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Two chemical routes were employed to prepare Si-Ti polymers, using acetylacetone (acacH) and acetic acid (HOAc) as modifying agents. The homogeneous and transparent sols were studied at different aging times. The characterization techniques were 29Si NMR, FTIR, UV-Vis and TGA. When HOAc was used, the oligomeric species in the first stages of polymerization were assigned by 29Si NMR. The Ti–O–Si bond vibration was detected by FTIR in the 950–960 cm–1region. UV-Vis spectroscopy showed bands of acac bonded to Ti at 300 nm and 365 nm, and OAc–bonded to Ti was found at 320 nm. The TGA study allowed the establishment of the xerogel formulas.

The crystal and molecular structure of the title compound, [Zn(II)]2(DAG)2, were determined and the results compared with those obtained for similar N-protected amino acids. In the crystalline state, 16-membered macrocyclic dimers are held together by hydrogen bridges in a triclinic lattice. The Zn(II) ions are pentacoordinated to oxygens in a slightly distorted trigonal bipyramid. The trigonal plane is formed by two carboxylic oxygens and an oxygen atom from a water molecule, whereas the apical positions are occupied by two other oxygens from the remaining coordinated water molecules. The ligands form bridges between cations providing the cyclic dimers, whereas similar but shorter systems form pseudo polymer sheets.

Crystal and molecular structures by X-ray diffraction analysis of Co, Cu and Zn complexes of 2,2-diacetoamidopropionic acid are reported. The results show that an uncommon bond from metal ion to a carbonyl-O-of-peptide atom is formed. The structures are isomorphic (Monoclinic,P21/c, with two formula units in the cell). The metal ion lies on a center of symmetry and it is six-oxygen coordinated in an octahedral-type configuration by pairs of water molecules, carboxylic (monodentate) groups and two carbonyl-O-of-peptide atoms. Ligand molecules bridge metal ions, so that the structure consists of a two-dimensional (sheet-type) polymer. Sheets are held together by a hydrogen-bond network making efficient use of the solvent water molecules.

Spectroscopic analysis of eight copper(II) complexes of Schiff bases derived from taurine and eight different salicylaldehydes and naphthaldehydes are reported. X-ray structural analysis of the copper(II) complex of the 5-NO2-sali-cylaldehyde imine of taurine (5-NO2-salicylaldimine ethylene sulfonic acid) as the tetran-butylammonium salt [Cu(C9H8N2O6S)2]2-2[(C4H9)4N]+ (CUTAU-TBA) has been carried out. The space group isP¯1, witha=8.761(4),b=10.410(3),c=16.528(4) Å,a=77.85(3),ß=86.53(4), ?=79.15(3)°, andZ=1. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.068 for 2807 observed reflections. The CUTAU cation is centrosymmetric, with the Cu atom sitting on a crystal-lographic centre of symmetry. The copper atom has a square-planar environment, coordinated by the potentially tridentate Schiff base only through the imino nitrogen and the phenolate oxygen with the deprotonated sulfonic group directed away from the coordination sphere of the Cu(II).

Two chemical routes were employed to prepare Si−Ti polymers, using acetylacetone (acacH) and acetic acid (HOAc) as modifying agents. The homogeneous and transparent sols were studied at different aging times. The characterization techniques were29Si NMR, FTIR, UV-Vis and TGA. When HOAc was used, the oligomeric species in the first stages of polymerization were assigned by29Si NMR. The Ti−O−Si bond vibration was detected by FTIR in the 950–960 cm−1region. UV-Vis spectroscopy showed bands of acac bonded to Ti at 300 nm and 365 nm, and OAc−bonded to Ti was found at 320 nm. The TGA study allowed the establishment of the xerogel formulas.