Thermal behaviour of 9-cyanoanthracene photodimer (9-CNAD)

Abstract

The monomerization reaction of 9-cyanoanthracene photodimer (9-CNAD) in the solid state has been reinvestigated both in isothermal and in linearly increasing temperature experiments using thermal methods and optical microscopy. From both kinds of calorigrams the heat of monomerization has been deduced in agreement with previous findings; the heat of melting of the crystalline monomer (9-CNA) formed during the monomerization reaction has also been redetermined. With supporting evidence from optical microscopy studies, a three-stage mechanism is proposed for the monomerization reaction; agreement with recent reports is found only for the induction period. Our isothermal experiments show that, in the temperature range of interest, the solid-state monomerization reaction of 9-CNAD requires times far longer than those recently reported by other authors. Additional evidence is presented supporting our previous interpretation of the nature of the initial exothermic peak typical of the monomerization thermal curves.