Structures of Three Chalcones Derived from 6-Methoxy-2-naphthaldehyde

In the molecular structures of three new structurally related chalcone derivatives, namely (2E)-1-(2-hydroxyphenyl)-3-(6-methoxy-2-naphthyl)prop-2-en-1-one, C20H16O3, I, (2E)-1-(2-chloropyridin-4-yl)-3-(6-methoxy2-naphthyl) prop-2-en-1-one, C19H14ClNO2, II, and (2E)-3(6-methoxy-2-naphthyl)-1-pyridin-4-ylprop-2-en-1-one, III, C19H15NO2, the configuration of the keto group is syn with respect to the olefinic double bond. In all three structures the molecules pack with weak intermolecular C-H center dot center dot center dot O interactions utilizing both the methoxy and keto oxygen's in I, the methoxy oxygen in II and the keto oxygen in III. These interactions link the molecules into chains diagonally along the (011) plane of the unit cell in I and III and along the (010) plane in II. The dihedral angle between the phenyl and 2-napthyl rings in I is 31.7(3)degrees. In II and III the dihedral angle between the pyridyl and 2-naphthyl rings is 14.4(9)degrees and 1.8(9)degrees, respectively. C-H center dot center dot center dot O hydrogen bonding interactions influence these twist angles of these rings in I-III while weak pi-pi stacking interactions between naphthyl rings in I and III and also between pyridyl and naphthyl rings in II help stabilize crystal packing. [I: P2(1)/c, a = 7.6635(4)angstrom, b = 11.8047(6)angstrom, c = 16.7584(7)angstrom, beta = 99.271(5)degrees, V = 1496.25(13)angstrom(3); II: Pbca, a = 14.1424(4)angstrom, b = 6.0957(2)angstrom, c = 33.1458(11) angstrom, V = 2857.43(16)angstrom(3); III: P2(1)/c, a = 11.5155(4)angstrom, b = 6.0020(2)angstrom, c = 22.4645(8)angstrom, beta = 103.002(4)degrees, V = 1512.85(9)angstrom(3)].