title: All-Metal Aromaticity: Revisiting the Ring Current Model among Transition Metal Clusters.
abstract: We present new insight into the nature of aromaticity in metal clusters. We give computational arguments in favor of using the ring-current model over local indices, such as nucleus independent chemical shifts, for the determination of the magnetic aromaticity. Two approaches for estimating magnetically induced ring currents are employed for this purpose, one based on the quantum theory of atoms in molecules (QTAIM) and the other where magnetically induced current densities (MICD) are explicitly calculated. We show that the two-zone aromaticity/antiaromaticity of a number of 3d metallic clusters (Sc3(-), Cu3(+), and Cu4(2-)) can be explained using the QTAIM-based magnetizabilities. The reliability of the calculated atomic and bond magnetizabilities of the metallic clusters are verified by comparison with MICD computed at the multiconfiguration self-consistent field (MCSCF) and density functional levels of theory. Integrated MCSCF current strength susceptibilities as well as a visual analysis of the calculated current densities confirm the interpretations based on the QTAIM magnetizabilities. In view of the new findings, we suggest a simple explanation based on classical electromagnetic theory to explain the anomalous magnetic shielding in different transition metal clusters. Our results suggest that the nature of magnetic aromaticity/antiaromaticity in transition-metal clusters should be assessed more carefully based on global indices.
authors.affiliation: CEITEC - Central European Institute of Technology, Masaryk University , Kamenice 5/A4, CZ-62500 Brno, Czech Republic.|School of Chemistry, College of Science, University of Tehran , Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Badri
authors.affiliation: Raman Center for Atomic, Molecular and Optical Sciences, Indian Association for the Cultivation of Science , Kolkata 700 032, India.
authors.forename: Shubhrodeep
authors.initials: S
authors.lastname: Pathak
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo , P.O. Box 1033, Blindern, N-0315 Oslo, Norway.
authors.forename: Heike
authors.initials: H
authors.lastname: Fliegl
authors.affiliation: School of Chemistry, College of Science, University of Tehran , Tehran, Iran.
authors.forename: Parviz
authors.initials: P
authors.lastname: Rashidi-Ranjbar
authors.affiliation: Laboratoire de Chimie et Physique Quantiques (UMR 5626), CNRS/Université de Toulouse 3 (Paul Sabatier) , 118 route de Narbonne, F-31062 Toulouse, France.|Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center , S-10691 Stockholm, Sweden.
authors.forename: Radovan
authors.initials: R
authors.lastname: Bast
authors.affiliation: CEITEC - Central European Institute of Technology, Masaryk University , Kamenice 5/A4, CZ-62500 Brno, Czech Republic.|National Center for Biomolecular Research, Faculty of Science, Masaryk University , Kamenice 5/A4, CZ-62500 Brno, Czech Republic.
authors.forename: Radek
authors.initials: R
authors.lastname: Marek
authors.affiliation: National Center for Biomolecular Research, Faculty of Science, Masaryk University , Kamenice 5/A4, CZ-62500 Brno, Czech Republic.
authors.forename: Cina
authors.initials: C
authors.lastname: Foroutan-Nejad
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø-The Arctic University of Norway , N-9037 Tromsø, Norway.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ruud