An exceptionally long-lived triplet state of red light-absorbing compact phenothiazine-styrylBodipy electron donor/acceptor dyads: a better alternative to the heavy atom-effect?

A series of phenothiazine-styrylborondipyrromethene compact electron donor/acceptor dyads were prepared to access heavy-atom-free triplet photosensitizers showing red-absorption and especially long-lived triplet states (303 mu s), based on the spin orbital charge transfer intersystem crossing (SOCT ISC) mechanism.