Abstract Under 254 nm irradiation cis-[Pt(C6H5CN)2Cl2] is converted to H2PtCl6. Absorption of light by both the metal complex and the solvent contribute to the first step of this process, suggested to form HPt(C6H5CN) Cl3. A linear dependence of the reaction rate on light intensity appears to rule out chlorination by trichloromethyl radicals. However, at higher light intensities a higher order dependence on intensity develops, and under 313 nm irradiation is dominant, and a reaction between trichloromethyl radical and the excited state complex is proposed to account for this.
{"title":"Kinetics of the Photosubstitution of ds-Bis(benzonitrile)dichloroplatinum(II) in Chloroform","authors":"E. M. Jaryszak, Son L. Phan, P. Hoggard","doi":"10.1515/irm-1999-0206","DOIUrl":"https://doi.org/10.1515/irm-1999-0206","url":null,"abstract":"Abstract Under 254 nm irradiation cis-[Pt(C6H5CN)2Cl2] is converted to H2PtCl6. Absorption of light by both the metal complex and the solvent contribute to the first step of this process, suggested to form HPt(C6H5CN) Cl3. A linear dependence of the reaction rate on light intensity appears to rule out chlorination by trichloromethyl radicals. However, at higher light intensities a higher order dependence on intensity develops, and under 313 nm irradiation is dominant, and a reaction between trichloromethyl radical and the excited state complex is proposed to account for this.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79328168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Hirose, I. Fujiwara, K. Iio, Shinichi Masunari, M. Minakami, L. Messori, K. Hiromi
Abstract Transferrin is an iron carrier protein. It is known that the conformational change in the protein moiety induced by binding of nonsynergistic anions influences the metal release rate constants from metal transferrins. The copper dissociation rate constants of dicupric human(serum)-transferrin and ovo-transferrin were measured under the conditions of various pHs and ionic strengths to estimate the residues which interact with nonsynergistic anions. The pH and the ionic strength dependence of the copper dissociation rate constants in the N-lobe of serum (human)-transferrin and both lobes of ovo-Tf clearly show that some residue which has a pKa around 6.0 is involved in the binding of nonsynergistic anions and accelerating the copper dissociation rate. In the C-lobe of serum(human)-Tf, the copper dissociation rate constants were almost independent of pH between pH 7.0 and 9.0, but the dissociation rates were constantly accelerated by the presence of 0.1 Μ KCl. This behavior suggests that the residue in the C-lobe of serum(human)-Tf is constantly protonated between pH 7.0 and 9.0 and is involved in the binding of nonsynergistic anions binding site.
{"title":"The Dependence of the Copper Dissociation Rate Constants from Human(Serum)- and Ονο-Transferrin on pH and the Anions","authors":"J. Hirose, I. Fujiwara, K. Iio, Shinichi Masunari, M. Minakami, L. Messori, K. Hiromi","doi":"10.1515/irm-1999-0205","DOIUrl":"https://doi.org/10.1515/irm-1999-0205","url":null,"abstract":"Abstract Transferrin is an iron carrier protein. It is known that the conformational change in the protein moiety induced by binding of nonsynergistic anions influences the metal release rate constants from metal transferrins. The copper dissociation rate constants of dicupric human(serum)-transferrin and ovo-transferrin were measured under the conditions of various pHs and ionic strengths to estimate the residues which interact with nonsynergistic anions. The pH and the ionic strength dependence of the copper dissociation rate constants in the N-lobe of serum (human)-transferrin and both lobes of ovo-Tf clearly show that some residue which has a pKa around 6.0 is involved in the binding of nonsynergistic anions and accelerating the copper dissociation rate. In the C-lobe of serum(human)-Tf, the copper dissociation rate constants were almost independent of pH between pH 7.0 and 9.0, but the dissociation rates were constantly accelerated by the presence of 0.1 Μ KCl. This behavior suggests that the residue in the C-lobe of serum(human)-Tf is constantly protonated between pH 7.0 and 9.0 and is involved in the binding of nonsynergistic anions binding site.