Aquation

About: Aquation is a research topic. Over the lifetime, 1443 publications have been published within this topic receiving 17507 citations.

Initial state and transition state contributions to solvent effects on activation enthalpies for substitution reactions of tris(1,10-phenanthroline)iron(II) in aqueous methanol

Abstract: Activation enthalpies have been determined for aquation of thetris(1,10-phenanthroline)iron(II) cation and for its reaction with hydroxide in 20, 40, and 80% (by volume) methanol, and for its reaction with cyanide in 20 and 40% methanol. Enthalpies of solution of the chloride salt of this cation, and of potassium cyanide, have been determined in the water-methanol mixtures. From these results and ancillary thermodynamic data we have dissected the variations of activation enthalpies for these three substitution reactions with solvent composition into their initial state and transition state components. In the water-rich mixtures (0 to 40% methanol) initial and transition state solvation effects are similar and dominated by the ligands, but in the reaction with hydroxide in 80% methanol there is a striking difference between initial and transition state behaviour.

Effects of Buffers and pH on the Reaction of a trans-Platinum Complex with 5′-Guanosine Monophosphate

Abstract: The aquation of platinum anticancer drugs is a crucial step for their activation and the consequent binding to the target DNA. These processes can be influenced by small molecules, such as carbonate and phosphate, which are present in high concentration in physiological conditions. In this work, the effects of buffer and pH on the reaction of trans-EE {trans-[PtCl2{E-HN=C(OCH3)CH3}2]} with 5′-guanosine monophosphate (5′-GMP) have been studied in detail. The reactions were monitored by HPLC at different pH in the presence of carbonate, phosphate, and HEPES [4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid] buffers. trans-EE showed a very low affinity for the nitrogen atoms of HEPES, but formed monofunctional adducts with carbonate and phosphate ions. The platination of GMP by trans-EE was significantly affected by the choice of buffer and pH. Carbonate buffer decreased the reaction rate, mostly due to its competition with GMP. Although phosphate buffer formed a similar monofunctional adduct with trans-EE, it had a negligible effect on the platination rate of GMP. This may be due to the formation of ternary adducts with trans-EE and GMP. In all cases, the platination reaction was slower at higher pH, probably due to the deprotonation of an aqua ligand on the mono-aqua complex of trans-EE. The results in this paper indicate that the solution conditions have a different effect on the reaction of trans-platinum complexes compared with cisplatin.

Photochemical studies of chromium (III) complexes. Photoisomerization and photochemical ammine ligand aquation of the isomeric ammineaquachromium (III) complexes

Abstract: Reactions photochimiques de 8 complexes differents, a 366 et 546 nm. Les rendements quantiques pour l'isomerisation et la perte de NH 3 coordine ne presentent pas de relation avec la longueur d'onde. Les distributions des produits des reactions photochimiques sont differentes de celles des reactions thermiques a 60-80°C