Weak interactions in barbituric acid derivatives. Unusually steady intermolecular organic 'sandwich' complexes. pi-pi stacking versus hydrogen bonding interactions

摘要

The 4-methoxy-6,6-dimethyl-5,6,7,8-tetrahydro[1,3]dioxolo[4,5-g]isoquinolin-6-ium (1) and 2-(1H-indol-3-yl)-1-ethanaminium (tryptaminium) (2) salts of 1,3-dimethyl-2,4,6-trioxoperhyciro-pyrimidine-5-spiro-6'-14'-methoxy-7'-(1,3-dimethyl-2,4,6-trioxoper-hydropyrimidin-5-yl)-5',6',7',8'-tetrahydro[1,3]dioxolo[4,5-g]naphthalene) (3) have been prepared and their structures have been investigated by single-crystal X-ray diffraction analysis. It has been found on the basis of the crystal packing arrangement as well as physical and chemical properties that derivatives I and 2 form unusually steady intermolecular sandwich-like complexes both in the crystal and in solution, which are stabilized by weak C-H center dot center dot center dot n(O=C) hydrogen bonds and pi-pi stacking. The interplay between the intermolecular pi-pi stacking and strong N-H center dot center dot center dot O hydrogen bond interactions and its influence on the "sandwich" structures of I and 2 are discussed. (C) 2007 Elsevier B.V. All rights reserved.