An additional methylene group driving the conformation and assembly of two arylsulfonamide para-alkoxychalcone hybrids

The structures of two arylsulfonamide para-alkoxychalcones, namely, N-{4-[(E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}benzenesulfonamide, C22H19NO4S, (I), and N-{4-[(E)-3-(4-ethoxyphenyl)prop-2-enoyl]phenyl}benzenesulfonamide, C23H21NO4S, (II), reveal the effect of the inclusion of one -CH2- group between the CH3 branch and the alkoxy O atom on the conformation and crystal structure. Although the molecular conformations and one-dimensional chain motifs are the same in both structures, their crystallographic symmetry, number of independent molecules and crystal packing are different. The crystal packing of (I) is stabilized by weak C-H center dot center dot center dot pi and pi-pi interactions, while only C-H center dot center dot center dot pi contacts occur in the structure of (II). The role of the additional methylene group in the crystal packing can also be seen in the fact that the alkoxy O atom is an acceptor in nonclassical hydrogen bonds only in the para-ethoxy analogue, (II). The remarkable similarity between the crystal packing features of (I) and (II) lies in the formation of N-H center dot center dot center dot O hydrogen-bonded ribbons, a synthon commonly found in related compounds.