Azo-based iminopyridine ligands: synthesis, optical properties, theoretical calculations and complexation studies

Abstract We describe herein the full characterization of azobenzene based iminopyridine ligands ( L1 – L4 ) synthesized by a condensation reaction between N , N -Dimethyl-4,4′-azodianiline or 4-(4-nitrophenylazo)aniline and 2-pyridinecarboxaldehyde or 2,6-pyridinedicarboxaldehyde. The UV–visible absorption bands of these ligands were fully assigned using DFT and TD-DFT computations. The complexation of ligand L1 and ligand L2 with AgNO 3 afforded two neutral silver metal complexes formulated as [ AgL1NO 3 ] and [ AgL2NO 3 ], respectively. The crystal structure analysis of the two complexes indicate the presence of a Y-shaped tricoordinated silver (I) ion for [ AgL1NO 3 ] and a tetracoordinated silver(I) ion displaying rather rare and distorted square planar geometry for [ AgL2NO 3 ]. In solid state, for both complexes, a 3D supramolecular architecture is generated via hydrogen bonds of type C–HċO and C–Hċπ. The UV–visible spectrophotometric titration studies of ligands L1 – L4 , by increasing amount of AgNO 3 or of ZnCl 2 indicates the possibility of forming transition metal complexes with these ligands.