Syntheses, Crystal Structures and Magnetic Properties of a Series of Cyanide-Bridged Trinuclear Cr(III)-Cu(II)-Cr(III) Complexes Based on Dicyanidechromate(III) Building Blocks

Three cyanide-bridged trinuclear chromate(III)-copper(II)-chromate(III) complexes [Cu(cyclam)][Cr(bpmb)(CN)(2)](2)center dot 4H(2)O (1) (cyclam=1,4,8,11-tetraazacyclotetradecane and bpmb(2-)=1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate), [Cu(cyclam)][Cr(bpdmb)(CN)(2)](2) (2) (bpdmb(2-)=1,2-bis(pyridine-2-carboxamido)-4,5-dimethylbenzenate) and [Cu(cyclam)][Cr(bpClb)(CN)(2)](2)center dot 4H(2)O (3) (bpClb(2-)=1,2-bis (pyridine-2-carboxamido)-4-chlorobenzenate), have been synthesized by the reaction of [Cu(cyclam)](ClO4)(2) with a series of dicyanidechromate(III) building blocks. Single crystal X-ray diffraction analyses show that complexes 1 similar to 3 have similar neutral trinuclear structures with Cr(III)-CN-Cu(II)-NC-Cr(III) linkages. Magnetic investigations indicate that complexes 1 similar to 3 exhibit weak ferromagnetic coupling between Cr(III) and Cu(II) centers through the cyanide bridge with J(CrCu)=1.53(2) cm(-1) for 1, 0.45(1) cm(-1) for 2 and 0.73(2) cm(-1) for 3 based on the spin exchange Hamiltonian (H) over cap=-2J(CrCu)(S) over cap (Cu)((S) over cap (Cr1)+(S) over cap (Cr2)). CCDC: 1444524, 1; 1444525, 2; 1444526, 3.