Abstract: The variations of the fluorescent spectral features with respect to a molecular array, N,N-bis[p-5′-(m-10′,15′,20′-triphenylporphyrin)phenyl]-perylene-3,4:9,10-tetracarboxyl-diimide(TrPP-PTCDI-TrPP), were investigated at different concentrations of trifluoroacetic acid, the molecular array displays the characteristic emission of the protonated free-base-porphyrin subunit upon the photo-excitation of both the protonated free-base-porphyrin(λ=439 nm) and perylene-diimide subunits(λ=491 nm), because the excited state of protonated free-base-porphyrin in the molecular array was a relative stable species in comparison with other excitations. The incorporation of the acid leads to the closure of the efficient charge transfer decay, while results in the open of the radiation decay. Addition of triethylamine into the solution affords the reverse processes, i.e. the open of the efficient charge transfer decay while the closure of the radiation decay. Thus the molecular array provides a proton-type of fluorescent switch based on acid-base control. Such a molecular array switch has advantages of facility due to the acid-base neutralization and broad-band sensitivity due to the simultaneous response to different excitation wavelengths.

Key words: Molecular array, Protonation, Acid-base neutralization, Fluorescent switch