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77782793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The reaction between [Ru(H2O)6]2+ and dimethylformamide (DMF) was studied as a function of the temperature and the pressure at pH 1. When a slight excess of Ru aquaion is used, [Ru(H2O)5DMF]2+ is the only product of the reaction observed in the NMR spectra and the DMF is bound through the oxygen atom. From variable temperature experiments, the rate constants, activation enthalpies and entropies for the formation and the dissociation of the monocomplex were determined. These are as follows: 104 x kf298=(8.2 ± 0.4) kg mol-1 s-1 ΔΗ☨f= 83.6 ± 3 k J mol-1 Δ S☨f = -23.7 ± 10 J K-1mol-1 for the formation reaction, 103 x kd298 = (1.10 ± 0.04) s-1 ΔΗ☨f= 90.2 ± 2 kJ mol-1 ΔS☨f, = +1.0 ± 7 J Κ-1 mol -1 for the dissociation reaction. The thermodynamic parameters (equilibrium constant at 298.15 K, reaction enthalpy and entropy) were also determined:K298eq = 0.74 ± 0.02 kg mol-1 , ΔH0 = -6.6 ± 2 k j mol-1 , ΔS0 =-24.7 ± 6 JK-1. The kf value is similar to the previously reported rate constants for monocomplex formation reactions with other ligands and confirms that the entering ligand has no effect on the rate. From variable pressure experiments, the activation volumes for the formation and the dissociation reactions and the reaction volume were determined: ΔVf☨ = +2.7 ± 0.6 cm3 mol-1 , ΔVd☨= 0.9 ± 0.7 cm3 mol-1 , ΔV° = +3.6 ± 0 . 9 cm3 mol -1 respectively. These results show that the volume of the transition state is intermediate between the volume of the reactants and the volume of the products. It demonstrates that the mechanism is the same as for the water exchange on [Ru(H2O)6 ] 2+ , i.e. an Id mechanism. Contraction of the bonds between Ru and the spectator ligands at the transition state may explain the abnormally small activation volumes. The need of theoretical calculations on these systems is emphasized.
{"title":"Reaction between [Ru(H2O)6]2+ and DMF: A Complete Volume Profile of a Monocomplex Formation Reaction on a d6 Low Spin Aquaion","authors":"N. Aebischer, A. Merbach","doi":"10.1515/irm-1999-0307","DOIUrl":"https://doi.org/10.1515/irm-1999-0307","url":null,"abstract":"Abstract The reaction between [Ru(H2O)6]2+ and dimethylformamide (DMF) was studied as a function of the temperature and the pressure at pH 1. When a slight excess of Ru aquaion is used, [Ru(H2O)5DMF]2+ is the only product of the reaction observed in the NMR spectra and the DMF is bound through the oxygen atom. From variable temperature experiments, the rate constants, activation enthalpies and entropies for the formation and the dissociation of the monocomplex were determined. These are as follows: 104 x kf298=(8.2 ± 0.4) kg mol-1 s-1 ΔΗ☨f= 83.6 ± 3 k J mol-1 Δ S☨f = -23.7 ± 10 J K-1mol-1 for the formation reaction, 103 x kd298 = (1.10 ± 0.04) s-1 ΔΗ☨f= 90.2 ± 2 kJ mol-1 ΔS☨f, = +1.0 ± 7 J Κ-1 mol -1 for the dissociation reaction. The thermodynamic parameters (equilibrium constant at 298.15 K, reaction enthalpy and entropy) were also determined:K298eq = 0.74 ± 0.02 kg mol-1 , ΔH0 = -6.6 ± 2 k j mol-1 , ΔS0 =-24.7 ± 6 JK-1. The kf value is similar to the previously reported rate constants for monocomplex formation reactions with other ligands and confirms that the entering ligand has no effect on the rate. From variable pressure experiments, the activation volumes for the formation and the dissociation reactions and the reaction volume were determined: ΔVf☨ = +2.7 ± 0.6 cm3 mol-1 , ΔVd☨= 0.9 ± 0.7 cm3 mol-1 , ΔV° = +3.6 ± 0 . 9 cm3 mol -1 respectively. These results show that the volume of the transition state is intermediate between the volume of the reactants and the volume of the products. It demonstrates that the mechanism is the same as for the water exchange on [Ru(H2O)6 ] 2+ , i.e. an Id mechanism. Contraction of the bonds between Ru and the spectator ligands at the transition state may explain the abnormally small activation volumes. The need of theoretical calculations on these systems is emphasized.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83252664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The kinetics and mechanism of picolinic acid (PA)- catalysed oxidation of formic acid have been studied in aqueous HClO4 media under the experimental conditions, 103[Cr(VI)]T = 0.67-2.67 mol dm-3, [PA]T = 0.01-0.12 mol dm-3, [HCO2H]T = 0.1-0.8 mol dm-3, [H+] = 0.35-1.5 mol dm-3,1 = 1.5 mol dm-3 in the temperature range 25-40° C. The kinetic parameters of the catalysed path have been compared with those of the relatively slower uncatalysed path which proceed parallelly with the catalysed path. In the catalysed path, Cr(VI)-PA cyclic complex formed at the pre-equilibrium step receives a nucleophilic attack at the Cr(VI) centre by the substrate leading to a ternary complex with the release of a proton in a reversible path. Then the ternary complex experiences the redox decomposition at the rate-determining step giving rise to Cr(IV)-PA complex and CO2. Then the Cr(IV)-PA complex reacts faster ultimately giving rise to Cr(III)-PA complex. The anionic surfactant sodium dodecyl sulfate (SDS) catalyses both the uncatalysed and catalysed paths in aqueous HClO4 media while the cationic surfactant cetyl pyridinium chloride (CPC) inhibits the reactions in aqueous H2SO4 media. In the presence of the surfactants, applicability of the Piszkiewicz model has been tested for the ΡΑ-catalysed path. Micellar effects are in conformity with the proposed mechanism.
