In situ infrared spectroscopic analysis of the adsorption of aromatic carboxylic acids to TiO2, ZrO2, Al2O3, and Ta2O5 from aqueous solutions

In situ infrared spectroscopy has been used to investigate the adsorption of a range of simple aromatic carboxylic acids from aqueous solution to metal oxides. Thin films of TiO2, ZrO2, Al2O3 and Ta2O5 were prepared by evaporation of aqueous sols on single reflection ZnSe prisms. Benzoic acid adsorbed very strongly to ZrO2, in a bridging bidentate fashion, but showed only weak adsorption to TiO2 and Ta2O5. Substituted aromatic carboxylic acids; salicylic, phthalic and thiosalicylic, were found to adsorb to each metal oxide. Salicylic and phthalic acids adsorbed to the metal oxides via bidentate interactions, involving coordination through both carboxylate and substituent groups. Thiosalicylic acid adsorbed to the metal oxides as a bridging bidentate carboxylate with no coordination through the thiol substituent group.     

On 3-regular graphs having crossing number at least 2

We give a planar proof of the fact that if G is a 3-regular graph minimal with respect to having crossing number at least 2, then the crossing number of G is 2.     

Crystal and molecular structure of dichlorobis(η5-t-butylcyclopentadienyl)titanium(IV)

Dichlorobis(η⁵-t-butylcyclopentadienyl)titanium(IV), (t-BuCp)₂TiCl₂, crystallises in space group P2₁2₁2 (orthorhombic) with a 12.862(14), b 10.709(9), c 6.602(9) Å, Z = 2. The two t-butyl groups are directed away from each other on opposite sides of the molecule; the overall molecular symmetry is C₂. The individual titanium-ring carbon atom distances are not all equal, but vary from 2.330(5) to 2.475(4) Å, the distortion from an exactly symmetric conformation being in a direction which increases the separation between the titanium atom and the carbon atom carrying the t-butyl substituent group.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.