Carbonyl Spectator Bonds as Sensitive Sensors for Charge Transfer Reactions on the Femtosecond Time Scale
摘要:
The feasibility of using the vibrational Stark effect for the observation of charge transfer reactions on a short time scale is demonstrated. The photoinduced oxidation of ferrocenophanone induces a fast shift of the carbonyl streaching frequency which is observable by femtosecond time-resolved IR spectroscopy. The observed shift is in good agreement with the IR spectrum of chemically oxidized ferrocenophanone and with theoretical predictions based on vibrational Stark effect calculations. The time dependence of the signal mirrors the charge transfer dynamics on the fs to ps time scale, as observed by optical spectroscopy. This shows that the vibrational Stark effect provides access to observing charge transfer reactions in the IR on the fs Lime scale. Since the Stark effect is sensitive to changes of the electric field alone, the sensor bond does not need to be part of the molecular system under investigation, but may be a noninvolved "spectator" bond located in its immediate surroundings.
Dissociative Intramolecular Charge Transfer after Local Two-Photon Ionization of Ferrocene Derivatives with Aromatic Chromophores
作者:J. E. Braun、H. J. Neusser、P. Härter、M. Stöckl
DOI:10.1021/jp992963u
日期:2000.3.1
Experimental evidence for dissociative intramolecular charge transfer processes is found for gas-phase ferrocene-aniline derivatives after local ionization at the aniline chromophore site via intermediate states with predominant aniline character. The direct ionization at the ferrocene site can be excluded since there is a rapid dissociation of ferrocene in the intermediate state prior to ionization so that no ferrocene ions would be produced in this case. Because of the higher local ionization energy of the chromophore, charge transfer takes place after local ionization. The released energy and additional photon absorption leads to breaking of bonds and results in a dissociation into intact ferrocene or ferrocene-containing cations and neutral fragments.
Insertion of Carbenoids into CpH Bonds of Ferrocenes: An Enantioselective-Catalytic Entry to Planar-Chiral Ferrocenes