Thienothiophenes compositions comprising a C.sub.3-8 secondary or tertiary
alkyl group are disclosed. The thienothiophenes may be represented by the
formula: ##STR00001## where R is C.sub.3-8 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').sub.3, (where R'
is C.sub.1-6 alkyl or --OC.sub.1-6 alkyl), boronic acid, boronic ester,
--CH.dbd.CHR'' (where R'' is H or C.sub.1-6 alkyl), --OC.sub.1-6 alkyl,
--COOC.sub.1-6 alkyl, --S--COR''', --COR''' (where R''' is H or C.sub.1-6
alkyl), --C.ident.CH, and polymerizable aromatic rings such as phenyl,
naphthalene, pyrrole, dithiophene, thienothiophene, thiophene and so
forth.
