Polarized two-photon fluorescence excitation spectra of indole and benzimidazole

✍ Scribed by Bruce E. Anderson; Richard D. Jones; Aden A. Rehms; Predrag Ilich; Patrik R. Callis

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 683 KB
• Volume: 125
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(86)85085-0

✦ Synopsis

PoIarized two-photon fluorescence excitation spectra of indole in hexane, benzimidazole in isopropanoi, and benzimidazole cation in methanol-HaSO.,, all at 0.2 M and 25°C are reported for the excitation range 470-600 nm, the region of their L, and L, bands. Relative two-photon absorptivities are deduced by correcting for different fluorescence response and are compared to toluene's L, band. The indole integrated absorptivity is about 10 times greater than that of toluene. The L, band of indole appears less dominant than in one-photon but still outweighs the L, band by a factor of 4. The two-photon polarization spectrum for indole indicates that the L, origin lies = 500-1000 cm-' above the L, origin in hexane. The benzimidazoIes absorb only about twice as strongly as toluene and show strong vibronic peaks; the L, bands are only faintly seen. Two-photon properties calculated from INDO/S CI wavefunctions with doubly excited configurations are in good agreement with those of indole, but predict the benzimidazole TPA to be several times stronger than observed. For the cation, the predicted results are nearly two orders of magnitude too high.