Studies in crystal engineering: crystal packing, topological photodimerization and structure–reactivity correlations in fluoro-substituted styrylcoumarins

Abstract

In continuation of our studies on the influence of fluoro substitution on the solid state photobehaviour and packing pattern of styrylcoumarins, the results obtained for 4-(3-fluorostyryl)coumarin 1, 4-styryl-6-fluorocoumarin 2 and 4-styryl-7-fluorocoumarin 3 are presented. The configuration of the dimers was established on the basis of crystal packing of 1 and 2 (α-packed). A rationale for the significantly lower dimer yield in the crystal for 2 is proposed. In the observed centrosymmetric arrangement of the reactants the CO · · · π (phenyl) contacts seem to provide additional attractive interactions. C–H · · · O and C–H · · · F hydrogen bonding seems to provide stability in these structures.