Photophysical properties of core-modified expanded porphyrins: Nature of aromaticky and enhancement of ring planarity

Min Chul Yoon, Rajneesh Misra, Zin Seok Yoon, Kil Suk Kim, Jong Min Lim, Tavarekere K. Chandrashekar, Dongho Kim

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We have investigated the excited-state dynamics and nonlinear optical properties of representative coremodified expanded porphyrins, tetrathiarubyrin, tetraselenarubyrin, pentathiaheptaphyrin, tetrathiaoctaphyrin, and tetraselenaoctaphyrin, containing 26, 30, and 34 π electrons using steady-state and time-resolved absorption and fluorescence spectroscopic measurements along with femtosecond Z-scan method, with a particular attention to the photophysical properties related to molecular planarity and aromaticity. Core-modification of macrocycles by sulfur and selenium leads to NIR-extended steady-state absorption and fluorescence spectra and shortlived excited-state due to the heavy-atom effect in time-resolved spectroscopic experiments. Large negative nucleus-independent chemical shift values ranging from -13 to -15 ppm indicate that all molecular systems are highly aromatic. The observed enhancement of two-photon absorption cross-section values over 104 GM for core-modified hepta- and octaphyrins is mainly attributable to their rigid and planar structures as well as their aromaticity. Overall, the observed spectroscopic and theoretical results consistently demonstrate the enhanced molecular planarity of core-modified expanded porphyrins compared with their corresponding allaza expanded porphyrins.

Original languageEnglish
Pages (from-to)6900-6905
Number of pages6
JournalJournal of Physical Chemistry B
Issue number23
StatePublished - 12 Jun 2008


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