In each of N-(6-amino-3, 4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)valine, C(10)H(15)N(5)O(4) (3) (orthorhombic, P2(1)2(1)2(1)), N-(6-amino-3, 4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)serine monohydrate, C(8)H(11)N(5)O(5).H(2)O (4) (orthorhombic, P2(1)2(1)2(1)), and N-(6-amino-3, 4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)threonine, C(9)H(13)N(5)O(5)(5) (monoclinic, P2(1)), the C-nitroso fragments exhibit almost equal C-N and N-O bond lengths: the C-N range is 1. 315 (3)-1.329 (3) A and the N-O range is 1.293 (3)-1.326 (3) A. In each compound there are also very short intermolecular O-H.O hydrogen bonds, in which carboxyl groups act as hydrogen-bond donors to the nitrosyl O atoms: the O.O distances range from 2.440 (2) to 2. 504 (4) A and the O-H.O angles lie between 161 and 163 degrees. An interpretation of the relationship between the unusual intramolecular bond lengths and the very short intermolecular hydrogen bonds has been developed based on database analysis and computational modelling. In each of (3)-(5) there is an extensive network of intermolecular hydrogen bonds, generating three-dimensional frameworks in (3) and (5), and two-dimensional sheets in (4).

Binding of anions of great environmental concern such as SO(4)(2-), PO(4)(3-), AsO(4)(3-), HgCl(4)(2-), and CrO(4)(2-) by the protonated forms of a tren-like (tren = tris(2-aminoethyl)amine) ligand (HL) functionalized with a pyrimidine residue was studied by means of potentiometric measurements and isothermal titration calorimetry (ITC) affording log K, ΔH°, and TΔS° values for the formation of the relevant complexes. The complexes show high to very high stability due to the particular topology and electronic properties of the ligand which is able to use two separated coordination environments to host the anions, the protonated tren site where electrostatic and hydrogen bond interactions are operating, and the pyrimidine ring which may act via anion-π interaction. A contribution of -8.9 ± 0.4 kJ/mol for pyrimidine-anion interaction in water was derived for SO(4)(2-) binding. The crystal structures of [H(3)L(HgCl(4))]·H(2)O (1), [H(3)L(HgBr(4))]·H(2)O (2), and that previously reported for [H(3)L(CdI(4))], clearly show these binding features in the solid state. A hybrid AC-HL material obtained by adsorption of HL on commercial activated carbon (AC) was used to study the removal of these anions from water. AC-HL shows enhanced adsorption capacity toward all the anions studied with respect to AC. This behavior is ascribed to the stronger interaction of anions with the HL function of AC-HL than with the Cπ-H(3)O(+) sites of the unfunctionalized AC.

Interaction of Pd(II), Pt(II), Ag(I), and Au(III) with 4,6-diamino-2-thiopyrimidine (DATP) and 4,6-diamino-2-methyl-thiopyrimidine (DAMTP) in aqueous medium resulted in the formation of new complexes which have been characterized by elemental analysis, ir, 1H-nmr spectroscopic techniques, magnetic susceptibility measurements in the solid state, and conductivity measurements in DMF solution. The ir and 1H-nmr spectra were consistent with coordination involving the non-protonated ring nitrogen atom, the exocyclic sulphur atom, or N,S-chelation.

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The syntheses, specific optical rotations, spectral features (1H-NMR, UV-visible and IR spectroscopy) and thermal characterization of seven 4-(O-acetyl)-glycopyranosylamino-5-nitrosopyrimidine derivatives are reported, With IR spectroscopy, the starting of the pyrolytic decomposition mechanism of the compounds was established.In view of the biological roles of pyrimidines, their nucleosides and nucleotides [1][2][3][4][5] and some of their metal complexes [3, 6], we have focused our interest on the study of pyrimidine derivatives and some of their nucleoside and nucleotide analogues.We recently carried out spectral and thermal studies on the following compounds: a) A series of seven 4-glycosylamino-6-oxopyrimidine derivatives [7]. b) The corresponding 4-glycopyranosylamino-5-nitroso-6-oxopyrimidine derivatives [8]. c) A series of seven 4-(O-acetyl)-glycopyranosylamino-6-oxopyrimidine homologues of the compounds in section a) [9].As a follow-up in the present paper we report studies on the seven 4-(O-acetyl)-glycopyranosylamino-5-nitroso-6-oxopyrimidine homologues of the section c) compounds, whose general structures are shown in Scheme I. 0 R \ ~l-'~i.r,,-N~o