Structural and Electronic Properties of Poly(thiaheterohelicene)s

Abstract

Quantum chemical methods have been applied on model oligomers of poly(thiaheterohelicene)s to investigate the structural and electronic properties of these systems. Specifically, the properties of the helical structures found for poly(heterohelicene) and poly(methyl-sulfonium), which were calculated using density functional theory calculations, are in good agreement with available experimental data. The geometrical parameters obtained for poly(methyl-sulfonium) reflect the enlargement of the inner carbon-carbon bond lengths at the thiophene rings, which are those closer to the helical screw axes, and lead to reduce their aromaticity of such heterocycles. On this basis, a relationship between the aromaticity and the lowest pi-pi* transition energy has been established. Finally, the lowest pi-pi* transitions have been extrapolated for infinite polymer chains of poly(heterohelicene) and poly(methyl-sulfonium) using different theoretical approaches.

Effects of pnictogen and chalcogen bonds on the aromaticities of carbazole-like and dibenzofuran-like molecular skeletons: Cambridge Crystallographic Data Centre (CCDC) Study

“…Aromatic systems, although acting as a medium in electronic charge interchange between the substituent groups, may also restrict this interaction to a certain extent because of its tendency of preserving aromatic character. This implies that the less aromatic π‐conjugated system should be a better medium in intercommunication between the substituents than its aromatic counterpart . The less aromatic ring systems, in particular two flanking benzenes, are promising candidates in designing and fine‐tuning functional materials because their electronic properties are easily controllable by substitution.…”

“…The less aromatic ring systems, in particular two flanking benzenes, are promising candidates in designing and fine‐tuning functional materials because their electronic properties are easily controllable by substitution. At this point, it should be remembered that lack of aromaticity of such monomers involving in the organizations of π‐conjugated polymers and oligomers leads to a decrease in HOMO–LUMO band gap . Therefore, the question requiring an answer is how to be affected aromaticities of five‐membered and six‐membered rings in the considered molecular skeletons by substitution.…”

“…Molecular or band gap (between Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) or π–π* gap) engineering is of critical importance in designing functional molecular structures . At this point, aromaticities of carbazole‐like and dibenzofuran‐like molecular skeletons play a central role in effective tailoring of the intrinsic properties of such conjugated monomers and their polyconjugated variants due to a linear relationship between aromaticity or bond length alternation and band gap. HOMO–LUMO band gap increases linearly with increasing aromaticity .…”

“…At this point, aromaticities of carbazole‐like and dibenzofuran‐like molecular skeletons play a central role in effective tailoring of the intrinsic properties of such conjugated monomers and their polyconjugated variants due to a linear relationship between aromaticity or bond length alternation and band gap. HOMO–LUMO band gap increases linearly with increasing aromaticity . Detriment of aromaticities of these molecular skeletons results in the formation of their energetically less stable variants due to a loss in their stabilization energy and leads to a smaller band gap.…”

“…HOMO-LUMO band gap increases linearly with increasing aromaticity. [3,15] Detriment of aromaticities of these molecular skeletons results in the formation of their energetically less stable variants due to a loss in their stabilization energy and leads to a smaller band gap. These facts attract attention to aromaticity of such molecular skeletons.…”