{"title":"Kinetics and Mechanism of the Chromium(VI) Oxidation of Formic Acid in the Presence of Picolinic Acid and in the Presence and Absence of Surfactants","authors":"A. Das","doi":"10.1515/irm-1999-0210","DOIUrl":"https://doi.org/10.1515/irm-1999-0210","url":null,"abstract":"Abstract The kinetics and mechanism of picolinic acid (PA)- catalysed oxidation of formic acid have been studied in aqueous HClO4 media under the experimental conditions, 103[Cr(VI)]T = 0.67-2.67 mol dm-3, [PA]T = 0.01-0.12 mol dm-3, [HCO2H]T = 0.1-0.8 mol dm-3, [H+] = 0.35-1.5 mol dm-3,1 = 1.5 mol dm-3 in the temperature range 25-40° C. The kinetic parameters of the catalysed path have been compared with those of the relatively slower uncatalysed path which proceed parallelly with the catalysed path. In the catalysed path, Cr(VI)-PA cyclic complex formed at the pre-equilibrium step receives a nucleophilic attack at the Cr(VI) centre by the substrate leading to a ternary complex with the release of a proton in a reversible path. Then the ternary complex experiences the redox decomposition at the rate-determining step giving rise to Cr(IV)-PA complex and CO2. Then the Cr(IV)-PA complex reacts faster ultimately giving rise to Cr(III)-PA complex. The anionic surfactant sodium dodecyl sulfate (SDS) catalyses both the uncatalysed and catalysed paths in aqueous HClO4 media while the cationic surfactant cetyl pyridinium chloride (CPC) inhibits the reactions in aqueous H2SO4 media. In the presence of the surfactants, applicability of the Piszkiewicz model has been tested for the ΡΑ-catalysed path. Micellar effects are in conformity with the proposed mechanism.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80008465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract New complexes of Ln(III) nitrate with 2-hydroxy-lbenzylidene- 2-furoyl hydrazine having the general formula [Ln(L)2NO3]H2O (where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y; L = 2-hydroxy-l-benzylidene- 2-furoyl hydrazine) have been prepared and characterized by elemental analysis, molar conductance, magnetic measurements, electronic, infrared, 1H NMR and thermal studies. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. Based on the spectral and TG studies, a coordination number of eight around the metal ions is proposed.
{"title":"Thermo-kinetic and Spectral Studies of Lanthanide(III) Complexes with 2-Hydroxy-l -benzylidene-2-furoyl Hydrazine","authors":"P. B. Maravalli, T. R. Goudar","doi":"10.1515/irm-1999-0305","DOIUrl":"https://doi.org/10.1515/irm-1999-0305","url":null,"abstract":"Abstract New complexes of Ln(III) nitrate with 2-hydroxy-lbenzylidene- 2-furoyl hydrazine having the general formula [Ln(L)2NO3]H2O (where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y; L = 2-hydroxy-l-benzylidene- 2-furoyl hydrazine) have been prepared and characterized by elemental analysis, molar conductance, magnetic measurements, electronic, infrared, 1H NMR and thermal studies. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. Based on the spectral and TG studies, a coordination number of eight around the metal ions is proposed.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82038574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The kinetics and mechanism of chromium(III) catalysed oxidation of propan-1-ol and butan-1-ol by cerium(IV) in aqueous sulfuric acid media have been studied at different temperatures (30-40° C) under the conditions, [substrate]T(0.025-0.70 mol dm-3) × [CeIV]T (2.5-4.5 × 10-3 mol dm-3) in the presence of [Cr]T = 0.0025-0.07 mol dm-3. At fixed [H+] and [HSO-4 ] the observed rate law conforms to: -d ln[CeIV]/df =kobs =A[S]T[Cr]T/{B + C[Cr]T(D + E[S]T)}, where, A, B, C, D and Ε are constants expressed in terms of different rate constants and equilibrium constants; [S]Tand [Cr]T denote the total substrate (i.e. propan-l-ol or butan-l-ol) and total chromium concentration respectively. The proposed mechanism involves the association of catalyst, substrate and oxidant at some pre-equilibrium steps before the electron transfer step. The overall process is found catalysed by H+ . From the [HSO-4] dependence, Ce(SO4)2 has been found kinetically active.
