Structures of a co-crystal of tautomers of (E)-N-7-chloro-4-(2-methoxycinnamolyhydrazinyl)quinoline and a single tautomer of the 4-methoxy analogue

Abstract

Abstract A crystal structure determination confirmed that the product from 7-chloroquinilin-4-ylhydrazine and 4-methoxycinnanamic acid had been isolated from MeOCH2CH2OH solution as [(E)-N′-7-chloro-4-(4-methoxycinnamolyhydrazinyl)quinoline, 1. In contrast, recrystallization of the 2-MeO derivative, 2, from the same solvent, produced a 1 : 1 co-crystalline mixture of two tautomers, namely (E)-N′-7-chloro-4-(2-methoxycinnaämolyhydrazinyl)quinoline and 7-chloro-4(1 H)quinolinone 3-(2-methoxycinnamoyl)hydrazone, molecules A and B, respectively. Molecules 1 and 2A have “L”-shapes and, in general, have very similar conformations, which differ from that of 2B, mainly arising from the rotation about the (O)C—N(N) bond within the linker unit between the quinolone and methoxyphenyl rings. In both 1 and 2, the 3-dimensional supramolecular arrangements involve strong N—H…N, N—H…O, C—H…O and C—H…π hydrogen bonds, while additionally in 2, there are π…π, C—Cl…π and C—H…Cl intermolecular interactions.