Highly fluorescent purine-containing conjugated copolymers with tailored optoelectronic properties

Conjugated copolymers containing electron donor and acceptor units in their main chain have emerged as promising materials for organic electronic devices due to their tunable optoelectronic properties.

Probing the nature of donor-acceptor effects in conjugated materials: a joint experimental and computational study of model conjugated oligomers

A series of model oligomers consisting of combinations of a traditional strong donor unit (3,4-ethylenedioxythiophene), a traditional strong acceptor unit (benzo[c][1,2,5]thiadiazole), and the ambipolar unit thieno[3,4-b]pyrazine were synthesized via cross-coupling methods. The prepared oligomers include all six possible dimeric combinations in order to characterize the extent and nature of donor-acceptor effects commonly used in the design of conjugated materials, with particular focus on understanding how the inclusion of ambipolar units influences donor-acceptor frameworks. The full oligomeric series was thoroughly investigated via photophysical and electrochemical studies, in parallel with density functional theory (DFT) calculations, in order to correlate the nature and extent of donor-acceptor effects on both frontier orbital energies and the desired narrowing of the HOMO-LUMO energy gap. The corresponding relationships revealed should then provide a deeper understanding of donor-acceptor interactions and their application to conjugated materials.

Optimized synthesis of thermally stable axially modified pyrazine-acene nanoribbon with gelation properties

A comprehensive synthesis study to axially modify N-heteroacene nanoribbon and its outstanding thermal and one-dimensional assembly properties.

Poly(thieno[3,4-b]pyrazine-alt-2,1,3-benzothiadiazole)s: A New Design Paradigm in Low Band Gap Polymers

A new design paradigm for the production of low band gap polymers is reported, in which an ambipolar unit exhibiting both donor and acceptor properties is combined with a conventional acceptor. As initial examples of this approach, the synthesis of two alternating copolymers of thieno[3,4-b]pyrazine and 2,1,3-benzothiadiazole via direct arylation polymerization is reported to give soluble, processable materials with band gaps of 0.97 and 1.05 eV. Although direct arylation polymerization has been previously used to synthesize donor-acceptor materials with band gaps below 1.5 eV, this represents only the second material generated by this polymerization method with a band gap below 1.0 eV.

Synthesis of Main Chain Purine-Based Copolymers and Effects of Monomer Design on Thermal and Optical Properties

The ability to incorporate diverse monomeric building blocks enables the development of advanced polymeric materials possessing a wide range of properties that suits them for myriad applications. Herein, that synthetic toolbox is expanded through the first report of purine-based copolymers in which purines are incorporated directly into the polymer main chain. Stille cross-coupling of dibromopurine monomers with benzodithiophene (BDT) comonomers is used to generate these "poly(purine)s", and variations in the substitution pattern of the purine monomer and BDT side-chains provides insight into the role of monomer design on their resultant thermal and photophysical properties. Specifically, thermal analyses show that poly(purine)s exhibit high thermal stability and high glass transition temperatures depending on the BDT side-chain substituents and substitution pattern of the purine-derived comonomer. Furthermore, optical properties measured via UV-vis and fluorescence spectroscopies show dependence on monomer substitution pattern. These findings demonstrate the viability of synthesizing poly(purine)s via metal-catalyzed cross-coupling reactions and highlight the potential to tailor poly(purine) properties via simple alterations of comonomers.

Synthesis, Characterization, and Electropolymerization of Extended Fused-Ring Thieno[3,4-b]pyrazine-Based Terthienyls

The synthesis, characterization, and electropolymerization of a series of extended fused-ring thieno[3,4-b]pyrazine-based terthienyls are reported. The target terthienyls contain a central extended thieno[3,4-b]pyrazine analogue containing 2-thienyl units at the reactive α-positions of the central thiophene. The extended fused-ring thieno[3,4-b]pyrazine analogues studied include acenaphtho[1,2-b]thieno[3,4-e]pyrazine, dibenzo[f,h]thieno[3,4-b]quinoxaline, and thieno[3′,4′:5,6]-pyrazino[2,3-f][1,10]phenanthroline. Comparison of the electrochemical and photophysical properties to simple thieno[3,4-b]pyrazine-based terthienyls and their polymeric analogues are reported in order to provide structure-function relationships within this series of compounds and materials.

Tuning the Light Absorption of Donor–Acceptor Conjugated Polymers: Effects of Side Chains and ‘Spacer' Units in Thieno[3,4-b]pyrazine-Fluorene Copolymers

Four donor–acceptor (D-A) copolymers of 2,3-difunctionalized thieno[3,4-b]pyrazine (TP) and 9,9-dioctylfluorene were prepared in order to illustrate the ability to tune the electronic and optical properties of TP-based D-A polymers by the choice of side chains on the TP unit. In addition, analogous polymers were prepared with and without thiophene spacer units in order to allow discussion of their effect on the material properties. This combination of effects allowed tuning of the band gap over the range of 1.6–2.1 eV. Full optical and electrochemical characterization is reported for all materials, as well as initial photovoltaic device data for representative materials.

Protonation induced shifting of electron-accepting centers in intramolecular charge transfer chromophores: a theoretical study

A new series of chameleonic molecules containing azulene and benzothiadiazole (BT) were designed and synthesized.