A study on copper(II)-Schiff base-azide coordination complexes:: Synthesis, X-ray structure and luminescence properties of [Cu(L)(N3)]X(L = Schiff bases;X = ClO4, PF6)

Two Schiff bases N,N'-(bis(pyridin-2-yl)benzylidene)propane-1,3-diamine (pbpd) and N,N'-(bis(pyridin-2-yl)formylidene)butane-1,4-diamine (pfbd) have been prepared and used to synthesize copper(II) complexes. Four complexes of the type (Cu(L)(N-3)]X (1-4) [L = pbpd; X = ClO4 (1); L = pbpd; X = PF6 (2); L = pfbd; X = ClO4 (3); L = pfbd; X = PF6 (4)] have been synthesized and characterized on the basis of microanalytical, spectroscopic, magnetic, electrochemical, luminescence and other physicochemical properties. Two representative complexes of the series, 2 and 3, have been characterized by single crystal X-ray diffraction measurements which reveal that in each complex the copper(I I) ion assumes a distorted trigonal bipyramidal environment through coordination of the metal centre by two pyridine N atoms and two imine N atoms of the Schiff base with the fifth position occupied by a N atom of a terminal N3. They display intraligand (1)(pi-pi*) fluorescence at room temperature and intraligand (3)(pi-pi*) phosphorescence in glassy solutions (MeOH at 77 K). A band (492 nm) observed for the complexes in their solid-state emission spectra is an excimeric emission arising due to an aromatic pi-pi interaction. Electrochemical electron transfer study reveals Cu-II-Cu-I reduction in methanolic solutions. (c) 2005 Elsevier Ltd. All rights reserved.