Analysis and improvement of rate constant determination of reactions involving charged reactants.
Kinetics of tris(2,2'-bipyridine)ruthenium(ii), Ru(bpy)(3)(2+), luminescence quenching by copper(ii) (in the form of chloride, nitrate, sulfate and perchlorate salt) was studied using pulse laser photolysis technique. The pseudo-first order rate constant versus quencher concentration plots obtained were found to be nonlinear, bending upward. The ionic strength effect contribution was evaluated by applying the Debye-Hückel extended law and was found to be as important as other effects such as cation-counter anion complex and ion-pairing complex formation which were all found to be dependent on the counter anion. It is shown that the slope of the tangent line to the pseudo-first order curve at zero quencher concentration is equal to the quenching rate constants at zero ionic strength. Also, this value corresponds to quenching solely by Cu(2+) and is free from contributions from other species that are present at higher concentrations. This method produced a value, (1.6 +/- 0.2) x 10(7) M(-1) s(-1), (lower than previously published ones) which is in agreement with the quenching rate constant measurement analysis presented. Comparison between Stern-Volmer plots obtained using steady-state fluorimetry data and laser photolysis data showed that in 50 mM CuCl(2) and CuSO(4) aqueous solutions about 5% of Ru(bpy)(3)(2+) is in the form of ion-pairing complexes. Our method was also applied to quenching by another divalent cation, methyl viologen, where it was found that charge transfer complexation effect contribution was about 50% of that of ionic strength effect, while ion-pairing complexation was not significant in the concentration range used. The quenching rate constant at zero ionic strength was found to be (2.3 +/- 0.2) x 10(8) M(-1) s(-1). The method proposed is also applicable to pulse radiolysis and stopped flow measurements.
Hydrates of copper dichloride in aqueous solution: a density functional theory and polarized continuum model investigation.
In this work, the hydrates of copper dichloride in gas and aqueous phase have been investigated using the B3LYP method. Low-lying conformers of CuCl(2)(H(2)O)(n) clusters for n = 1-10 were obtained by an extensive conformation search. Contact ion pair (CIP) and solvent-shared ion pair (SSIP) with one dissociated chloride atom (SSIP/s) and SSIP with two dissociated chloride atoms (SSIP/d) all were considered. Our calculations present such a trend that a four-fold CIP conformer is more favorable for CuCl(2)(H(2)O)(n) cluster (n < or = 7) and four-fold SSIP/s for n = 8-10 in the gas phase, while in aqueous solution, more stable structures are five-fold SSIP/s conformer for n = 7-9 and four-fold CIP conformer for n = 2-6. Hydrogen bond (HB) plays an important role in the CuCl(2) solvation, especially HBs formed between the first and second solvation shell water molecules. Electronic absorption spectra of CuCl(2)(H(2)O)(n) clusters were obtained using long-range-corrected time-dependent density functional theory. The calculated electronic absorption peak around 270 nm of CIP conformers is coincident with the absorption of [CuCl(2)](0)(aq) species resolved from the spectra obtained in solutions of trace CuCl(2) (ca. 10(-5) mol/kg) + LiCl (0-18 m), while those of SSIP/s (approximately 250 nm) and SSIP/d (approximately 180 nm) conformers probably correspond to the absorption spectra of [CuCl](+)(aq) and [Cu](2+)(aq) species, respectively. Natural bond orbital charge population analyses show that charge transfer (CT) between a central copper(II) atom and ligands (Cl and H(2)O) increases as the hydrated cluster expands, especially CT from Cu(2+) to the first solvation shell, which enhances the strength of HBs. Such CT becomes more apparent for SSIP structure with the dissociation of chloride ion. OH stretching vibration frequencies of proton donor type water in CuCl(2)(H(2)O)(n) clusters are obviously red-shifted in comparison to those of water clusters, due to CT between the central atom Cu and ligands. SSIP conformers have apparent IR absorption peaks of OH stretching vibration at approximately 3000 cm(-1) for the effect of half-dissociated chloride atoms.
Production of new antituberculosis drug and other medical preparations by electron beam treatment
Abstract Possibility of electron beam usage for immobilization of hydrazidum of an isonicotinic acid (HIA) on dextrane was studied to produce a drug for treatment of a tuberculosis. As a result of irradiation of dextrane the processes of oxidation and formation of polysaccharide occur due to carbonyl groups which are to link isoniasidum. The HIA immobilized on dextrane may be used as an effective medical preparation having prolonged action for action on endo and extracellular population of Micobacterium tuberculosis .