Selective Inclusion of Electron-Donating Molecules into Porphyrin Nanochannels Derived from the Self-Assembly of Saddle-Distorted, Protonated Porphyrins and Photoinduced Electron Transfer from Guest Molecules to Porphyrin Dications
| Autor: | Takahiko Kojima, Seigo Yamauchi, Tatsuaki Nakanishi, Ryosuke Harada, Shunichi Fukuzumi, Kei Ohkubo |
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| Rok vydání: | 2007 |
| Předmět: |
Models
Molecular Steric effects Porphyrins Photochemistry Electrons Crystallography X-Ray Catalysis Photoinduced electron transfer chemistry.chemical_compound Electron transfer Cations Electrochemistry Singlet state chemistry.chemical_classification Molecular Structure Organic Chemistry Electron Spin Resonance Spectroscopy Temperature General Chemistry Electron acceptor Porphyrin Nanostructures Models Chemical chemistry Flash photolysis Density functional theory |
| Zdroj: | Chemistry - A European Journal. 13:8714-8725 |
| ISSN: | 1521-3765 0947-6539 |
| Popis: | A doubly protonated hydrochloride salt of a saddle-distorted dodecaphenylporphyrin (H 2 DPP), [H 4 DPPP]Cl 2 , forms a porphyrin nanochannel (PNC). X-ray crystallography was used to determine the structure of the molecule, which revealed the inclusion of guest molecules within the PNC. Electron-donating molecules, such as p-hydroquinone and p-xylene, were selectively included within the PNC in sharp contrast to electron acceptors, such as the corresponding quinones, which were not encapsulated. This result indicates that the PNC can recognize the electronic character and steric hindrance of the guest molecules during the course of inclusion. ESR measurements (photoirradiation at 2> 340 nm at room temperature) of the PNC that contains p-hydroquinone, catechol, and tetrafluorohydroquinone guest molecules gave well-resolved signals, which were assigned to cation radicals formed without deprotonation based on results from computer simulations of the ESR spectra and density functional theory (DFT) calculations. The radicals are derived from photoinduced electron transfer from the guest molecules to the singlet state of H 4 DPP 2+ . Transient absorption spectroscopy by femtosecond laser flash photolysis allowed us to observe the formation of 1 (H 4 DPP 2+ )*, which is converted to H 4 DPP +. by electron transfer from the guest molecules to 1 (H 4 DPP 2+ )*, followed by fast disproportionation of H 4 DPP +. , and charge recombination to give diamagnetic species and the triplet excited state 3 (H 4 DPP 2+ )*, respectively. |
| Databáze: | OpenAIRE |
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