DUGi

All-metal aromatic clusters M4 2- (M = B, Al, and Ga). Are π-electrons distortive or not?

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@11388

The π-electrons in benzene, the quintessential aromatic molecule, were previously shown to be distortive, i.e., they prefer localized double bonds alternating with single bonds. It is the σ-electrons that force the double bonds to delocalize, leading to a regular, D6h geometry. Herein, we computationally investigate the double-bond localizing or delocalizing propensities of σ- and π-electrons in the archetypal all-metal aromatic cluster Al4 2- and its second- and fourth-period analogs B4 2- and Ga4 2-, using Kohn-Sham molecular orbital (MO) theory at BP86/TZ2P in combination with quantitative bond energy decomposition analyses (EDA). We compare the three all-metal aromatic clusters with the structurally related organic species C4H 4 2+, C4H4, and C4H 4 2-. Our analyses reveal that the π-electrons in the group-13 M4 2- molecules have a weak preference for localizing the double bonds. Instead, the σ-electrons enforce the regular D4h equilibrium geometry with delocalized double bonds

We thank the following organizations for financial support: the HPC-Europa2 Transnational Access program of the European Union, the Netherlands Organization for Scientific Research (NWO), the Ministerio de Ciencia e Innovacion (MICINN, project numbers CTQ2008-03077/BQU, CTQ200806532/BQU and CTQ2011-23156/BQU), the Catalan Departament d’Innovacio , Universitats i Empresa (DIUE, project number 2009SGR637) and the National Research School Combination - Catalysis (NRSC-C). J. P. thanks the MICINN for the Ramon y Cajal contract. Support for the research of M. S. was received through the ICREA Academia 2009 prize for excellence in research funded by the DIUE of the Generalitat de Catalunya

Royal Society of Chemistry (RSC)