Helicenes with aryl electron-withdrawing or/and electron-donating groups at one/both end/s are potential candidates for
second order nonlinear optical applications. We have prepared such helicenes and related compounds. A single crystal
X-ray structure showed the structure and architecture of 2,7-di-1-naphthylbenzo[1,2-b:4,3-b'] dithiophene to be racemic
chiral helixes. Both terminal aryl rings contribute to the π-π stacking. Theoretically, there are two synthetic routes (A and B)
for the synthesis of 2-(4-methoxylphenyl)trithia--heterohelicene and 2-(4-methoxylphenyl)-9-(4-cyanophenyl)trithia-
-heterohelicene. Although route A is more complicated, it is more efficient because substituents improve solubility.
Introducing an electron-donating group increases the yields of all reactions in A.
The field-effect mobility in two isomers of thieno[f,f']bisbenzothiophene was studied as a function of structure. Both regioisomers exhibit substantial mobilities up to 0.12 cm2/Vs, a value that is at most one order of magnitude lower than the best known organic transistors based on silicon dioxide gate insulators. The devices based on these materials exhibit another phenomenon, namely a shift in the threshold voltage during operation. This shift differs from usually observed threshold voltage changes in amount and irreversibility. In this paper, we present possible explanations for the observed behavior.