Zinc Induced a Dramatic Enhancement of the Nonlinear Optical Properties of an Azo-Based Iminopyridine Ligand

An azobenzene based iminopyridine ligand 1 has been synthesized by a condensation reaction between N,N -dimethyl-4,4′-azodianiline and 2-formylpyridine. The complexation of the ligand with ZnCl 2 afforded a tetrahedral neutral zinc metal complex ( 2 ) formulated as [(Azo-Imino-Py)ZnCl 2 ]. The crystal structure analysis of the complex indicates the formation of a tetracoordinated zinc(II) ion with the expected tetrahedral geometry. In solid state, a 2D supramolecular architecture reinforced by π–π stacking and hydrogen bonding is observed. The UV–visible spectrophotometric titration studies of the ligand, by increasing amount of ZnCl 2, confirm the existence of single complex species in solution. The nonlinear optical (NLO) investigations by Z-scan technique of both ligand 1 and complex 2 indicate a dramatic enhancement of the NLO absorption of the ligand upon complexation with ZnCl 2 . This enhancement is likely to be due to a large dipole moment found for the complex 2 as calculated by DFT/B3LYP methodology.