Structures of three methoxy-substituted benzaldehyde 7-chloro-1-methyl-4H-quinolinyl-4-ylidene-hydrazones: variations in π···π interactions

Abstract

Abstract Three crystal structures are reported here: (E,E)-arenecarbaldehyde 7-chloro-1-methyl-4H-quinolinyl-4-ylidene-hydrazones, 3, [arenecarbaldehyde = 3-MeOC6H4CHO (3a), 3,4-(MeO)2C6H3CHO (3b) and 2,3-(MeO)2C6H3CHO (3c)]. While in each compound π···π stacking and other intermolecular interactions make contributions to the overall supramolecular arrangements, very different arrangements result for the relatively flat molecules of 3a and 3b and the non-planar molecules of 3c. In 3a, all possible π···π interactions [π(quin)···π(quin), π(quin)···π(phen) and π(phen)···π(phen)] are present and together generate a sheet of molecules, one molecule thick) [quin = quinolinyl; phen = methoxyphenyl]. In 3b, π(phen)···π(phen)] interactions are absent: however, π(quin)···π(quin) and π(quin)···π(phen) interactions are both involved in producing a column of molecules, two molecules wide. In 3c, two distinct dimeric π···π stacked structural subsets are formed: (i) one dimer is composed of the two independent molecules, A and B, and generated from π(quin)···π(quin) interactions and (ii) the other AB dimeric unit is formed from π(phen)···π(phen) interactions. The differences in the π···π intermolecular interactions found in 3a, 3b and 3c are consequences of the steric effects presented by the methoxy substituents in the phenyl ring.