Tayloring of the optical properties by symmetry modification of substituted quaterthiophene single crystals

We report an optical study of polymorphic single crystals of a polysubstituted alpha-conjugated quaterthiophene. The crystals exhibit two crystalline symmetries (monoclinic and triclinic) with different energy gaps and lifetimes of the elementary excitations. Their optical properties are correlated to the molecular structure, showing that the functionalization process determines an intrinsic tuning of the crystal properties. (C) 1998 American Institute of Physics.