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

Research output: Contribution to journalArticle

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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

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Porphyrins
Isomerization
Isomers
Proton transfer
Hydrogen bonds
Activation energy
Kinetics
Hot Temperature

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

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Tautomerism-Induced Cis-Trans Isomerization of Pyridylethenyl N-Confused Porphyrin. / Sakashita, Ryuichi; Oka, Yasutaka; Akimaru, Hisanori; Kesavan, Praseetha E.; Ishida, Masatoshi; Toganoh, Motoki; Ishizuka, Tomoya; Mori, Shigeki; Furuta, Hiroyuki.

In: Journal of Organic Chemistry, Vol. 82, No. 16, 18.08.2017, p. 8686-8696.

Research output: Contribution to journalArticle

Sakashita, Ryuichi ; Oka, Yasutaka ; Akimaru, Hisanori ; Kesavan, Praseetha E. ; Ishida, Masatoshi ; Toganoh, Motoki ; Ishizuka, Tomoya ; Mori, Shigeki ; Furuta, Hiroyuki. / Tautomerism-Induced Cis-Trans Isomerization of Pyridylethenyl N-Confused Porphyrin. In: Journal of Organic Chemistry. 2017 ; Vol. 82, No. 16. pp. 8686-8696.
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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 ΔG0‡cis→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.",
author = "Ryuichi Sakashita and Yasutaka Oka and Hisanori Akimaru and Kesavan, {Praseetha E.} and Masatoshi Ishida and Motoki Toganoh and Tomoya Ishizuka and Shigeki Mori and Hiroyuki Furuta",
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AU - Oka, Yasutaka

AU - Akimaru, Hisanori

AU - Kesavan, Praseetha E.

AU - Ishida, Masatoshi

AU - Toganoh, Motoki

AU - Ishizuka, Tomoya

AU - Mori, Shigeki

AU - Furuta, Hiroyuki

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N2 - 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 ΔG0‡cis→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.

AB - 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 ΔG0‡cis→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.

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