Reactions of copper(II) bromide with 2,6-diacetylpyridine bis(phenyl-hydrazone) (L)-molecular and crystal structure of L and its mixed-valence complex [CuIIL2][CuI2Br4]

Abstract

Utilizing X-ray crystallography the crystal and molecular structures of 2,6-diacetylpyridine bis(phenylhydrazone) (L) were determined. Energetics of the intermolecular interactions in the crystal structure was assessed with computational methods, revealing that dispersion interactions are dominant. The basic structural unit of the crystal packing is revealed to be the herring-bone type arrangement of L molecules. Assignation of the IR spectrum of L with the aid of DFT calculations was performed. Furthermore, new reactions of L with CuBr2 in different solvents are described, which led to the synthesis of the mixed Cu(II)-Cu(I) complex of the formula [CuIIL2][CuI2Br4] (1), and its structural characterization. In the complex cation, two molecules of tridentate N3 ligand are meridionally arranged in a very distorted octahedral environment of a Cu(II) ion. In [Cu2Br4]2-, bromide ions are arranged in a trigonal-planar geometry around each copper(I) atom. Finally, for the ligand, 1, and the previously synthesized complex [CuL2]Br2, thermal properties were examined. The thermal stability of the com-plexes is lower than that of the ligand and decreases in order: L (250?C) > > [CuL2]Br2 (221?C) > [CuIIL2][CuI2Br4] (212?C). The differences in thermal stability of the complexes are due to differences in packing efficacy of the constitutional ions.

Some Aromatic Schiff Bases and Their Metal Complexes

“…The ligands together form a pentagonal bipyramidal surrounding of Zn(II). Recently the crystal structure of 2,6-diacetylpyridine bis(phenylhydrazone) (DAP-PH) and its mixedvalence copper complex is published [114]. In the described compound two DAP-PH Schiff bases coordinate to Cu(II) and give a bis(ligand) complex cation.…”