The Synthesis and Optoelectronic Applications for Tellurophene-Based Small Molecules and Polymers

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

Preparation and photoluminescent properties of amino 2,1,3-benzoxadiazoles (Am-BODs) with D-A-D and D-A-A conjugation systems

A series of D-A-D and D-A-A conjugated compounds composed of a benzoxadiazole core and corresponding amino were synthesized. Their photoluminescent properties in different states were investigated as well. In the solution state, some compounds were observed the usual anti-Kasha's emission in toluene and the solvatofluorochromic phenomenon. Meanwhile, compound 1a could be utilized as fluorescent chemosensors for the environmental acidity, and 2c could be developed for detecting fluoride anion. Moreover, they were emissive in powders and films, and 2d could be applied to the emissive layer in red OLEDs.

Hydroelementation of diynes

This review highlights the hydroelementation reactions of conjugated and separated diynes, which depending on the process conditions, catalytic system, as well as the type of reagents, leads to the formation of various products: enynes, dienes, allenes, polymers, or cyclic compounds. The presence of two triple bonds in the diyne structure makes these compounds important reagents but selective product formation is often difficult owing to problems associated with maintaining appropriate reaction regio- and stereoselectivity. Herein we review this topic to gain knowledge on the reactivity of diynes and to systematise the range of information relating to their use in hydroelementation reactions. The review is divided according to the addition of the E-H (E = Mg, B, Al, Si, Ge, Sn, N, P, O, S, Se, Te) bond to the triple bond(s) in the diyne, as well as to the type of the reagent used, and the product formed. Not only are the hydroelementation reactions comprehensively discussed, but the synthetic potential of the obtained products is also presented. The majority of published research is included within this review, illustrating the potential as well as limitations of these processes, with the intent to showcase the power of these transformations and the obtained products in synthesis and materials chemistry.

Rongalite in PEG-400 as a general and reusable system for the synthesis of 2,5-disubstituted chalcogenophenes

Herein we report the use of rongalite in PEG-400 as a general, efficient, and environmentally benign reductive system for the synthesis of a wide range of 2,5-disubstituted chalcogenophenes from elemental sulfur, selenium and tellurium.

Tellura(benzo)bithiophenes: Synthesis, Oligomerization, and Phosphorescence

A series of planar π-extended Te-containing heteroacenes, termed tellura(benzo)bithiophenes, were synthesized. This new structural class of heterocycle features a tellurophene ring fused to a benzobithiophene unit with aromatic side groups (either -C₆H₄ⁱPr or -C₆H₄OCH₃) positioned at the 2- and 5-positions of the tellurophene moiety. Although attempts to enhance molecular rigidity and extend ring-framework π-delocalization in a cumenyl (-C₆H₄ⁱPr)-capped tellura(benzo)bithiophene led to oxidation (and Te-C bond scission) to form a diene-one, the formation of an oligomeric tellura(benzo)bithiophene was possible via Kumada catalyst-transfer polycondensation (KCTP). Furthermore, one tellura(benzo)bithiophene derivative exhibits orange-red phosphorescence at room temperature in air when incorporated into a poly(methyl methacrylate) host; accompanying TD-DFT computations provided insight into a potential mechanism for the observed phosphorescence.

Polyynes to Polycycles: Domino Reactions Forming Polyfused Chalcogenophenes

Polyfused chalcogenophenes are prepared in one step through polyelectrophilic cyclization of polyynes using the ambiphilic reagent MeACl (A = S, Se, or Te). Up to four new rings have been generated under mild conditions, including thiophenes, selenophenes, and tellurophenes.

Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene)

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s-PSSe, PSTe, and PSeTe-through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)-from a thiophene unit via a selenophene unit to a tellurophene unit-to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.

Recent advances in poly(3,4-ethylenedioxyselenophene) and related polymers

This review highlights the recent progress in synthesis, properties, applications and future outlook of PEDOS based conjugated polymers.

Metallacycle Transfer and its Link to Light-Emitting Materials and Conjugated Polymers

Major advances in optoelectronic technologies (e. g., solar cells, organic light-emitting diodes, etc…) are prefaced by the discovery of new synthetic methodologies. In this review, the key role of the Fagan-Nugent reaction in enabling our team (and others) to gain access to new building blocks for luminescent materials and conjugated polymers bearing p-block elements will be described. The Fagan-Nugent reaction is extremely powerful as a synthetic tool since the efficient zirconium-element atom exchange involved affords a wide range of unsaturated inorganic heterocycles of controllable composition and function.