Showing papers on "Aquation published in 2013"
TL;DR: Quantum chemical calculations provide redox potentials and pK(a) values for proton-coupled electron transfer reactions from Ru(II)-OH2 to Ru(IV)═O in good agreement with experiments and provide an explanation for mechanistic differences between d-1H2O and p-1h2O with respect to water oxidation.
Abstract: A ligation of Ru(tpy)Cl3 (tpy = 2,2′:6′,2″-terpyridine) with 2-(2-pyridyl)-1,8-naphthyridine) (pynp) in the presence of LiCl gave distal-[Ru(tpy)(pynp)Cl]+ (d-1Cl) selectively, whereas the ligation gave proximal-[Ru(tpy)(pynp)OH2]2+ (p-1H2O) selectively in the absence of halide ions. (The proximal/distal isomers were defined by the structural configuration between the 1,8-naphthyridine moiety and the aquo or chloro ligand.) An aquation reaction of d-1Cl quantitatively afforded distal-[Ru(tpy)(pynp)OH2]2+ (d-1H2O) in water, and d-1H2O is quantitatively photoisomerized to p-1H2O. The mechanism of the photoisomerization was investigated by transient absorption spectroscopy and quantum chemical calculations. The temperature dependence of the transient absorption spectral change suggests existence of the thermally activated process from the 3MLCT state with the activation energy (ΔE = 49 kJ mol–1), which is close to that (41.7 kJ mol–1) of the overall photoisomerization reaction. However, quantum chemical calc...
68 citations
TL;DR: In general, complexes with biphenyl as arene ligand inhibited the growth of tumor cells more effectively than the cymene analogues, consistent with the increase in lipophilicity.
Abstract: With the aim of systematical- ly studying fundamental structure-ac- tivity relationships as a basis for the de- velopment of Ru II arene complexes (arene = p-cymene or biphenyl) bearing mono-, bi-, or tridentate am(m)ine li- gands as anticancer agents, a series of ammine, ethylenediamine, and dieth- A complexes were pre- pared by different synthetic routes. Es- pecially the synthesis of mono-, di-, and triammine complexes was found to be highly dependent on the reaction conditions, such as stoichiometry, tem- perature, and time. Hydrolysis and pro- tein-binding studies were performed to determine the reactivity of the com- pounds, and only those containing chlorido ligands undergo aquation or form protein adducts. These properties correlate well with in vitro tumor-in- hibiting potency of the compounds. The complexes were found to be active in anticancer assays when meeting the following criteria: stability in aqueous solution and low rates of hydrolysis and binding to proteins. Therefore, the complexes least reactive to proteins were found to be the most cytotoxic in cancer cells. In general, complexes with biphenyl as arene ligand inhibited the growth of tumor cells more effectively than the cymene analogues, consistent with the increase in lipophilicity. This study highlights the importance of find- ing a proper balance between reactivity and stability in the development of or- ganometallic anticancer agents.
31 citations
TL;DR: In this paper, the nonlinear optical active chiral complex (Co(2,5-pdc)(H2O)2} H2O]n was synthesized via a solvothermal technique using the achiral 2,5pdc ligand, and the crystal structure of phase 3 was determined by powder X-ray diffraction analysis.
Abstract: The nonlinear optical active chiral complex 1 [{Co(2,5-pdc)(H2O)2}H2O]n (2,5-pdc = 2,5-pyridine dicarboxylate) has been synthesized via a solvothermal technique using the achiral 2,5-pdc ligand. Complex 1 (phase 1), a two-dimensional coordination polymer, undergoes crystalline to amorphous (phase 2) transformation upon deaquation, which under reaquation generates a new microcrystalline phase (phase 3). The crystal structure of phase 3 has been determined by powder X-ray diffraction analysis (PXRD), which reveals that the resultant microcrystalline phase 3 is an achiral complex consisting of one-dimensional coordination chains. Phase 3 undergoes reversible structural transformation via amorphous phase (phase 2) upon dehydration and subsequent rehydration. This amorphous phase shows selective adsorption of water from a water–DMF mixture and water–CCl4 mixture. Phase 1 to phase 3 structural transformation proceeds through selective bond breaking. The magnetic studies of the two crystalline and the amorphous ...
