Promoting Intersystem Crossing of Fluorescent Molecule via Single Functional Group Modification

Ran Liu (1) , Xing Gao (2) , Mario Barbatti (3) , Jun Jiang (1) , Guozhen Zhang (1)

1 USTC - University of Science and Technology of China [Hefei]
2 University of Michigan [Ann Arbor]
3 ICR - Institut de Chimie Radicalaire

Pure light-atoms organic phosphorescent molecules have been under scientific scrutiny because they are inexpensive, flexible, and environment friendly. The development of such materials, however, faces a bottleneck problem of intrinsically small spin-orbit couplings (SOC), which can be addressed by seeking a proper balance between intersystem crossing (ISC) and fluorescence rates. Using N-substituted naphthalimides (NNI) as the prototype molecule, we applied chemical modifications with several electrophilic and nucleophilic functional groups, to approach the goal. The selected electron donating groups actively restrain the fluorescence, enabling an efficient ISC to the triplet manifold. Electron withdrawing groups do not change the luminescent properties of the parent species. The changes in ISC and fluorescence rates are related to the nature of the lowest singlet state, which changes from localized excitation into charge-transfer excitation. This finding opens an alternative strategy for designing pure light-atoms organic phosphorescent molecules for emerging luminescent materials applications.

Domains: Chemical Sciences; Theoretical and/or physical chemistry

Ran Liu, Xing Gao, Mario Barbatti, Jun Jiang, Guozhen Zhang. Promoting Intersystem Crossing of Fluorescent Molecule via Single Functional Group Modification. Journal of Physical Chemistry Letters, 2019, 10 (6), pp.1388-1393. ⟨10.1021/acs.jpclett.9b00286⟩. ⟨hal-02288787⟩