A Neutral Donor-Acceptor p-Stack: Solid-State Structures of 1 : 1 Pyromellitic Diimide-Dialkoxynaphthalene Cocrystals

Pyromellitic diimide forms orange-coloured cocrystals of 1 : 1 stoichiometry with dialkoxynaphthalene derivatives. The solid-state structures of two examples are presented. The cocrystal formed with 2,6-dimethoxynaphthalene presents vertical stacks of alternating π-rich and π-deficient subunits with the long axes of the respective components approximately parallel. Investigation of the packing in the cocrystal also reveals a stabilizing array of hydrogen bonds between the components of adjacent stacks. Cocrystallization with 1,5-[2-(2-hydroxyethoxy)ethoxy]naphthalene, a derivative bearing hydroxy terminated ethyleneoxy chains, gives rise to an altered structural arrangement. Alternating donor- acceptor stacks once again dominate the structure but adopt a geometry where the long axes of the constituents are essentially perpendicular. Hydrogen-bonding interactions result in the formation of continuous non-covalently linked columns of donor and acceptor subunits by linking the terminal hydroxy functions of the naphthalene component to the imide protons. The structural preferences revealed by these solid-state analyses indicate that these complexes are useful prototypes of more complex neutral supramolecular assemblies.