title: Electronic structure, spectra, and magnetic circular dichroism of cyclohexa-, cyclohepta-, and cyclooctapyrrole.
abstract: Three recently obtained expanded porphyrins represent nice examples of compounds for which the electronic and spectral properties can be predicted from symmetry considerations alone. Perimeter-model-based theoretical analysis of the electronic structure of doubly protonated cyclo[6], cyclo[7], and cyclo[8]pyrrole leads to the anticipation of qualitatively the same electronic absorption and magnetic circular dichroism patterns for all three compounds. These predictions are fully confirmed by experiments, as well as DFT and INDO/S calculations. Due to a characteristic pattern of frontier molecular orbitals, a degenerate HOMO and a strongly split LUMO pair, the three cyclopyrroles show comparable absorption intensity in the Q and Soret regions. Magnetic circular dichroism spectra reveal both A and B Faraday terms, of which the signs and magnitudes are in remarkably good agreement with theoretical expectations. The values of the magnetic moments of the two lowest degenerate excited states have also been obtained.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gorski
authors.forename: Thomas
authors.initials: T
authors.lastname: Köhler
authors.forename: Daniel
authors.initials: D
authors.lastname: Seidel
authors.forename: Jeong Tae
authors.initials: JT
authors.lastname: Lee
authors.forename: Grazyna
authors.initials: G
authors.lastname: Orzanowska
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
authors.forename: Jacek
authors.initials: J
authors.lastname: Waluk
mesh_terms: D002942:Circular Dichroism; D011758:Pyrroles / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D011758:Pyrroles