Charge Density Studies of Weak Interactions in Organic Solids

Krzysztof Woźniak, Paul Mallinson, Paulina M. Dominiak

Department of Chemistry, The University of Warsaw, Pasteura 1, 02 093 Warszawa, Poland.

E-mail: kwozniak@chem.uw.edu.pl

Experimental charge density distributions in a series of ionic complexes of 1,8-bis(dimethylamino)naphthalene (DMAN) with four different acids: 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), 4,5-dichlorophthalic acid, dicyanoimidazole, and o-benzoic sulfimide dihydrate (saccharin) proved that all the interactions studied {[O…H…O]^-, C-H…O, [N-H…N]⁺, O-H…O, C-H…N, Cp…Np, Cp…Cp, C-H…Cl, N-H⁺} follow exponential dependences of the electron density, local kinetic and potential energies at the bond critical points on the length of the interaction line^1,2. The local potential energy density at the bond critical points has a near-linear relationship to the electron density. There is also a Morse-like dependence of the laplacian of rho on the length of interaction line, which allows a differentiation of ionic and covalent bond characters. The strength of the interactions studied varies systematically with the relative penetration of the critical points into the van der Waals spheres of the donor and acceptor atoms, as well as on the interpenetration of the van der Waals spheres themselves. We hope to extend the results using some more data regarding a series of Schiff bases.

(1) Mallinson, P. R.; Smith, G. T.; Wilson, C. C.; Grech, E.; Wozniak, K. J. Am. Chem. Soc., 2003, 125, pp. 4259-4270.

(2) Wozniak, K.; Mallinson, P. R.; Smith, G. T.; Wilson, C. C.; Grech, E. J. Phys. Org. Chem. Chem., 2003, 16(10), pp. 764-771.