EFFECT OF CHALCOGEN SUBSTITUENTS (X=Se, S, O) ON MOLECULAR PROPERTIES OF 5-p-CHLOROBENZYLIDENE-3-METHYL-2-X-HYDANTOIN: X-RAY, PM-3 AND DATABASE STUDY

Abstract

The X-ray structure analysis of a single crystal of 5-p-chlorobenzylidene-3-metyl-2-Se-hydantoin was carried out. It revealed that the molecule is a 2 isomer with approximately planar conformation, the angle between the hydantoin and p-chlorophenyl planes being 4.2(1)°. The molecules form dimers linked by weak hydrogen bonds N-H^···, Se and C-H^··· Se about an inversion center. Semiempirical quantum mechanics calculations (PM-3) were performed for the three molecules of 5-p-chlorobenzylidene-3-methyl-2-X-hydantoin, where X=Se, S, O. Their results suggest that the planar conformation of these molecules is less energetically favourable than that with the planar molecular fragments significantly tilted to each other. Thus, the planar conformation which was found for many benzylidene derivatives in the crystalline state using Cambridge Structural Database System may be stabilized by intermolecular interactions. The net atomic charges and the bond lengths in the hydantoin ring are strongly affected by the X substituents. The electronegativity of X and the charge distribution in the hydantoin ring seem to be the most important factors in determining the anticonvulsant activity in the three compounds.

Key Words:

• hydantoin
• crystal structure
• hydrogen bonding
• selenoorganic compounds