Crystal structure of 5,7-dihydroxy-3-methylcoumarin.

coumarin derivatives are of great interest in view of their sensitizing abilities in photodynamic effects and their wide occurrence in the plant kingdom. Umbelliferone, 7hydroxycoumarin, which has been known as a strongly fluorescing compound, also exhibits chemiluminescence.1 On the other hand, 7-hydroxy-4-methyl coumarin2 (Fig. 1-(I))has been applied in laser gain studies. The title compound (Fig.1(II)) has an additional hydroxy group at the 5-position of (I). To understand the structure–function relationships of hydroxycoumarins, the X-ray analysis of the title compound has been undertaken. The colorless rod-like crystal with the dimensions of 0.3 × 0.3 × 0.2 mm was obtained from an acetonitrile solution at 293(1)K and was used for the diffraction experiments. The crystal and experimental data are given in Table 1. The structure was solved by direct methods and refined by full-matrix leastsquares methods with anisotropic temperature factors for non-H atoms. All H atoms were found from difference Fourier maps and were refined with isotropic temperature factors. Atomic 803 ANALYTICAL SCIENCES JUNE 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry