Journal Article Unveiling a New Aspect of Simple Arylboronic Esters: Long-Lived Room-Temperature Phosphorescence from Heavy-Atom-Free Molecules

庄子, 良晃  ,  Shoji, Yoshiaki  ,  Ikabata, Yasuhiro  ,  Wang, Qi  ,  根本, 大輔  ,  Nemoto, Daisuke  ,  坂本, 淳  ,  sakamoto, atsushi  ,  田中, 直樹  ,  Tanaka, Naoki  ,  Seino, Junji  ,  Nakai, Hiromi  ,  福島, 孝典  ,  Fukushima, Takanori

Arylboronic esters can be used as versatile reagents in organic synthesis, as represented by Suzuki–Miyaura cross-coupling. Here we report a serendipitous finding that simple arylboronic esters are phosphorescent in the solid state at room temperature with a lifetime on the order of several seconds. The phosphorescence properties of arylboronic esters are remarkable in light of the general notion that phosphorescent organic molecules require heavy atoms and/or carbonyl groups for the efficient generation of a triplet excited state. Theoretical calculations on phenylboronic acid pinacol ester indicated that this molecule undergoes an out-of-plane distortion at the (pinacol)B–Cipso moiety in the T1 excited state, which is responsible for its phosphorescence. A compound survey with 19 arylboron compounds suggested that the phosphorescence properties might be determined by solid-state molecular packing rather than by the patterns and numbers of boron substituents on the aryl units. The present finding may update the general notion of phosphorescent organic molecules.

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