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)(N3)]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(II) 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(π–π∗) fluorescence at room temperature and intraligand 3(π–π∗) 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 π–π interaction. Electrochemical electron transfer study reveals CuII–CuI reduction in methanolic solutions.

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 used to synthesize four complexes of the type [Cu(L)(N3)]X (1–4) [L = pbpd; X = ClO4 (1); L = pbpd; X = PF6 (2); L = pfbd; X = ClO4 (3); L = pfbd; X = PF6 (4)]. Two representative members of the series, 2 and 3, have been characterized by single crystal X-ray diffraction measurements. They display intraligand 1(π–π∗) fluorescence at room temperature and intraligand 3(π–π∗) phosphorescence in glassy solutions (MeOH at 77 K). Electrochemical electron transfer study reveals CuII–CuI reduction in methanolic solutions.Figure optionsDownload as PowerPoint slide