Absorbance variation in time, connected to complex formation, is spectrophotometrically observed at two different temperatures. Spectra broadening upon reaction suggests some aggregation of the formed metal complex. Due to the presence of high metal ion amounts respect to ligand (pseudo-first order conditions) the curves can be analysed by a mono-exponential equation, yielding for each curve amplitude (amp) and reciprocal relaxation time (1/t) parameters. The initial rate (slope of the very first part of the plot) can also be obtained. Constancy of the curves amplitude and zero intercept of the 1/t vs. [Pd] plot indicate a quantitative process taking place (kd = 0). The slope of the dilogarithmic plot of the initial rates values is equal to one, indicating a first order reaction respect to palladium in agreement with formation of a 1:1 complex. The above considerations are true both at 25 °C and at 40°C.Addition of DNA produces bathochromic and hypochromic effects consistent with intercalation of the metal complex between DNA base pairs. However, the non-perfect isosbestic points suggest non-simple equilibria i.e. complex mechanism of interaction. Calculations on the binding isotherm resulting form titrations indicate quantitative binding, even in the presence of relatively high salt content (1.0 M NaCl).
(meso-Tetrakis(1-methyl-4-pyridinium)porphyrinato)Pd(II) complex: kinetics of formation and DNA binding
BIVER, TARITA;
2015-01-01
Abstract
Absorbance variation in time, connected to complex formation, is spectrophotometrically observed at two different temperatures. Spectra broadening upon reaction suggests some aggregation of the formed metal complex. Due to the presence of high metal ion amounts respect to ligand (pseudo-first order conditions) the curves can be analysed by a mono-exponential equation, yielding for each curve amplitude (amp) and reciprocal relaxation time (1/t) parameters. The initial rate (slope of the very first part of the plot) can also be obtained. Constancy of the curves amplitude and zero intercept of the 1/t vs. [Pd] plot indicate a quantitative process taking place (kd = 0). The slope of the dilogarithmic plot of the initial rates values is equal to one, indicating a first order reaction respect to palladium in agreement with formation of a 1:1 complex. The above considerations are true both at 25 °C and at 40°C.Addition of DNA produces bathochromic and hypochromic effects consistent with intercalation of the metal complex between DNA base pairs. However, the non-perfect isosbestic points suggest non-simple equilibria i.e. complex mechanism of interaction. Calculations on the binding isotherm resulting form titrations indicate quantitative binding, even in the presence of relatively high salt content (1.0 M NaCl).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
