A COMPREHENSIVE KINETIC, THERMODYNAMIC AND PHOTOCHEMICAL STUDY OF SOME SPIRO-INDOLINE-OXAZINES

The thermoreversible photochromic reaction of spiro-indoline-oxazines to photo-merocyanines has been studied by stationary spectrophotometri c techniques. Two methods are described for determining the molar abso rption coefficient of the metastable photomerocyanine and the quantum yield of the colour-forming photoreaction. Kinetic parameters (reactio n rate and activation energy) and thermodynamic quantities (equilibriu m constant and enthalpy) of the thermal reaction have also been determ ined. Based on the results obtained, some general correlations between the structure of these molecules and their photochromic and thermochr omic properties have been drawn.