Nickel(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structures, spectral aspects and Hirshfeld surface analysis

Abstract

Seven Ni(II) complexes {[NiL12]·2H2O (1), [Ni2L22SO4]·1½H2O (2), [Ni(HL2)2](NO3)2·H2O·EtOH (3), [NiL2(HL2)]OAc·3H2O (4), [Ni(HL2)2](ClO4)2·2H2O (5), [NiL3OAc]·2½H2O (6), [NiL3NO3]·3H2O (7)} of three thiosemicarbazone ligands, vizpyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone (HL1), pyridine-2-carbaldehyde-N(4)-phenethyl thiosemicarbazone (HL2) and pyridine-2-carbaldehyde-N(4)-pyridyl thiosemicarbazone [HL3] were synthesized and physico-chemically characterized by means of partial elemental analyses, molar conductivity measurements, electronic, infrared spectral studies and magnetic susceptibility measurements. In the complexes, the thiosemicarbazones coordinate both in the thione form and in the deprotonated thiolate form. Pyridine nitrogen, azomethine nitrogen and thiolate/thione sulfur are involved in coordination in all the complexes. The single crystal X-ray structures of complexes 1a, 5 and [NiL32]·H2O (7a) are discussed, show octahedral coordination around Ni(II). Structural studies corroborate spectral characterization. Supramolecular interactions of the three complexes are verified by Hirshfeld surface analyses, which reveal the dominant role of van der Waals forces (H···H interactions) and confirm the reinforcement of π-π/C–H···π interactions in the crystal lattice packing of these complexes.