Synthesis, reactions, and electronic properties of 16 π-electron octaisobutyltetraphenylporphyrin

Yohsuke Yamamoto, Yusuke Hirata, Megumi Kodama, Torahiko Yamaguchi, Shiro Matsukawa, Kin Ya Akiba, Daisuke Hashizume, Fujiko Iwasaki, Atsuya Muranaka, Masanobu Uchiyama, Ping Chen, Karl M. Kadish, Nagao Kobayashi

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

The reaction of the doubly oxidized β-octaisobutyl-meso- tetraphenylporphyrin (OiBTPP, 4), which has a 16 π-electronic structure at the porphyrin core, with a variety of metal reagents was investigated. The reaction of 4 with SnCl2 followed by ethanolysis afforded an 18 π-electron tin complex, (OiBTPP)Sn(OEt)2 (5), in a redox manner. No reactions were observed using zerovalent metals (Zn, Cu, and Pd). However, the reaction of 16π [(OiBTPP)Li]+[BF4]- (6), which was easily derived from 4, with Zn, Cu, and Pd2(dba) 3 gave the corresponding 18π metalloporphyrins (OiBTPP)M (7, M = Zn(EtOH); 8, M = Cu; and 9, M = Pd). One-electron oxidation of the copper complex 8 by AgSbF6 afforded a 17 π-electron cation radical complex, [(OiBTPP)Cu]+[SbF6]- (10). The UV-visible and electron spin resonance spectra of 10 were quite similar to those of previously reported β-octaethyl-meso-tetraphenylporphyrin (OETPP) derivatives, [(OETPP)Cu]o+X- (X = ClO4, I). In contrast to the reaction of 6 with Zn to give the 18π complex 7, the reaction of 4 with divalent ZnCl2 enabled us to isolate a new 16π porphyrin-zinc(II) complex, [(OiBTPP)Zn(Cl)]+[ZnCl3] - (11), in 92% yield. The solid-state structures of 5 and 7-11 were unambiguously determined by single-crystal X-ray crystallography. The porphyrin cores of 10 (17π) and 11 (16π) are much more distorted than those of the 18π derivatives 5 and 7-9. Furthermore, the bond distances of 10 and 11 clearly showed the presence of bond alternation in contrast to aromatic 18π species 8 and 7, respectively. Nucleus-independent chemical shift calculations of 4 and some metalated porphyrins indicated that the highly distorted 16π porphyrins are essentially nonaromatic, with only weak antiaromaticity. Magnetic circular dichroism studies in conjunction with ZINDO/S calculations assisted in identifying the electronic transitions of the UV-vis spectra of key porphyrins. Electrochemical and thin-layer UV-vis spectroelectrochemical experiments on 4 (16π) and 11 (16π) indicated that both compounds can be electroreduced to give the 18π species, with the 16π/18π transition being reversible in the case of [(OiBTPP)Zn(Cl)]+[ZnCl3]- (11).

Original languageEnglish
Pages (from-to)12627-12638
Number of pages12
JournalJournal of the American Chemical Society
Volume132
Issue number36
DOIs
Publication statusPublished - 2010 Sep 15

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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