STUDIES IN CRYSTAL ENGINEERING - STRUCTURE-REACTIVITY CORRELATIONS OFSUBSTITUTED STYRYLCOUMARINS AND RELATED SYSTEMS

The solid state photochemical behaviour of 7-hydroxy-4-styrylcoumarin 1 and several of its derivatives and analogues has been investigated. All the compounds with the exception of 7-methoxy-4-styrylcoumarin 2 a re photolabile and yield anti-HT dimers. It has been observed that chl oro substitution in the systems studied does not lead to the expected beta-packing mode. The photobehaviour of 1 and 2 has been correlated w ith their crystal structures. Reasons for alpha-packing have been exam ined. The systematics in the arrangement of the carbonyl group and phe nyl group of the close neighbours in the crystals of 1, 2 and a few ot her cases are presented.