Comparative photophysical properties of free-base, bis-Zn(II), bis-Cu(II), and bis-Co(II) doubly N-confused hexaphyrins(1.1.1.1.1.1)

Dongho Kim, Jung Ho Kwon, Tae Kyu Ahn, Min Chul Yoon, Deok Yun Kim, Mi Kyoung Koh, Hiroyuki Furuta, Masaakl Suzuki, Atsuhiro Osuka

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Abstract

We have comparatively investigated the photophysics of a series of bis-metal doubly N-confused hexaphyrins(1.1.1.1.1.1) using time-resolved fluorescence, femtosecond transient absorption, two-photon absorption measurements, and geometry-optimized ab initio calculations. Bis-Zn(II) and free-base doubly N-confused hexaphyrins exhibit well-resolved and red-shifted B- and Q-like absorption bands compared with porphyrins. Their allowed transitions are (π,π*) transitions of the hexaphyrin ring, as confirmed by the HOMO and LUMO frontier orbitals based on ab initio calculations at the B3LYP/6-31G level. On the other hand, the absorption spectra of bis-Cu(II) and bis-Co(II) doubly N-confused hexaphyrins are relatively broad, presumably due to large couplings between the metal d-orbitals and π-electrons of the hexaphyrin ring. Owing to these couplings, bis-Cu(II) and bis-Co(II) doubly N-confused hexaphyrins have much shorter excited-state lifetimes of 9.4 ± 0.3 ps and 670 fs, respectively, than those (267 ± 16 and 62.4 ± 1.2 ps, respectively) of bis-Zn(II) and free-base doubly N-confused hexaphyrins. The two-photon absorption cross section (σ(2)) values, which are believed to depend strongly on the ring planarity (π-conjugation), are in line with the excited-state lifetime trends.

Original languageEnglish
Pages (from-to)11683-11690
Number of pages8
JournalJournal of Physical Chemistry B
Volume110
Issue number24
DOIs
Publication statusPublished - Jun 22 2006

All Science Journal Classification (ASJC) codes

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

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