Thienothiophenes compositions comprising a C3-8 secondary or
tertiary alkyl group are disclosed. The thienothiophenes may berepresented by the formula: where R is C3-8 secondary or
tertiary alkyl, e.g.,
isopropyl, tert-butyl, tert-pentyl, isopentyl, and 2-ethylhexyl, X and X′ are independently selected from the group consisting of H,
halogen atoms (e.g., F, Cl, Br, and I), MgCl, MgBr, Mgl, Sn(R′)3, (where R′ is C1-6
alkyl or —OC1-6 alkyl),
boronic acid, boronic ester, —CH═CHR″ (where R″ is H or C1-6 alkyl), —OC1-6 alkyl, —COOC1-6 alkyl, —S—COR′″, —COR′″ (where R′″ is H or C1-6 alkyl), —C≡CH, and polymerizable aromatic rings such as phenyl,
naphthalene,
pyrrole, dithiophene, thienothiophene,
thiophene and so forth.