Zinc(II) complexes of N(4)-monosubstituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Structural and spectroscopic studies

Abstract

• Five new Zn(II) complexes of two thiosemicarbazone ligands are reported. • Spectroscopic studies reveal thione and deprotonated thiolate coordination of the ligands. • Crystal structure of a complex shows distorted square pyramidal geometry around Zn(II). • Extensive intermolecular interactions are quantified by Hirshfeld surface analysis. Five zinc(II) complexes of pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL 1 ] and pyridine-2-carbaldehyde-N(4)-2-phenylethyl thiosemicarbazone [HL 2 ] were synthesized and physico-chemically characterized by means of partial elemental analyses, molar conductance measurements, electronic and infrared spectral studies. The complexes were given the formulae as [Zn(HL 1 )Cl 2 ] ( 1 ), [Zn(HL 1 ) 2 ] ⋅ (NO 3 ) 2 ( 2 ), [Zn(L 2 )Br] ⋅ C 2 H 5 OH ( 3 ), [Zn 2 (L 2 ) 2 SO 4 ] ⋅ 2H 2 O ( 4 ) and [Zn(HL 2 )Cl 2 ] ( 5 ). In the complexes 1, 2 and 5 the thiosemicarbazones are coordinated in the thione form, while complexes 3 and 4 were formed through the coordination of the thiolate form of HL 2 . The structure of the complex 1 is solved by single crystal X-ray crystallography and was found to be a distorted square pyramidal geometry around Zn(II). Extensive intermolecular hydrogen bonding interactions found in the packing of the crystal lattice are mutually complemented and reinforced by π … π stacking interactions, which are further confirmed quantitatively by Hirshfeld surface analysis.