TRANSITION-METAL COMPLEXES WITH MONODEPROTONATED ISOOROTIC AND 2-THIOISOOROTIC ACIDS - CRYSTAL-STRUCTURE, SPECTRAL AND MAGNETIC STUDY, AND ANTIMICROBIAL ACTIVITY

The reaction, in ethanol or water medium, of Mn(II), Fe(II), Co(II), N i(II), Cu(II), Zn(II), Pd(II), and Pt(II) ions with isoorotic and 2-th ioisoorotic acids (H3L) has allowed the isolation of complexes with th e general formula MII(H2L)2.2H2O. These were characterized by means of elemental analysis, spectral techniques (UV-Vis-NIR, IR, EPR, C-13 an d H-1 NMR), magnetic moments, and conductivity measurements. The molar conductivities in dimethylsulphoxide indicate the non-ionic nature of isolated compounds. The most common coordination mode of uracil monoa nions seems to be a O4-OCO bidentate scheme which leads to a six-membe red chelate ring. Complexes of first row transition ions display an oc tahedral structure, whereas for Pd(II) and Pt(II) compounds a square-p lanar structure is suggested. The MO6 octahedral structure has been co rroborated from the single crystal x-ray study of bis;isoorotato-diaqu azinc(II). This compound is monoclinic, space group P2(1)/c, with a = 5.067(5) angstrom, b = 15.072(4) angstrom, c = 11.239(8) angstrom, bet a = 125.80(9)degrees, V = 696(1) angstrom3, and Z = 2. The structure w as solved by means of the heavy atom method from the zinc special posi tion. Full matrix refinements based on F(o) were performed to R = 0.06 0 for 1884 data. The structure consists of discrete [Zn(H2CU)2(H2O)2] units in which the Zn(II) ion is octahedrally MO6 coordinated by two b identate O4-OCO isoorotato ligands (M-O, 2.033 and 2.039 angstrom) and two water molecules occupying the axial positions (M-O(w), 2.170 angs trom). Likewise, a previous study of biological activity of these comp lexes against several bacteria and yeasts was carried out. In general, complexes with the 2-thioisoorotato ligand possess greater antimicrob ial activity than those with the isoorotate ligand, specially in the c ase of cobalt(II) complexes.