Ultrafast intramolecular charge transfer of formyl perylene observed using femtosecond transient absorption spectroscopy.
The excited-state photophysics of formylperylene (FPe) have been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of experimental and theoretical methods were employed including femtosecond transient absorption (fs-TA) spectroscopy with 130 fs temporal resolution. We report that the ultrafast intramolecular charge transfer from the perylene unit to the formyl (CHO) group can be facilitated drastically by hydrogen-bonding interactions between the carbonyl group oxygen of FPe and hydrogen-donating solvents in the electronically excited state. The excited-state absorption of FPe in methanol (MeOH) is close to the reported perylene radical cation produced by bimolecular quenching by an electron acceptor. This is a strong indication for a substantial charge transfer in the S(1) state in protic solvents. The larger increase of the dipole moment change in the protic solvents than that in aprotic ones strongly supports this observation. Relaxation mechanisms including vibrational cooling and solvation coupled to the charge-transfer state are also discussed.
Mohammed
Omar F
OF
Physical Biology Center for Ultrafast Science & Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, USA. omar3070@caltech.edu
D006860:Hydrogen Bonding; D000432:Methanol / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010569:Perylene / Q000031:analogs & derivatives / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D010569:Perylene; D010100:Oxygen; D000432:Methanol