Yves Ducommun

High-Pressure Stopped-Flow Spectrometer for Kinetic Studies of Fast Reactions by Absorbance and Fluorescence Detection

The development of a stopped-flow instrument that operates over a temperature range of -40 to +100 °C and up to 200 MPa is described. The system has been designed so that measurements can be performed in absorbance and fluorescence modes simultaneously, without dismantling the unit. It can easily be combined with an optical system of a conventional ambient pressure setup by using light guides. Optimum optical performance and a wide operating wavelength range (220-850 nm) are achieved as the light is not passing through the pressurizing fluid. A special design for the pistons has been developed; thus, the apparatus has proven to be leak-free, even under extreme conditions (high pressure, low temperature, various solvents). The dead time of the system is found to be less than 2 ms at 298 K and is pressure independent up to 200 MPa. We examined the kinetics for the formation of the Mg(2+)-8-hydroxyquinoline chelate in aqueous solutions at pH 8.0 in order to develop a convenient alternative test method for high-pressure stopped-flow spectrometers with absorption and fluorescence detection.

Solvent exchange and complex formation reactions of Pd(II) in aqueous solution: mechanistic information from high pressure studies

Abstract High pressure NMR and stopped-flow techniques have been employed to study a series of water exchange and complex formation reactions of Pd(II) outlined in (1) and (2). The volumes of activation show an interesting correlation with the partial molar volume of the entering ligand and underline the operation of an associative substitution mechanism in all cases.