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Magnetic Circular Dichroism Study of Directly Fused Porphyrins
Author(s) -
Muranaka Atsuya,
Yokoyama Masaki,
Matsumoto Yotaro,
Uchiyama Masanobu,
Tsuda Akihiko,
Osuka Atsuhiro,
Kobayashi Nagao
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400378
Subject(s) - magnetic circular dichroism , chemistry , linear dichroism , molecular orbital , circular dichroism , homo/lumo , crystallography , x ray magnetic circular dichroism , atomic orbital , vibrational circular dichroism , monomer , spectral line , molecule , physics , polymer , organic chemistry , quantum mechanics , astronomy , electron
The magnetic circular dichroism (MCD) spectra of doubly and triply linked fused bisporphyrins ( 2MD and 2MT , M=Ni, Zn, Cu, Pd, and H 2 ) and triply linked higher oligomers ( 3ZnT and 4ZnT ) have been measured, and their Q‐bands assigned based on the results of INDO/s calculations. In contrast to the Faraday A term observed for the Q(0,0) band of Ni II tetraphenylporphyrin, a single positive Faraday B term was observed for the lowest energy transition of the fused systems. The calculations indicated that the molecular orbitals (MOs) of the directly fused porphyrins consist of linear combinations of the constituent monomeric MOs, and that the effect of lowering the symmetry is always larger on the lowest unoccupied molecular orbital (LUMO) than on the highest occupied molecular orbital (HOMO). On the basis of Michl's perimeter model, these features can be correlated with the observed positive MCD signs in the near infrared region. A weak absorption band at 600–700 nm for the fused dimers can be assigned to a short‐axis polarized Q transition.