title: Oligo- and polyselenophenes: a theoretical study.
abstract: Recently, a family of conducting polyselenophenes was synthesized, and they were shown to have a number of interesting properties. Here we have studied oligoselenophenes, their cation radicals and dications up to the 50-mer (50 Se), as well as polyselenophene at the B3LYP/6-31G(d) level of theory, and compared them with the corresponding oligothiophenes. Although the calculations reveal many similarities between oligo- and polyselenophenes and their thiophene-based counterparts, they also show the important differences between those two types of conjugated systems. Oligo- and polyselenophenes have a more quinoid character, lower band gap, and importantly, they are more difficult to twist. The theoretical results suggest that the HOMO-LUMO gap (band gap), bond-length alternation (BLA), and charge distribution in oligo- and polyselenophenes are strongly dependent on inter-ring twisting, yet twisting costs little energy. The inter-ring distances in oligo- and polyselenophenes are shorter than the related distances in oligothiophenes, whereas the bond lengths within the selenophene rings are comparable to those of the corresponding oligothiophenes.
authors: School of Chemistry, Indian Institute of Science Education and Research, Kolkata (India).
authors: Sanjio S
authors: SS
authors: Zade
authors: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100 (Israel), Fax: (+972) 8934-4142.
authors: Natalia
authors: N
authors: Zamoshchik
authors: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100 (Israel), Fax: (+972) 8934-4142.
authors: Michael
authors: M
authors: Bendikov