Kinetic-morphological peculiarities of solid-state isomerization of complexes

Abstract

The thermal solid-state isomerizations of Copy2Cl 2 (py = pyridine), Nien2(NO2) 2 and Nien2(NCS) 2 (en = ethylenediamine) were studied by thermal analysis, thermomieroscopy, Xray diffraction and IR-speetroscopy. It was shown that the reactions proceed by nuclear formation and growth. The kinetic-morphological peculiarities of the processes suggest that the process-determining stage is a phase Stage, i. e. structural transformation. The topography and kinetics of processes are therefore determined by the crystal structures of the initial material and the reaction product, and by the contact conditions at the interface. The stress relaxation processes affect the morphology of the products and the kinetics of the transformation.In recent years an increasingly large number of investigations involving solidstate isomerizations of coordination compounds have been reported. On the basis of kinetic and structural studies, the mechanisms of these processes have been proposed in some cases. However, little has been accomplished as regards the topochemistry of these reactions.This report presents a brief summary of research on the topochemical peculiarities (topography, kinetics and product morphology) of the thermal solidstate isomerizations of certain Co(II) and Ni(II) complexes: Copy2Cl 2 (py = pyridine), NienE(NO2) 2 (en = ethylenediamine).

Solventless isomerisation reactions: A crystallographic and thermomicroscopic investigation of some six coordinate RuCl2L2L′2complexes

“…This is a classical process well described in the literature. 17,18 However, the nucleation sites grow anisotropically. Significant isomerisation (darkening) is initially localised (pictures 4 and 5), followed by anisotropic interface advance (mainly along crystal edges, pictures 6-9) that combines with nucleation sites that have hitherto experienced only limited growth.…”