A fused polycyclic compound containing phenothiazine and diazapyrene skeletons with weak D-A interactions

A small fused polycyclic molecule containing a phenothiazine and diazapyrene skeleton as the donor and acceptor, respectively, has a redox potential similar to those of the corresponding donor and acceptor molecules, indicating that the inherent electronic properties of the donor and acceptor were retained due to weak orbital interactions.

Pyrene and triphenylamine substituted cyanostyrene and cyanostilbene derivatives with dual-state emission for high-contrast mechanofluorochromism and cell imaging

Two α-cyanostilbene derivatives exhibiting bright emission in both well-dissolved solutions (Φ > 49%) and the solid state (Φ > 95%) have been synthesized as novel DSEgens for high-contrast mechanofluorochromism (>50 nm) and live cell imaging.

Luminescent Behavior Elucidation of a Disilane-Bridged D-A-D Triad Composed of Phenothiazine and Thienopyrazine

A σ-π extended aryldisilane, comprising a thienopyrazine group as an acceptor fragment and phenothiazine groups as the donor moiety, has been prepared through the introduction of two Si-Si bridges (compound 1). X-ray diffraction analysis determined the crystal structure of 1, and experimental and theoretical approaches investigated its optical properties. Solvatochromic studies revealed the dual emission of 1 in all solvents tested. Compound 1 also exhibited fluorescence in the solid state upon excitation with a hand-held UV lamp, as well as mechanochromic luminescent properties. The packing mode in the crystal structure, variation of phenothiazine conformation, morphological changes between crystalline and amorphous phases are the major factors showing reversible fluorescence under external stimuli. A theoretical conformer study found that 1 exists in distinct conformational groups differing in Gibbs free energy by less than 3 kcal mol^-1 . The conformer in the crystalline state of 1 can promote the complete separation of the HOMO and LUMO between the phenothiazine donor and the thienopyrazine acceptor, linked by the disilane linker. HOMO-LUMO energy transition in the crystalline state is forbidden due to the lack of frontier orbital overlap. Crystalline state emission showed LUMO → HOMO-1 transition (locally excited (LE) state). In the amorphous state, the partial presence of quasi-axial conformers allows intramolecular charge-transfer type emission via energy transfer from dominant quasi-equatorial conformers. The strategy proposed in this work provides important guidance for developing stimuli-responsive materials with controlled excited states.

Molecular engineering of carbazole–acrylonitrile fluorophores: substituent-dependent optical properties and mechanochromism

Controlling the fluorescence properties of organic molecules in the aggregation state and understanding the structure–activity relationship are important for developing excellent luminophors with tunable solid emission.