Showing papers on "Aquation published in 2019"
TL;DR: This work elucidate the mechanism of photoaquation in the model system iron(ii) hexacyanide, where UV excitation results in the exchange of a CN- ligand with a water molecule from the solvent, and explains the ∼20 ps time scale for aquation as involving interconversion between the square pyramidal (SP) and trigonal bipyramidal pentacoordinated geometries.
Abstract: Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest in new means of probing their mechanisms. Using a combination of time-resolved x-ray absorption spectroscopy and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations and x-ray absorption near-edge spectroscopy calculations, we elucidate the mechanism of photoaquation in the model system iron(ii) hexacyanide, where UV excitation results in the exchange of a CN- ligand with a water molecule from the solvent. We take advantage of the high flux and stability of synchrotron x-rays to capture high precision x-ray absorption spectra that allow us to overcome the usual limitation of the relatively long x-ray pulses and extract the spectrum of the short-lived intermediate pentacoordinated species. Additionally, we determine its lifetime to be 19 (±5) ps. The QM/MM simulations support our experimental findings and explain the ∼20 ps time scale for aquation as involving interconversion between the square pyramidal (SP) and trigonal bipyramidal pentacoordinated geometries, with aquation being only active in the SP configuration.
23 citations
TL;DR: Ta powder reacts with I2 at 650 °C with the formation of Ta6I14, which belongs to the family of {M6(μ-X)12} clusters as discussed by the authors.
Abstract: Ta powder reacts with I2 at 650 °C with the formation of Ta6I14, which belongs to the family of {M6(μ-X)12} clusters. It undergoes aquation with the formation of the intensely colored [Ta6I12(H2O)6]2+. The crystal structure was determined for [Ta6I12(H2O)6](BPh4)2·xH2O (Ta-Ta 2.9322(6) A, Ta-I 2.8104(7) A, Ta-O 2.3430(5) A). With DMF, [Ta6I12(DMF)6]I2·xDMF was isolated (Ta-Ta 2.9500(2) A, Ta-I 2.8310(4) A, Ta-O 2.2880(7) A). Cyclic voltammetry of [Ta6I12(H2O)6]2+ shows two consecutive quasi-reversible one-electron oxidations (E1/2 0.61 and 0.92 V vs Ag/AgCl). Reaction of Ta6I14 with Bu4NCN yields (Bu4N)4[Ta6I12(CN)6]·xCH3CN (Ta-Ta 2.9777(4) A, Ta-I 2.8165(6) A, Ta-C 2.2730(7) A). Quantum chemical calculations reproduce well the experimental geometry of the aqua complex and show the essentially Ta-centered nature of both the HOMO and LUMO. The long-term stability of [Ta6I12(H2O)6]2+ solutions can be greatly enhanced in the presence of polystyrenesulfonate (PSS), which forms nanoparticle associates with the aqua complex in water (ca. 1 cluster per 3 PSS monomeric units).
19 citations
TL;DR: The aquation process of a Ru(II) arene complex with potent anticancer activity was examined and characterized and provided important information for rational design of such kind of metal complexes with better cancer therapeutic potency.
11 citations
TL;DR: The results emphasize the relevance of glycans in bioinorganic chemistry and underpin a fundamental molecular description of the HS-Pt interactions that alter the profile of platinum agents from cytotoxic to metastatic in a systematic manner.
