15034-27-2Relevant articles and documents
Primary photochemical processes for Pt(IV) diazido complexes prospectIVe in photodynamic therapy of tumors
Shushakov, Anton A.,Pozdnyakov, Ivan P.,Grivin, Vjacheslav P.,Plyusnin, Victor F.,Vasilchenko, Danila B.,Zadesenets, Andrei V.,Melnikov, Alexei A.,Chekalin, Sergey V.,Glebov, Evgeni M.
, p. 9440 - 9450 (2017/08/03)
Diazide diamino complexes of Pt(iv) are considered as prospective prodrugs in oxygen-free photodynamic therapy (PDT). Primary photophysical and photochemical processes for cis,trans,cis-[Pt(N3)2(OH)2(NH3)2] and trans,trans,trans-[Pt(N3)2(OH)2(NH3)2] complexes were studied by means of stationary photolysis, nanosecond laser flash photolysis and ultrafast kinetic spectroscopy. The process of photolysis is multistage. The first stage is the photosubstitution of an azide ligand to a water molecule. This process was shown to be a chain reaction involving redox stages. Pt(iv) and Pt(iii) intermediates responsible for the chain propagation were recorded using ultrafast kinetic spectroscopy and nanosecond laser flash photolysis. The mechanism of photosubstitution is proposed.
Acid-base equilibrium dynamics in methanol and dimethyl sulfoxide probed by two-dimensional infrared spectroscopy
Lee, Chiho,Son, Hyewon,Park, Sungnam
, p. 17557 - 17561 (2015/07/07)
Two-dimensional infrared (2DIR) spectroscopy, which has been proven to be an excellent experimental method for studying thermally-driven chemical processes, was successfully used to investigate the acid dissociation equilibrium of HN3 in methanol (CH3OH) and dimethyl sulfoxide (DMSO) for the first time. Our 2DIR experimental results indicate that the acid-base equilibrium occurs on picosecond timescales in CH3OH but that it occurs on much longer timescales in DMSO. Our results imply that the different timescales of the acid-base equilibrium originate from different proton transfer mechanisms between the acidic (HN3) and basic (N3-) species in CH3OH and DMSO. In CH3OH, the acid-base equilibrium is assisted by the surrounding CH3OH molecules which can directly donate H+ to N3- and accept H+ from HN3 and the proton migrates through the hydrogen-bonded chain of CH3OH. On the other hand, the acid-base equilibrium in DMSO occurs through the mutual diffusion of HN3 and N3- or direct proton transfer. Our 2DIR experimental results corroborate different proton transfer mechanisms in the acid-base equilibrium in protic (CH3OH) and aprotic (DMSO) solvents.
Kinetic and spectroscopic observations on the azidyl, N3{radical dot}, radical oxidation of fac-(Lspectator)ReI(CO)3(Lacceptor ) to fac-(Lspectator)ReII(CO)3(Laccepto r), Lspectator = 4,4′-bpy; Lacceptor ...
Ruiz,Juliarena,Wolcan,Ferraudi
, p. 3681 - 3687 (2008/10/09)
Full title: Kinetic and spectroscopic observations on the azidyl, N3{radical dot}, radical oxidation of fac-(Lspectator)ReI(CO)3(Lacceptor ) to fac-(Lspectator)ReII(CO)3(Laccepto r), Lspectator = 4,4′-bpy; Lacceptor = dipyridyl[3,2-a:2′3′-c]phenazine or Lspectator = Cl-; Lacceptor = bathocuproindisulfonate: A revisitation to the self-exchange rate constants of the N3{radical dot} / N3- and Re(II)/Re(I) couples and to the redox potential of the N3{radical dot} radical The oxidation of two triscarbonyl fac-(Lspectator)ReI(CO)3(Lacceptor )z complexes (Lspectator = 4,4′-bpy; Lacceptor = dipyridyl[3,2-a:2′3′-c]phenazine (dppz) and z = + or Lspectator = Cl-; Lacceptor = bathocuproinedisulfonate (bcds2-) and z = 2-) by azidyl radicals, N3{radical dot}, was investigated by pulse radiolysis. Reaction rate constants were determined for the electron transfer reactions between the Re(II) products and reductants, Ru (bipy)33 + and Ni(Me6-[14]dieneN4)2+, and used for the calculation of the self-exchange rate constant of the Re(II)/Re(I) couples. The self-exchange rate constants, k ～ 107 M-1 s-1, were one order of magnitude larger than the constant, k ～ 106 M-1 s-1, communicated in the literature for the [Re(DMPE)3]+/2+ (DMPE = 1,2-bis(dimethylphosphine)ethane). The larger rate constants of the triscarbonyl complexes are in agreement with the smaller inner sphere reorganization energy of the complexes relative to [Re(DMPE)3]+/2+. Moreover, the study demonstrated that the redox potential of the azidyl radicals is EN3{radical dot} / N3-0 = 1.70 V versus NHE, a value larger than one communicated earlier, and that the self-exchange rate constant of the N3{radical dot} / N3- couple is kN3{radical dot} / N3- = 2.7 × 106 M- 1 s- 1. The small value of the N3{radical dot} / N3- self-exchange rate constant has been related to the large solvent reorganization energy of the reaction.
