1 research outputs found
Siloxy Group-Induced Highly Efficient Room Temperature Phosphorescence with Long Lifetime
The
design and development of organic phosphors that exhibit efficient
emission at room temperature but do not contain precious metals such
as iridium and platinum have attracted increasing attention. We report
herein highly efficient green phosphorescence-emitting 1,4-dibenzoyl-2,5-bisÂ(siloxy)Âbenzene
crystals in air at room temperature. Remarkable luminescence quantum
yields of 0.46 to 0.64 and long lifetimes ranging from 76.0 to 98.3
ms were observed. X-ray diffraction analysis of the single crystals
revealed that there were several intermolecular interactions causing
suppression of intramolecular motion, thereby minimizing nonradiative
decay of the triplet excited state. Comparison with the corresponding
2,5-bisÂ(dimethylphenylsilylmethyl) and 2,5-bisÂ(trimethylsilyl) derivatives
revealed that the siloxy groups are essential for efficient room temperature
phosphorescence. Density functional calculations suggested that σ–n
conjugation was operative in the siloxy moieties. Electron spin resonance
measurement indicated that the radiative process included generation
of the triplet diradical species, whose electron distribution was
very similar to that of naphthalene. The present study largely expands
the possibilities for the molecular design of precious metal- and
halogen-free organic phosphors exhibiting efficient room temperature
phosphorescence