Influence of Chlorine and Methyl Substituents and Their Position on the Antimicrobial Activities and Crystal Structures of 4-Methyl-1,6-diphenylpyrimidine-2(1h)-selenone Derivatives.

Derivatives of 4-methyl-1,6-diphenylpyrimidine-2(1H)-selenone show very strong antimicrobial activity. In order to extend the current knowledge about the features responsible for the biological activity, crystal structure analyses are presented for 4-methyl-1-(2-methylphenyl)-6-phenylpyrimidine-2(1H)-selenone (1), 4-methyl-1-(3-methylphenyl)-6-phenylpyrimidine-2(1H)-selenone (2), 4-methyl-1-(4-methylphenyl)-6-phenylpyrimidine-2(1H)-selenone (3) (all C18H16N2Se) and 1-(4-chlorophenyl)-4-methyl-6-phenylpyrimidine-2(1H)-selenone (4) (C17H13ClN2Se). Furthermore, the antibacterial and antifungal activities of these compounds were evaluated. All the presented derivatives crystallize in the space group P21/c with one molecule in the asymmetric unit. The molecular geometries differ slightly in the mutual orientation of the rings. The packing of molecules in the crystals is dominated by C-H...N and C-H...Se intermolecular interactions. Additionally, in the crystal structure of 4, C-H...Cl intermolecular interactions are observed. The introduction of a methyl or chlorine substituent improves the biological activity, while its position significantly affects biological activity only in case of the chlorine substituent.