{"title":"Kinetics and Mechanism of Chromium(III) Catalysed Oxidation of Propan-1-ol and Butan-1-ol by Cerium(IV) in Aqueous Sulfuric acid Media","authors":"A. Das, S. Mondal, D. Kar, M. Das","doi":"10.1515/irm-1999-0211","DOIUrl":"https://doi.org/10.1515/irm-1999-0211","url":null,"abstract":"The kinetics and mechanism of chromium(III) catalysed oxidation of propan-1-ol and butan-1-ol by cerium(IV) in aqueous sulfuric acid media have been studied at different temperatures (30-40° C) under the conditions, [substrate]T(0.025-0.70 mol dm-3) × [CeIV]T (2.5-4.5 × 10-3 mol dm-3) in the presence of [Cr]T = 0.0025-0.07 mol dm-3. At fixed [H+] and [HSO-4 ] the observed rate law conforms to: -d ln[CeIV]/df =kobs =A[S]T[Cr]T/{B + C[Cr]T(D + E[S]T)}, where, A, B, C, D and Ε are constants expressed in terms of different rate constants and equilibrium constants; [S]Tand [Cr]T denote the total substrate (i.e. propan-l-ol or butan-l-ol) and total chromium concentration respectively. The proposed mechanism involves the association of catalyst, substrate and oxidant at some pre-equilibrium steps before the electron transfer step. The overall process is found catalysed by H+ . From the [HSO-4] dependence, Ce(SO4)2 has been found kinetically active.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84333865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The title trivalent nickel complex, Ni(III)L, oxidizes formate in slightly acidic solutions via an inner sphere, single electron, rate determining step. The rate of oxidation of the formate in Ni(III)L(H2O) (HCO2)+2 is considerably faster than in Ni(III)L(H2PO4 )(HCO2-)+ and in Ni(III)L(HCO2-)+2. The results point out that formate has an ambivalent role in this process; on the one hand it is the reducing agent but on the other hand it stabilizes the trivalent nickel complex.
{"title":"On the Mechanism of Oxidation of Formate by Ni(III) (meso-5,7,7,12,14,14-hexamethy 1-1,4,8,11 - tetraazacyclotetradecane) in Aqueous Solutions","authors":"A. Meshulam, A. Masarwa, H. Cohen, D. Meyerstein","doi":"10.1515/irm-1999-0303","DOIUrl":"https://doi.org/10.1515/irm-1999-0303","url":null,"abstract":"Abstract The title trivalent nickel complex, Ni(III)L, oxidizes formate in slightly acidic solutions via an inner sphere, single electron, rate determining step. The rate of oxidation of the formate in Ni(III)L(H2O) (HCO2)+2 is considerably faster than in Ni(III)L(H2PO4 )(HCO2-)+ and in Ni(III)L(HCO2-)+2. The results point out that formate has an ambivalent role in this process; on the one hand it is the reducing agent but on the other hand it stabilizes the trivalent nickel complex.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89984214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The kinetics of the interaction of adenosine with [Pt(en)(H2O)2]2+ has been studied spectrophotometrically as a function of [Pt(en)(H2O)2+], [Adenosine] and temperature at a particular pH (4.0) where the substrate complex exists predominantly as the diaqua species and the ligand adenosine as a neutral molecule. The interaction reaction shows distinct two step consecutive process; the first step is the ligand assisted anation and the second step is the chelation step. The activation parameters for both the steps are calculated (Δ H≠1 = 63.7 ± 1.6 kJ mol-1 ΔS1≠ = - 58± 5 JK -1 mol -1 and Δ H2≠ = 41.0 ± 0.5 kj mol -1 ΔS2≠ = 197 ± 1.5 JK1 mol-1 ).
