Effect of Donor–Acceptor Substitution on Optoelectronic Properties of Conducting Organic Polymers

Abstract

The impact of donor-acceptor substitution on optical and electronic properties of conducting polymers was investigated with time-dependent density functional theory (TDDFT). A series of donor-acceptor systems with thiophene, 3,4-ethylenedioxythiophene, and pyrrole as donors and 3,4-difluorothiophene, diketopyrrolopyrrole, 2,1,3-benzothiadiazole, 4-dicyanomethylene-4H-cyclopenta[2,1-b;3,4-b']dithiophene, and indeno[1-2b]-fluorene-6,12-dimalonitrile as acceptors as examples of donor-acceptor systems with increasing donor-acceptor character was studied. Spectral properties were analyzed in terms of differences in ionization potentials and electron affinities of donors and acceptors, charge separations between donors and acceptors in ground and excited states, and electron distribution in the acceptor units. A shift in electron density away from the backbone caused by some of the acceptors correlates with localization of the conduction band on the acceptor. Localization does not correlate with energy level differences between donor and acceptor. Localization results in shift of oscillator strength from the HOMO-LUMO peak to a higher energy feature where the first delocalized orbital acts as the acceptor. The "camel back" absorption with two equally strong peaks that gives rise to green polymers is the intermediate case associated with partial localization of the conduction band. Stronger localization causes the HOMO-LUMO band to almost vanish.

Pyrrolyl–Silicon Compounds as Precursors for Donor–Acceptor Systems Stabilized by Noncovalent Interactions

“…Accordingly, this monomer presents electron-rich Py ring and electron-deficient silanol, indicative of donor-acceptor character. [74][75][76] Similar indication is obtained from computed local reactivity descriptors, namely local Tables 2 and 3, where the corresponding isovalent surfaces (0.004 electron/bohr 3 ) of spin electron density are included. Regardless the nature of the substituent, f k − is higher on α,α' and β,β' carbon atoms of Py ring with ε HOMO localized on the double bonds (Table 2), indicating these sites electronically enriched.…”

Effect of Chalcogens on Electronic and Photophysical Properties of Vinylene-Based Diketopyrrolopyrrole Copolymers

“…49 To compare the intramolecular transport properties of the three systems, the 10 highest occupied and the 10 lowest unoccupied energy levels of the tetramers are plotted in Figure 8. The four levels lying below the energy gap represent the valence bands of the corresponding polymers; the four levels above the energy gap represent the conduction bands.…”

Sulfur-containing, triphenylamine-based red-emitting conjugated polymer/I− assembly as turn-on optical probe for mercury(II) ion

“…As compared to turn-off probes, fluorescence enhancing (turn-on) probes displayed superiority from the view-point of ease in detection (the optical signals were strengthened during the detection) and anti-interference [23][24][25]. On the other hand, it is well known that the introduction of S-containing moieties, such as electron-withdrawing benzo [2,1,3]thiadiazole (BT) and electron-donating thiophene groups, into CPs is an efficient and commonly adopted strategy to regulate the optoelectronic properties of CPs [26]. As a result, the construction of sulfur-containing, fluorescence 'turn-on' type Hg 2+ probe will be a good complement A c c e p t e d M a n u s c r i p t 5 for the development of CPs-based, multi-color Hg 2+ probe.…”