Ferromagnetic ordering and slow magnetic relaxation observed in a triple-bridged azido-Cu( ii ) chain compound with mixed carboxylate/ethanol linkers

Solvothermal reactions of copper salts with NaN 3 and carboxylate led to the formation of a new magnetic compound, [Cu(3-fba)(N 3 )(C 2 H 5 OH)] n (3-fba = 3-fluorobenzoic acid) ( 1 ). Single crystal X-ray analysis indicates that only one crystallographically independent Cu( ii ) ion in the asymmetric unit of 1 displays stretched octahedral geometry in which two azido N atoms and two carboxylic O atoms locate in the equatorial square, while two ethanol O atoms occupy the apical positions, yielding a 1D Cu( ii ) chain with an alternating triple-bridge of EO-azido, syn , syn -carboxylate, and μ2-ethanol. Magnetic measurements reveal that the resulting compound is composed of well-isolated 1D Cu( ii ) chains with strong intrachain ferromagnetic interactions. The dominant ferromagnetic couplings between neighbouring Cu( ii ) ions occurring in the compound ( J = 59.74 cm −1 ) are due to the counter-complementarity of the multiple superexchange pathways, contributing to inspiring plots of ferromagnetic order ( T c = 11.0 K) and slow magnetic relaxation that are rarely observed in most reported azido-Cu( ii ) architectures. Heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in 1 . Moreover, density functional theory (DFT) calculations (using different methods and basis sets) have been performed on the compound to obtain the theoretical interpretation of the magnetic behaviors.