Molecular design for the highly-sensitive piezochromic fluorophores with tri-armed framework containing triphenyl-quinoline moiety

•Two piezofluorochromic compounds with novel tri-arm architecture were prepared.•The new compounds have extremely sensitivity toward external pressure.•By gentle grinding, one compound showed a large fluorescent shift of 112 nm.•The magnitude of the fluorescence shift strongly depends on the size of the arm.•The two new compounds also vary their fluorescence under solvent annealing.

Two tri-armed piezochromic fluorescent molecules of tris(4-(4-phenylquinolin-2-yl)phenyl)amine (TPA-3Qu) and tris(4-(6-(9H-carbazol-9-yl)-4-phenylquinolin-2-yl)phenyl)amine (TPA-3QuCz) were prepared and found to exhibit keen fluorescence responses toward compression. With the framework of a twisted, pyramidal triphenylamine (TPA) center connecting to three large quinolinecarbazole (QuCz) arms, the amorphous TPA-3QuCz exhibited a large bathochromic shift of 112 nm under gentle grinding forces, which is different from the small shift of 32 nm for TPA-3Qu under applying a relatively-large pressure of 10 MPa. Conformational transformations involving planarization of the arms were proposed to account for the observed fluorescence responses of TPA-3QuCz and TPA-3Qu towards pressure.

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