STRUCTURAL CHARACTERIZATION OF CLOSELY-RELATED MONONUCLEAR CU-II COMPLEXES OF 5-NITROSOOXIME PYRIMIDINES - A COMBINED X-RAY AND EPR STUDY

In reactions of trans-bis(oximato) complexes [(L2Cu)-L-1(H2O)(2)] and [(L2Cu)-L-2(H2O)(2)] ((HL)-L-1 = 6-amino-1,3-dimethyl-5-nitrosouracil and (HL)-L-2 = 6-methylamino-1,3-dimethyl-5-nitrosouracil) with [Cu(bi py)(2)](2+), one of the pyrimidine ligands was replaced by bipy (bipy= 2,2'-bipyridine) affording mononuclear mixed-ligand complexes of the t ype [LCu(bipy)X] (X is H2O, EtOH or Cl-). Under the reaction condition s, the 6-methylamino group of (HL)-L-2 undergoes hydrolysis leading to violuric acid (5-nitroso-2,4,6-trioxopyrimidine; (HL)-L-3). Three clo sely related mononuclear copper(II) complexes, [Cu(L-1)(bipy)(H2O)]ClO 4 . H2O (1), u(L-3)(bipy)(EtOH)][Cu(L-3)(ClO4)(bipy)(EtOH)]ClO4 (2) an d [Cu(L-3)Cl(bipy)]. 0.5H(2)O (3), have been prepared, their crystal s tructures were determined and an EPR study was carried out.