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

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)(4)bpe] (1), [Cu-2(NioxH)(4)bpe] (2), [Cu-2(dpgH)(4)bpe] (3), and [Cu-2(dpgH)(4)bpe][Cu(dpgH)(2)bpe](2)center dot 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. (C) 2011 Elsevier Ltd. All rights reserved.