Abstract: We report herein a detailed NMR study of the aquation and subsequent covalent binding of the trinuclear clinical agent [{trans-PtCl(15NH3)2}2{μ-trans-Pt(15NH3)2(15NH2(CH2)615NH2)2}]4+ (1, 1,0,1/t,t,t or Triplatin) with three d-glucosamine residues containing varied O-sulfate and N-sulfate or N-acetyl substitutions, which represent monosaccharide fragments present within the repeating disaccharide sequences of cell surface heparan sulfate (HS). The monosaccharides GlcNS(6S), GlcNS, and GlcNAc(6S) were synthesized in good yield from a common 4,6-diol α-methyl glucopyranoside intermediate. The reactions of 15N-1 with sodium sulfate, GlcNS(6S), GlcNS, and GlcNAc(6S) were followed by 2D [1H,15N] heteronuclear single quantum coherence (HSQC) NMR spectroscopy using conditions (298 K, pH ≈5.4) similar to those previously used for other anionic systems, allowing for a direct comparison. The equilibrium constants (pK1) for the aquation of 1 in the presence of GlcNS(6S) and GlcNS were slightly higher compared to tha...
11 citations
TL;DR: Analyses of the XAS of Rh-treated bulk cells were consistent with structure-reactivity relationships in which the more reactive A1 was predominantly antimetastatic and the less reactive A2 was predominantly cytotoxic, showing relationships parallel to typical Ru(III) anticancer agents.
Abstract: Rhodium(III) anticancer drugs can exert preferential antimetastatic or cytotoxic activities, which are dependent on subtle structural changes. In order to delineate factors affecting the biotransformations and speciation, mer,cis-[RhCl3( S-dmso)2( O-dmso)] (A1) and mer,cis-[RhCl3( S-dmso)2(2N-indazole)] (A2) have been studied by X-ray absorption spectroscopy (XAS). Interactions of these complexes with saline buffer, cell culture media, serum proteins (albumin and apo-transferrin), native and chemically degraded collagen gels, and A549 cells have been studied using linear combination fitting (LCF) and 3D scatter plots of XAS data. Following initial aquation and hydrolysis reactions involving stepwise displacement of Cl- and S-/ O-dmso ligands, the Rh(III) complexes underwent further ligand substitution reactions with biological nucleophiles (e.g., amino acid residues of serum proteins). The reaction of A1 with chemically degraded collagen gel was postulated to be a key reason for its antimetastatic activity. Analyses of the XAS of Rh-treated bulk cells were consistent with structure-reactivity relationships in which the more reactive A1 was predominantly antimetastatic and the less reactive A2 was predominantly cytotoxic, showing relationships parallel to typical Ru(III) anticancer agents, i.e., NAMI-A ([ImH] trans-[RuCl4( S-dmso)( N-imidazole)2], ImH = imidazolium cation) and KP1019/NKP1339 (KP1019, [IndH] trans-[RuCl4(N-indazole)2], IndH = indazolium cation; NKP1339, sodium trans-[RuCl4(2N-indazole)2]), respectively.
8 citations
TL;DR: Dinuclear Pt(II) complexes of imidazophenanthroline-based dinucleating ligands exhibit antiproliferative activity against HeLa, HepG2, and MCF-7 cell lines.
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
7 citations
TL;DR: Fine-tuning of the properties of a recently reported 1,3-indandione-based organoruthenium complex is attempted to optimize the stability under physiological conditions and reveals new analogs that were stable at pH 7.4 and 8.5.
Abstract: Fine-tuning of the properties of a recently reported 1,3-indandione-based organoruthenium complex is attempted to optimize the stability under physiological conditions. Previous work has shown its capacity of inhibiting topoisomerase IIα; however, fast aquation leads to undesired reactions and ligand cleavage in the blood stream before the tumor tissue is reached. Exchange of the chlorido ligand for six different N-donor ligands resulted in new analogs that were stable at pH 7.4 and 8.5. Only a lowered pH level, as encountered in the extracellular space of the tumor tissue, was capable of aquating the complexes. The 50% inhibitory concentration (IC50) values in three human cancer cell lines differed only slightly, and their dependence on the utilized leaving group was smaller than what would be expected from their differences in cellular accumulation, but in accordance with the very minor variation revealed in measurements of the complexes’ lipophilicity.
6 citations
TL;DR: In this article, the carboxylic acid groups deprotonate at ambient pH, providing a more anionic coordination environment that stabilizes its Mn(II) complex in water.
