Cyanide-bridged complexes based on dinuclear Cu(II)-M(II) [M = Pb and Cu] building blocks: Synthesis, crystal structures and magnetic properties

Four cyanide-bridged heterometallic complexes {[CuPb(L1)][FeIII(bpb)(CN)2]}2·(ClO4)2·2H2O·2CH3CN (1), {[CuPb(L1)]2[FeII(CN)6](H2O)2}·10H2O (2), {[Cu2(L2)][FeIII(bpb)(CN)2]2}·2H2O·2CH3OH (3) and {[Cu2(L2)]3[FeIII(CN)6]2(H2O)2}·10H2O (4) have been synthesized by treating K[FeIII(bpb)(CN)2] [bpb2−=1,2-bis(pyridine-2-carboxamido)benzenate] and K3[FeIII(CN)]6 with dinuclear compartmental macrocyclic Schiff-base complexes [CuPb(L1)]·(ClO4)2 or [Cu2(L2)]·(ClO4)2, in which H2L1 was derived from 2,6-diformyl-4-methyl-phenol, ethylenediamine, and diethylenetriamine in the molar ratio of 2:1:1 and H2L2 from 2,6-diformyl-4-methyl-phenol and propylenediamine in the molar ratio of 1:1. Single crystal X-ray diffraction analysis reveals that compound 1 displays a cyclic hexanuclear heterotrimetallic molecular structure with alternating [FeIII(bpb)(CN)2]− and [CuPb(L1)]2+ units. Complex 2 is of a neutral dumb-bell-type pentanuclear molecular configuration consisting of one [Fe(CN)6]4− anion sandwiched in two [CuPu(L1)]2+ cations, and the pentanuclear moieties are further connected by the hydrogen bonding to give a 2D supramolecular framework. Heterobimetallic complex 3 is a tetranuclear molecule composed of a centrosymmetric [Cu2(L2)]2+ segment and two terminal cyanide-containing blocks [FeIII(bpb)(CN)2]−. Octanuclear compound 4 is built from two [Fe(CN)6]3− anions sandwiched in the three [Cu2L2]2+ cations. Investigation of their magnetic properties reveals the overall antiferromagnetic behavior in the series of complexes except 2.