Synthesis, characterisation and density functional theory (DFT) studies of a triazine ring with a mixed ligand Schiff base complexes

The novel Schiff base, (E)-4-((2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (L1), and its mixed ligand complexes with 2,4,6-tri(pyridin-2-yl)-1,3,5-triazine as an auxiliary ligand (L2) and different transition metal ions (Mn(II), Fe(III), Co(II), Ni(II), Zn(II) and Cd(II)) were synthesised. The 1H NMR spectra of L1 supported their geometrical structures, which was confirmed by X-ray crystallography. The packing of L1 is dominated by H…H, O…H, H…C, C…C, C…N, C…O and N…H interactions. Density functional theory (DFT) calculations showed excellent straight-line correlations between the calculated and experimental geometric parameters where the most stable isomer of L1 is stabilised by an OH…N hydrogen bond, and which agrees with the reported X-ray structure. The prepared complexes were characterised by elemental analyses, molar conductance measurements, IR, UV–vis, and 1H NMR spectroscopic methods. The elemental analysis data suggested a 1:1:1 [M:L1:L2] ratio for all the complexes. The molar conductance measurements of the complexes indicate their electrolytic nature in DMSO as solvent. The electronic absorption spectral data revealed the existence of an octahedral geometry for all complexes.