High-performance blue OLED using multiresonance thermally activated delayed fluorescence host materials containing silicon atoms.

We report three highly efficient multiresonance thermally activated delayed fluorescence blue-emitter host materials that include 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (DOBNA) and tetraphenylsilyl groups. The host materials doped with the conventional N7,N7,N13,N13,5,9,11,15-octaphenyl-5,9,11,15-tetrahydro-5,9,11,15-tetraaza-19b,20b-diboradinaphtho[3,2,1-de:1',2',3'-jk]pentacene-7,13-diamine (ν-DABNA) blue emitter exhibit a high photoluminescence quantum yield greater than 0.82, a high horizontal orientation greater than 88%, and a short photoluminescence decay time of 0.96-1.93 µs. Among devices fabricated using six synthesized compounds, the device with (4-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)phenyl)triphenylsilane (TDBA-Si) shows high external quantum efficiency values of 36.2/35.0/31.3% at maximum luminance/500 cd m-2/1,000 cd m-2. This high performance is attributed to fast energy transfer from the host to the dopant. Other factors possibly contributing to the high performance are a T1 excited-state contribution, inhibition of aggregation by the bulky tetraphenylsilyl groups, high horizontal orientation, and high thermal stability. We achieve a high efficiency greater than 30% and a small roll-off value of 4.9% at 1,000 cd m-2 using the TDBA-Si host material.

Ground-state elevation approach to suppress side reactions in gold-sensing systems based on alkyne activation.

A novel approach to suppress the side reactions observed in the reaction-based gold-sensing systems based on the alkyne activation is disclosed. By elevating steric strain around the reaction site, the gold ion promoted ring-opening process in rhodamine-lactam probes is significantly accelerated, which also leads to suppression of those possible side reactions. As a result, the probes show very high sensitivity in addition to excellent selectivity toward gold species. Furthermore, bioimaging of gold species in live cells was demonstrated with a FRET version.

A reaction-based sensing scheme for gold species: introduction of a (2-ethynyl)benzoate reactive moiety.

To alleviate side reactions identified in an N-propargyl-rhodamine lactam sensing system, we devised the novel reaction-based sensing scheme for gold species based on the alkynophilicity. A fluorescein (2-ethynyl)benzoate underwent Au(III)-promoted ester hydrolysis selectively over other metal ions with high sensitivity, which accompanies a turn-on fluorescence change in pH 7.4 HEPES buffer. The work offers a versatile reactive moiety for the development of gold probes with improved sensing properties.

"Turn-on" fluorescent sensing with "reactive" probes.

Chemical probes are valuable tools for the investigation of biochemical processes, diagnosis of disease markers, detection of hazardous compounds, and other purposes. Therefore, the development of chemical probes continues to grow through various approaches with different disciplines and design strategies. Fluorescent probes have received much attention because they are sensitive and easy-to-operate, in general. To realize desired selectivity toward a given analyte, the recognition site of a fluorescent probe is designed in such a way to maximize the binding interactions, usually through weak molecular forces such as hydrogen bonding, toward the analyte over other competing ones. In addition to such a supramolecular approach, the development of fluorescent probes that sense analytes through chemical reactions has witnessed its usefulness for achieving high selectivity, in many cases, superior to that obtainable by the supramolecular approach. Creative incorporations of the reactive groups to latent fluorophores have provided novel chemical probes for various analytes. In this feature article, we overview the recent progress in the development of turn-on fluorescent probes that are operating through chemical reactions triggered by target analytes. Various chemical reactions have been implemented in the development of many reactive probes with very high selectivity and sensitivity toward target analytes. A major emphasis has been focused on the type of chemical reactions utilized, with the hope that further explorations can be made with new chemical reactions to develop reactive probes useful for various applications.

Fluorogenic and chromogenic detection of palladium species through a catalytic conversion of a rhodamine B derivative.

A simple yet efficient detection method for palladium species is developed based on a molecular sensing system that undergoes a palladium-catalyzed oxidative addition. A rhodamine B derivative thus developed undergoes the catalytic process triggered by palladium insertion and gives both turn-on fluorescence and color changes. A usefulness of the sensing system is demonstrated by determining the residual palladium contents in a purified sample prepared through a palladium-catalyzed reaction.