Novel Supramolecular Assemblies of Co(III) & Cu(II) with Diethylenetriamine and Azide: Synthesis, Structure, Spectroscopic and Magnetic Studies

Abstract

In exploring the role of increased ligand basicity as well as denticity on moving from ethylenediamine (en) or 1,3-diaminopropane (1,3-dap), on supramolecular solid formation, complexation involving diethylenetriamine (det) and azide with CoII and CuII afforded three new complexes [Co(det)2](N3)3 (1), [Co(det)(N3)3] (2) and [Cu2(det)2(N3)5(H2O)2Na] (3) under self assembling conditions and are characterized structurally and magnetically. Formation of 1 and 2 is sensitive to temperature of crystallization, while such a temperature influence could not be observed for CuII system due to lack of crystals at low temperatures. As expected with a tridentate ligand, strong chelation stabilizes 1 at LT and is a thermodynamically stable product, while isolation of 2 at RT conditions is under kinetic control. Decomposition of 2 at high temperatures (above 70 °C) as revealed through temperature dependent UV-vis spectral studies also confirms its instability. Presence of three donor sites of det, leads to interesting structural pattern in Jahn-Teller active CuII, resulting in cationic chains of [Cu(det)(N3)]n + bridged by μ-1,3 azido bridges to the neighboring [Na(H2O)2(N3)2]− units, thus leading to a 2-D assembly of alternating layers of cationic and anionic chains in the unit cell of 3. Magnetic studies of 3 reveals anti-ferromagnetic interaction between the copper ions (J=– 0.479 cm–1), in conformity with the bridge angle dependent magnetic behavior in azido bridged copper complexes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim