Direct synthesis, crystal structure, high-Field EPR, and magnetic studies on an octanuclear heterometallic Cu(II)/Cd complex of triethanolamine.

The reaction of zerovalent copper with cadmium iodide and triethanolamine (H(3)L) in dimethylformamide (dmf) carried out under open-air conditions afforded a novel heterometallic complex Cu(3)(HL)(3)CdI(2) x 4 dmf. The crystal lattice consists of an octanuclear molecule Cu(3)(HL)(3)CdI(2), which has an inversion center at the midpoint of the central Cu(2)O(2) unit, and of two non-coordinating dmf molecules. Eight metal atoms linked by alkoxide arms of triethanolamine ligands form a zigzag Cd-Cu1-Cu2-Cu3-Cu4-Cu5-Cu6-Cd chain with the separations between bridged Cu atoms in the range 2.935(2)-3.403(2) A. The complex is further stabilized by intramolecular O-H...O hydrogen bonds. High-field electron paramagnetic resonance (EPR) spectra of the S = 1 spin state with D((S=1)) = -0.843 cm(-1), E((S=1)) = -0.081 cm(-1) were observed. Fitting the magnetic susceptibility temperature dependence by using the exchange Hamiltonian H(HDVV) = J(1)(S(1)S(2) + S(5)S(6)) + J(2)(S(2)S(3) + S(4)S(5) )+ J(3)S(3)S(4), to which terms expressing the zero-field splitting and Zeeman splitting of the ground S = 1 state were added, resulted in J(1) = 68, J(2) = 19, J(3) = -57 cm(-1). "Broken symmetry" DFT calculations correctly predicted the triplet ground state of the hexa-copper system.