Naphtho[1,2‑<i>c</i>:5,6‑<i>c</i>′]bis[1,2,5]thiadiazole-Based Nonfullerene Acceptors: Effect of Substituents on the Thiophene Unit on Properties and Photovoltaic Characteristics

The development of new electron-accepting π-conjugated systems for application as nonfullerene acceptors in organic solar cells (OSCs) is urgently needed. Although π-conjugated systems based on naphtho­[1,2-<i>c</i>:5,6-<i>c</i>′]­bis­[1,2,5]­thiadiazole (<b>NTz</b>) and naphthalimide (<b>Np</b>) as central and terminal units, respectively, represent possible candidates for nonfullerene acceptors, our knowledge of the structure–property–device performance relationship of these compounds remains limited. We report herein on an investigation of the effect of the substituents on the thiophene (<b>T</b>) linker between <b>NTz</b> and <b>Np</b> on the properties and photovoltaic performance. The photophysical and physicochemical measurements showed that the absorption behavior as well as frontier-orbital energy levels can be fine-tuned by the choice of the substituent on the thiophene rings. Bulk-heterojunction-type OSCs based on these acceptors under blending with poly­(3-hexylthiophene) as a donor showed various power conversion efficiencies, ranging from 0.26 to 2.14%. The substituents on the thiophene rings also have a significant influence on the blend film properties, which explain the differences in the short-circuit current densities and fill factors in the OSCs. These results indicate the importance of molecular design in preparing nonfullerene acceptors with <b>NTz</b> and <b>Np</b> units in terms of tuning both the molecular properties of the materials and donor–acceptor interface engineering in the blended films

Electronegative Oligothiophenes Based on a Hexafluorocyclopentene-Annelated Thiophene Unit

The synthesis of hexafluorocyclopenta[c]thiophene and its based oligothiophenes is described. The effectiveness of a hexafluorocyclopentene unit to lower the LUMO level without disturbing the effective conjugation could be unambiguously clarified by spectroscopic measurements and X-ray analysis

Electronegative Oligothiophenes Based on a Hexafluorocyclopentene-Annelated Thiophene Unit

The synthesis of hexafluorocyclopenta[c]thiophene and its based oligothiophenes is described. The effectiveness of a hexafluorocyclopentene unit to lower the LUMO level without disturbing the effective conjugation could be unambiguously clarified by spectroscopic measurements and X-ray analysis

Electronegative Oligothiophenes Based on a Hexafluorocyclopentene-Annelated Thiophene Unit

The synthesis of hexafluorocyclopenta[c]thiophene and its based oligothiophenes is described. The effectiveness of a hexafluorocyclopentene unit to lower the LUMO level without disturbing the effective conjugation could be unambiguously clarified by spectroscopic measurements and X-ray analysis

Ru₃(CO)₁₂- and Rh₄(CO)₁₂-Catalyzed Reactions of Pyridylolefins or <i>N</i>-(2-Pyridyl)enamines with CO and Olefins. Carbonylation at Olefinic C−H Bonds

This paper describes a study of the Ru3(CO)12-catalyzed carbonylation at an olefinic C−H bond. The reaction of pyridylolefins with CO and ethylene in the presence of a catalytic amount of Ru3(CO)12 in toluene results in propionylation at an olefinic C−H bond in pyridylolefins. The carbonylation occurs regioselectively at a position γ to the pyridine nitrogen. Transition-metal complexes other than Ru3(CO)12, that have thus far been examined exhibit no catalytic activity, and ethylene serves as the only olefin. A similar tendency has been noted in the previously reported carbonylation at a C−H bond in the benzene ring of pyridylbenzenes. This reaction can be also applied to N-(2-pyridyl)enamines, in which an olefin unit is separated from the pyridine ring by an sp3-nitrogen atom. The reaction of N-(2-pyridyl)enamines with CO and ethylene gives the corresponding ethyl ketones as the coupling products. Interestingly, Rh4(CO)12 also shows high catalytic activity in the case of N-(2-pyridyl)enamines. In addition, olefins such as propene, 1-hexene, 3,3-dimethyl-1-butene, styrene, cyclopentene, acryl acid methyl ester, ethyl vinyl ether, and trimethylvinylsilane can also be used. This is in sharp contrast to the case of the carbonylation at a C−H bond in pyridylbenzenes reported previously and to the results of pyridylolefins as mentioned above, where Ru3(CO)12 is the only active catalyst and hexene cannot substitute for ethylene

Ru₃(CO)₁₂-Catalyzed Decarbonylative Cleavage of a C−C Bond of Alkyl Phenyl Ketones

Ru3(CO)12-Catalyzed Decarbonylative Cleavage of a C−C Bond of Alkyl Phenyl Ketone

Synthesis of 10-nm Scale Oligothiophene Molecular Wires Bearing Anchor Units at Both Terminal Positions

Oligothiophenes with the length of ca.10 nm bearing anchor units (a protected thiol group or trimethylsilylethynyl) at both terminal positions in the conjugated backbone have been synthesized by the block-coupling synthetic strategy. Their electronic properties were clarified by spectroscopic and electrochemical measurements

Pyradinodithiazole: An Electron-Accepting Monomer Unit for Hole-Transporting and Electron-Transporting Conjugated Copolymers

Pyradinodithiazole (<b>PDTz</b>) was designed as a new electron-accepting unit. The physical property measurements indicated that the <b>PDTz</b> unit has stronger electron-accepting characteristics than thiazolothiazole and benzodithiazole. A donor–acceptor copolymer containing <b>PDTz</b> as an acceptor unit was synthesized for hole-transporting semiconductors in organic photovoltaics (OPV). Furthermore, an acceptor–acceptor copolymer containing <b>PDTz</b> has also been developed for electron-transporting OPV materials. These copolymer-based blend films showed expected photovoltaic characteristics in individual OPV devices

Deviation from Point Dipole Analysis for Exciton Quenching in Quaterthiophene-Terminated Self-Assembled Monolayers on Au(111)

A geometry-specific analysis of exciton quenching in the quaterthiophene (4T)-terminated alkanethiolate self-assembled monolayers (4TCnS-SAMs, where n is the number of methylene units; n = 3, 5, 6, 7, 8, 9, and 13) on Au(111) has been performed. In the previous studies we elucidated the n-dependent lifetime (τ) of the photoexcited 4T group in SAMs. In this study, using X-ray reflectivity (XRR) measurements, we evaluated the actual intralayer thickness of 4TCnS-SAMs on Au(111) and examined the quenching process as a function of distance (d) between the photoexcited moiety and the Au substrate. We confirmed that τ precisely follows the power law, i.e., τ ∝ dα, which is expected from the point dipole model analysis of the excitation energy transfer (ET) processes. Therefore, we attribute the dominant quenching mechanism to ET from the exciton state of 4T to the Au substrate rather than the quantum tunneling (QT) of excited electrons. However, the fitted parameter, α, is 4.28 ± 0.14 and thus deviates from the theoretical value on bulk-dumping models and previously measured values for admolecules on Au substrates, i.e., typically α ≈ 3. The origin of the deviation from the typical value is quantitatively discussed

The Ruthenium-Catalyzed Reductive Decarboxylation of Esters: Catalytic Reactions Involving the Cleavage of Acyl−Oxygen Bonds of Esters

The Ruthenium-Catalyzed Reductive Decarboxylation of Esters:  Catalytic Reactions Involving the Cleavage of Acyl−Oxygen Bonds of Ester