzimidazolyltriazene (H3TBIT) ligand of [Co(H2TBIT)(HTBIT)] (1), {[Cu(H2TBIT)(SCN)]center dot H2O} (2), [Cd-2(H3TBIT)(2)(H2O)(2)Cl-4] (3) and {[Ni-3(H2TBIT)(2)(HTBIT)(2)(en)(2)]center dot IPA center dot 2H(2)O} (en = ethylenediamine, IPA = isopropanol) (4) have been synthesized and characterized by single crystal X-ray diffraction analysis. In 1-4, the triazene ligand acts in different coordinating or bridging modes resulting in two mononuclear structures for 1 and 2, one dinuclear structure for 3 and one trinuclear structure for 4. Different structural 1-4 are further self-assembled through hydrogen bonds or pi-pi, C-H/center dot center dot center dot pi or metal-pi interactions to form 3D supramolecular structures. The electrochemical properties in aqueous solutions as well as the photoluminescent properties in ethanol of H3TBIT and 1-4 are investigated. The TD-DFT calculations at the B3LYP/6-311++G(d, p) level for H3TBIT has been used to demonstrate the characteristic absorption spectrum.