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

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 AgNO3 afforded two neutral silver metal complexes formulated as [AgL1NO3] and [AgL2NO3], respectively. The crystal structure analysis of the two complexes indicate the presence of a Y-shaped tricoordinated silver (I) ion for [AgL1NO3] and a tetracoordinated silver(I) ion displaying rather rare and distorted square planar geometry for [AgL2NO3]. 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 AgNO3 or of ZnCl2 indicates the possibility of forming transition metal complexes with these ligands.

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