Studying the properties of conjugated donor acceptor complexes with naphthaleneimide acceptors and dialkoxybenzene donors linked by a triple bond
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The self-assembly of aromatic electron donor and acceptor units into alternating stacks has been studied extensively by the Iverson research group as well as others. As an extension of previous research in this area, novel conjugated donor/acceptor molecules made from 1,4-naphthalenedicarboxylicimide and 1,3-dialkoxybenzene units linked by a triple bond have been designed. These complexes are similar in structure to the naphthalenediimide acceptors and dialkoxynaphthalene donors that have been extensively studied by the Iverson research group, but these new complexes are designed to have a large molecular dipole. The molecular dipole allows the molecule to switch stacking conformations in the mesophase when in an electric field. Crystal structures of some initial complexes show an unexpected and unusual stacking conformation: only half of the units stack donor to acceptor. These complexes have interesting optical properties, which include fluorescence both in solution and in the solid state as well as solvatochromism. These properties are due to aromatic stacking as well as conjugation. In an attempt to alter the stacking structure in the solid state, a nitro substituted naphthaleneimide acceptor linked to a dialkoxybenzene donor by a triple bond was synthesized. The X-ray crystal structures reveal that this molecule stacks donor over acceptor in a perfectly alternating fashion. The data show that the electronic properties of the molecule play a large role in determining its stacking conformation in the solid state, and even its properties in solution. Future work that needs to be done in the project includes making a liquid crystalline naphthaleneimide / dialkoxynaphthalene donor molecule by derivatizing the donor unit. Attempts at synthesizing a derivatizable donor unit have been unsuccessful so far. The electronic properties of a liquid crystalline naphthaleneimide acceptor / dialkoxynaphthalene donor molecule also need to be studied.