Absorption and Emission Properties of Acenaphthoporphyrins

Acenaphtho[1,2-b]porphyrins (AcePs) were prepared by the [3 + 1] condensation method and their photochemical properties were investigated. The fluorescence spectra of the free-base AcePs in CHCl3 showed two emission bands at 660 and 720 nm, whose intensity drastically changed depending on the excitation wavelength. However, those of zinc complexes did not show such a wavelength dependence and showed similar emission spectra by the excitation at various wavelengths. The fluorescence excitation spectra and quantum yields of the free-base AcePs in CHCl3 showed the similar excitation wavelength dependence. This fact indicates that two electronic structures exist in the free-base AcePs and their fluorescence is emitted from one structure in higher quantum yield (λ EM = 660 nm) and from the other in lower yield (λ EM = 720 nm), respectively.