Intramolecular versus intermolecular exchange pathways in the binuclear complex [Cu_2(H_2tea)_2(4,4'-bipy)](ClO_4)_2·3H_2O (H_3tea=triethanolamine and 4,4'-bipy=4,4'-bipyridine)

摘要

The binuclear copper(II) complex of formula [Cu_2(H_2tea)_2(4,4'-bipy)](ClO_4)_2·3H_2O (1) (H_3tea = triethanolamine and 4,4'-bipy = 4,4'-bipyridine) has been isolated and characterized by X-ray diffraction. Its structure consists of dinuclear [Cu_2(H_2tea)_2(4,4'-bipy)]~(2+) cations, uncoordinated perchlorate anions and crystallizatiohn water molecules. Each copper atom exhibits a trigonal-bipyramidal environment with the three triethanolamine-oxygen atoms building the equatorial plane, and the triethanolamine-nitrogen and one of the 4,4'-bipy nitrogen atoms defining the three-fold axis. The 4,4'-bipy molecule acts as a bismonodentate bridging ligand, the copper-copper separation across it being 11.068(2)A, a value which is much longer that the shorter intermolecular one (4.821(1) A) through the pathway Cu(1)-O(2)…O(3A)~i-Cu(1)~i, with (i) = -x+1, -y+1, -z+1. Variable-temperature magnetic susceptibility measurements in the temperature range 1.9-290 K reveals the occurrence of a weak but singificant intermolecular antiferromagnetic interaction (J = -5.0 cm~(-1)) between the copper(II) ions belonging to two neighboring binuclear units (the Hamiltonian being H = -JS_1·S_2). The intramolecular copper-copper exchange interaction across the 4,4'-bipy bridge is assumed to be extremely weak (J approx -0.1 cm~(-1)).…