title: New insights into aromatic pathways of carbachlorins and carbaporphyrins based on calculations of magnetically induced current densities.
abstract: Magnetically induced current densities have been calculated and analyzed for a number of synthesized carbachlorins and carbaporphyrins using density functional theory and the gauge including magnetically induced current (GIMIC) method. Aromatic properties have been determined by using accurate numerical integration of the current flow yielding reliable current strengths and pathways that are related to the degree of aromaticity and the aromatic character of the studied molecules. All investigated compounds are found to be aromatic. However, the obtained aromatic pathways differ from those previously deduced from spectroscopic data and magnetic shielding calculations. For all studied compounds, the ring current divides into an outer and an inner branch at each pyrrolic subring, showing that all π-electrons of the pyrrolic rings take part in the delocalization pathway. The calculations do not support the common notion that the main share of the current takes the inner route at the pyrrolic rings without an inner hydrogen and follows an 18π aromatic pathway. The aromatic pathways of the investigated carbaporphyrins and carbachlorins are very similar, since the current strength via the Cβ[double bond, length as m-dash]Cβ' bond of the cyclopentadienyl ring of the carbaporphyrins is almost as weak as the current density passing the corresponding saturated Cβ-Cβ' bond of the carbachlorins.
authors.affiliation: University of Helsinki, Department of Chemistry, P. O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland. Dage.Sundholm@helsinki.fi.
authors.forename: Isaac
authors.initials: I
authors.lastname: Benkyi
authors.affiliation: Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P. O. Box 1033 Blindern, 0315 Oslo, Norway. Heike.Fliegl@kjemi.uio.no.
authors.forename: Heike
authors.initials: H
authors.lastname: Fliegl
authors.affiliation: Tomsk Polytechnic University, 43a Lenin Avenue, Building 2, Tomsk 634050, Russian Federation and Tomsk State University, Lenina Avenue 36, Tomsk, Russian Federation. valievrashid@mail.ru.
authors.forename: Rashid R
authors.initials: RR
authors.lastname: Valiev
authors.affiliation: University of Helsinki, Department of Chemistry, P. O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland. Dage.Sundholm@helsinki.fi.
authors.forename: Dage
authors.initials: D
authors.lastname: Sundholm