Phosphorescent Pt(II) complexes having tetradentate ligands have emerged as promising materials for use in organic light emitting devices (OLEDs). One drawback that retards the full exploitation of their electroluminescence is a strong propensity for bathochromically shifted emissions. The chromic shift results from intermolecular association. Molecular strategies that avoid the intermolecular interactions are needed, particularly for producing blue electrophosphorescence. We have designed and synthesized a series of phosphorescent cycloplatinate complexes having bis(1-pyrazolylphenyl)methane tetradentate ligands (PtSN1−3). The ligands have been systematically modified to incorporate methyl substituents at different positions of the pyrazole moieties (PtSN1, no methyl substituent; PtSN2, 4-methyl substituents; PtSN3, 3-methyl substituents) with the aim of preserving intrinsic sky-blue phosphorescence while suppressing intermolecular interactions. The synthetic modifications control the extent of out-of-plane distortions in the cycloplatinate scaffold. Excimer emission is obtained from PtSN1−2 of planar platinacycles in diluted solutions (10 μM) or in thin mCBP:TSPO1 (8 wt %) films (1:1, wt/wt; mCBP = 3,3-di(9H-carbazol-9-yl)biphenyl; TSPO1 = diphenyl(4-(triphenylsilyl)phenyl)phosphine oxide) due to strong spontaneous excimer formation with free energy changes of −4.4 to −3.1 kJ mol −1 . By contrast, helically distorted PtSN3 is capable of preserving its inherent sky-blue phosphorescence in concentrated states as it effectively suppresses excimer formation. An additional benefit of our synthetic control is improved stability against degradation for PtSN3. Finally, electroluminescence performances were evaluated by constructing and analyzing multilayer OLEDs employing the PtSN complexes as dopants. As expected, the PtSN3 devices produced sky-blue electrophosphorescence with a Commission Internationale de l'E ́clairage coordinate of (0.16, 0.24) and a peak external quantum efficiency of 8.5%. The electrophosphorescence spectra of the PtSN1−2 devices were contaminated with excimer luminescence. These results collectively demonstrated the effectiveness of the helical distortion approach for obtaining blue electrophosphorescence.

The combined use of a singlet oxygen photosensitizer and 1,3-diarylisobenzothiophene enables efficient generation of hydrogen sulfide under visible light illumination.

Electrides, which have excess anionic electrons, are solid-state sources of solvated electrons that can be used as powerful reducing agents for organic syntheses. However, the abrupt decomposition of electrides in organic solvents makes controlling the transfer inefficient, thereby limiting the utilization of their superior electron-donating ability. Here, we demonstrate the efficient reductive transformation strategy which combines the stable two-dimensional [Gd2C]2+·2e– electride electron donor and cyclometalated Pt­(II) complex photocatalysts. Strongly localized anionic electrons at the interlayer space in the [Gd2C]2+·2e– electride are released via moderate alcoholysis in 2,2,2-trifluoroethanol, enabling persistent electron donation. The Pt­(II) complexes are adsorbed onto the surface of the [Gd2C]2+·2e– electride and rapidly capture the released electrons at a rate of 107 s–1 upon photoexcitation. The one-electron-reduced Pt complex is electrochemically stable enough to deliver the electron to substrates in the bulk, which completes the photoredox cycle. The key benefit of this system is the suppression of undesirable charge recombination because back electron transfer is prohibited due to the irreversible disruption of the electride after the electron transfer. These desirable properties collectively serve as the photoredox catalysis principle for the reductive generation of the benzyl radical from benzyl halide, which is the key intermediate for dehalogenated or homocoupled products.