Polyazamacrocyclic Copper-Based Cyanide-Bridged Bimetallic Sandwich-Like Complexes: Synthesis, Crystal Structure, and Magnetic Properties

Abstract

By employing three dicyanometallates as building blocks (K[Fe(bpb)(CN)₂], K[Cr(bpb)(CN)₂] (bpb²⁻ = 1,2-bis(pyridine-2-carboxamido)benzenate), K[Fe(bpmb)(CN)₂] (bpmb²⁻ = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate)) and one 14-membered polyazamacrocycle Cu(II) compound as an assembling segment, three cyanide-bridged complexes {[Cu(6,13-dihydroxylcyclam)][Fe(bpb)(CN)₂]₂}·2CH₃OH·H₂O (1), {[Cu(6,13-dihydroxylcyclam][Cr(bpb)(CN)₂]₂}·2CH₃OH (2), and {[Cu(6,13-dihydroxylcyclam)][Fe(bpmb) (CN)₂]₂}·2H₂O (3) (6,13-dihydroxylcyclam = 6,13-dihydroxyl-1,4,8,11-tetraazacyclotetradecane) are successfully prepared and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. The single X-ray diffraction analysis shows that all the three complexes containing the M₂Cu (M = Fe, Cr) core have neutral trinuclear sandwich-like structures in which the central Cu(II) ion is face-to-face coordinated to two Fe or Cr ions of the cyanide precursors functioning as a monodentate ligand through one of its two cyanide groups. The investigation of their magnetic properties reveals the antiferromagneitic and ferromagnetic coupling between the cyanide-bridged Fe(III)-Cu(II) and Cr(III)-Cu(II) ions, respectively.