Crystal structures and Hirshfeld surface analyses of 6,8-dimeth-oxy-3-methyl-1H-isochromen-1-one and 5-bromo-6,8-dimeth-oxy-3-methyl-1H-isochromen-1-one chloro-form monosolvate.

In the mol-ecule of 6,8-dimeth-oxy-3-methyl-1H-isochromen-1-one, C12H12O4, (I), the two meth-oxy groups are directed anti with respect to each other. In the mol-ecule of the brom-inated derivative, 5-bromo-6,8-dimeth-oxy-3-methyl-1H-isochromen-1-one, that crystallized as a chloro-form monosolvate, C12H11BrO4·CHCl3, (II·CHCl3 ), the meth-oxy groups are directed syn to each other. In the crystal of I, mol-ecules are linked by bifurcated C-H⋯O hydrogen bonds, forming chains along the c-axis direction. The chains are linked by C-H⋯π inter-actions, forming a supra-molecular framework. In the crystal of II·CHCl3 , mol-ecules are linked by C-H⋯O hydrogen bonds forming 21 helices parallel to the b-axis direction. The chloro-form solvate mol-ecules are linked to the helices by C-H⋯O(carbon-yl) hydrogen bonds. The helices stack up the c-axis direction and are linked by offset π-π inter-actions [inter-centroid 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 chloro-form solvate are disordered over two positions and were refined with a fixed occupancy ratio of 0.5:0.5.