A cyclophane-type of dimeric quinquethiophenes (4a-e) with the bridge chains consecutively varying from two to six methylenes has been synthesized and studied as ideal π-dimer models. The double-decker structures of these compounds are verified by upfield shifts for the proton NMR signals of the inside thiophenes, as compared to those of monomeric dimethylquinquethiophene (3). The electronic absorption and emission ...