Aquation

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

Aquation and Anation Kinetics of Rhenium(I) Dicarbonyl Complexes: Relation to Cell Toxicity and Bioavailability.

Abstract: The aquation reactions of four rhenium(I) dicarbonyl complexes, [Re(CO)2(NN)(PR3)(Cl)], where NN = 1,10-phenanthroline (Phen) and 2,9-dimethyl-1,10-phenanthroline (DMPhen) and PR3 = 1,3,5-triaza-7-phosphaadamantane (PTA) and 1,4-diacetyl-1,3,7-triaza-5-phosphabicylco[3.3.1]nonane (DAPTA). Additionally, the anation reactions of the corresponding aqua complexes with Cl- were investigated. Single crystals of [Re(CO)2(DMPhen)(PTA)(Cl)]·DMF and [Re(CO)2(DMPhen)(DAPTA)(Cl)] were obtained, and their structures were determined using X-ray diffraction. The Re-Cl interatomic distances are 2.4991(13) and 2.4922(6) A, respectively, indicating a mild trans influence effect of the phosphine ligands. The rate constants, kaq, for the aquation reactions of these complexes spanned a range of (3.7 ± 0.3) × 10-4 to (15.7 ± 0.3) × 10-4 s-1 with the two Phen complexes having rate constants that are 2.5 times greater than those of the DMPhen complexes at 298 K. Similarly, the second-order anation rate constants (kCl) of the resulting aqua complexes, [Re(CO)2(NN)(PR3)(H2O)]+, with Cl- ions at 298 K varied between (2.99 ± 0.05) × 10-3 and (6.79 ± 0.09) × 10-3 M-1 s-1. Likewise, these rate constants for the Phen complexes were almost 2 times faster than those of the DMPhen complexes. The pKa values of the four aqua complexes were determined to be greater than 9.0 for all of the complexes with [Re(CO)2(Phen)(PTA)(H2O)]+ having the highest pKa value of 9.28 ± 0.03. From the pKa values and the ratios of the aquation and anation rate contants, which give thermodynamic Cl- binding constants, the speciation of the rhenium(I) complexes in blood plasma, the cytoplasm, and the cell nucleus were estimated. The data suggest that the aqua complexes would be the dominant species in all three environments. This result may have important implications on the potential biological activity of these complexes.

The influence of electrolytic dissociation upon rates of reactions. Part IV. The aquation of chloropentamminechromium(III) in acidic salt solutions

Abstract: The rate of aquation of chloropentamminechromium(III) is accelerated by nitrate, sulphate, malonate, phthalate, and tartrate solutions. These effects are ascribed to the more reactive ion-pairs and their rate constants have been calculated by applying the Wyatt–Davies treatment. These rate constants are broadly related to the dissociation constants of the ion-pairs (obtained for the dicarboxylates by a glass electrode–calomel cell) but this relationship is only approximate.

Kinetics and mechanisms of substitution of aqua ligands from cis-diaquo-bis[2-(m-tolylazo)pyridine]ruthenium(II) by 8-hydroxy- quinoline in ethanol—water mixtures

Abstract: The kinetics of aqua ligand substitution from cis-[Ru-(tap)2(H2O)2]2+ (tap = 2-[m-tolylazo]pyridine) by 8-hydroxyquinoline (oxine) have been studied spectro-photometrically in various water-ethanol mixtures at different temperatures (30–45° C). The following rate law has been established in the pH range 4.5 to 6.5; $$ {⤪ d[(2)]/dt=k_{1}k_{2}[(1)][L]/(k_{-1}+k_{2}[L])} $$ where (1), (2) and L represent ds-[Ru(tap)2(H2O)2]2+, [Ru(tap)2(oxine)]2+ and oxine respectively. k1 is the water dissociation rate constant of (1); k−1 is the aquation rate constant and k2 is the oxine capturing rate of the pentacoordinate intermediate, [Ru(tap)2(H2O)]2+. Ionic strength has very little effect on the rate constants. The rate increases with the increase in pH. The experimental results are consistent with a dissociative mechanism.

Dinuclear platinum(II) complexes of imidazophenanthroline-based bridging ligands as potential anticancer agents: synthesis, characterization, and in vitro cytotoxicity studies

Abstract: The synthesis and characterization of the dinucleating ligands 1,2-bis(2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)ethane (L1) and 1,2-bis(2-(1H-imidazo[4,5-f][1, 10]phenanthrolin-2-yl)phenoxy)hexane (L2) and their dinuclear complexes [Pt2(L1)Cl4] (1) and [Pt2(L2)Cl4] (2) and the in vitro cytotoxicity of the complexes against HeLa, HepG2, and MCF-7 cell lines are reported. Ligand L1 crystallizes in the orthorhombic system with the space group Pbca. The complexes 1 and 2 undergo aquation following first-order kinetics. The MTT and trypan blue assays indicate higher cytotoxicity of the complexes towards the HepG2 and MCF-7 cell lines compared to cisplatin. The AO/EB assay and flow cytometry by Annexin V alexa fluor®488/PI double staining assay demonstrate distinct morphological changes of apoptosis in a dose dependent manner. The cell cycle analysis shows a marked decrease in the DNA content in the G0/G1 phase with an increase in the G2/M phase on increasing the concentration of the complexes. The potential of the complexes as anticancer agents is demonstrated by their antiproliferative activity on the cell lines. The complexes interact with the major groove of DNA through H-bonding between the imidazole N–H protons and the nucleotide residues DC`21/N4 (cytosine) for complex 1 and DT`7/O2 (thymine) and DT`19/O2 (thymine) for complex 2, with the binding energy of − 1.98 and − 4.45 kcal/mol, respectively. Dinuclear Pt(II) complexes of imidazophenanthroline-based dinucleating ligands exhibit antiproliferative activity against HeLa, HepG2, and MCF-7 cell lines