Long-Lived Photoinduced Charge Separation in Inclusion Complexes Composed of a Phenothiazine-Bridged Cyclic Porphyrin Dimer and Fullerenes

Takuya Kamimura, Kei Ohkubo, Yuki Kawashima, Shuwa Ozako, Ken Ichi Sakaguchi, Shunichi Fukuzumi, Fumito Tani

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

C60, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), lithium-cation-encapsulated C60 (Li+@C60), and [6,6]-diphenyl-C62-bis(butyric acid methyl ester) (bis-PCBM) were included into a phenothiazine-bridged cyclic free-base porphyrin dimer (H4-Ptz-CPDPy(TEO)) in a polar solvent (benzonitrile) with large association constants of 1.3 × 106, 6.4 × 105, 3.2 × 106, and 2.5 × 105 M-1, respectively. Based on the electrochemical data, the lowest energy levels of the charge-separated (CS) states for the inclusion complexes of H4-Ptz-CPDPy(TEO) with C60, PCBM, Li+@C60, and bis-PCBM (designated as C60⊂H4-Ptz-CPDPy(TEO), PCBM⊂H4-Ptz-CPDPy(TEO), Li+@C60⊂H4-Ptz-CPDPy(TEO), and bis-PCBM⊂H4-Ptz-CPDPy(TEO)) composed of the phenothiazine donor and fullerene acceptors were determined to be 1.30, 1.40, 0.66, and 1.51 eV, respectively. Both C60⊂H4-Ptz-CPDPy(TEO) and PCBM⊂H4-Ptz-CPDPy(TEO) underwent electron transfer upon photoexcitation of the porphyrin and fullerene chromophores, and the resultant photoinduced CS states comprised the phenothiazine cation and the fullerene anions with lifetimes of 0.71 ms determined by time-resolved transient absorption spectra. Li+@C60⊂H4-Ptz-CPDPy(TEO) also afforded a similar CS state with a lifetime of 0.56 ms. These lifetimes are the longest values ever reported for the CS states of phenothiazine-fullerene complexes in solution. The spin states of these long-lived CS states were assigned to be triplet by ESR spectroscopy. The remarkably long CS lifetimes are attributable mainly to the lower CS energies than the triplet energies of the phenothiazine, fullerenes, and porphyrin moieties and the spin-forbidden slow back-electron-transfer processes. On the other hand, the photoinduced CS state of bis-PCBM⊂H4-Ptz-CPDPy(TEO) was quenched rapidly by fast back electron transfer due to the relatively high CS energy comparable to the triplet energies of the porphyrin and fullerene.

Original languageEnglish
Pages (from-to)25634-25650
Number of pages17
JournalJournal of Physical Chemistry C
Volume119
Issue number45
DOIs
Publication statusPublished - Oct 23 2015

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Fullerenes
phenothiazines
Porphyrins
polarization (charge separation)
Butyric acid
butyric acid
porphyrins
Dimers
fullerenes
Butyric Acid
dimers
esters
inclusions
Esters
life (durability)
electron transfer
Cations
Electrons
Positive ions
cations

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Cite this

Long-Lived Photoinduced Charge Separation in Inclusion Complexes Composed of a Phenothiazine-Bridged Cyclic Porphyrin Dimer and Fullerenes. / Kamimura, Takuya; Ohkubo, Kei; Kawashima, Yuki; Ozako, Shuwa; Sakaguchi, Ken Ichi; Fukuzumi, Shunichi; Tani, Fumito.

In: Journal of Physical Chemistry C, Vol. 119, No. 45, 23.10.2015, p. 25634-25650.

Research output: Contribution to journalArticle

Kamimura, Takuya ; Ohkubo, Kei ; Kawashima, Yuki ; Ozako, Shuwa ; Sakaguchi, Ken Ichi ; Fukuzumi, Shunichi ; Tani, Fumito. / Long-Lived Photoinduced Charge Separation in Inclusion Complexes Composed of a Phenothiazine-Bridged Cyclic Porphyrin Dimer and Fullerenes. In: Journal of Physical Chemistry C. 2015 ; Vol. 119, No. 45. pp. 25634-25650.
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abstract = "C60, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), lithium-cation-encapsulated C60 (Li+@C60), and [6,6]-diphenyl-C62-bis(butyric acid methyl ester) (bis-PCBM) were included into a phenothiazine-bridged cyclic free-base porphyrin dimer (H4-Ptz-CPDPy(TEO)) in a polar solvent (benzonitrile) with large association constants of 1.3 × 106, 6.4 × 105, 3.2 × 106, and 2.5 × 105 M-1, respectively. Based on the electrochemical data, the lowest energy levels of the charge-separated (CS) states for the inclusion complexes of H4-Ptz-CPDPy(TEO) with C60, PCBM, Li+@C60, and bis-PCBM (designated as C60⊂H4-Ptz-CPDPy(TEO), PCBM⊂H4-Ptz-CPDPy(TEO), Li+@C60⊂H4-Ptz-CPDPy(TEO), and bis-PCBM⊂H4-Ptz-CPDPy(TEO)) composed of the phenothiazine donor and fullerene acceptors were determined to be 1.30, 1.40, 0.66, and 1.51 eV, respectively. Both C60⊂H4-Ptz-CPDPy(TEO) and PCBM⊂H4-Ptz-CPDPy(TEO) underwent electron transfer upon photoexcitation of the porphyrin and fullerene chromophores, and the resultant photoinduced CS states comprised the phenothiazine cation and the fullerene anions with lifetimes of 0.71 ms determined by time-resolved transient absorption spectra. Li+@C60⊂H4-Ptz-CPDPy(TEO) also afforded a similar CS state with a lifetime of 0.56 ms. These lifetimes are the longest values ever reported for the CS states of phenothiazine-fullerene complexes in solution. The spin states of these long-lived CS states were assigned to be triplet by ESR spectroscopy. The remarkably long CS lifetimes are attributable mainly to the lower CS energies than the triplet energies of the phenothiazine, fullerenes, and porphyrin moieties and the spin-forbidden slow back-electron-transfer processes. On the other hand, the photoinduced CS state of bis-PCBM⊂H4-Ptz-CPDPy(TEO) was quenched rapidly by fast back electron transfer due to the relatively high CS energy comparable to the triplet energies of the porphyrin and fullerene.",
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T1 - Long-Lived Photoinduced Charge Separation in Inclusion Complexes Composed of a Phenothiazine-Bridged Cyclic Porphyrin Dimer and Fullerenes

