Abstract
New mononuclear copper(II) complexes of the first topical receptor-selective retinoid drug, Tazarotene (Tz), of the type [Cu(Tz)(2)X-2] (X = Cl (1) and Br (2a)) were synthesized, characterized (elemental analysis, TG, FT IR, UV-Vis, EPR, magnetic susceptibility, molar conductance measurements and single crystal X-ray analysis) and tested for their antimicrobial activities against Staphylococcus aureus and Escherichia coli. Tazarotene behaves as a neutral monodentate ligand via the pyridine nitrogen atom. Complex 1 crystallizes in the monoclinic P2(1)/c space group. The environment around the metal center in 1 could be described as an intermediate between tetrahedral and square-planar geometries. Crystals of the polymeric {[Cu(Tz)(mu-Br)]}(n) (2b) complex were obtained by the slow evaporation of the reaction filtrate of complex 2a. The distorted tetrahedral environment around Cu(I) is formed from the pyridine N atom of Tz, the S atom of another Tz molecule as well as two bridged bromine atoms, with a Cu center dot center dot center dot Cu' distance of 3.327 angstrom. Time-dependent density functional theory calculations were carried out to understand the electronic structure and to explain the related experimental findings. The electronic arrangement, type of hybridization and nature of bonding were obtained from natural bond orbital analysis. (C) 2016 Elsevier Ltd. All rights reserved.