16 citations
TL;DR: In this paper, the kinetics of 1':'1 complex formation and hydrolysis between catechol and 3-substituted catechols with vanadium(V) at pH ∼ 1 have been investigated in NaAOT derived aqueous reverse micelle microemulsions in isooctane.
Abstract: The kinetics of 1 : 1 complex formation and hydrolysis between catechol and 3-substituted catechols with aqueous vanadium(V) at pH ∼ 1 have been investigated in NaAOT (sodium bis(2-ethylhexyl)sulfosuccinate) derived aqueous reverse micelle microemulsions in isooctane. Compared with the reaction in bulk water, the forward rate constant of catechol complexation was modestly accelerated (2 fold) in the reverse micelle microemulsions for even the smallest nanosized water pools (wo = 2). In contrast, the first order reverse (aquation) reaction was significantly suppressed in the water pools below wo = 10. The modest rate acceleration of complex formation within the microemulsions is attributed to changes in water solvation, reaction properties and compartmentalization of the reactants. The dramatic fall off in the rate of catechol dissociation from [VO2(cat)(OH2)2]− is attributed to the reduction in water content as the size of the nanopools is decreased below 200 water molecules. The result is a 10 fold increase in the kinetic formation constant for [VO2(cat)(OH2)2]− under confinement in the RM microemulsion environment. This increase predicts that vanadium catechol complexes will be more stable in vivo and may suggest a general principle for fine-tuning efficacy of metal-based drugs.
14 citations
TL;DR: Aqueous solutions of ruthenium nitrosyl chloride complexes have been studied by 14N, 15N, 17O, 99Ru, and 35Cl NMR as mentioned in this paper.
Abstract: Aqueous solutions of ruthenium nitrosyl chloride complexes have been studied by14N, 15N, 17O, 99Ru, and 35Cl NMR. Individual complex species have been identified and the corresponding chemical shifts have been determined. The primary aquation product of the pentachloronitrosylruthenate ion is the cis-[RuNO(H2O)Cl4]− complex, which subsequently undergoes isomerization. The equilibrium constants of interconversions of ruthenium nitrosyl chloride complexes in an aqueous solution at room temperature have been estimated.
13 citations
TL;DR: The results show that cross-link preference is kinetically controlled and will depend critically on the reaction conditions, explaining why in a previous reaction of 1 with duplex I the major adduct isolated by HPLC had two simultaneous 3'-3' 1,2-interstrand cross-links.
Abstract: 2D [1H, 15N] HSQC NMR spectroscopy has been used to monitor the reaction of fully 15N-labelled [{trans-PtCl(NH3)2}2(μ-trans-Pt(NH3)2{NH2(CH2)6NH2}2)]4+ (Triplatin, BBR3464 or 1,0,1/t,t,t (15N-1)) with the self-complementary 10-mer DNA duplex 5′-{d(ACGTATACGT)2} (duplex I) at pH 5.4 and 298 K. Initial electrostatic interactions were observed in the minor groove of the duplex, followed directly by aquation to form the monoaqua monochloro species. There was evidence for two discrete monofunctional adducts, through covalent binding at the guanine N7 sites, and one had distinctly different 1H/15N chemical shifts to those observed previously in analogous reactions. Bifunctional adduct formation followed by binding at a second guanine N7 site with evidence for both the 3′–3′ 1,2-GG and 5′–5′ 1,6-GG interstrand cross-links in a ratio of 2 : 1. The results show that cross-link preference is kinetically controlled and will depend critically on the reaction conditions, explaining why in a previous reaction of 1 with duplex I the major adduct isolated by HPLC had two simultaneous 3′–3′ 1,2-interstrand cross-links.
8 citations
TL;DR: Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes and rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes.
Abstract: The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η
6-arene)MII(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of RuII and OsII arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes.
6 citations
TL;DR: In this paper, the first reaction for Trisparaginatochromium(III), [Cr(Asn)3]0 and [CrAsn]2(H2O)2]+ is the chelate ring opening at the Cr-NH2 bond, leading to metastable intermediates.
