Exploring the lower limit in hydrogen bonds: analysis of weak C-H···O and C-H···π interactions in substituted coumarins from charge density analysis

Munshi, Parthapratim ; Guru Row, Tayur N. (2004) Exploring the lower limit in hydrogen bonds: analysis of weak C-H···O and C-H···π interactions in substituted coumarins from charge density analysis Journal of Physical Chemistry A, 109 (4). pp. 659-672. ISSN 1089-5639

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp046388s

Related URL: http://dx.doi.org/10.1021/jp046388s

Abstract

Experimental electron densities in coumarin, 1-thiocoumarin, and 3-acetylcoumarin have been analyzed based on the X-ray diffraction data at 90 K. These compounds pack in the crystal lattice with weak C-H…O and C-H…π interactions, and variations in charge density properties and derived local energy densities have been investigated in the regions of intermolecular interactions. Theoretical charge density calculations on crystals using the B3LYP/6-31G∗∗ method show remarkable agreement with the derived properties and energy densities from the experiment. The intermolecular interactions follow an exponential dependence of electron density and energy densities at the bond critical points. The Laplacian follows a "Morse-like" dependence on the length of the interaction line. Based on the set of criteria defined using the theory of "atoms in molecules", it has become possible to distinguish between a hydrogen bond (C-H…O) and a van der Waals interaction (C-H…π). This has resulted in the identification of a "region of overlap" in terms of electron densities, energy densities, and mutual penetration of the hydrogen and acceptor atoms with respect to the interaction length. This approach suggests a possible tool to distinguish between the two types of interactions.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:12071
Deposited On:10 Nov 2010 04:46
Last Modified:02 Jun 2011 12:02

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