Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li<sup>+</sup>@C<inf>60</inf>

Yuki Kawashima, Kei Ohkubo, Vicente Manuel Blas-Ferrando, Hayato Sakai, Enrique Font-Sanchis, Javier Ortíz, Fernando Fernández-Lázaro, Taku Hasobe, Ángela Sastre-Santos, Shunichi Fukuzumi

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Abstract

Two phthalocyanines possessing carboxylate groups ((TBA)<inf>4</inf> H<inf>2</inf> Pc·1 and (TBA)<inf>4</inf> H<inf>2</inf> Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C<inf>60</inf> (Li<sup>+</sup>@C<inf>60</inf> ) [H<inf>2</inf> Pc·1<sup>4-</sup>/(Li<sup>+</sup>@C<inf>60</inf> )<inf>2</inf> and H<inf>2</inf> Pc·2<sup>4-</sup>/(Li<sup>+</sup>@C<inf>60</inf> )<inf>2</inf> ] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 10<sup>12</sup> M<sup>-2</sup>. Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H<inf>2</inf> Pc·2<sup>4-</sup>/(Li<sup>+</sup>@C<inf>60</inf> )<inf>2</inf> , which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H<inf>2</inf> Pc·1<sup>4-</sup>/(Li<sup>+</sup>@C<inf>60</inf> )<inf>2</inf> also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm<sup>-1</sup> from the temperature dependence of the rate constant for the charge recombination of the CS state of H<inf>2</inf> Pc·1<sup>4-</sup>/(Li<sup>+</sup>@C<inf>60</inf> )<inf>2</inf> . The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li<sup>+</sup>@C<inf>60</inf> were also prepared and investigated. The ZnPc·4<sup>4-</sup>/Li<sup>+</sup>@C<inf>60</inf> supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO<inf>2</inf> (OTE/SnO<inf>2</inf> ) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO<inf>2</inf> /(ZnPc·4<sup>4-</sup>/Li<sup>+</sup>@C<inf>60</inf> )<inf>n</inf> were much higher than the sum of the two IPCE values of the individual systems OTE/SnO<inf>2</inf> /(Li<sup>+</sup>@C<inf>60</inf> )<inf>n</inf> and OTE/SnO<inf>2</inf> /(ZnPc·4<sup>4-</sup>)<inf>n</inf> , covering the near-infrared region.

Original languageEnglish
Pages (from-to)7690-7697
Number of pages8
JournalJournal of Physical Chemistry B
Volume119
Issue number24
DOIs
Publication statusPublished - 2015 Jun 18

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polarization (charge separation)
Infrared radiation
electron transfer
Electrodes
electrodes
Photocurrents
photocurrents
Electrons
Photons
Fullerenes
life (durability)
Photoexcitation
Nanoclusters
photons
nanoclusters
photoexcitation
Lithium
electronics
carboxylates
fullerenes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li<sup>+</sup>@C<inf>60</inf> / Kawashima, Yuki; Ohkubo, Kei; Blas-Ferrando, Vicente Manuel; Sakai, Hayato; Font-Sanchis, Enrique; Ortíz, Javier; Fernández-Lázaro, Fernando; Hasobe, Taku; Sastre-Santos, Ángela; Fukuzumi, Shunichi.

In: Journal of Physical Chemistry B, Vol. 119, No. 24, 18.06.2015, p. 7690-7697.

Research output: Contribution to journalArticle

Kawashima, Y, Ohkubo, K, Blas-Ferrando, VM, Sakai, H, Font-Sanchis, E, Ortíz, J, Fernández-Lázaro, F, Hasobe, T, Sastre-Santos, Á & Fukuzumi, S 2015, 'Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li<sup>+</sup>@C<inf>60</inf>', Journal of Physical Chemistry B, vol. 119, no. 24, pp. 7690-7697. https://doi.org/10.1021/jp5123163
Kawashima, Yuki ; Ohkubo, Kei ; Blas-Ferrando, Vicente Manuel ; Sakai, Hayato ; Font-Sanchis, Enrique ; Ortíz, Javier ; Fernández-Lázaro, Fernando ; Hasobe, Taku ; Sastre-Santos, Ángela ; Fukuzumi, Shunichi. / Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li<sup>+</sup>@C<inf>60</inf>. In: Journal of Physical Chemistry B. 2015 ; Vol. 119, No. 24. pp. 7690-7697.
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title = "Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li+@C60",
abstract = "Two phthalocyanines possessing carboxylate groups ((TBA)4 H2 Pc·1 and (TBA)4 H2 Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C60 (Li+@C60 ) [H2 Pc·14-/(Li+@C60 )2 and H2 Pc·24-/(Li+@C60 )2 ] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 1012 M-2. Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H2 Pc·24-/(Li+@C60 )2 , which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H2 Pc·14-/(Li+@C60 )2 also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm-1 from the temperature dependence of the rate constant for the charge recombination of the CS state of H2 Pc·14-/(Li+@C60 )2 . The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li+@C60 were also prepared and investigated. The ZnPc·44-/Li+@C60 supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO2 (OTE/SnO2 ) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO2 /(ZnPc·44-/Li+@C60 )n were much higher than the sum of the two IPCE values of the individual systems OTE/SnO2 /(Li+@C60 )n and OTE/SnO2 /(ZnPc·44-)n , covering the near-infrared region.",
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T1 - Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li+@C60

AU - Kawashima, Yuki

AU - Ohkubo, Kei

AU - Blas-Ferrando, Vicente Manuel

AU - Sakai, Hayato

AU - Font-Sanchis, Enrique

AU - Ortíz, Javier

AU - Fernández-Lázaro, Fernando

AU - Hasobe, Taku

AU - Sastre-Santos, Ángela

AU - Fukuzumi, Shunichi

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N2 - Two phthalocyanines possessing carboxylate groups ((TBA)4 H2 Pc·1 and (TBA)4 H2 Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C60 (Li+@C60 ) [H2 Pc·14-/(Li+@C60 )2 and H2 Pc·24-/(Li+@C60 )2 ] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 1012 M-2. Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H2 Pc·24-/(Li+@C60 )2 , which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H2 Pc·14-/(Li+@C60 )2 also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm-1 from the temperature dependence of the rate constant for the charge recombination of the CS state of H2 Pc·14-/(Li+@C60 )2 . The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li+@C60 were also prepared and investigated. The ZnPc·44-/Li+@C60 supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO2 (OTE/SnO2 ) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO2 /(ZnPc·44-/Li+@C60 )n were much higher than the sum of the two IPCE values of the individual systems OTE/SnO2 /(Li+@C60 )n and OTE/SnO2 /(ZnPc·44-)n , covering the near-infrared region.

AB - Two phthalocyanines possessing carboxylate groups ((TBA)4 H2 Pc·1 and (TBA)4 H2 Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C60 (Li+@C60 ) [H2 Pc·14-/(Li+@C60 )2 and H2 Pc·24-/(Li+@C60 )2 ] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 1012 M-2. Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H2 Pc·24-/(Li+@C60 )2 , which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H2 Pc·14-/(Li+@C60 )2 also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm-1 from the temperature dependence of the rate constant for the charge recombination of the CS state of H2 Pc·14-/(Li+@C60 )2 . The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li+@C60 were also prepared and investigated. The ZnPc·44-/Li+@C60 supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO2 (OTE/SnO2 ) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO2 /(ZnPc·44-/Li+@C60 )n were much higher than the sum of the two IPCE values of the individual systems OTE/SnO2 /(Li+@C60 )n and OTE/SnO2 /(ZnPc·44-)n , covering the near-infrared region.

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