Tetranuclear copper azido complex of 4,5-diazafluoren-9-one

Abstract

A tetranuclear CuII complex, Cu4(dafone) 4(N3)8 (1, dafone = 4,5-diazafluoren-9-one) is described. The propensity of dafone to chelate through one short and one long bond is readily accommodated by the tendency of CuII to undergo Jahn-Teller elongation in its six-coordinate complexes. The crystal structure of 1 consists of two distortion isomers of the tetranuclear complex molecule. In each isomer, there are four μ1,1-azido bridges and two μ1,1,1-azido bridges as well as two terminally coordinated azide ions. The isomers, both of which are centrosymmetric, differ in the way the Jahn-Teller axes of the different CuII sites are aligned. Magnetic susceptibility measurements show an overall ferromagnetic interaction, which could be fitted with a two parameter model (J1 = 22.8 cm -1, J3 = -8.2 cm-1). The magnetic interaction was modelled by using DFT calculations, which showed that the two isomers are magnetically quite different; one is a ferromagnetically coupled tetramer, and the other may be viewed as two ferromagnetic dimers. The X-band EPR spectra are in broad agreement with this model. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.