Synthesis, characterization, and investigation of some properties of the new symmetrical bisimine Ni(II), Zn(II), and Fe(III) complexes derived from the monoimine ligand

Abstract

The new symmetrical bisimine (ONNO donor, salen type) Ni(II), Zn(II), andFe(III) complexes were synthesized in one step from metal ions and mon-oimine ligand (HL: 4-amino-3-{[(2-hydroxynaphthalen-1-yl)methylidene]amino}phenyl)(phenyl)methanone). The complexes were characterized by ana-lytical, spectral, conductance, magnetic, and thermal data. According to theseanalysis results, while the bisimine ligand, spontaneously forming during com-plexation, is attached to the metal by two nitrogen atoms and two phenolicoxygen atoms (N2O2) in all complexes, in the Fe(III) complex, the fifth coordi-nation is completed by the chlorine molecule. A square pyramidal geometryfor [FeLCl] and a square planar geometry for [NiL], [ZnL] were proposed. Thethree-dimensional structure of [FeLC1] was also evaluated by single-crystal X-ray diffraction, and the square pyramidal structure was clearly revealed. Themolar conductivity data of the complexes confirmed their nonelectrolyticnature. Poly(imine) (PL) was obtained by the oxidative polymerization reactionof HL, and some of its properties were investigated. The electrochemical prop-erties of the ligand and the complexes were studied by means of cyclicvoltammetry. Highest and lowest occupied molecular orbital (HOMO-LUMO)energy levels and electrochemical band gaps were calculated. The ther-mogravimetric analysis (TGA) and differential thermal analysis (DTA) of thesynthesized compounds were carried out. TGA results showed that the thermalstability of the complexes is high. The solid-state electrical conductivities of theiodine doped states of the synthesized compounds were measured by the four-point probe technique. PL has approximately 35 times higher electrical con-ductivity than the HL and complexes. Fluorescence-sensor properties of HLwere also investigated and predicted that HL could be a selective fluorescenceprobe for Pb2+