A tetranuclear copper(II) complex: crystal structure, assembly, EPR, electrochemistry and magnetism

A tetranuclear copper(II) complex, [Cu2L]2(ClO4)2 · 4H2O (1), where H3L = N,N′-bis(4-(3′-formyl-5′-chlorosalicyclidene)iminoethyl)-4-chloro-2,6-bimethyliminophenol, has been synthesized and structurally characterized by ES-MS, IR and X-ray crystallography. The complex is a dimer of two dinuclear copper(II) acylic enantiomorph subunits ([Cu2L]ClO4 · 2H2O), held together by π–π, coordination and hydrogen bond interactions. The Cu–Cu separation in each subunit, bridged by one phenoxide, is 3.228 A, and the shortest distance of Cu–Cu between the two subunits is 3.252 A. There are two crystallographically unique copper(II) environments, one (Cu1) is square-based pyramidal with O3N2 donor set, another (Cu2) square planar with O2N2 donor set. The cyclic voltammogram of the complex shows that it undergoes two stepwise reduction processes, E pc = −0.707 and −0.850 V, respectively. Magnetic measurements in the 2–300 K range indicate strong antiferromagnetic interactions between Cu(II) ions in each subunit with the ...