Three chiral cyanide-bridged Cr–Cu complexes: Synthesis, crystal structures and magnetic properties

Abstract

Two trans-dicyanidochromium(III)-containing building blocks and one chiral copper(II) compound have been employed to assemble cyanide-bridged heterometallic complexes, resulting in three chiral cyanide-bridged Cr(III)–Cu(II) complexes, {[Cu(L¹)₂Cr(L³)(CN)₂]ClO₄}₂·CH₃OH·H₂O (1a, L¹ = (S,S)-1,2-diaminocyclohexane, L³ = 1,2-bis(pyridine-2-carboxamido)benzenate), {[Cu(L²)₂Cr(L²)(CN)₂]ClO₄}₂·CH₃OH·H₂O (1b, L² = (R,R)-1,2-diaminocyclohexane) {[Cu(L³)₂Cr(L⁴)(CN)₂][Cr(L⁴)(CN)₂]}·CH₃OH·2H₂O (2), (L⁴ = 1,2-bis(pyridine-2-carboxamido)-4-chlorobenzenate). All the three complexes have been characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single-crystal X-ray diffraction analysis shows that the two enantiomeric complexes 1a, 1b and the complex 2 belong to cyanide-bridged cationic binuclear structure type with ClO₄^– or the anionic cyanide building block as balance anion for complexes 1a, 1b or 2, respectively. Investigation of the magnetic properties of the complexes 1a and 2 reveals the weak ferromagnetic coupling between the neighboring Cr(III) and Cu(II) ions through the bridging cyanide group.