Structure and magnetism of heptanuclear complex self-assembled by the encapsulation of hexacyanoferrate with copper(II) cations of tridentate ligands

A new heptanuclear compound [{Cu(DPA)(H2O)CN}4{Cu(DPA)CN}2Fe][PF6]8·4H2O (1) (DPA = bis(pyridin-2-ylmethyl)amine ) was synthesized by the reaction of [Cu(DPA)]2+ unit and K3Fe(CN)6. The cyanometalate core is encapsulated by mononuclear copper moieties via each cyanide, and Fe(III) is reduced to Fe(II). 1 crystallizes in triclinic space group P-1 with a = 13.414(6) Å, b = 16.254(6) Å, c = 16.418(6) Å, α = 117.98(4)°, β = 94.49(3)°, γ = 107.61(4)° and Z = 1. Variable temperature magnetic measurements have demonstrated that very weak ferromagnetic interaction between the nearest paramagnetic CuII centers is exhibited. Thus weak ferromagnetic coupling might be transferred by –NC–Fe–CN– bridging units.