STUDIES IN CRYSTAL ENGINEERING - CRYSTAL PACKING, TOPOLOGICAL PHOTODIMERIZATION AND STRUCTURE-REACTIVITY CORRELATIONS IN FLUORO-SUBSTITUTEDSTYRYLCOUMARINS

In continuation of our studies on the influence of fluoro substitution on the solid state photobehaviour and packing pattern of styrylcoumar ins, the results obtained for 4-(3-fluorostyryl)coumarin 1, 4-styryl-6 -fluorocoumarin 2 and 4-styryl-7-fluorocoumarin 3 are presented. The c onfiguration of the dimers was established on the basis of crystal pac king of 1 and 2 (alpha-packed). A rationale for the significantly lowe r dimer yield in the crystal for 2 is proposed. In the observed centro symmetric arrangement of the reactants the C=O ...pi (phenyl) contacts seem to provide additional attractive interactions. C-H ... O and C-H ... F hydrogen bonding seems to provide stability in these structures .