SYNTHESIS, CHARACTERIZATION, SPECTROSCOPY, AND MAGNETISM OF DINUCLEAR AZIDO-BRIDGED AND ALKOXO-BRIDGED COPPER(II) COMPLEXES OF BIS(2-BENZIMIDAZOLYL) ALKANES - X-RAY STRUCTURES OF [CU-2(TBZ)(2)(CH3O)(2)](CLO4)(2)(CH3OH)(2), [CU-2(TBZ)(2)(NO3)(CH3O)(2)](NO3)(CH3OH)(2), AND [CU(TBZ)(N-3)(2)](2)(CH3OH)(2) (TBZ=BIS(2-BENZIMIDAZOLYL)PROPANE)

A group of new compounds with the general formula Cu(L)(sol(-))(A(-))(Hsol), where A = ClO4-, CF3SO3-, BF4(-), and NO3-, L = bis(2-benzimidazolyl)propane (abbreviated as tbz) and bis(2-benzimidazolyl)butane (abbreviated as qbz), and Hsol = methanol and ethanol, and with the formula [Cu(tbz)(N-3(-))(Hsol)] has been prepared and characterized structurally, magnetically, and spectroscopically. Three representative compounds [CU2(tbZ)(2)(CH3O)(2)](ClO4)(2)(CH3OH)(2) (1), [CU2(tbz)(2)(NO3)(CH3O)(2)](NO3)(CH3OH)(2) (5), and [Cu(tbz)(N-3)(2)](2)(CH3 OH)(2) (13) were characterized structurally with X-ray diffraction. Crystal data for 1: monoclinic, space group P2(1)/c with a = 9.6863(10) Angstrom, b = 12.9445(10) Angstrom, c = 19.394(2) Angstrom, beta = 113.259(10)degrees, and Z = 2. Crystal data for 5: monoclinic, space group P2(1) with a = 9.5497(6) Angstrom, b = 12.5073(7) Angstrom, c = 17.5920(12) Angstrom, beta = 90.996(6)degrees, and Z = 2. Crystal data for 13: orthorhombic, space group Pbca (No. 61) with a = 11.3325(7) Angstrom, b = 18.7096(16) Angstrom, c = 19.2011(16) Angstrom, and Z = 4. The structure refinement converged to wR2 = 0.1381, R1 = 0.0534 for 1, wR2 = 0.0674, R1 = 0.0271 for 5, and wR2 = 0.1119, R1 = 0.0701 for 5. The structures 1 and 5 consist of dinuclear units with bridging methoxo groups and one ligand linked to each copper via the N, providing square planar CuN2O2 chromophores. Structure 5 consists of a dinuclear unit in which one of the copper atoms is linked to a nitrate O, to yield a unit with two different copper environments, one square planar and the other square pyramidal. Structure 13 consists also of dinuclear units with the two copper atoms bridged by mu-(1,1)azido groups. Furthermore each copper is surrounded by two nitrogens of the ligand and a nitrogen of a nonbridging end-on mu-(1,1)-azido moiety resulting in a distorted square pyramidal geometry. The Cu-Cu distances (Angstrom) within the dinuclear units are as follows: 1, 2.9827(6); 5, 3.0072(4); 13, 3.2422(9). The Cu-O-Cu bridging angles (deg) are as follows: 1, 102.89(14); 5, 103.97(9), 103.06(9)degrees. The Cu-N-Cu bridging angle for 13 is 104.66(17)degrees. Far-infrared spectroscopy shows bands which are characteristic for the bridging CU2O2N4 chromophore; Cu-O vibrations are found at about 457 and 330 cm(-1) for the ethoxo-bridged compounds and at about 390 and 232 cm(-1) for the methoxo-bridged compounds. The magnetic susceptibility measurements of the alkoxo-bridged compounds display a diamagnetic behavior below room temperature with an estimated exchange parameter 2J of < -600 cm(-1). These dinuclear species are EPR silent, and only a weak signal of monomeric impurities is observed. The mu-(1,1)-azido-bridged dimer shows a ferromagnetic behavior with a calculated J value of + 23 cm(-)1 and a weak, very broad isotropic EPR signal at g = 2.14.