“Heavy-Atom” Donor-Acceptor Conjugated Polymers

Synthesis of indacenodithienothiophene-based conjugated polymers containing electron-donating/accepting comonomers and their phototransistor characteristics

IDTT-based conjugated polymers with electron-accepting comonomers exhibit higher hole mobility (10-fold) and photoresponsivity (2-fold) than those with electron-donating comonomers.

Synthesis of Aggregation-Induced Emission-Active Conjugated Polymers Composed of Group 13 Diiminate Complexes with Tunable Energy Levels via Alteration of Central Element

Conjugated polymers containing boron and gallium diiminate complexes were prepared with various electron-donating comonomers via pre- and post-complexation methods, respectively. From a comparison of emission quantum yields between solution and film states, it was seen that all polymers containing group 13 elements possessed an aggregation-induced emission property. Additionally, the frontier orbital energies and the optical and electrochemical properties of the polymers can be tuned by altering a central element at the complex moieties as well as by changing a comonomer unit. In particular, it was demonstrated that the gallium atom can contribute to stabilizing the energy levels of the lowest unoccupied molecular orbitals, resulting in narrow band gaps of the conjugated polymers. This study presents the potential of gallium not only for preparing solid-state emissive conjugated polymers but also for fabricating low-band gap materials by employing the conjugated ligand.

Effect of Selenium Substitution on Intersystem Crossing in π-Conjugated Donor-Acceptor-Donor Chromophores: The LUMO Matters the Most

This study explores the effect of substitution of selenium (Se) for sulfur (S) on the photophysical properties of a series of π-conjugated donor-acceptor-donor chromophores based on 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (TBT). The effect of Se substitution is studied systematically, where the substitution is in the thiophene donors only, the benzothiadiazole acceptor only, and in all of the positions. The fluorescence quantum yield decreases with an increase in Se substitution. Nanosecond-microsecond transient absorption and singlet oxygen sensitization experiments show that the effect of Se is due to an increase in the rate and efficiency of intersystem crossing with increased Se substitution. The relationship between intersystem crossing efficiency and heteroatom substitution pattern shows that the effects are largest when the heavy atom Se is in the acceptor benzothiadiazole unit. DFT calculations support the hypothesis that the effect arises because the LUMO is concentrated in the acceptor moiety, enhancing the spin-orbit coupling effect imparted by the Se atom.

Synthesis of π-Conjugated Polymers Containing Benzodipyrrole Moieties in the Main Chain through Cleavage of C-H Bonds in 1,4-Bis(acetylamino)benzene

Rhodium-catalyzed copolymerization between 1,4-bis(acetylamino)benzene and diynes through C-H bond cleavage afforded π-conjugated polymers containing benzodipyrrole moieties. The polymers with substituted benzene units exhibited nearly the same absorption peaks and HOMO levels. Fluorenone and benzothiadiazole moieties can be also introduced as electron-acceptor units to the main chain by polymerization in tert-amyl alcohol and tetrahydropyran as mixed solvent, leading to absorption at longer wavelength.

Chalcogen bonding in solution: interactions of benzotelluradiazoles with anionic and uncharged Lewis bases

Chalcogen bonding is the noncovalent interaction between an electron-deficient, covalently bonded chalcogen (Te, Se, S) and a Lewis base. Although substantial evidence supports the existence of chalcogen bonding in the solid state, quantitative data regarding the strengths of the interactions in the solution phase are lacking. Herein, determinations of the association constants of benzotelluradiazoles with a variety of Lewis bases (Cl(-), Br(-), I(-), NO3(-) and quinuclidine, in organic solvent) are described. The participation of the benzotelluradiazoles in chalcogen bonding interactions was probed by UV-vis, (1)H and (19)F NMR spectroscopy as well as nano-ESI mass spectrometry. Trends in the free energy of chalcogen bonds upon variation of the donor, acceptor and solvent are evident from these data, including a linear free energy relationship between chalcogen bond donor ability and calculated electrostatic potential at the tellurium center. Calculations using the dispersion-corrected B97-D3 functional were found to give good agreement with the experimental free energies of chalcogen bonding.

‘Blocky’ donor–acceptor polymers containing selenophene, benzodithiophene and thienothiophene for improved molecular ordering

A straightforward synthetic route to blocky D–A copolymers consisting of selenophene, benzodithiophene, and thienothiophene is reported.