Synthesis, crystal structures and theoretical studies of Zinc(II) coordination compounds with 4-trifluoromethylphenyl)imino-methyl]pyridine bidentate Schiff base ligand

Abstract [Zn(dip)(Br)2] (1) and [Zn2(dip)2Cl4] (2) zinc(II) coordination compounds were synthesized using 4-trifluoromethylphenyl)imino-methyl]pyridine (dip) bidentate Schiff base ligand and ZnBr2 and ZnCl2 salts. In structure 1, zinc(II) ion exhibits a tetrahedral arrangement while adopting a ZnN2Cl3 trigonal bipyramidal geometry in structure 2. Moreover, in structures 1 and 2, the neutral molecules form a 1D chain structure through the C-H•••F hydrogen bonds. Complex 1 is a monomeric structure while complex 2 has a dimeric structure. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. Density Functional Theory (DFT) calculations at the B3LYP level of theory have been carried out to investigate three types of reactions between ZnCl2 and ZnBr2 metal salts and ligand L in both gas and solution phases. The optimized geometrical parameters of the complexes were evaluated using SDD, CEP-121G, and LANL2DZ basis sets. The gas phase calculations show that the binuclear Zn2L2X4 (Zn2L2Cl4 and Zn2L2Br4) complexes are more stable than mononuclear ZnLX2 (ZnLCl2 and ZnLBr2) and ZnL22+ complexes. However, the solution studies indicate that the formation of Zn2L2Cl4 and ZnLBr2 complexes is energetically more favorable compared with the other complexes.