Enhancement of Light Absorption Ability of Synthetic Chlorophyll Derivatives by Conjugation with a Difluoroboron Diketonate Group |
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| Authors: | Dr Yusuke Kinoshita Dr Yuichi Kitagawa Prof Dr Hitoshi Tamiaki |
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| Affiliation: | 1. Graduate School of Life Sciences, Ritsumeikan University, Shiga, Japan;2. Division of Materials Chemistry, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan |
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| Abstract: | The enhancement of the light absorption ability of synthetic chlorophyll derivatives is demonstrated. Chlorophyll derivatives directly conjugated with a difluoroboron 1,3‐diketonate group at the C3 position were synthesized from methyl pyropheophorbide‐d through Barbier acylmethylation of the C3‐formyl moiety, oxidation of the C3‐carbinol, and difluoroboron complexation of the diketonate. Electronic absorption spectra in a diluted solution showed that the synthetic conjugates gave an absorption band at λ=400–500 nm, with a Qy band shifted to a longer wavelength of λ≈700 nm. DFT calculations demonstrated that the absorption bands and redshifts were ascribable to the coupling of the LUMO of chlorin with that of the difluoroboron diketonate moiety. The introduction of a pyrenyl group at the C33‐position of the conjugate afforded an additional charge‐transfer band over λ=500 nm, producing a pigment that bridged the green gap in standard chlorophylls. |
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| Keywords: | absorption charge transfer chromophores enols porphyrinoids |
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