Youhei Takeda

1,4‐Bis(alkenyl)‐2,5‐dipiperidinobenzenes: Minimal Fluorophores Exhibiting Highly Efficient Emission in the Solid State

Minimum requirements: Crystals and thin films of 1,4-bis(alkenyl)-2,5-dipiperidinobenzenes, which contain only one benzene ring as the aromatic component, emit visible light with excellent solid-state quantum yields upon irradiation with UV light. Polystyrene thin films doped with the benzenes also exhibit brilliant fluorescence. By modifying the alkenyl groups, the emission color can be tuned in the range from blue to red.

Generation of Nitrile Oxides from Oximes Using t-BuOI and Their Cycloaddition

tert-Butyl hypoiodite (t-BuOI) was found to be a powerful reagent for the cycloaddition of oximes and alkenes/alkynes, leading to the formation of a variety of isoxazolines or isoxazoles under mild conditions.

Dibenzo[a,j]phenazine‐Cored Donor–Acceptor–Donor Compounds as Green‐to‐Red/NIR Thermally Activated Delayed Fluorescence Organic Light Emitters

A new family of thermally activated delayed fluorescence (TADF) emitters based on U-shaped D-A-D architecture with a novel accepting unit has been developed. All investigated compounds have small singlet-triplet energy splitting (ΔEST ) ranging from 0.02 to 0.20 eV and showed efficient TADF properties. The lowest triplet state of the acceptor unit plays the key role in the TADF mechanism. OLEDs fabricated with these TADF emitters achieved excellent efficiencies up to 16 % external quantum efficiency (EQE).

An Air-Stable Low-Bandgap n-Type Organic Polymer Semiconductor Exhibiting Selective Solubility in Perfluorinated Solvents†

A thin-film transistor: An n-type polymer semiconductor, poly(2,3-bis(perfluorohexyl)thieno[3,4-b]pyrazine), was synthesized through a Pd-catalyzed polycondensation employing a perfluorinated multiphase solvent system. This is the first example of an n-type polymer semiconductor with exclusive solubility in fluorinated solvents. The fabrication of organic field effect transistors containing this new n-type polymer semiconductor is shown.

Pd/NHC-catalyzed enantiospecific and regioselective Suzuki-Miyaura arylation of 2-arylaziridines: synthesis of enantioenriched 2-arylphenethylamine derivatives.

A palladium-catalyzed stereospecific and regioselective cross-coupling of enantiopure 2-arylaziridines with arylboronic acids under mild conditions to construct a tertiary stereogenic center has been developed. N-heterocyclic carbene (NHC) ligands efficiently promote the coupling, suppressing β-hydride elimination. The enantiospecific cross-coupling allowed us for preparation of a series of biologically important 2-arylphenethylamine derivatives in an enantiopure form.

2-Halogenoimidazolium Salt Catalyzed Aza-Diels–Alder Reaction through Halogen-Bond Formation

2-Halogenoimidazolium salts are found to catalyze aza-Diels-Alder reaction of aldimines with Danishefsky diene in an efficient manner. Comparative studies and titration experiments support the formation of halogen bonding between imines and catalysts.

Oxidative Dimerization of Aromatic Amines using tBuOI: Entry to Unsymmetric Aromatic Azo Compounds†

Its all the hype: An oxidative dimerization reaction of aromatic amines utilizing tert-butyl hypoiodite (tBuOI) under mild reaction conditions leads to aromatic azo compounds. The method allows access to unsymmetric aromatic azo compounds, which are difficult to prepare by conventional synthetic methods, in a selective manner.

Oxidative dimerization of (hetero)aromatic amines utilizing t-BuOI leading to (hetero)aromatic azo compounds: scope and mechanistic studies.

A straightforward synthetic method of both symmetric and unsymmetric aromatic azo compounds through an efficient and cross-selective oxidative dimerization of aromatic amines using tert-butyl hypoiodite (t-BuOI) under metal-free and mild conditions has been developed. This method was also found applicable to the synthesis of heteroaromatic azo compounds. The spectroscopic study indicates the involvement of N,N-diiodoanilines in the oxidative reaction as the key intermediate.

Selective Functionalization of Fullerenes with N,N‐Dihalosulfonamides as an N1 Unit: Versatile Syntheses of Aza[60]fulleroids and Aziridino[60]fullerenes and their Application to Photovoltaic Cells

Highly selective and versatile methods for the synthesis of aza[60]fulleroids and aziridino[60]fullerenes from C(60) have been developed. The reactions utilized N,N-dihalosulfonamides as an N(1) source. The photophysical, electrochemical, and thermal properties of the iminofullerenes were investigated by means of UV/Vis spectroscopy, cyclic voltammetry, and thermogravimetry, respectively. Furthermore, photovoltaic cells based on the synthesized iminofullerenes were fabricated. The power conversion efficiencies (PCEs) of the devices showed moderate values ranging from 1.33 to 2.35 %.

2,6‐Diphospha‐s‐indacene‐1,3,5,7(2 H,6 H)‐tetraone: A Phosphorus Analogue of Aromatic Diimides with the Minimal Core Exhibiting High Electron‐Accepting Ability

Phosphorus analogues of pyrromellitic diimides (PyDIs), which represent a family of privileged electron-accepting organic compounds, have been successfully synthesized as novel electron-accepting π-conjugated molecules. Investigation into their physicochemical properties uncovered their prominent electron-accepting abilities over the corresponding PyDI. Furthermore, theoretical studies revealed the significant contribution of σ*-π* hyperconjugation in stabilizing the LUMO+1.