Abstract: Tris-asparaginatochromium(III), [Cr(Asn)3]0 (where Asn forms a 5-membered chelate ring via amine nitrogen and α-carboxylate oxygen atoms) and its mono- and diaqua-derivatives were obtained, and their acid-catalyzed aquation was studied. The first reaction for [Cr(Asn)3]0 and [Cr(Asn)2(H2O)2]+ is the chelate ring opening at the Cr-NH2 bond, leading to metastable intermediates. Kinetics of these processes were studied spectrophotometrically in 0.1–1.0 M HClO4 at 303 and 333 K, respectively. A linear dependence of kobs on [H+], kobs = a + b[H+] was determined for both the complexes. Additionally, oxidation of chromium(III) to chromate(VI) by hydrogen peroxide was studied. The process proceeds through a chromium(V) intermediate, which is next transformed, in faster parallel steps into CrO42− and [Cr(O2)2]3− anions. The latter species, a chromium(V)-peroxo complex, is metastable under a large excess of H2O2. Kinetics of oxidation of [Cr(Asn)3]0 were studied at 298 K, at constant [OH−], within 0.2–1.0 M H2O2 range. A linear dependence of kobs on H2O2 was established. A mechanism is proposed, where the rate-determining step is an inner sphere 2-electron transfer within a precursor chromium(III) complex with coordinated O2H− anion of the [Cr(Asn)2(OH)(HO2)]− formula. EPR results provided clear evidence for formation of a relatively stable tetrakis(η2-peroxo)chromate(V) complex, [Cr(O2)4]3−.
6 citations
TL;DR: The mechanism of substitution reaction of chloroaqua and diaqua complexes, trans -[Pt(2-pic)(NH 3 )Cl(H 2 O)] + and trans -(2 -pic)(NH 3) 2+ , which are formed after intracellular aquation of the anticancer drug AMD443, with the DNA purine bases guanine (G) and adenine (A) were studied computationally by TST–DFT method.
4 citations
TL;DR: The structure of (NH4)4[OS2OCl10] has been determined by X-ray diffraction as discussed by the authors, and the binuclear anion has been established spectrophotometrically to remain structurally unchanged in freshly prepared aqueous and hydrochloric acid solutions.
Abstract: The structure of (NH4)4[OS2OCl10] has been determined by X-ray diffraction. The crystals are tetragonal, space group I4/mmm, a = 7.292(1) A, c = 17.157(3) A, Z = 2. The binuclear anion has D
4h
symmetry; the osmium atom is coordinated to five chlorine atoms and the oxygen atom. The Os-O distances are 1.8242(5) A; Os-Cleqv, 2.3743(18) A; Os-Clax, 2.335(3) A; the Cl1OsCl2 angle is 86.84(4)°. The anion has been established spectrophotometrically to remain structurally unchanged in freshly prepared aqueous and hydrochloric acid solutions. Slow aquation with retention of a binuclear structure occurs with time in 1 and 6 M HCl. At 75 or 90°C, the process is faster with the disrupture of the Os-O-Os bond and the formation [OsCl6]2− ions in 6 M HCl and a mixture of [OsCl6]2− and [Os(H2O)Cl5]− ions in 1 M HCl.
TL;DR: In this article, the biological effect, aquation, and kinetics of bis(2-aminobenzothiazole)dichlorocobalt(II) complex by periodate in aqueous acidic solutions were studied.
Abstract: The biological effect, aquation, and kinetics of oxidation of bis(2-aminobenzothiazole)dichlorocobalt(II) complex by periodate in aqueous acidic solutions were studied. The complex exhibited a broad resistance toward the studied pathogens. The average value of the aquation constant was calculated spectrophotometrically as 2.55 × 10−5 mol2 dm−6. Kinetics of the oxidation reaction showed first-order dependence on each reactant concentration and increased by increasing pH over the 3.80–4.80 range, 35–50°C, and decreased by increasing the ionic strength over the 0.1–0.5 mol dm−3 range. The polymerization of acrylonitrile was taken as an evidence for an inner-sphere mechanism through the formation of free radical intermediates of Co(III) complexes, which were slowly converted to the final Co(III)products.