SYNTHESIS, CRYSTAL STRUCTURE, AND PROPERTIES OF COPPER(II) COMPLEXES WITH 1,4,7-TRIS(2-AMINOETHYL)-1,4,7-TRIAZACYCLONONANE

Three kinds of copper(II) complexes with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane (taetacn), [Cu(taetacn)](ClO4)(2) (1), [Cu(Htaetacn)](ClO4)(3) (2), and [Cu(Htaetacn)](BF4)(3) (3) were synthesized and characterized by elemental analyses, IR and UV-Vis spectroscopies. The spectral features are in harmony with an octahedral geometry for 1 and a square-pyramidal coordination for 2 and 3. The crystal structure of 2 was determined by the single-crystal X-ray diffraction method at 293 K. It crystallizes in the orthorhombic space group Pnma with a = 20.605(3) angstrom, b = 12.7944(18) angstrom, c = 9.8972(14) angstrom, V = 2609.2(6) angstrom(3), D-x = 1.582 g/cm(3), and Z = 4. The R1 [I > 2 sigma(I)] and wR2 (all data) values are 0.0723 and 0.2389, respectively, for all 3253 independent reflections. The compound consists of square-pyramidal copper(II) cation with protonated Htaetacn and tetrahedral ClO4- anions. The temperature dependence of magnetic susceptibilities obeyed the Curie-Weiss law with theta = -2.4, -5.2 and -7.2 K for 1, 2, and 3, respectively. Cyclic voltammetry of 2 in DMF showed two quasi-reversible reduction waves (E-pc = -0.98, E-pc = -0.92; E-pc = -1.30, E-pc = -1.22 V versus Fc/Fc(+)).