Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

A series of vibratile pi-extended dihydrophenazines (BPs) and a tetrahydrodiphenazine (TP) were synthesized via direct C-N coupling reactions. Structural alterations of the fused acene wings lead to diverse intermolecular packing arrangements as well as tunable photophysical properties. These compounds exhibit intriguing features, including large Stokes shift, multiple emissions, and environmental effects. Notably, a dramatic hypsochromic shift in emission is observed when the acene wing is linearly extended from benzene to naphthalene and anthracene. This unusual pi-conjugation length-dependent emission is explained by the close correlation between the calculated fluorescence-emitting energy and the pi-conjugation length of the acene subunit. In addition, the TP bearing two flexible units exhibits dynamic photophysical properties resembling those of BPs. Our results reveal a balanced control over pi-conjugation and luminescence in vibratile pi-systems, thereby providing new insight into the molecular design of organic near-infrared fluorophores with large Stokes shifts and dynamic emissions. [GRAPHICS] .

Automated summary

A series of vibratile pi-extended dihydrophenazines and a tetrahydrodiphenazine were synthesized and their structural alterations were found to result in diverse intermolecular packing arrangements and photophysical properties. The emissions of these compounds showed significant changes depending on the length of the pi-conjugated system, which can be explained by the correlation between the calculated fluorescence-emitting energy and the pi-conjugation length. Additionally, a compound with flexible units exhibited similar photophysical properties to the dihydrophenazines.