CRYSTAL AND MOLECULAR STRUCTURES OF SCHIFF BASES AND THEIR DERIVATIVES

Beata Stepien, Romana Anulewicz and Tadeusz Marek Krygowski

Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
E-mail: bestep@chem.uw.edu.pl

Crystal and molecular structures of

1. N-(3,5-dichlorosalicydene)phenylamine-N-oxide,
2. N-(3-methoxysalicydene)phenylamine-N-oxide,
3. N-(4,6-dimethoxysalicydene) aniline,
4. N-(5-methoxysalicydene)benzyloamine were determined by X-ray diffraction technique. Analysis of

H-bonding of the above systems is enriched by the data retrieved from CSD for the related compounds. The main conclusions are as follows: The spacer between the H-donating and H-accepting parts of the H-bond exhibit a quite significant delocalization of p-electrons. It is also observed a great differentiation of the degree of delocalization measured by an application of HOMA index.^1-3 This kind of effects may be related to an old idea of quasiaromaticity. No relation between quasiaromaticity of the spacer and the aromatic character of the ring partly contributing to the spacer was found.

1. J. Kruszewski, T. M. Krygowski, Tetrahedron Lett., (1972) 3839-3842
2. T. M. Krygowski, J. Chem. Inf. Comput. Sci. 33 (1993) 70-78
3. T.M. Krygowski, M. Cyranski, Tetrahedron 52, (1996) 1713-1722