Relationship between optical and structural properties in substituted quaterthiophene crystals

The optical properties of polysubstituted α-conjugated quaterthiophene crystals display marked differences depending on substitution pattern and molecular conformation. The combination of optical spectroscopy and x-ray diffraction elucidates the correlation among molecular functionalization, crystalline structure, and electronic states. The data are quantitatively interpreted by a semiempirical technique that provides the excited state energies starting from the measured molecular geometry.