3-Hy-droxy-2-(4-meth-oxy-phen-yl)-4H-chromen-4-one

3-Hydroxy-2-(4-methylphenyl)-4H-chromen-4-one

Our work in the area of carbon-monoxide-releasing molecules led to the synthesis and crystallization of new flavone derivatives as intermediates. Herein we report the first crystal structure of the title compound, C16H12O3, a hydroxy-substituted flavone where the 2-phenyl group has been replaced by a p-tolyl group. The introduction of the 3-hydroxy group allows the formation of intermolecular O—H...O=C hydrogen bonds, used to build centrosymmetric R 2 2(10) ring motifs in the crystal.

Crystal structure of 2-(4-tert-butyl-phen-yl)-3-hydroxy-4H-chromen-4-one

Yellow-green fluorescent crystals of the title compound, C19H18O3, were obtained by the reaction of hy-droxy-aceto-phenone and 4-tert-butyl-benzaldehyde with hydrogen peroxide as oxidant. The plane of the benzene ring is slightly twisted to the mean plane of the 4H-chromene-4-one moiety (r.m.s. deviation = 0.0191 Å) by 10.53 (8)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(10) ring motif. The dimers are linked via C-H⋯π inter-actions, forming sheets parallel to (10-1).

2-(4-Hy-droxy-phen-yl)-3-meth-oxy-4H-chromen-4-one

In the title compound, C₁₆H₁₂O₄, the substituent benzene ring and meth­oxy group are twisted relative to the 4H-chromene skeleton by 24.1 (1) and 61.3 (1)°, respectively. In the crystal, mol­ecules are connected by classical O—H⋯O and weak C—H⋯O hydrogen bonds, forming chains parallel to [201]. The 4H-chromene ring systems of adjacent mol­ecules are either parallel or inclined at an angle of 28.9 (1)°.

2-(4-Chloro-phen-yl)chromen-4-one

The title compound, C(15)H(9)ClO(2), is a synthetic flavonoid obtained by the cyclization of 3-(4-chloro-phen-yl)-1-(2-hy-droxy-phen-yl)prop-2-en-1-one. The 4-chloro-phenyl ring is twisted at an angle of 11.54° with respect to the chromen-4-one skeleton. In the crystal, pairs of mol-ecules are inter-connected by weak Cl⋯Cl inter-actions [3.3089 (10) Å] forming dimmers which are further peripherally connected through inter-molecular C-H⋯O hydrogen bonds.