Photochemical “Triode” Molecular Signal Transducer

摘要

Abstract: A molecular “hexad” in which five bis(phenylethynyl)anthracene (BPEA) fluorophores and andithienylethene photochrome are organized by a central hexaphenylbenzene unit has been prepared.nSinglet singlet energy transfer among the BPEA units occurs on the 0.4 and 60 ps time scales, and whennthe dithienylethene is in the open form, the BPEA units fluoresce in the 515 nm region with a quantumnyield near unity. When the dithienylethene is photoisomerized by UV light to the closed form, which absorbsnin the 500 700 nm region, the closed isomer strongly quenches all of the excited singlet states of BPEAnvia energy transfer, causing the fluorescence quantum yield to drop to near zero. This photochemicalnbehavior permits the hexad to function in a manner analogous to a triode vacuum tube or transistor. Whenna solution of the hexad is irradiated with steady-state light at 350 nm and with red light ( 610 nm) ofnmodulated intensity, the BPEA fluorescence excited by the 350 nm light is modulated accordingly. Thenfluorescence corresponds to the output of a triode tube or transistor and the modulated red light to the gridnsignal of the tube or gate voltage of the transistor. Frequency modulation, amplitude modulation, and phasenmodulation are all observed. The unusual ability to modulate intense, shorter-wavelength fluorescencenwith longer-wavelength light could be useful for the detection of fluorescence from probe molecules withoutninterference from other emitters in biomolecular or nanotechnological applications.