Crystal structure of three solvated Alpinumisoflavones

Single crystals of alpinumisoflavone, C₂₀H₁₆O₅, {systematic name: 5-hydroxy-7-(4 hydroxyphenyl)-2, 2-dimethyl-2H, 6H-benzo 1, 2-b: 5, 4-b′]-dipyran-6-one}, solvated with water, methanol, and ethanol, have been obtained. The incorporation of the solvent molecules into the crystal structure creates a new short inter-molecular O–H···O and C–H···O contacts between the alpinumisoflavone moiety and its solvate molecule. The temperatures at which the solvated molecules lose their solvent molecules are 53, 54, and 65 °C for water, methanol, and ethanol, respectively. The observed temperatures at which the solvates efflorescence are reflective of the progressive increase in mass of the solvates from water to ethanol in the series. The benzopyrone moiety shows the usual planar conformation with the pyran ring deformed into a half-chair conformer as seen previously in the other analogous compounds with puckering parameters Å], 0.2656(8), 0.3703(8), and 0.3957(9), respectively, for the water, ethanol, and methanol solvates. These are higher than the non-solvated alpinumisoflavone compound previously studied. The size of a substituent group proximal to the keto group has a more pronounced effect on the degree of puckering than substitution on the terminal phenyl ring. The attached phenyl ring shows consistent out-of-plane twist from the mean plane of the benzopyrone system as observed previously for this class of compounds. The observed dihedral angles are 30.26(3), 37.75(3), and 34.00(3)°, respectively, for the water, methanol, and ethanol solvates.