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)]Fe^III(bpb)(CN)₂]}₂·(ClO₄)₂·2H₂O·2CH₃CN (1), {CuPb(L¹)]₂Fe^II(CN)₆](H₂O)₂}·10H₂O (2), {Cu₂(L²)]Fe^III(bpb)(CN)₂]₂}·2H₂O·2CH₃OH (3) and {Cu₂(L²)]₃Fe^III(CN)₆]₂(H₂O)₂}·10H₂O (4) have been synthesized by treating KFe^III(bpb)(CN)₂] bpb^2?=1,2-bis(pyridine-2-carboxamido)benzenate] and K₃Fe^III(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 Fe^III(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 Fe^III(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.