Synthesis, X-ray structure, Hirshfeld analysis and DFT studies of Ni(II) complexes with pyridine-type ligands and monoanionic (SCN¯, N3¯ and NO3¯) ligands

Abstract

The molecular and supramolecular structures of two self-assembled Ni(II) complexes with pyridine-type ligands (34Lut: 3,4-lutidine and 4Pic: 4-picoline) comprising different anions (SCN¯, N3¯and NO3¯) were presented. The dinuclear [Ni(34Lut)3(SCN)2]2(1) complexcomprises a hexa-coordinated Ni(II) with NiN5S coordination environment from three 34Lut, one isothiocyanate, in addition to two SCN¯ connecting the two Ni(II) centres via µ(1,3) coordination mode. Structure of complex 2 has the two complex units [Ni(4Pic)4(N3)2][Ni(4Pic)4(NO3)2], in which the two Ni(II) centers have also hexa-coordinated environments with NiN6 and NiN4O2 coordination spheres. In both units, there are four 4Pic ligand units coordinating the Ni(II) via the pyridine nitrogen atom and two anions in anti-positions to one another. In the first unit, the two azides have terminal coordination mode. In the second unit, there are two monodentate nitrate ions coordinating the Ni(II) ion via one oxygen atom. Molecular packing analysis using Hirshfeld calculations revealed the importance of the S…H (20.4%) and CH…π (25.2%) interactions in 1. For complex 2, the N…H (16.2%) and O…H (20.7%) contacts are the most important in [Ni(4Pic)4(N3)2] and [Ni(4Pic)4(NO3)2] complex units, respectively. The H…H contact percentages are 50.5, 54.6 and 51.3%, respectively which are the most common in all complex units. Using DFT calculations, the charge of the Ni(II) ion decreased to 0.7792, 0.8136 and 0.9377 e in the thiocyanato, azido and nitrato complexes, respectively. Using AIM calculations, the Ni-N, Ni-S and Ni-O bonds showed the characteristics of mainly closed shell interactions.