Misono, Yasuhito and Nishizawa, Ei‐ichi and Limantara, Leenawaty and Koyama, Yasushi and Itoh, Koichi (1995) Solvent effects on the resonance Raman spectra of bacteriochlorophyll a cation radical. Chemical Physics Letters, 236 (4-5). pp. 413-418. ISSN 00092614
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Resonance Raman and electronic absorption spectra of bacteriochlorophyll a cation radical (BChl a•+) were recorded in 14 different kinds of solvents. The frequency of the ring-breathing Raman band of BChl a•+ was in the region of 1596−1599 cm-1 in solvents forming the pentacoordinated state in neutral bacteriochlorophyll a (BChl a), while it was in the region of 1584−1588 cm-1 in solvents forming the hexacoordinated state. BChl a•+ exhibited a key absorption band in the regions 546−554 and 557−563 nm in the above penta- and hexacoordinating solvents. Therefore, it has been concluded that the penta- and hexacoordinated states are retained even after conversion of BChl a into BChl a•+ (one-electron oxidation). Application of this rule to the case of 2-propanol solution showed transformation from the penta- to the hexacoordinated state upon one-electron oxidation in this particular solution. The coordination states of BChl a•+ could be correlated with the donor number (DN) and the Taft parameters, β and π*, of the solvent: The hexacoordinated state was formed in solvents with DN ≥ 18 or β > 0.5 showing higher electron-donating power, while the pentacoordinated state was formed in solvents with π* > 0.65 showing higher dielectric stabilization. Preferential solvation of a hexacoordinating solvent over a pentacoordinating solvent in their mixture (methanol/acetone or tetrahydrofuran/methylene chloride) was seen in both BChl a and BChl a•+, but the constant of preferential solvation was increased approximately 3 times by one-electron oxidation.
| Item Type: | Artikel Jurnal/Prosiding |
|---|---|
| Subjects: | Q Science > QD Chemistry |
| Divisions: | Fakultas Teknologi dan Desain > Teknik Sipil |
| Depositing User: | Admin Repository |
| Date Deposited: | 15 Apr 2020 04:11 |
| Last Modified: | 03 Jun 2022 03:29 |
| URI: | http://eprints.upj.ac.id/id/eprint/76 |
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