Multi-stimuli-responsive fluorescent materials based on N, O-chelated BF2 complexes: Self-assembling, sensory properties and detection of latent fingerprint

Abstract

Four new D-π-A type N,O-chelated BF2 complexes (TCBOB, TCBTB, TCQB and TCPB) were synthesized. It was found that TCPB bearing the ligand of N-(1-pyridinyl)benzoamide shows gelation ability in methylcyclohexane, DCM/peteroleum ether, etc. The time-dependent UV–vis absorption and fluorescent emission spectral changes during the gel formation revealed that π-π interactions play important roles in the self-assembling processes. Particularly, the emission of the xerogel-based film of TCPB can be quenched by TFA (trifluoroacetic acid) vapor, and it showed high performance in the detection of TFA compared with the spin-coating films of TCBOB, TCBTB and TCQB. In addition, the BF2 complexes exhibited reversible mechanofluorochromic behavior under the treatment of grinding/fuming or heating, and TCPB gave high-contrast mechanofluorochromism compared with others. XRD patterns in different solid states demonstrated that the external mechanical forces can induce the transformation from the crystalline to the amorphous states. Powder of TCPB was also used to image latent fingerprints on surface of glasses, and distinct fluorescent images were obtained.