Synthesis and Spectroscopic and Electrochemical Studies of Novel Benzo- or 2,3-Naphtho-Fused Tetraazachlorins, Bacteriochlorins, and Isobacteriochlorins

Takamitsu Fukuda, Elena A. Makarova, Evgeny A. Luk'yanets, Nagao Kobayashi

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)

Abstract

Benzene- or 2,3-naphthalenering-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized by using tetramethylsuccinonitrile as a source of hydrogenated sites. The derived compounds were characterized by using NMR spectroscopy, X-ray crystallography, electronic and magnetic circular dichroism (MCD) spectroscopy, and electrochemical and spectroelectrochemical methods. X-ray analysis revealed that the benzene-fused TAiBC deviates slightly from planarity at the hydrogenated sites as a result of the presence of sp3 carbons, which prefer a nonplanar tetrahedral conformation. The spectral data were analyzed by using a band deconvolution technique. In the electronic absorption spectra of TAC and TABC species, the Q band splits into two intense components and smaller splittings were observed for the 2,3-naphthalene-fused derivatives relative to the benzo-fused species. In contrast, in the case of TAiBCs, the Q band splitting was apparently not observed in absorption spectra, as expected from the C2v molecular symmetry. However, MCD signals of the Q band in TAiBCs showed Faraday B terms, implying that the accidental degeneracy of the LUMO and LUMO + 1 was broken even for adjacently ring-fused species. Relative molecular orbital energies were estimated by using cyclic and differential pulse voltammetry. The first reduction potentials were close for TACs and TABCs, although those of TAiBCs shifted to more negative potentials. In contrast, although TABCs and TAiBCs exhibited similar first oxidation potentials, those of TACs appeared at more positive potentials. These properties were reproduced and rationalized by molecular orbital and configuration interaction calculations within the framework of the ZINDO/S Hamiltonian. DFT-level frequency calculations have succeeded in reproducing the IR spectra for low-symmetry tetraazaporphyrin (TAP) derivatives for the first time. The relationship between structures and spectral features is discussed.

Original languageEnglish
Pages (from-to)117-133
Number of pages17
JournalChemistry - A European Journal
Volume10
Issue number1
DOIs
Publication statusPublished - 2004 Jan 5

Keywords

  • IR spectroscopy
  • Phthalocyanines
  • Porphyrinoids
  • UV/Vis spectroscopy

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

Fingerprint Dive into the research topics of 'Synthesis and Spectroscopic and Electrochemical Studies of Novel Benzo- or 2,3-Naphtho-Fused Tetraazachlorins, Bacteriochlorins, and Isobacteriochlorins'. Together they form a unique fingerprint.

Cite this