Synthesis, crystal structure and chromotropism study of copper complexes containing tridentate and pseudo halide ligands; amide linkage isomerism

The synthesis, structure, and chromotropism properties (solvato- halo- and ionochromism) of two mononuclear copper(II) complexes are described. Their positive solvatochromism were investigated by stepwise multiple linear regression computational method. The complexes were studied that functions as pH-induced “off–on–off” switches owing to protonation and deprotonation of amide moiety at room temperature. The complexes exhibited ionochromism and demonstrated high-sensitive and selective towards CN− and N3− anions in presence of other halides and pseudo-halides. [Display omitted] •Two new copper(II) complex containing hemilabile ligand was prepared and characterized.•The color of the complexes change reversibly over the pH range 2.0–10.1.•The complexes exhibit solvatochromism, halochromism and ionochromism.•The halochromism is due to presence of hemilabile amide groups in the complexes. Two mononuclear complexes of [CuL(N3)]ClO4, 1 and [CuL(SCN)]ClO4, 2, with tridentate ligand of N,N-dimethyl,N-3-propylamideethylenediamine, L, were synthesized and characterized by elemental analyses, molar conductance measurements, UV–Vis and FT-IR spectroscopy techniques. The crystal structure of 1 has been identified by single-crystal X-ray diffraction analyses and confirmed that the copper(II) ion has a distorted square pyramidal environment. The chromotropism of the complexes were studied using spectral analysis. The solvatochromism of the complexes were analyzed by multi-parametric equation using SPSS/PC software. The stepwise multiple linear regression method revealed that the donor power of the solvent acting the most important role in the observed positive solvatochromism of the compounds. The complexes demonstrated halochromism in aqueous solution. The pH effects on the visible absorption spectra of the complexes were studied that functions as pH-induced “off–on–off” switches owing to protonation and deprotonation of amide moiety at room temperature. The complexes exhibited noticeable ionochromism and demonstrated high-sensitive and selective towards CN− and N3− anions in presence of other halides and pseudo-halides.