Theoretical study of torsion potentials in t r a n s-stilbene and substituted t r a n s-stilbenes: Modeling torsions in poly(paraphenylene vinylene) and derivatives

We present ab initio and semiempirical quantum-chemical calculations as well as simple molecular mechanics calculations on the gas-phase torsion potentials of 1,1′-(trans-1,2-ethenediyl) bisbenzene, commonly known as trans-stilbene, and derivatives of trans-stilbene substituted by methyl or methoxy side groups: 1,1′-(trans-1,2-ethenediyl), bis-2,5-dimethylbenzene, and 1,1′-(trans-1,2-ethenediyl) bis-2,5-dimethoxybenzene. Our results are discussed in light of recent experimental data on poly(paraphenylene vinylene), poly(dimethyl paraphenylene vinylene), and poly(dimethoxy paraphenylene vinylene).