title: Observation of exceptionally low-lying π-π* excited states in oxidized forms of quadruple-decker phthalocyanine complexes.
abstract: Spectroscopic investigations have been performed for the oxidized forms of two quadruple-decker phthalocyanine complexes in order to clarify the electronic structures of multiply stacked π-systems. Up to three-electron-oxidized species were isolated by using phenoxathiin hexachloroantimonate as the oxidant. As the oxidations proceed, the Q-bands in the visible region shift bathochromically along with the clear isosbestic points. The one- and three-electron-oxidized species exhibited typical π-radical signals in the ESR spectra, while the neutral and two-electron oxidized species gave no indication of the presence of π-radicals. The electronic transitions observed for the oxidized species reach even into the so-called fingerprint region in IR spectroscopy (~1000 cm(-1)). With the aid of theoretical calculations, these bands can be assigned to the π-π* transitions. Our results provide new insights into π-electronic systems having exceptionally small MO energy gaps.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. tfukuda@chem.sci.osaka-u.ac.jp
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Fukuda
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hata
authors.forename: Naoto
authors.initials: N
authors.lastname: Ishikawa
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D004583:Electrons; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D011789:Quantum Theory
chemical_list: D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D002104:Cadmium; C013647:phthalocyanine