Tautomerism-Induced Cis-Trans Isomerization of Pyridylethenyl N-Confused Porphyrin

Ryuichi Sakashita, Yasutaka Oka, Hisanori Akimaru, Praseetha E. Kesavan, Masatoshi Ishida, Motoki Toganoh, Tomoya Ishizuka, Shigeki Mori, Hiroyuki Furuta

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12 Citations (Scopus)

Abstract

Pyridylethenyl-substituted N-confused porphyrins (NCPs) were synthesized, and their cis-trans isomerization was studied. Among four possible isomers, trans-3H and cis-2H types of structures, of which aromaticity and absorption/emission properties differ largely, were isolated. The cis-isomer was largely stabilized by the intramolecular hydrogen bonding between the pyrrolic-NH and the pyridinic-N in the vicinity. The thermal cis-trans isomerization proceeded even at 30 °C, which was significantly accelerated by the pyridine added to the system. The kinetic studies revealed that the isomerization reaction was second-order and the activation energy of the thermal isomerization from cis to trans isomer was ΔG0cis→trans = 35.7 kcal/mol at 298 K, which is significantly smaller than that of Ni complex (42.3 kcal/mol). An intermolecular proton transfer induced cis-trans isomerization mechanism was proposed.

Original languageEnglish
Pages (from-to)8686-8696
Number of pages11
JournalJournal of Organic Chemistry
Volume82
Issue number16
DOIs
Publication statusPublished - Aug 18 2017

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

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