{"title":"Kinetic and Mechanistic Studies on the Interaction of Adenosine with Diaquaethylenediamineplatinum(II) Ion","authors":"S. Ghosh, G. S. De, A. Ghosh","doi":"10.1515/irm-1999-0302","DOIUrl":"https://doi.org/10.1515/irm-1999-0302","url":null,"abstract":"Abstract The kinetics of the interaction of adenosine with [Pt(en)(H2O)2]2+ has been studied spectrophotometrically as a function of [Pt(en)(H2O)2+], [Adenosine] and temperature at a particular pH (4.0) where the substrate complex exists predominantly as the diaqua species and the ligand adenosine as a neutral molecule. The interaction reaction shows distinct two step consecutive process; the first step is the ligand assisted anation and the second step is the chelation step. The activation parameters for both the steps are calculated (Δ H≠1 = 63.7 ± 1.6 kJ mol-1 ΔS1≠ = - 58± 5 JK -1 mol -1 and Δ H2≠ = 41.0 ± 0.5 kj mol -1 ΔS2≠ = 197 ± 1.5 JK1 mol-1 ).","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84023265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nausica De Barrios, Gabriel González, A. Grandas, Manuel A Martínez, V. Moreno
Abstract The substitution reactions on cis-[Pd(L-Histidine)- (H2O)2 ]2 + by chloride, adenine, guanosine, adenosine, 5 -GMP, 5'-AMP, 3-AMP, d(ApG) and d(GpA) has been studied at pH = 1.0-3.0 at different temperatures. The study at physiological pH had to be avoided due to undesired polymerization reactions. The results indicate a certain degree of unsensitivity of the substitution reactions by purine based ligands at this low pH when compared with other published studies. In particular, no cooperative effect is observed in the 5'-monophosphates and N(7)adenine and N(7)guanine are found to react at the same rate within experimental error. Results agree with the published values for similar systems and differences for the 5'- and 3'-monophosphates are detected both in the monophosphates and in the dinucleotides.
{"title":"Substitution Reactions on Pd(II) L-Histidine-diaqua Complexes: Comparative View from Chloride to Nucleobases and Dinucleotides","authors":"Nausica De Barrios, Gabriel González, A. Grandas, Manuel A Martínez, V. Moreno","doi":"10.1515/irm-1999-0304","DOIUrl":"https://doi.org/10.1515/irm-1999-0304","url":null,"abstract":"Abstract The substitution reactions on cis-[Pd(L-Histidine)- (H2O)2 ]2 + by chloride, adenine, guanosine, adenosine, 5 -GMP, 5'-AMP, 3-AMP, d(ApG) and d(GpA) has been studied at pH = 1.0-3.0 at different temperatures. The study at physiological pH had to be avoided due to undesired polymerization reactions. The results indicate a certain degree of unsensitivity of the substitution reactions by purine based ligands at this low pH when compared with other published studies. In particular, no cooperative effect is observed in the 5'-monophosphates and N(7)adenine and N(7)guanine are found to react at the same rate within experimental error. Results agree with the published values for similar systems and differences for the 5'- and 3'-monophosphates are detected both in the monophosphates and in the dinucleotides.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76494063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The kinetics of oxidation of tellurium(IV) (Te(IV)) by diperiodatonickelate(IV) (DPN) in aqueous alkaline medium has been studied spectrophotometrically. The reaction exhibits first order in [DPN] and fractional order both in [Te(IV)] and [OH-]. Periodate has a retarding effect on the rate of reaction. Effects of added products, ionic strength and dielectric constant of the reaction medium have been investigated. A mechanism involving the monoperiodatonickelate( IV) (MPN) as the reactive species of the oxidant has been proposed. The constants involved in the mechanism are obtained. There is a good agreement between the observed and calculated rate constants. The activation parameters are computed with respect to the slow step of the mechanism.
{"title":"Kinetics and Mechanism of Oxidation of Tellurium(IV) by Alkaline Diperiodatonickelate(IV)","authors":"A. L. Harihar, M. R. Kembhavi, S. Nandibewoor","doi":"10.1515/irm-1999-0208","DOIUrl":"https://doi.org/10.1515/irm-1999-0208","url":null,"abstract":"Abstract The kinetics of oxidation of tellurium(IV) (Te(IV)) by diperiodatonickelate(IV) (DPN) in aqueous alkaline medium has been studied spectrophotometrically. The reaction exhibits first order in [DPN] and fractional order both in [Te(IV)] and [OH-]. Periodate has a retarding effect on the rate of reaction. Effects of added products, ionic strength and dielectric constant of the reaction medium have been investigated. A mechanism involving the monoperiodatonickelate( IV) (MPN) as the reactive species of the oxidant has been proposed. The constants involved in the mechanism are obtained. There is a good agreement between the observed and calculated rate constants. The activation parameters are computed with respect to the slow step of the mechanism.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89027617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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