Multiple Photohiminescence from l,2-Dinaphthyl-ortho-Carborane

摘要

A special feature of multiple photoluminescence in a single organic molecule is that it is only reported for geometrically unique systems. These molecules have drawn much attention because of their paradoxical photophysical behavior, contradicting Kasha's rule, which is a principle in the excited molecules. The rule states that photoluminescence occurs in an appreciable yield only from the lowest excited state. Multiple emissions arise from the corresponding nonequili-brated excited states, rather than from the most stable excited state. The existence of energetically feasible excited states comes from the restricted molecular conformation where organic functional groups occupy the most favorable geometrical positions at only small energy costs. A few examples are available in which multiple photoluminescence are elaborated: adiabatic photoreactions such as excited-state proton transfer (ESIPT), and excimer and twisted intramolecular charge-transfer (TICT) state formation (see each example in Scheme 1).