AU - Kamimura, Takuya

AU - Ohkubo, Kei

AU - Kawashima, Yuki

AU - Ozako, Shuwa

AU - Sakaguchi, Ken Ichi

AU - Fukuzumi, Shunichi

AU - Tani, Fumito

PY - 2015/10/23

Y1 - 2015/10/23

N2 - C60, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), lithium-cation-encapsulated C60 (Li+@C60), and [6,6]-diphenyl-C62-bis(butyric acid methyl ester) (bis-PCBM) were included into a phenothiazine-bridged cyclic free-base porphyrin dimer (H4-Ptz-CPDPy(TEO)) in a polar solvent (benzonitrile) with large association constants of 1.3 × 106, 6.4 × 105, 3.2 × 106, and 2.5 × 105 M-1, respectively. Based on the electrochemical data, the lowest energy levels of the charge-separated (CS) states for the inclusion complexes of H4-Ptz-CPDPy(TEO) with C60, PCBM, Li+@C60, and bis-PCBM (designated as C60⊂H4-Ptz-CPDPy(TEO), PCBM⊂H4-Ptz-CPDPy(TEO), Li+@C60⊂H4-Ptz-CPDPy(TEO), and bis-PCBM⊂H4-Ptz-CPDPy(TEO)) composed of the phenothiazine donor and fullerene acceptors were determined to be 1.30, 1.40, 0.66, and 1.51 eV, respectively. Both C60⊂H4-Ptz-CPDPy(TEO) and PCBM⊂H4-Ptz-CPDPy(TEO) underwent electron transfer upon photoexcitation of the porphyrin and fullerene chromophores, and the resultant photoinduced CS states comprised the phenothiazine cation and the fullerene anions with lifetimes of 0.71 ms determined by time-resolved transient absorption spectra. Li+@C60⊂H4-Ptz-CPDPy(TEO) also afforded a similar CS state with a lifetime of 0.56 ms. These lifetimes are the longest values ever reported for the CS states of phenothiazine-fullerene complexes in solution. The spin states of these long-lived CS states were assigned to be triplet by ESR spectroscopy. The remarkably long CS lifetimes are attributable mainly to the lower CS energies than the triplet energies of the phenothiazine, fullerenes, and porphyrin moieties and the spin-forbidden slow back-electron-transfer processes. On the other hand, the photoinduced CS state of bis-PCBM⊂H4-Ptz-CPDPy(TEO) was quenched rapidly by fast back electron transfer due to the relatively high CS energy comparable to the triplet energies of the porphyrin and fullerene.

AB - C60, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), lithium-cation-encapsulated C60 (Li+@C60), and [6,6]-diphenyl-C62-bis(butyric acid methyl ester) (bis-PCBM) were included into a phenothiazine-bridged cyclic free-base porphyrin dimer (H4-Ptz-CPDPy(TEO)) in a polar solvent (benzonitrile) with large association constants of 1.3 × 106, 6.4 × 105, 3.2 × 106, and 2.5 × 105 M-1, respectively. Based on the electrochemical data, the lowest energy levels of the charge-separated (CS) states for the inclusion complexes of H4-Ptz-CPDPy(TEO) with C60, PCBM, Li+@C60, and bis-PCBM (designated as C60⊂H4-Ptz-CPDPy(TEO), PCBM⊂H4-Ptz-CPDPy(TEO), Li+@C60⊂H4-Ptz-CPDPy(TEO), and bis-PCBM⊂H4-Ptz-CPDPy(TEO)) composed of the phenothiazine donor and fullerene acceptors were determined to be 1.30, 1.40, 0.66, and 1.51 eV, respectively. Both C60⊂H4-Ptz-CPDPy(TEO) and PCBM⊂H4-Ptz-CPDPy(TEO) underwent electron transfer upon photoexcitation of the porphyrin and fullerene chromophores, and the resultant photoinduced CS states comprised the phenothiazine cation and the fullerene anions with lifetimes of 0.71 ms determined by time-resolved transient absorption spectra. Li+@C60⊂H4-Ptz-CPDPy(TEO) also afforded a similar CS state with a lifetime of 0.56 ms. These lifetimes are the longest values ever reported for the CS states of phenothiazine-fullerene complexes in solution. The spin states of these long-lived CS states were assigned to be triplet by ESR spectroscopy. The remarkably long CS lifetimes are attributable mainly to the lower CS energies than the triplet energies of the phenothiazine, fullerenes, and porphyrin moieties and the spin-forbidden slow back-electron-transfer processes. On the other hand, the photoinduced CS state of bis-PCBM⊂H4-Ptz-CPDPy(TEO) was quenched rapidly by fast back electron transfer due to the relatively high CS energy comparable to the triplet energies of the porphyrin and fullerene.

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