Correction to “Chemical Bonding and Aromaticity in Furan, Pyrrole, and Thiophene: A Magnetic Shielding Study”

Abstract

The NICS(0), NICS(0.5), and NICS(1) values in our paper were taken from the data used to construct the isotropic shielding contour plots for furan, pyrrole, and thiophene shown in Figures 1–6, at the points with coordinates (0.0, 0.0, 0.0), (0.0, 0.0, 0.5), and (0.0, 0.0, 1.0) (in angstroms; the x and y coordinates are along the horizontal and vertical axes, respectively, in Figures 1a–3a). These points are shifted from the geometric ring centers along the respective y axes; to follow the convention for calculating NICS, separate NICS(0), NICS(0.5), and NICS(1) calculations should have been performed at the points with coordinates corresponding to the exact geometric ring centers, (0.0, −0.01277, 0.0), (0.0, −0.01277, 0.5), and (0.0, −0.01277, 1.0) for furan, (0.0, −0.03584, 0.0), (0.0, −0.03584, 0.5), and (0.0, −0.03584, 1.0) for pyrrole, and (0.0, −0.27121, 0.0), (0.0, −0.27121, 0.5), and (0.0, −0.27121, 1.0) for thiophene. The correct NICS(0), NICS(0.5), and NICS(1) values for the three molecules are shown in the corrected Table 1 (all nuclear shieldings remain unchanged). The changes to the NICS values for furan and pyrrole are relatively minor, but the changes to the NICS values for thiophene are more substantial. The correct HF-GIAO NICS(1), MP2-GIAO NICS(0.5), and MP2-GIAO NICS(1) values still indicate that thiophene is more aromatic than pyrrole, but the correct HF-GIAO NICS(0), HF-GIAO NICS(0.5), and MP2-GIAO NICS(0) values make the opposite suggestion. It is important to emphasize that the analysis of the behavior of the isotropic shielding in molecular space illustrated by the contour plots in Figures 1–6 that employs considerably more data than single-point NICS calculations strongly favors the aromaticity order thiophene > pyrrole > furan supported by experimental evidence. The authors thank Emiel Vanden Berghe (Ph.D. researcher in the group of Patrick Bultinck, University of Ghent, Ghent, Belgium) who carried out HF-GIAO NICS(0) and NICS(1) calculations at the geometries of furan, pyrrole, and thiophene used in the paper and informed us of discrepancies with the published results. C₁ is the carbon adjacent to heteroatom Z. This article has not yet been cited by other publications.