Photoinduced electron transfer from a tetrathiafulvalene-calix[4]pyrrole to a porphyrin carboxylate within a supramolecular ensemble

Christina M. Davis, Yuki Kawashima, Kei Ohkubo, Jong Min Lim, Dongho Kim, Shunichi Fukuzumi, Jonathan L. Sessler

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

A supramolecular assembly is formed upon mixing millimolar concentrations of a tetrakis-tetrathiafulvalene calix[4]pyrrole (TTF-C4P) and a porphyrin tetraethylammonium carboxylate salt in benzonitrile (PhCN). The TTF-C4P binds to the carboxylate moiety of the porphyrin with a 1:1 stoichiometry and a binding constant of 6.3 × 104 M-1 in this solvent at 298 K. Laser photoexcitation of the supramolecular complex results in formation of the triplet charge-separated (CS) state composed of a radical cation of the TTF-C4P receptor and the radical anion of the porphyrin carboxylate. These processes and the resulting states were characterized by means of transient absorption and electron spin resonance (ESR) spectroscopies. The rate constants corresponding to the forward and backward intramolecular electron-transfer (ET) processes were determined to be 2.1 × 104 and 3.6 × 102 s-1, respectively. The rate constants of intermolecular forward and backward electron transfer were also determined to be 4.4 × 108 and 9.8 × 108 M-1 s-1, respectively. The electronic coupling constant (V), 1.2 × 10-2 cm-1, and the reorganization energy (λ), 0.76 eV, for back electron transfer were evaluated from the temperature dependence of the rate constants of intramolecular electron transfer. The small V value indicates little spinforbidden interaction between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and substantiates the long-lived CS lifetime. These results were corroborated by density function theory (DFT) calculations, which provided support for the conclusion that the HOMO and LUMO, located on a TTF moiety of the TTF-C4P and the porphyrin core, respectively, have little interaction though space.

Original languageEnglish
Pages (from-to)13505-13513
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number25
DOIs
Publication statusPublished - 2014 Jun 26

All Science Journal Classification (ASJC) codes

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

Fingerprint Dive into the research topics of 'Photoinduced electron transfer from a tetrathiafulvalene-calix[4]pyrrole to a porphyrin carboxylate within a supramolecular ensemble'. Together they form a unique fingerprint.

Cite this