| Summary: | In the molecule of 6,8-dimethoxy-3-methyl-1H-isochromen-1-one, C12H12O4, (I), the two methoxy groups are directed anti with respect to each other. In the molecule of the brominated derivative, 5-bromo-6,8-dimethoxy-3-methyl-1H-isochromen-1-one, that crystallized as a chloroform monosolvate, C12H11BrO4·CHCl3, (II·CHCl3), the methoxy groups are directed syn to each other. In the crystal of I, molecules are linked by bifurcated C—H...O hydrogen bonds, forming chains along the c-axis direction. The chains are linked by C—H...π interactions, forming a supramolecular framework. In the crystal of II·CHCl3, molecules are linked by C—H...O hydrogen bonds forming 21 helices parallel to the b-axis direction. The chloroform solvate molecules are linked to the helices by C—H...O(carbonyl) hydrogen bonds. The helices stack up the c-axis direction and are linked by offset π–π interactions [intercentroid distance = 3.517 (3) Å], forming layers parallel to the (100) plane. Compound II·CHCl3 was refined as a two-component twin. Two chlorine atoms of the chloroform solvate are disordered over two positions and were refined with a fixed occupancy ratio of 0.5:0.5.
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