| |
[摘要]：Density functional calculations at the BP86/6-311G(d,p) level of theory were realized to analyze the existence of intramolecular hydrogen bonds in a series of neutral 2-anilinonaphthoquinones. The ortho position of the aniline ring (C-2a) was unsubstituted in two of them, substituted by a fluorine atom in another two compounds, and substituted by a methoxy group in an additional pair of compounds. The characteristic features of hydrogen bond formation (elongation of O=C-1, N-H, F-C-2a and O-C-2a bonds, increase in the out-of-plane N-H bending frequency, decrease in the N-H stretching frequency) suggest the formation of a regular (two-center) intramolecular hydrogen bond in 2-anilinonaphtoquinones, involving nitrogen as donor and an oxygen in the naphtoquinone fragment as acceptor. The geometry and frequency changes also suggest the formation of a second and weaker hydrogen bond, resembling a bifurcated (three-center) intramolecular hydrogen bond, in fluorine- or methoxy-ortho-substituted 2-anilinonaphtoquinones. (c) 2012 Elsevier B.V. All rights reserved. |
|
