Synthesis, solid-state, and charge-transport properties of conjugated polythiophene-S ,S -dioxides

Correlation of Coexistent Charge Transfer States in F4TCNQ-Doped P3HT with Microstructure

Understanding the interaction between organic semiconductors (OSCs) and dopants in thin films is critical for device optimization. The proclivity of a doped OSC to form free charges is predicated on the chemical and electronic interactions that occur between dopant and host. To date, doping has been assumed to occur via one of two mechanistic pathways: an integer charge transfer (ICT) between the OSC and dopant or hybridization of the frontier orbitals of both molecules to form a partial charge transfer complex (CPX). Using a combination of spectroscopies, we demonstrate that CPX and ICT states are present simultaneously in F₄TCNQ-doped P3HT films and that the nature of the charge transfer interaction is strongly dependent on the local energetic environment. Our results suggest a multiphase model, where the local charge transfer mechanism is defined by the electronic driving force, governed by local microstructure in regioregular and regiorandom P3HT.

Synthesis of N,N-Dioxopyridazines

Despite many efforts, one of the smallest heterocycles containing two nitrogen atoms, pyridazine, could not be converted to its N,N-dioxide (see, however, Nakadate et al. Chem. Pharm. Bull. 1970 , 18 , 1211 - 1218 ). HOF·CH₃CN, made easily from diluted fluorine, was able to accomplish this task in a fast reaction with good yields.

The role of sulfur oxidation in controlling the electronic properties of sulfur-containing host molecules for phosphorescent organic light-emitting diodes

In this study a series of dibenzothiophene (DBT) derivatives having different valence states of sulfur atoms have been reported as host materials for blue phosphorescent organic light-emitting diodes. Their electronic properties have also been thoroughly investigated to develop structure-property relationships which include the consideration of the effect of various oxidation states of the sulfur atom in the core moiety and linking (C-N linkage) of subunits with the core at different positions. The results obtained from the electronic structure calculations highlight that the triplet energy (E_T), singlet-triplet energy difference (ΔE_ST), reorganization energy for the hole and the injection barrier for the electron decrease with an increase in the oxidation state of the sulfur atom in DBT. On the other hand, the injection barrier for the hole and the reorganization energy for the electron increase upon increasing the oxidation state of the sulfur atom present in the DBT.

Tris(S,S-dioxide)-trithiasumanene: strong fluorescence and cocrystal with 1,2,6,7,10,11-hexabutoxytriphenylene

Trithiasumanene was regioselectively transformed into tris(S,S-dioxide)-trithiasumanene, which displays strong fluorescence and forms a chiral cocrystal with HBT, showing a yellow emission.

Theoretical studies on the carrier tunability of oxidized oligothiophenes

Upon increasing the molecular length hole conducting TDO1 is converted to electron conducting TDO4.

HOF·CH3CN: probably the best oxygen transfer agent organic chemistry has to offer

The complex HOF·CH3CN is readily obtained by bubbling dilute fluorine into aqueous acetonitrile solution. It does not have to be purified or isolated, and its solution can react as is, after the concentration has been establish by any iodometric method. It is the only reagent possessing a distinctive positive oxygen species. This enables electrophilic oxygen transfer with results no other reagent can match. HOF·CH3CN demonstrates its ability in epoxidations that either could not be performed before or could only obtained 5 orders of magnitude slower. This complex is also an excellent tool for oxygenation of compounds at the α position of a carbonyl, including the synthesis of some hard-to-come-by indanediones, which are important for fingerprint visualization on paper. HOF·CH3CN proves itself as a very efficient reagent for oxygenating tertiary nitrogen atoms both in aliphatic (including azides) and in aromatic amines, which could not be accomplished despite many attempts in the last 50 years. Oxygenation of two tertiary nitrogen atoms in the same molecule also becomes feasible as demonstrated for various phenanthrolines, bipyridines, diazafluorenones, and quinoxalines. It was also used to oxygenate primary amines, and because of the exceptionally mild conditions, it could transform vicinal aliphatic diamines to vicinal dinitro derivatives as well as amino acids to the corresponding nitro ones, practically unknown transformations before. Its ability to react with azines and hydrazones and convert them to the original carbonyls helped to establish these groups as good protecting tools for a variety of carbonyls. HOF·CH3CN excels in oxygenation of various sulfur and selenium compounds that could not be oxygenated in the past. The selectivity of the oxidation is quite good, and if there are alcohols, double bonds, and sulfides in the same molecule, usually the sulfur atom will be attacked first. Of special interest is the reaction with oligothiophenes resulting at will in either [all]-S,S-dioxooligothiophenes or in partially oxygenated ones. Some of these last derivatives have the narrowest HOMO-LUMO gap of all oligothiophenes tested, a very desirable feature. This reagent can also oxidize thiols or disulfides to either sulfonic or sulfinic acids at will, all in seconds and in very high yields. Since the oxygen atom of HOF·CH3CN originates in water, it is very easy and relatively inexpensive to introduce the heavy oxygen isotope in many sites of a variety of molecules, some of them quite important. The (18)O tirapazamine and any desirable alcohol, R(Ar)(18)OH, are two examples.

Bandgap engineering through controlled oxidation of polythiophenes

The use of Rozen's reagent (HOF⋅CH3 CN) to convert polythiophenes to polymers containing thiophene-1,1-dioxide (TDO) is described. The oxidation of polythiophenes can be controlled with this potent, yet orthogonal reagent under mild conditions. The oxidation of poly(3-alkylthiophenes) proceeds at room temperature in a matter of minutes, introducing up to 60 % TDO moieties in the polymer backbone. The resulting polymers have a markedly low-lying lowest unoccupied molecular orbital (LUMO), consequently exhibiting a small bandgap. This approach demonstrates that modulating the backbone electronic structure of well-defined polymers, rather than varying the monomers, is an efficient means of tuning the electronic properties of conjugated polymers.

Synthesis of thiophene 1,1-dioxides and tuning their optoelectronic properties

A 2,5-bis(tributylstannyl)thiophene 1,1-dioxide was prepared from 2,5-bis(trimethylsilyl)thiophene 1,1-dioxide, bis(tributyltin) oxide, and tetrabutylammonium fluoride (TBAF). The 2,5-bis(tributylstannyl)thiophene 1,1-dioxide and a 2,5-diiodothiophene 1,1-dioxide were utilized in a series of Stille cross-coupling reactions to afford thiophene 1,1-dioxides with either electron-donating or electron-withdrawing substituents. Electron-withdrawing groups greatly facilitate the reduction of these sulfone heterocycles, and -C6H4-p-NO2 substituents produce a 510 mV shift as compared to a thiophene 1,1-dioxide with two phenyl groups.