The design of ligands for aluminium oxy/hydroxide surfaces

• Main Author: Henderson, David K.
• Published: University of Edinburgh 2001
• Subjects: 546.3
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652330

1,3,5-triazine derivatives are considered as potentially polynucleating surface-ligands in chapter 2. Synthetic routes to novel hydroxy and thiol functionalised, alkylamino containing triazines developed. A range of such compounds with different subtitution patterns has been characterised. X-ray structure determination of 6-(diethylamino)-1,3,5-triazine-2,4-dithione (H₂SSta) and 6-(diethylamino)-1,3,5-triazine-2-thione-4-one (H₂OSta) showed them to be present in the thione/one tautomeric forms. All the crystallographically characterised triazines show strong intermolecular hydrogen bonding. Formation of transition metal complexes was found to be accompanied by ligand rearrangement. Condensation reactions, forming novel thioether bridged ligands <i>in-situ</i> have been observed in the crystallographically characterised complexes [Ni{Sta)S(S₂ta)}] and [Co₆NaO(OStaH)₇{S(Ota)₂}₂(O₂CPh)₂(H₂O)₂]. The instability of these compounds in solution in the presence of metal Lewis acids limits their study by isotherm determination and makes them poor candidates for the rational development of surface treatments for aluminium. The structurally related ligands 2-hydroxypyridine and uracil were shown by the isotherm studies to adsorb only weakly onto an A1(OH)₃ surface. Known carboxylic acid-based corrosion inhibitors for iron are considered in aluminium chemistry in chapter 3. Isotherm studies on the 3-ketocarboxylic acid, 3-(4-methylbenzolyl)-propionic acid and its non keto analogue 4-<i>p</i>-tolyl-butyric acid have reinforced the concept that secondary interactions, such as hydrogen bonding to surface hydroxides, can play an important role in determining the binding characteristics of surface ligands. In accordance with a survey of the Cambridge Crystallographic Database which revealed that there are few examples of carboxylic acids functioning as polynucleating ligands for aluminium(III), it was found impossible to isolate crystalline aluminium(III) complexes. However, the coordination chemistry of 3-ketocarboxylic acids was extended by the synthesis of two mixed ligand, 3-benzoyl-propionoic acid (Hbpa)/ 6-x-2-hydroxypyridine [Hxhp, where x = m (methyl) or c (chloro)], polynuclear nickel clusters, [Ni₃(chp)₄(bpa)₂(MeOH)₆].2MeOH and [Ni₆Na₂C1₂(OH)₆(Hmhp)₆(bpa)₆].