New nickel(ii) and copper(ii) complexes with unsymmetrical Schiff bases derived from (1R,2R)(−)cyclohexanediamine and the application of Cu(ii) complexes for hybrid thin layers deposition

Abstract

New unsymmetrical Schiff bases obtained by condensation of (1R,2R)(−)cyclohexanediamine with 2-hydroxy-3,5-di-tert-butylbenzaldehyde (3,5-^tbba) and 2-hydroxy-3-methoxybenzaldehyde (3-metoxba) or 2-hydroxy-5-nitrobenzaldehyde (5-nba) and 2-hydroxyacetophenone (hacphen) were used for the synthesis of Cu(II) and Ni(II) complexes. The ligands and complexes were characterized by circular dichroism (CD), UV-vis, IR, ¹H (NOE diff) (ligand) and ¹³C NMR (ligand) spectra. The X-ray crystal structures solved for Ni(II)(1R,2R)(−)chxn(3,5-^tbba)(hacphen) exhibit distortion of the coordination sphere towards tetrahedral in the solid phase. The complex crystallized in the orthorhombic non-centrosymmetric P2(1)2(1)2(1) space group. Thin layers of copper(II) complexes were deposited on Si(111) by a spin coating technique and characterized by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM) and fluorescence spectroscopy. Layer deposition conditions were studied and optimal parameters were found (1500 rpm, time 30 s). For copper(II) layers the most intensive fluorescence band from intraligand transition at 514 nm was observed. CD spectra of complexes in MeCN suggest the tetrahedral distortion from the square planar geometry of the central ion of the coordination sphere in solution. The ¹H NMR NOE diff. spectra of ligands were measured and the positions of the nearest hydrogen atoms in the cyclohexane and aromatic rings were discussed.