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A convenient method for the preparation of transparent, photocatalytic titania thin films is described. The films do not require annealing or thermal processing to develop photoactivity, thus can be applied to many thermally-sensitive substrates. Oxalic acid is used in place of the usual mineral acids to peptize the precipitated hydrous titania formed from the hydrolysis of titanium iso- propoxide. This leaves no inorganic residues in the film resulting in a higher quality film. The mineral phase and the photocatalytic activity produced are strongly influenced by the ratio of oxalic acid:titanium iso- propoxide employed. The peptization is carried out at 65 °C with vigorous stirring for 1 h in water containing 15% v/v ethanol, followed by a hydrothermal step at 95 °C. High oxalic acid:Ti molar ratios (0.5:1) result in rutile free sols, while lower ratios (0.25:1) result in anatase, rutile, brookite and TiO 2 (B) in varying proportions. The films were exposed to low level UV light to cure, and photodecompose the residual organic components in the film. The photodecomposition of residual oxalic acid in the cast films were monitored using infrared spectroscopy. Photo-activity of the UV-cured films was compared by monitoring the decoloration of methylene blue stains on the film, by UV–Vis spectroscopy. Transmission was greater than 99% across the visible light region (400–800 nm).

Aqueous titanium citrate solutions were prepared from the reaction of citric acid with titanium 2-propoxide in a range of molar ratios. Solutions containing two or fewer citrates per titanium resulted in the slow crystallization of an insoluble titanium oxo-citrate complex. Single-crystal X-ray analysis identified the species as Ti(8)O(10)(citrate)(4)(H(2)O)(12).14H(2)O.3HOPr(i)(), crystallized in the tetragonal space group I4(1)/a, with a = 30.775(7) A, c = 14.528(7) A, V = 13 759(8) A(3), and Z = 8. The trianionic citrate ligands supply both carboxylate and alkoxide coordination and stabilize the structure using simultaneous chelating and bridging modes of attachment. The compound is a neutral species, exhibiting titanium in three contrasting environments. Laser Raman microscopy and (13)C CPMAS solid-state NMR data were consistent with those of the X-ray crystal structure. When exposed to air, the crystals rapidly lost water and became a powder. The dehydrated powder was noncrystalline to X-rays and insoluble, but (13)C NMR results demonstrated retention of the carboxylate linkages.

A family of triethanolamine complexes of titanium with varying metal/ligand ratios have been prepared from reactions of titanium tetraisopropoxide with triethanolamine. Three nonhydrolytic products, having essentially all isopropoxide ligands substituted by triethanolamine, were prepared as hygroscopic, glassy solids. Crystals of two hexameric titanatrane partial hydrolysis analogues [Ti3(mu 2-O)((HOCH2CH2)2NCH2CH2O)(OCH2CH2)2(mu 2-OCH2CH2)N)2(OCH2CH2)(mu 2- OCH2CH2)2N)]2 (1), and [Ti3(mu 2-O)(OCH(CH3)2)((OCH2CH2)2(mu 2-OCH2CH2)N)2(OCH2CH2)(mu 2- OCH2CH2)2N)]2 (2) were isolated and structurally characterized. The structures consist of a central core of two oxo-bridged dititanatranes (TEA)TiOTi(TEA) (TEAH3 = triethanolamine) with the nonhydrolytic residue (TEA)Ti(TEAH2) included as an adduct in (1), analogously to (TEA)Ti(OPri) in (2).

TiO2 (anatase)-based photocatalyst powders containing up to 20 mol% calcium, strontium or barium ions were prepared from α-titanic acid by calcining gels prepared from triethanolamine-based sols at 600°C. The powders were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance ultraviolet spectrophotometry, nitrogen sorption porosimetry and in situ infrared spectroscopy to examine surface adsorbed species. Compositions containing greater than 15 mol% alkaline earth ions resulted in largely amorphous materials. The residual anatase showed decreased crystallite sizes and increased crystallographic cell volumes with increasing concentration of alkaline earth ions, while the BET surface areas of the materials increased from around 80 m2 g−1 (no additive) to 160 m2 g−1 at higher levels of additive. Electronic spectroscopy showed that the band gaps of the materials increased with increasing Ca2+ content, due to the decreasing particle sizes. Under the synthesis conditions used, no other crystalline phase was observed, except rutile (

Ti6O6(MDEA)6·2CH2Cl2 (MDEA = N-methyldiethoxoamine) was obtained by the controlled hydrolysis of the Ti(MDEA)2 complex and analysed by X-ray diffraction. The compound consists of a ring of six [TiO5N] octahedra, edge bridged by μ2-oxide and a μ2-alkoxide arm of the aminoalkoxide ligand.

A series of mixed-ligand–titanium complexes is reported which incorporate a tridentate N-methyldiethoxoamine (mdea) ligand in conjunction with chelating diolate ligand. X-ray crystal structures of the complexes [Ti(mdea) (O-O)]2 (where O-O = OC(CH3)2C(CH3)2O (1), OC(C2H5)2C(C2H5)2O (2), OC(CH3)2CH2CH(CH3)O (3), and OC(CH3)2CH2C(CH3)2O (4)) show them to exist as dimers in the solid state, with one arm of the aminodialkoxy ligand μ-bridging two titanium centres. Solution-state 1H and 13C NMR studies concur with the solid-state structures of (1)–(4) at low temperature. The room-temperature spectra of (3) and (4) suggest that bridging bond scission and reformation occurs increasing the apparent symmetry of the complexes. Complexes (3) and (4) dissociate into monomers in the vapour phase. The influence of the diolate ligand on the bridging bond strengths is discussed.

A highly fluxional dititanium N-methyldiethoxoamine hexaisopropoxide complex was isolated from reactions of N-methyldiethanolamine with Ti(OPri)4. X-ray crystallography identified the solid state compound as the unsymmetrical complex Ti2(μ2-(OCH2CH2)2NCH3)(μ2-OPri)(OPri)5. In solution, the time-averaged structure was shown by NMR to be symmetrical. The amine function coordinates to both titanium atoms alternately, while the isopropoxide ligands exchange to maintain equal coordination numbers on both titaniums. Variable temperature NMR demonstrates that the exchange processes slow on cooling, and a spectrum consistent with the solid-state structure is apparent at –50�C.

A method for producing amino alcohol complexes of titanium from hydrated titania (α-titanic acid) is described. Thus hydrated titania was completely converted into triethanolamine and diethanolamine complexes during reaction at 120°C for 6 h. This represents a synthetic method for titanium sol–gel precursors which are free from chlorine-containing impurities. Products were characterized with assistance from 1 H and 13 C nuclear magnetic resonance spectroscopy, and electrospray mass spectrometry. A single-crystal X-ray structure of titanium bis[2,2´- (methyl-imino)ethanolate], tetragonal, space group P4 – 2 1 c, is presented. The titanium centre is coordinated by an N2O4 donor set which can be most closely described as a bifacially capped tetrahedral geometry.