The synthesis and coordination chemistry of 3-hydroxypyridin-4-ones.

Four novel 3-hydroxypyridin-4-ones, namely 1-benzyl-2-ethyl-3-liydroxypyridin-4-one, 1-(4-methyl)ben2yl-2-ethyl-3-liydroxypyridin-4-one, l-(4-fluoro)ben2yl-2-etliyl-3-hydroxypyridjn-4-one and 1-(4-trifluormethyl)benzyl-2-ethyl-3-hydroxypyridin-4-one, have been prepared and characterised. X-ray crystallography was used to study the ligands showing them to be dimers. 1-(4-fluoro)benzyl-2-ethyl-3-hydroxypyridin-4-one and 1-(4-methyl)benzyl-2-ethyl-3-hydroxypyridin-4-one crystallised as anhydrates while 1-benzyl-2-ethyl-3-hydroxypyridin-4-one and 1-(4-trifIuormethyl)benzyl-2-ethyl-3- hydroxypyridin-4-one crystallised as hydrates. The partition coefficients of the ligands were measured showing them to be highly lipophilic. Several iron(III), aluminium(III), gallium(III) and indium(III) complexes were prepared using the ligands and were characterised. The iron complexes were also studied using EXAFS spectroscopy, both in the solid state and as 20:80 H2O:MeOH solutions. They had three waters associated with the metal in both cases. The gallium complexes were also found to have three waters associated with the metal in the solid state, using EXAFS spectroscopy. Copper(II) and nickel(II) complexes of tetradentate ligands derived from the condensation reactions of 1,2-diaminobenzene, 3,4-diaminobenzotrifluoride and 3,4-diamo-1-fluorobenzene with salicylaldehyde have been prepared and characterised. The novel ligand derived from 3,4-diamino-1-fluorobenzene was studied by X-ray crystallography as was its nickel(II) complex. This showed that planarity was induced into the ligand with a general shortening of bond lengths except in the case of the C=N and the C(6)-C(1)/C(20)-C(19) bonds, upon complexation. The copper(II) complex of the ligand derived from 1,2-diaminobenzene was also studied by X-ray crystallography. Previous authors had assumed that the complex dimerised with interactions between the copper atoms and the oxygens of the adjacent layer. This work shows that the interaction is in fact between the coppers and the nitrogens of adjacent layers and that there is also a copper-copper interaction of 3.4 A. The solvatochromic behaviour of various novel fluoro and non-fluoro iron(II) Schiffbase complexes has been investigated. The complexes are Fe(CN)2[C5H4NCMeNC2H4C4F9]2 (1), K[Fe(CN)3{lcub}pyridine-2,6-dimethyl-(4-fluorobenzyl)imine{rcub}] (3), K[Fe(CN)3{lcub}pyridine- 2,6-dimethyl-(N-benzyl)imine{rcub}] (4) and K[Fe(CN)3{lcub}pyridiae-2,6-dimethyl-(4-methylbenzyl)imine{rcub}] (5). (1) was shown to be a particularly versatile solvatochromic monitor of solvation.