Conformational polymorphism of oligothiophenes: X-ray structure of the monoclinic form of 3,3',4'',3'''-tetrakis(methylsulfanyl)-2,2':5',2'':5'',2'''-quaterthiophene

Conformational polymorphism of an oligothiophene, the title compound (T4S), is reported for the first time. Efficient synthesis of T4S produced, in addition to the triclinic, deep orange crystals reported previously, a second (yellow monoclinic) form of T4S. whose structure as revealed by single-crystal X-ray diffraction is presented here. The synthetic pathway is outlined and the molecular structure and crystal packing are dis cussed. The significantly different pi-delocalization in the two conformations indicates the need for very careful molecular characterization.