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Title: Ultrafast photophysics and photochemistry of [Ni]-bacteriochlorophyll a

Abstract

The ultrafast photodynamics of bacteriochlorophyll with the central Mg{sup 2+}-ion replaced by Ni{sup 2+} ([Ni]-BChl) in toluene and pyridine have been studied by femtosecond time-resolved fluorescence and absorption spectroscopy with a time resolution of 100 fs in the spectral range of 470--900 nm. Excitation of tetracoordinated [Ni]-BChl in toluene in its red-most absorption band leads to four transient states which decay single-exponentially with lifetimes of 100 fs, 450 fs, 4 ps, 25 ps. Except for the 4 ps component these kinetics arise from an internal conversion cascade conserving the overall multiplicity of the singlet configuration. The spectral characteristics of the intermediates indicate a deactivation process via several {pi}- and metal-centered excited states. The 4 ps kinetic results from a relaxation within the metal d-states caused by a change of size of the central nickel ion upon electronic excitation. A different deactivation pattern is observed for [Ni]-BChl in pyridine, where the central metal is additionally coordinated by two axial solvent molecules. On the basis of their dynamics and their spectral positions, three different intermediates have been identified. The fastest decay with 150 fs reflects an internal conversion process. This is followed by a process that can be approximately described by timemore » constants of 6 and 90 ps. This decay pattern, concomitant with the spectral changes, is attributed to the ejection of the axial solvent ligands accompanied by intersystem crossing. The slowest component has a characteristic time of > 2 ns and is attributed to the rebinding of the pyridine ligands.« less

Authors:
; ; ; ; ;  [1];  [2]
  1. Technische Univ. Muenchen, Garching (Germany). Inst. fuer Physikalische und Theoretische Chemie
  2. Ludwig-Maximilians-Univ. Muenchen (Germany). Botanisches Inst.
Publication Date:
OSTI Identifier:
691307
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 103; Journal Issue: 33; Other Information: PBD: 19 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; PHOTOSYNTHESIS; CHLOROPHYLL; PHOTOCHEMISTRY; MAGNESIUM; NICKEL

Citation Formats

Musewald, C., Hartwich, G., Lossau, H., Gilch, P., Poellinger-Dammer, F., Michel-Beyerle, M.E., and Scheer, H. Ultrafast photophysics and photochemistry of [Ni]-bacteriochlorophyll a. United States: N. p., 1999. Web. doi:10.1021/jp991388r.
Musewald, C., Hartwich, G., Lossau, H., Gilch, P., Poellinger-Dammer, F., Michel-Beyerle, M.E., & Scheer, H. Ultrafast photophysics and photochemistry of [Ni]-bacteriochlorophyll a. United States. doi:10.1021/jp991388r.
Musewald, C., Hartwich, G., Lossau, H., Gilch, P., Poellinger-Dammer, F., Michel-Beyerle, M.E., and Scheer, H. Thu . "Ultrafast photophysics and photochemistry of [Ni]-bacteriochlorophyll a". United States. doi:10.1021/jp991388r.
@article{osti_691307,
title = {Ultrafast photophysics and photochemistry of [Ni]-bacteriochlorophyll a},
author = {Musewald, C. and Hartwich, G. and Lossau, H. and Gilch, P. and Poellinger-Dammer, F. and Michel-Beyerle, M.E. and Scheer, H.},
abstractNote = {The ultrafast photodynamics of bacteriochlorophyll with the central Mg{sup 2+}-ion replaced by Ni{sup 2+} ([Ni]-BChl) in toluene and pyridine have been studied by femtosecond time-resolved fluorescence and absorption spectroscopy with a time resolution of 100 fs in the spectral range of 470--900 nm. Excitation of tetracoordinated [Ni]-BChl in toluene in its red-most absorption band leads to four transient states which decay single-exponentially with lifetimes of 100 fs, 450 fs, 4 ps, 25 ps. Except for the 4 ps component these kinetics arise from an internal conversion cascade conserving the overall multiplicity of the singlet configuration. The spectral characteristics of the intermediates indicate a deactivation process via several {pi}- and metal-centered excited states. The 4 ps kinetic results from a relaxation within the metal d-states caused by a change of size of the central nickel ion upon electronic excitation. A different deactivation pattern is observed for [Ni]-BChl in pyridine, where the central metal is additionally coordinated by two axial solvent molecules. On the basis of their dynamics and their spectral positions, three different intermediates have been identified. The fastest decay with 150 fs reflects an internal conversion process. This is followed by a process that can be approximately described by time constants of 6 and 90 ps. This decay pattern, concomitant with the spectral changes, is attributed to the ejection of the axial solvent ligands accompanied by intersystem crossing. The slowest component has a characteristic time of > 2 ns and is attributed to the rebinding of the pyridine ligands.},
doi = {10.1021/jp991388r},
journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
number = 33,
volume = 103,
place = {United States},
year = {1999},
month = {8}
}