Quantum-Chemical Study of Geometrical and Electronic Structures of Thiophene-Based Bicyclic Polymers

Abstract

A quantum-chemical study was performed to investigate the geometrical and electronic structures of a variety of thiophene-based bicyclic polymers [−(C6H2SX) n −], where X = CH2, SiH2, CO, CS, or CCH2. These two (S and X) types of the bridging groups are different from each other in that S favors the aromatic form of a cyclic polymer and X the quinonoid form. Geometrical structures of the polymers were obtained from AM1 band calculations and the electronic properties from the modified extended Hückel band calculations. It is predicted that the bicyclic polymers with weak electron-donating groups (CH2 and SiH2 groups) are of the aromatic forms in the ground state and that the polymers with electron-withdrawing groups (CO, CS, and CCH2 groups) are of the quinonoid forms as observed in the thiophene copolymers, −[(C4H2S)−(C4H2X)] n −. The band gaps (which correspond to the absorption peaks of π−π* band transition) of the bicyclic polymers in the ground state are estimated to be in the range of 1.4−1.9 eV. The band gaps were analyzed in terms of the bond-length alternation along the conjugated carbon backbone, the C1−C4 interactions, and the electronic effect of the bridging groups. In comparison with the contributions found in the thiophene copolymers, the contribution from the bond-length alternation to the band gaps decreases, and the contributions from the C1−C4 interactions and the electronic perturbation of S increase. As a result, the band gaps of the bicyclic polymers are about 0.2 eV smaller than those of the corresponding thiophene copolymers.

Studi Semiempiris Struktur Molekul Dan Band Gap Monomer Dan Dimer 1,3,4 Tiadiazol Dan Derivatnya

“…Hal ini disebabkan karena polimernya dapat mempunyai Eg 1 -3,5 eV, yang dikategorikan sebagai Eg semikonduktor. Hong dan Song mendapatkan bahwa polimer bisiklik dari -(C6 H5 SX )n -dimana X adalah CH2, C=O, C=S, C=CH2 dan SiH2 mempunyai Eg sekitar 0,2 eV lebih kecil dari kopolimer tiofen [7] . Doping dengan logam tertentu pada polimer tiofen mengakibatkan struktur elektroniknya dan absorbsi optiknya akan mengalami perubahan.…”

Thiophene Deposition on Paper Surface by Pulsed RF-Plasma

“…[1][2][3] Polythiophene (PT) has been widely investigated as a potential conducting material in the field of molecular electronics. [4][5][6][7] Polythiophene is of great interest because of its redox and photochemical properties and its proposed use in textile products, [7] electrochemical materials, [9,10] and plastic electronics. [11] There is growing interest in thiophene, pyrrole, and aniline for the development of electrical and optical properties of organic and polymeric materials.…”

“…These chemicals, which have an extended π -conjugated structure, offer many advantages in terms of processability, and they show exceptional electrical conductivity properties. [2,5,9,[11][12][13][14][15] A significant portion of recent literature on plasma modification/deposition of substrates has focused on better controllability of film chemistry during depositions, with the goal of producing surface-active coatings. [16][17][18] Exant literature has explained clearly that pulsed plasma interactions on substrate surfaces, in general, result in higher retention of the monomer structure compared to continuous wave (CW) plasma polymerization.…”

Poly(thiophenes) functionalised with thiazole heterocycles as electroluminescent polymers

“…In general, it has been recognized that more stable an isomer, the larger is its HOMO-LUMO separation. [26][27][28] The DFT method has been successfully used to study HOMO-LUMO separation in conjugated organic polymers, which also provides a good estimate of the excitation energy. [29][30][31][32][33] Salzner et al 12 combined the improved geometries of the DFT approach with the improved HOMO-LUMO separation from hybrid functional calculations.…”