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Topology-Driven Physicochemical Properties of π-Εlectron Systems. 1. Does the Clar Rule Work in Cyclic π-Electron Systems with the Intramolecular Hydrogen or Lithium Bond?

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journal contribution
posted on 29.09.2006 by T. M. Krygowski, J. E. Zachara, B. Ośmiałowski, R. Gawinecki
The Clar model predicting stability and electron distribution in benzenoid hydrocarbons seems to be also a good predictor for related properties in lithium o-acylphenolates and to a lesser extent in the phenols themselves. This conclusion is based on analysis of geometry changes in the analogues of naphthalene, phenanthrene, anthracene, and triphenylene, where benzene rings are systematically replaced with a quasi-ring formed as a β-ketoenol or β-ketoenolate complex with a lithium cation, i.e., where CH−CH−CH fragments are replaced with O···Li···O or O···H···O fragments. These systems were optimized at the MP2/6-31G(2d,p) level of theory. The energy of bond separation reactions in line with aromaticity indices HOMA and NICSs supported the above statement.