MIXED COMPLEXES OF 6-AMINOURACIL DERIVATIVES - SYNTHESIS, SPECTRAL PROPERTIES AND CRYSTAL-STRUCTURE OF 6-AMINO-1,3-DIMETHYL-5-NITROSOURACILATO -5,N-6)-2,2'-BIPYRIDINE(N,N')ETHANOL(O)-COPPER(II) NITRATE

In absolute ethanol medium, copper(II) nitrate reacts with 6-amino-1,3 -dimethyl-5-nitrosouracil (HDANU) and 2,2'-bipyridine to give a mixed complex with the formula [Cu(DANU)(bipy)(EtOH)](NO3). This compound ha s been characterized by means of analytical techniques (elemental anal ysis and TG), spectral methods (IR, UV-VIS-NIR, EPR), magnetic measure ments (77-290 K) and single-crystal X-ray diffraction. The structure c onsists of monomeric CuN4O units in which the copper ion displays a 41 square-pyramidal coordination. The base of the polyhedron is occupie d by four nitrogen atoms (Cu-N ca 2 Angstrom, two from bipy and the ot her two from 5-nitroso and 6-amino groups of the uracil derivative in the N6-mono-deprotonated form, leaving two five-membered chelate rings . In the apical position of the pyramid, an O-coordinated ethanol mole cule with a long Cu-O distance (2.248 Angstrom) is located, the metall ic centre being 0.144 Angstrom above the base of the polyhedron. The n itrate group is out of the coordination sphere, stabilizing the comple x by hydrogen bonds formed between the hydrogen atom attached to the e thanolic oxygen and an oxygen atom from the nitrate group. The molecul es are stacked as planes perpendicular to the a axis. Copyright (C) 19 96 Elsevier Science Ltd