Fluorescence from the highly excited states and vibrational energy relaxation in directly linked porphyrin arrays

Nam Woong Song, Hyun Sun Cho, Min Chul Yoon, Sae Chae Jeoung, Naoya Yoshida, Atsuhiro Osuka, Dongho Kim

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15 Citations (Scopus)

Abstract

The fluorescence decay profiles of zinc(II) 5,15-di-(3,5-di-tert-butylphenyl) porphyrin monomer (Z1) and its meso, meso-linked dimer (Z2), trimer (Z3) and tetramer (Z4) were investigated by using the fluorescence upconversion technique. Fluorescence from the S 2 state in Z1 was observed to decay with the time constant of 1.2 ps at 460 nm. Corresponding fluorescence rise due to the internal conversion from S 2 to S 1 states in Z1 was also observed at 635 nm with the time constant of 1.5 ps. The S 2 state lifetime of Z2 was largely reduced (90 fs) due to the participation of exciton-split Soret band as a ladder type deactivation channel. Fluorescence decay profile and time-resolved spectra in 530 - 600 nm region revealed that the intramolecular vibrational relaxation (IVR) rate is retarded as the excess vibrational energy decreases in the porphyrin arrays as well as in Z1. The IVR rate was increased from Z1 to Z2 probably due to the additional normal modes related with the inter-unit bond as an efficient internal bath. Furthermore it was observed that a bottleneck in the bath modes limits the increase of IVR rate with the increased number of internal modes in the arrays over Z2 molecule.

Original languageEnglish
Pages (from-to)1023-1029
Number of pages7
JournalBulletin of the Chemical Society of Japan
Volume75
Issue number5
DOIs
Publication statusPublished - 2002 May

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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