6 citations
TL;DR: In this paper, the authors used 19F NMR to monitor the aquation of complexes with highly electron withdrawing trifluoroacetato ligands in the axial positions of Diaminetetracarboxylatoplatinum(IV) complexes and reinterpreted the reduction of these complexes by ascorbate and cysteine and their biological behaviour in the light of aquation results.
5 citations
TL;DR: In this paper, it was shown that the Martin-Basolo model does not explain the charge independence of aquation rate constants with the mutual compensation between charge separation and charge neutralization in the transition state.
4 citations
TL;DR: In this article, the effect of macrocyclic cavit and cucurbit[7]uril on carboplatin aquation rates in two biologically relevant media (PBS buffer solution and RPMI-1640 medium for cell growth) has been studied by means of 1H nuclear magnetic resonance spectroscopy.
Abstract: The aquation of carboplatin, a second-generation Pt(II)-based antitumor drug, in two biologically relevant media (PBS buffer solution and RPMI-1640 medium for cell growth) has been studied by means of 1H nuclear magnetic resonance spectroscopy The effect of the macrocyclic cavitand cucurbit[7]uril on the carboplatin aquation rates in these two types of media has also been studied Although, the cucurbit[7]uril does not form stable inclusion complex with carboplatin, it greatly affects the carboplatin aquation rates, presumably, through the two mechanisms: prevention of the carboplatin dimer formation and encapsulation of some components of the medium
TL;DR: In this paper, solid electron paramagnetic resonance (EPR) signals of the mer-[Cr(pic)3] complex were found for the solid with g values of 3.45 and 3.47 at room temperature and frozen at 100 K, respectively.
TL;DR: In this paper, the synthesis, characterization and kinetic studies of [RuL2(mac)]n+ complexes were reported, and the product of these reactions were characterized by ultraviolet-visible (UV-Vis) spectroscopy.
Abstract: We report here the synthesis, characterization and kinetic studies of [RuL2(mac)]n+ complexes [mac = 1,4,8,11-tetraazacyclotetradecane (cyclam) or 1,4,7,10-tetraazacyclododecane (cyclen); and L = Cl−, OH−, OH2]. The dichloride complexes release one Cl− producing [RuCl(L)(mac)]n+ or two Cl− producing [Ru(L)2(mac)]n+ (L = OH2, OH−) in aqueous solution within pH 1–7. The product of these reactions were characterized by ultraviolet–visible (UV–Vis) spectroscopy. The chloride affinity of Ru(III) depends on the macrocyclic ring size and geometric structure. The k1 and thermodynamic activation parameters (at pH 4.4, T = 25 °C) of cis-[RuCl2(cyclen)]+ complex are k1 = 3.6 × 10−3 s−1 (25 °C); ΔH# = 40.2 kJ mol−1 and ΔS# = − 138 J K mol−1; under similar conditions, for cis-[RuCl2(cyclam)]+ these values are 2.4 × 10−3 s−1, ΔH# = 50.8 kJ mol−1 and ΔS# = − 119 J K mol−1. The rate of chloride aquation reactions for cis-[RuCl2(cyclen)]+ is about 1.5 times faster than for the cyclam complex. The reactivity difference could be due to a combination of the σ-trans effect, the nephelauxetic effect and the effect of solvation.
TL;DR: The kinetics of the aquation reaction of the [VO(ida)(bipy)]·2H2O complex (where ida = iminodiacetate anion and bipy = 2,2,2-bipyridine) promoted by [Fe(H 2O)6]3+ ions were investigated in this article.
Abstract: The kinetics of the aquation reaction of the [VO(ida)(bipy)]·2H2O (VO(ida)(bipy)) complex (where ida = iminodiacetate anion and bipy = 2,2’-bipyridine) promoted by [Fe(H2O)6]3+ ions were investigat...