A series of chiral cyanide-bridged Fe–Cu complexes: Synthesis, crystal structures and magnetic properties

Abstract

Four trans-dicyanideiron(III)-containing building blocks and two chiral copper(II) compounds have been employed to assemble cyanide-bridged heterometallic complexes, resulting in six chiral cyanide-bridged Fe(III)–Cu(II) complexes, {[Cu(S,S/R,R-Chxn)2Fe(bpb)(CN)2]ClO4}2·xCH3OH·yH2O (1, 2), {[Cu(S,S/R/R-Chxn)2Fe(bpClb)(CN)2][Fe(bpClb)(CN)2]}·xCH3OH·yH2O (3, 4), {[Cu(R/R-Chxn)2Fe(bpdmb)(CN)2][Fe(bpdmb)(CN)2]}·4CH3OH (5) and {[Cu(R/R-Chxn)2][Fe(bpdBrb)(CN)2]2}·4CH3OH (6) (bpb2−=1,2-bis(pyridine-2-carboxamido)-4,5-enzenate, bpClb2−=1,2-bis(pyridine-2-carboxamido)-4-chlorobenzenate, bpdmb2−=1,2-bis(pyridine-2-carboxamido)-4,5-dimethylbenzenate, bpdBrb2−=1,2-bis(pyridine-2-carboxamido)-4,5-dibromobenzenate, (S,S/R,R)-Chxn=(S,S/R,R)-1,2-diaminocyclohexane). The whole serials of complexes have been characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis shows that complexes 1–5 belong to cyanide-bridged cationic binuclear structure type with ClO4− or the anionic cyanide building block as balance anion for complexes 1, 2 and 3–5, respectively, while complex 6 can be structurally characterized as neutral sandwich-like trinuclear Fe2Cu entity. Investigation of the magnetic properties of complexes 1–6 reveals the weak antiferromagnetic coupling in complexes 1, 2 and the weak ferromagnetic interaction in complexes 3–6 between the neighboring Fe(III) and Cu(II) ions through the bridging cyanide group.