Reactions of laser-ablated osmium and ruthenium atoms with nitrogen. Matrix infrared spectra and density functional calculations of osmium and ruthenium nitrides and dinitrides
Citra, Angelo,Andrews, Lester
, p. 1152 - 1161 (2007/10/03)
Laser-ablated osmium and ruthenium atoms were reacted with nitrogen molecules; the products were isolated in solid argon and nitrogen and identified by infrared spectroscopy. Both MN and NMN nitrides are observed, and estimates for the triatomic bond angles are made using nitrogen and ruthenium isotopic data. The growth of NOsN on annealing in solid argon suggests that osmium atoms insert into the dinitrogen triple bond at cryogenic temperatures, allowing a lower limit of ～473 kJ/mol to be estimated for the average Os-N bond energy in NOsN. The force constants for MN and NMN (M= Fe, Ru, Os) were calculated using all available isotopic data; force constants increase moving down the metal group, and diatomic MN force constants are larger than those for the corresponding NMN triatomic molecules. DFT calculations for the ruthenium and osmium nitrides give reasonable agreement with experiment. Bonding analyses for these molecules show . that the M-N bonds are largely nonpolar with bond orders in the range 2.5-3.0. Several metal dinitrogen complexes are also observed and assignments are proposed.
Reactions of laser-ablated aluminum atoms with nitrogen atoms and molecules. Infrared spectra and density functional calculations for the AlN2, Al2N, Al2N2, AlN3, and Al3N molecules
Andrews, Lester,Zhou, Mingfei,Chertihin, George V.,Bare, William D.,Hannachi, Yacine
, p. 1656 - 1661 (2007/10/03)
Laser-ablated aluminum atoms react with dinitrogen on condensation at 10 K to form N3 radical and the subject molecules, which are identified by nitrogen isotopic substitution, further reactions on annealing, and comparison with isotopic frequencies computed by density functional theory. The major AlN3 product is identified from three fundamentals and a statistically mixed nitrogen isotopic octet pattern. The aluminum rich Al2N and Al3N species are major products on annealing to allow diffusion and further reaction of trapped species. This work provides the first experimental evidence for molecular AlxNy species that may be involved in ceramic film growth.
Reduction potentials of so3·- , so5·- , and S4O6·3- radicals in aqueous solution
Das, Tomi Nath,Huie, Robert E.,Neta
, p. 3581 - 3588 (2007/10/03)
Reduction potentials of the SC3·- , SO5·- , and S4O63·- radicals in aqueous solutions are measured by pulse radiolysis at 294 K. These radicals are produced by reaction of ·OH or N3· radicals with sulfite, peroxymonosulfate, and thiosulfate anions, respectively. The potentials for the couples SO3·-/SO32- and SO5·-/ SO52- are determined from equilibrium constants with three reference couples of the phenoxyl/phenoxide type, i.e., those derived from phenol, 3-cresol, and tyrosine. The potential for PhO·/PhO- is redetermined against ClO2·/ClO2- and confirms the published value. The potentials for the other two phenols are determined against PhO·/PhO-. The potential for the SO3·-/SO32- couple is found to be 0.73 ± 0.01 V vs·NHE. The potential for SO5·-/SO52- is found to be 0.81 ± 0.02 V. The reduction potential of the radical formed from the one-electron oxidation of thiosulfate, which exhibits a λmax at 375 nm, is also determined. This radical was identified before as either the monomeric S2O3·- or the dimeric S4O6·3-. Equilibrium measurements for this species, using N3· and the 4-cyanophenoxyl radical as references, support the dimeric assignment and yield a value of 1.07 ± 0.03 V for the reduction potential for the couple S4O6·3- /2S2O32-.
