An ab initio study on the magnetic susceptibility and magnetically induced current density distribution of the bicyclo[3.2.1]octa-3,6-dien-2-yl anion

Abstract

The molecular susceptibility and the atomic contributions including the basin and surface components calculated at the RHF/6-31+G(d)//6-31+G(d) level of theory along with vector current densities obtained at the 6-31++G(d,p)//6-31+G(d) and 6-31+G(d)//6-31+G(d) levels are reported for benzene (1) and correlated - the agreement is excellent - with the results obtained by Keith and Bader with the 6-311++G(2d,2p) basis. This validates our similar studies on the bicyclo[3.2.1]octa-3,6-dien-2-yl anion (2) - initially considered to be a bishomoaromatic species - its parent hydrocarbon bicyclo[3.2.1]octa-2,5-diene (3), the bicyclo[3.2.1]oct-3-ene-2-yl anion (4), and 5, the lithium complex of 2. While a magnetic susceptibility exhalation is found in going from 4 to 2, the increase in atomic surface contribution to Δχ arises predominately (42.6%) from the ethenyl bridge carbons C6 and C7, with C2 + C4 and C3 exhibiting substantially smaller increases (27.4 and 8.3%, respectively). This result, in conjunction with the nature of the vector current density maps of 2 and 4, provides further evidence that 2 does not possess a ring current as depicted in 2-bh, the usual representation of "bishomoaromatic" 2.Key words: ab initio calculations, IGAIM, CSGT, magnetic susceptibility, induced current density distributions, bicyclo[3.2.1]octa-3,6-dien-2-yl anion.