TY - JOUR
T1 - Direct deconvolution of two-state pump-probe X-ray absorption spectra and the structural changes in a 100 ps transient of Ni(II)-tetramesitylporphyrin
AU - Della-Longa, S.
AU - Chen, L. X.
AU - Frank, P.
AU - Hayakawa, K.
AU - Hatada, K.
AU - Benfatto, M.
PY - 2009/5/4
Y1 - 2009/5/4
N2 - Full multiple scattering (FMS) Minuit XANES (MXAN) has been combined with laser pump-probe K-edge X-ray absorption spectroscopy (XAS) to determine the structure of photoexcited Ni(II)tetramesitylporphyrin, Ni(II)TMP, in dilute toluene solution. It is shown that an excellent simulation of the XANES spectrum is obtained, excluding the lowest-energy bound- state transitions. In ground-state Ni(II)TMP, the first-shell and second-shell distances are, respectively, d(Ni-N) = (1.93 ± 0.02) A° and d(Ni-C) = (2.94 ± 0.03) A, in agreement with a previous EXAFS result 1 The time-resolved XANES difference spectrum was obtained 1 from the spectra of Ni(II)TMP in its photoexcited T 1 state and its ground state, S 0. The XANES difference spectrum has been analyzed to obtain both the structure and the fraction of the T 1 state. If the T 1 fraction is kept fixed at the value (0.37 ± 0.10) determined by optical transient spectroscopy, a 0.07 A elongation of the Ni-N and Ni-C distances [d(Ni-N) and d(Ni-C)] is found, in agreement with the EXAFS result. However, an evaluation of both the distance elongation and the T1 fraction can also be obtained using XANES data only. According to experimental evidence, and MXAN simulations, the T 1 fraction is (0.60 ± 0.15) with d(Ni-N) = (1.98 ± 0.03) A° (0.05 A° elongation). The overall uncertainty of these results depends on the statistical correlation between the distances and T 1 fraction, and the chemical shift of the ionization energy because of subtle changes of metal charge between the T 1 and S 0 states. The T 1 excited-state structure results, independently obtained without the excited-state fraction from optical transient spectroscopy, are still in agreement with previous EXAFS investigations. Thus, full multiple scattering theory applied through the MXAN formalism can be used to provide structural information, not only on the ground-state molecules but also on very shortlived excited states through differential analysis applied to transient photoexcited species from time-resolved experiments.
AB - Full multiple scattering (FMS) Minuit XANES (MXAN) has been combined with laser pump-probe K-edge X-ray absorption spectroscopy (XAS) to determine the structure of photoexcited Ni(II)tetramesitylporphyrin, Ni(II)TMP, in dilute toluene solution. It is shown that an excellent simulation of the XANES spectrum is obtained, excluding the lowest-energy bound- state transitions. In ground-state Ni(II)TMP, the first-shell and second-shell distances are, respectively, d(Ni-N) = (1.93 ± 0.02) A° and d(Ni-C) = (2.94 ± 0.03) A, in agreement with a previous EXAFS result 1 The time-resolved XANES difference spectrum was obtained 1 from the spectra of Ni(II)TMP in its photoexcited T 1 state and its ground state, S 0. The XANES difference spectrum has been analyzed to obtain both the structure and the fraction of the T 1 state. If the T 1 fraction is kept fixed at the value (0.37 ± 0.10) determined by optical transient spectroscopy, a 0.07 A elongation of the Ni-N and Ni-C distances [d(Ni-N) and d(Ni-C)] is found, in agreement with the EXAFS result. However, an evaluation of both the distance elongation and the T1 fraction can also be obtained using XANES data only. According to experimental evidence, and MXAN simulations, the T 1 fraction is (0.60 ± 0.15) with d(Ni-N) = (1.98 ± 0.03) A° (0.05 A° elongation). The overall uncertainty of these results depends on the statistical correlation between the distances and T 1 fraction, and the chemical shift of the ionization energy because of subtle changes of metal charge between the T 1 and S 0 states. The T 1 excited-state structure results, independently obtained without the excited-state fraction from optical transient spectroscopy, are still in agreement with previous EXAFS investigations. Thus, full multiple scattering theory applied through the MXAN formalism can be used to provide structural information, not only on the ground-state molecules but also on very shortlived excited states through differential analysis applied to transient photoexcited species from time-resolved experiments.
UR - http://www.scopus.com/inward/record.url?scp=66149122214&partnerID=8YFLogxK
U2 - 10.1021/ic8008943
DO - 10.1021/ic8008943
M3 - 学術論文
C2 - 19326890
AN - SCOPUS:66149122214
SN - 0020-1669
VL - 48
SP - 3934
EP - 3942
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 9
ER -