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

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. (C) 2013 Elsevier Ltd. All rights reserved.