Crystal structure of head-to-head and tail-to-tail β, β'-dibromo-substituted bithiophenes as model compounds for poly(3-bromothiophene)

The X-ray structures of 4,4′-dibromo-2,2′-bithiophene 1, 3,3′-dibromo-2,2′-bithiophene 2 and 3,3′,5,5′-tetrabromo-2,2′-bi-thiophene 3 are rweported. The tail-to-tail dimer 1 is found in an anti planar conformation whereas a large distortion is present in the two head-to-head bithiophenes 2 and 3. These bromo derivatives are model compounds for structural studies on poly(3-bromothiophene).