Structural insights into methyl- or methoxy-substituted 1-(a-aminobenzyl)-2-naphthol structures: the role of C--H p interactions

Aminobenzylnaphthols are a class of compounds containing a large aromatic molecular surface which makes them suitable candidates to study the role of C--H···pi interactions. We have investigated the effect of methyl or methoxy substituents on the assembling of aromatic units by preparing and determining the crystal structures of (S,S)-1-{(4-methylphenyl)[(1-phenylethyl)amino]methyl}-naphthalen-2-ol, C26H25NO, and (S,S)-1-{(4-methoxyphenyl)[(1-phenylethyl)-amino]methyl}naphthalen-2-ol, C26H25NO2. The methyl group influenced the overall crystal packing even if the H atoms of the methyl group did not participate directly either in hydrogen bonding or C--H ···pi interactions. The introduction of the methoxy moiety caused the formation of new hydrogen bonds, in which the O atom of the methoxy group was directly involved. Moreover, the methoxy group promoted the formation of an interesting C--H ···pi interaction which altered the orientation of an aromatic unit.