A NEW 3-DIMENSIONAL, HYDROGEN-BONDED METAL-PTERIDINE COMPLEX - SYNTHESIS, CHARACTERIZATION AND CRYSTAL-STRUCTURE OF DIAQUA IS(1,3-DIMETHYLPTERIDINE-2,4(1H,3H)-DIONE-O-4,N-5) COPPER(II) NITRATE DIHYDRATE

In absolute methanol, copper(II) nitrate reacted with 1,3-dimethyl-(1H ,3H)-pteridin-2,4-dion (1,3-dimethyllumazine, DMLM) giving a complex w ith formula [Cu(DMLM)(2)(H2O)(2)] (NO3)(2) . 2H(2)O. This compound has been characterized by means of analytical techniques (elemental analy sis and TG), spectral methods (IR, UV-vis-NIR, EPR), magnetic measurem ents (77-290 K) and single-crystal X-ray diffraction. The copper(II) i on occupies an inversion centre and exhibits an elongated octahedral c oordination. The equatorial plane consists of two N(5) atoms of the pt eridine ligands and two oxygen atoms from water molecules, and the two axial sites are occupied by two O(4) atoms of the ligands. The non-co ordinated water molecules and nitrate anions, as well as the pteridine ligands are involved in a two-dimensional H-bond network, the metal-p teridine moieties being linked to the non-coordinated water molecules and nitrate anions of neighbouring molecules through the O(2) atom of the pteridine ligands. The molecules are packed in planes parallel to the b-axis, these planes being stacked at a mean distance of 3.297 Ang strom to each other. A three-dimensional arrangement is defined by the involvement of the coordinated water molecules in a hydrogen bond wit h one oxygen atom from the uncoordinated water and another oxygen from the nitrate group of the adjacent layers. Copyright (C) 1996 Elsevier Science Ltd