1,3,5-Trifluoro-2,4,6-triiodobenzene: A neglected NIR phosphor with prolonged lifetime by σ-hole and π-hole capture.

Room temperature phosphorescence (RTP) materials have become a hot topic in fields of organic light-emitting dioes, biological sensing and imaging. The present work reports firstly that 1,3,5-trifluoro-2,4,6-triiodobenzene (TITFB) can act as a simple pure organic NIR phosphor due to its novel function in promoting n-π∗ transition. Also, TITFB crystal has longer phosphorescence lifetime than other ordinary multiiodoluminophors and TITFB powder. Based on the TITFB crystal structure, σ-hole and π-hole capture mechanism of n-electron is proposed, i.e., the excited state energy is decreased and n-electrons are stabilized to cause slower radiative decay rate due to the restriction of σ-hole and π-hole bond. Both computational and experimental studies support the mechanism. The new electron-capture mode is more conducive to understanding pure organic ultralong lifetime RTP.