Structures and photoinduced electron transfer of protonated complexes of porphyrins and metallophthalocyanines

Shunichi Fukuzumi, Tatsuhiko Honda, Takahiko Kojima

Research output: Contribution to journalReview articlepeer-review

89 Scopus citations

Abstract

Porphyrins and phthalocyanines are planar two-dimensional π-compounds, which are normally difficult to protonate because of the low basicity. When many bulky substituents are introduced to porphyrins and phthalocyanines, however, the macrocyclic π-plane is distorted due to the steric repulsion of the bulky substituents. The π-plane distortion facilitates protonation to afford stable protonated porphyrins and phthalocyanines. Crystal structures of protonated porphyrins and phthalocyanines were determined to clarify the role of hydrogen bonding in the supramolecular assemblies. Protonated porphyrinoids can act as an electron acceptor rather than an electron donor in photoinduced electron-transfer reactions. The rate constants of photoinduced electron-transfer reactions of diprotonated porphyrin with different degrees of distortion were determined and they are evaluated in light of the Marcus theory of electron transfer to determine the reorganization energies of electron transfer, which are affected by the distortion of the π-plane. A distortion of the macrocyclic ligands also affords higher Lewis acidity at a metal center to allow facile axial coordination of ligands, due to poor overlap of the lone pair orbitals with d x2-y2 or p x and p y orbitals of the metal center. Thus, the distortion of the macrocyclic ligands enables one to construct various molecular and supramolecular complexes composed of porphyrins and phthalocyanines. The photodynamics of photoinduced electron-transfer reactions of various supramolecular complexes of distorted porphyrin and phthalocyanines are discussed in relation to structure and photofunction.

Original languageEnglish
Pages (from-to)2488-2502
Number of pages15
JournalCoordination Chemistry Reviews
Volume256
Issue number21-22
DOIs
StatePublished - Nov 2012

Bibliographical note

Funding Information:
The author gratefully acknowledges the contributions of their collaborators and coworkers mentioned in the references. The authors acknowledge continuous support of their study by Grants-in-Aid (Nos. 20108010 and 23111703 ) from the Ministry of Education, Culture, Sports, Science and Technology, Japan and KOSEF/MEST through WCU project ( R31-2008-000-10010-0 ) in Korea. T.H. appreciates support from the Global COE program “Global Education and Research Center for Bio-Environmental Chemistry” of Osaka University and a JSPS fellowship for young scientists.

Keywords

  • Distortion
  • Photoinduced electron transfer
  • Protonated phthalocyanine
  • Protonated porphyrin
  • Supramolecular complexes

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