Synthesis and an Evaluation of Molecular Conformation and Crystal Packing in Two Substituted 4-Phenylquinolines

Abstract

The title compounds, namely Methyl 2-methyl-4 -phenylquinoline-3-carboxylate (I), C18H15NO2, and (2E)-3-(3,4-dimethoxyphenyl)-1-(2-methyl-4 -phenylquinolin-3-yl)prop-2-en-1-one (II), C27H23NO3, comprising of the phenyl ring, exhibit differences in conformational behaviour with respect to the plane of the quinoline fragment. (I) contains the methyl ester moiety whereas (II) contains the chalcone fragment, consisting of a double bond and phenyl group containing dimethoxy groups as substituents. The dihedral angles between the phenyl group and the quinoline ring is 82.77 (7)° in (I), and 79.02 (8)° in (II) respectively. It is the weak C–H···O=C H-bond and C–H···π interactions which dictate packing of molecules in (I). In (II), it is C–H···N and C–H···π, involving the dimethoxy ring, which controls packing of molecules in the crystal lattice. In addition, π···π aromatic stacking interactions involving the quinoline fragment is present in all the molecules. The title compounds, namely methyl-2-methyl-4 -phenylquinoline-3-carboxylate (I), C18H15NO2, and (2E)-3-(3,4-dimethoxyphenyl)-1-(2-methyl-4 -phenylquinolin-3-yl)prop-2-en-1-one (II), C27H23NO3, comprising of the phenyl ring, exhibit differences in conformational behaviour with respect to the plane of the quinoline fragment. (I) contains the methyl ester moiety whereas (III) contains the chalcone fragment, consisting of a double bond and phenyl group containing dimethoxy groups as substituents. The dihedral angles between the phenyl group and the quinoline ring is 82.77 (7)° in (I), and 79.02 (8)° in (II) respectively. It is the weak C–H···O=C H-bond and C–H···π interactions which dictate packing of molecules in (I). In (II), it is C–H···N and C–H···π, involving the dimethoxy ring, which controls packing of molecules in the crystal lattice. In addition, π···π aromatic stacking interactions involving the quinoline fragment is present in all the molecules.