Synthesis, crystal structures and magnetic properties of mer-cyanideiron(III)-based 1D heterobimetallic cyanide-bridged chiral coordination polymers

Two pairs of cyanide-bridged Fe((III)) Mn((III))/Cu((II)) chiral enantiomer coordination polymers {[Mn(S, S/R, R-Salcy)( CH3OH)(2)]{[Mn(S,S/R,R-Salcy)][Fe(bbp)(CN)(3)]}}(2n) (1,2) (bbp = bis(2-benzimidazolyl) pyridine dianion) and {[Cu( S,S/R,R-Chxn)(2)](2)[Fe-2(tbbp)(CN)(6)]}(n) (3,4) (tbbp = tetra(3-benzimidazolyl)- 4,4'-bipyridine tetraanion) have been successfully prepared by employing mer-tricyanometallate [PPh4](2)[Fe(bbp)(CN)(3)] or the newly bimetallic mer-cyanideiron((III)) precursor K-4[Fe-2(tbbp)(CN)(6)] as building blocks and with chiral manganese((III))/copper((II)) compounds as assemble segments. The four complexes have been characterized by elemental analysis, IR spectroscopy, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra. Single X-ray diffraction reveals that complexes 1 and 2 possess a single anionic chain structure consisting of the asymmetric chiral {[Mn(S,S/R,R-Salcy)][Fe(bbp)(CN)(3)]}(2)(2) unit with free [Mn(S,S/R, R-Salcy)](+) as balanced cations. The cyanide-bridged Fe((III))- Cu((II)) complexes 3 and 4 can be structurally characterized as neutral ladder-like double chains composed of the alternating cyanide-bridged Fe-Cu units. Our investigation of magnetic susceptibilities reveals the antiferromagnetic coupling between the cyanide-bridged Fe((III)) and Mn((III))/Cu((II)) ions for complexes 1-4. These results have been further confirmed by theoretical simulation through numerical matrix diagonalization techniques using a Fortran program or a uniform chain model, leading to the coupling constants J = -7.36 cm(-1), D = -1.52 cm(-1) (1) and J = -4.35 cm(-1) (3), respectively.