Single-Molecular White Emission of Organic Thianthrene-Based Luminophores Exhibiting Efficient Fluorescence and Room Temperature Phosphorescence Induced by Halogen Atoms

Because of the contradiction of the efficiencies of fluorescence (FL) and room temperature phosphorescence (RTP) under ambient conditions, achievement of the molecular design of efficient monomolecular white emission resulting from the overlapping of FL and RTP is attractive but very challenging. With the aim of obtaining efficient white emission from a single organic molecule, phenyl(thianthren-2-yl)methanone and its tan derivatives with halogen atoms are developed. Single-molecular white emitters are investigated by experimental and theoretical approaches including steady-state and time-resolved spectroscopy, X-ray analyses, and density functional theory calculations. Photoluminescence quantum yields (PLQYs) of white emission of the molecular dispersion of phenyl(thianthren-2-yl)methanone in the rigid host ZEONEX at room temperature are significantly enhanced from 19 to 84% after the removal of oxygen. Based on the results of X-ray analysis of the single crystal, the high PLQY values are partly attributed to the absence of π–π intermolecular interactions and the low number of weak van der Waals intermolecular stacking due to the strong bending of heterocyclic thianthrene moiety and the high dihedral angle between thianthrene and benzoyl groups. The structural peculiarities of the newly synthesized thianthrene derivatives may result in the development of even more efficient organic monomolecular white emitters.