Crystal Structure of 3-Bromo-7-(dimethylamino)-4-methylcoumarin

Abstract

Coumarin derivatives are a useful component for developing new materials, such as fluorescence materials and laser dyes; non-linear optical materials and reagents; photorefractive materials; photoresistors; intermediates for drug synthesis; luminescence materials; analytical reagents, etc.1,2 Coumarin 311, 7-(dimethylamino)-4-methylcoumarin, is also used as laser dyes. It gives laser emission at around 453 nm in ethanol. The crystal structure of coumarin 311 has already been reported.3 However the fluorence property and crystal structure of 3-bromo-7-(dimethylamino)-4-methylcoumarin (1) has not yet been reported. We now report on the crystal structure of 1 with the aim of the contributing to a deeper understanding of the substituent effect at the 3-position of coumarin 311 on the structure and crystal packing. Compound (1), shown in Fig. 1, was synthesized by the reaction of 7-(dimethylamino)-4-methylcoumarin with bromine in glacial acetic acid, as reported in a previous paper.4 The spectral data of 1 are as follows: mp 168 – 169 C, 1H NMR (CDCl3) d 2.53 (3H, s), 3.06 (6H, s), 6.48 (1H, d, J = 2.6 Hz), 6.62 (1H, dd, J = 9.0 Hz, 2.6 Hz), and 7.43 (1H, d, J = 9.0 Hz). 13C NMR (CDCl3) d 19.15, 40.1(2C), 97.7, 106.2, 109.3, 109.4, 125.8, 151.5, 152.8, 154.1, and 158.0. Compound (1) gave a strong emission band at 442 nm in chloroform solution (1.0 ¥ 10–5 M) when excited at 380 nm. Single crystals of 1 were grown in chloroform at room temperature. Data collection and refinement parameters are listed in Table 1. The H atoms were positioned with the idealized geometry, and were refined to be isotropic (Uiso(H) = 1.2Ueq(C)) using a riding model with C–H = 0.95 A for aromatic H atoms and C–H = 0.98 A for methyl H atoms. The selected bond distances and angles are collected in Table 2. An ORTEP drawing of the molecule of 1 is shown in Fig. 2. The molecule is almost planar with a maximum deviation of –0.154(2)A for N1. The dihedral angle between the pyrone ring Crystal Structure of 3-Bromo-7-(dimethylamino)-4-methylcoumarin