“Wheel-and-axle” binuclear Cu(II) dioximates mediated by 1,2-bis(4-pyridyl)ethane: Synthesis, X-ray study and luminescent properties

Abstract

The reaction of copper(II) acetate or fluoride with classic dioximes in the presence of 1,2-bis(4-pyridyl)ethane resulted in four novel compounds with the compositions [Cu 2(dmgH) 4bpe] ( 1), [Cu 2(NioxH) 4bpe] ( 2), [Cu 2(dpgH) 4bpe] ( 3), and [Cu 2(dpgH) 4bpe][Cu(dpgH) 2bpe] 2·2DMF ( 4) (where dmgH 2 = dimethylglyoxime, NioxH 2 = 1,2-cyclohexanedionedioxime, dpgH 2 = diphenylglyoxime, bpe = 1,2-bis(4-pyridyl)ethane, and DMF = N, N′-dimethylformamide), whose crystal structures were determined by single crystal X-ray diffraction. In the binuclear molecules 1– 3, as well as in both binuclear and mononuclear molecules in 4 each Cu(II) atom has an identical N 5-environment formulated by four oximic nitrogen atoms of two monodeprotonated ligands in a slightly distorted square planar mode, and the nitrogen atom of the bpe molecule being in the apical position. The new compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Luminescence investigations for 1, 2 and 4 were carried out to clarify whether the guest inclusion in the crystal lattice is accompanied by changes in the emission spectra.