Discrepancy between the structural and magnetic dimensionality in the (μ-terephthalato)bis[(diethylenetriamine)Cu(II)]perchlorate complex

Abstract The crystal structure of [(dien)Cu(μ-tp)Cu(dien)](ClO 4 ) 2 , where tp is the dianion of terephthalic acid and dien is diethylenetriamine, has been determined by direct X-ray methods. The complex crystallizes in the monoclinic space group P 2 1 / c with a =8.911(6), b =8.002(5), c =19.61(2) A, β=90.2(1)°, Z =2 and V =1398.3 A 3 . Solution of the structure of a twin crystal of the compound led to final values of R =0.069 and R w =0.079 with 174 least-squares parameters for 2263 unique reflections with I >2σ( I ). The compound is a perchlorate salt of a dicationic centrosymmetric binuclear copper(II) complex, [(dien)Cu(μ-tp)Cu(dien)] 2+ — the crystallographic inversion center being located at the center of the benzene ring of the tp bridging ligand. Within the binuclear unit the copper(II) ions are bridged by tp ligand in a bis-unidentate fashion, the coordination geometry about each Cu(II) ion is distorted octahedral; the CuCu distance in each binuclear entity is 11.006(5) A. Moreover, two Cu(II) centers of two different dimeric units are bridged by an oxygen atom of a carboxylate group. Thus, chains along the b direction and layers parallel to (100) are formed. The variable-temperature (4.2–290 K) magnetic susceptibility data of the complex, interpreted with a dimer law with a molecular field approximation, yielded to J , g and zJ′ values of −3.66 cm −1 2.07 and −0.03 cm −1 , respectively. An orbital interpretation of the coupling is proposed.