Synthesis and Characterization of a Novel Gd(III)-Cu(II) Dinuclear Adduct

Two novel Gd(III)-Cu(II) dinuclear complexes have been prepared by the acid-base reaction between Gd(hfa)(3) and Cu(2,2-oxomac) (1, Cu(2,2-oxomac)Gd(hfa)(3)) and between Gd(hfa)(3) and Cu(3,2-oxomac) (2, Cu(3,2-oxomac)Gd(hfa)(3)). These complexes have been characterized by elemental analysis and infrared spectroscopy. The structure of 1 has been determined by X-ray diffraction. The copper atom is square pyramidal, bound to the four planar nitrogen atoms of the macrocycle and weakly bound to the oxygen atom of a dimethylformamide (dmf) molecule. The gadolinium atom is at the center of a tricapped trigonal prism. The nine-coordinate gadolinium atom is bound to six oxygen atoms of three hfa ligands, the two oxamide oxygen atoms of the copper macrocycle, and one oxygen atom of a second coordinated dmf molecule. Unsymmetric binding of the copper macrocycle to gadolinium leads to a distortion in the bridging atoms not observed in reactions of the copper macrocycles with transition metal hfa's. GRAPHICAL ABSTRACT: The reaction of Cu(2,2-oxomac) with Gd(hfa)(3) yields a Gd(III)-Cu(II) dinuclear complex with an oxamide bridge between copper(II) and gadolinium(III). The gadolinium atom adopts a tricapped trigonal prismatic geometry.