Abstract: Six benzylidene derivatives with dialkylaniline substituents as the electron donor and pyridine orpyridinium substituents as the acceptor were synthesized and their intermolecular π-π interactions werestudied.It is found that the derivatives with dialkylaniline substituent as donor and pyfidine group as ac-ceptor tended to form J-aggregates in solution and solid state and their electronic configurations of excitedstates were subjected to great changes, while the derivatives with diakylaniline substituent as donor andpyridinium group as acceptor tended to form H-aggregates and the configurations were subjected to smallchanges.The strength of the π-π interactions can be mediated by the length of the alkyl substituents.

Key words: Donor and acceptor substituted molecule, π-&pi, Interactions, J-Aggregate, H-Aggregate