Synthesis and X-ray Crystal Structure Determination of the First Copper(II) Complexes of Tetraazamacrocycle—Glyoxal Condensates.

Novel Cu[sup II] complexes CuLC[sub I]2 (L = 1-4) have been synthesized containing the metal bound to a well-known type of tetracyclic bisaminal formed from the condensation of glyoxal and tetraazamacrocycles (1 = cyclam-glyoxal condensate, 2 = [13]aneN4-glyoxat condensate, 3 = cyclen-glyoxal condensate, 4 = isocyclam-glyoxal condensate). The four-coordinate complexes were characterized by X-ray crystallography, electronic spectroscopy, solid-state magnetic moments, and electron spin resonance spectroscopy. The tetracyclic bisaminals, although having four potential donor atoms, are bound in a cis-bidentate fashion to Cu[sup II] with two additional cis-chloride donors. The ligands take up folded conformations, and with the exception of ligand 4, only nonadjacent nitrogen atoms coordinate. As expected, ligand 2 in Cu(2)Cl[sub 2] has a folded structure similar to those of the previously characterized 1 and 3. The conformation of 4 in the complex Cu(4)CI[sub 2] differs from 1-3 in that three nitrogens direct their lone pairs to one side of the folded tetracycle, with adjacent nitrogen atoms coordinated to Cu[sup II]. This difference is probably caused by the presence of the more flexible seven-membered ring rather than the five- to six-membered rings in 1-3. Air oxidation of Cu[sup I] in the presence of 1 or 3 results in bis(µ-hydroxo) dimers as characterized by X-ray crystal structures, suggesting dioxygen binding, followed by O-O bond splitting to give the Cu[sub 2]O[sub 2] diamond core. [ABSTRACT FROM AUTHOR]