Oxidation of peroxynitrite by inorganic radicals: A pulse radiolysis study
Goldstein, Sara,Saha, Abhijit,Lymar, Sergei V.,Czapski, Gidon
, p. 5549 - 5554 (2007/10/03)
Reactivity of the peroxynitrite ion toward a number of inorganic radicals was determined by using the pulse radiolysis technique. The rate constants for the oxidation of the ONOO- ion by CO3·-, ·N3, and ClO2· radicals were determined from their decay kinetics to be (7.7 ± 1.2) x 106 (I = 0.6 M), (7.2 ± 0.9) x 108, and (3.2 ± 0.3) x 104 M-1 s-(l), respectively. For the ·OH radical, the rate constant of (4.8 ± 0.8) x 109 M-1 s-1 was obtained by using competition kinetic analysis. The oxidation potential of the ONOO- ion was estimated as 0.8 V from the kinetic data. Although thermodynamically favorable, oxidation of ONOO- by the °NO2 radical was not observed; an upper limit of 2.5 x 104 M-1 s-1 could be set for this reaction. Contribution from some of these reactions to the decomposition of peroxynitrite in the presence and absence of CO2 is discussed.
Substitution kinetics of the aqua ligand in [Re(NO)(H2O)(CN)4]2- by the monodentate nucleophiles SCN-, N3- and thiourea and the X-ray crystal structure of (AsPh4)2[Re(NO)(SC(NH2)2)(CN) 4]
Smith, John,Purcell, Walter,Lamprecht, Gert J.,Roodt, Andreas
, p. 1389 - 1395 (2008/10/09)
The substitution reactions between [Re(NO)(H2O)(CN)4]2- and the nucleophiles SCN-, N3- and thiourea revealed that both the aqua and the hydroxo ligands are substituted with respective rate constants of 3.6(1) × 10-3 and 1.57(5) × 10-3 M-1 s-1 at 40°C in the case of SCN-. The pKa1 was spectrophotometrically determined as 9.90(2) at 25°C and kinetically as 9.50(4) at 40°C with NCS- as the incoming nucleophile. The (AsPh4)2[Re(NO)(SC(NH2)2)(CN) 4] complex was isolated as the product for the reaction between [Re(NO)(H2O)(CN)4]2- and thiourea and its X-ray crystal structure determined. The Re - NO and N - O bond lengths are 1.736(11) and 1.146(13) A, respectively, while the Re - S bond distance is 2.503(4) A. The thiourea is bonded cis with respect to the nitrosyl group.
Decrease in the Oxidation Potential of the Tris-2,2'-bipyridyl Ruthenium(II) Complex Upon Electrostatic Binding to Colloidal Silica as Evidenced on the Basis of the Reaction with the Azidyl Radical
Naik, Devidas B.,Schnabel, Wolfram
, p. 1559 - 1562 (2007/10/02)
The azidyl radical which is otherwise unreactive towards the Ru(bpy)32+ complex reacts with this complex in aqueous solution provided negatively charged colloidal silica particles are present.The increase in reactivity is explained in terms of ion binding, i.e.Ru(bpy)32+ complexes becoming rather firmly attached to the negatively charged particles.The attachment causes a decrease in the redox potential of the system Ru(bpy)33+/Ru(bpy)32+ from E0 = 1.27 V vs.NHE (in the absence of colloidal silica) to E0 = 1.17 V vs.NHE (in the presence of colloidal silica).This value was obtained on the basis of E0 = 1.35 V vs.NHE for the system .N3/N3-. - Keywords: Colloides / Complex Compounds /Radiation Chemistry / Radicals
Temperature Dependence of the Rate Constants for Reaction of Dihalide and Azide Radicals with Inorganic Reductants
Shoute, L. C. T.,Alfassi, Z. B.,Neta, P.,Huie, R. E.
, p. 3238 - 3242 (2007/10/02)
Rate constants for several reactions of inorganic radicals with inorganic reductants in aqueous solutions have been measured by pulse radiolysis as a function of temperature, generally between 5 and 75 deg C.The reactions studied were of the dihalide radicals, Cl2.-, Br2.-, and I2.-, the (SCN).- radical, and the neutral radical N3., reacting with the substitution-inert metal complexes, Fe(CN)6(4-), Mo(CN)8(4-), and W(CN)8(4-), and with the anions SO3(2-), HSO3(1-), NO2(1-), and ClO2(1-).The rate constants measured were in the range of 1E6 to 5E9 M-1 s-1and the calculated Arrhenius activation energies ranged from 5 to 35 kJ mol-1.The preexponential factors also varied considerably, with log A ranging from 8.9 to 13.1.The temperature dependence of the reaction rate constant is correlated to the reaction exothermicity for the metal complexes, which apparently react by outer-sphere electron transfer.The simple anions, however, have lower activation energies, which do not correlate well with the exothermicities, suggesting that these anions probably react by inner-sphere mechanism.
