A NEUTRAL DONOR-ACCEPTOR PI-STACK - SOLID-STATE STRUCTURES OF 1 1 PYROMELLITIC DIIMIDE-DIALKOXYNAPHTHALENE COCRYSTALS/

Pyromellitic diimide forms orange-coloured cocrystals of 1:1 stoichiom etry with dialkoxynaphthalene derivatives. The solid-state structures of two examples are presented. The cocrystal formed with 2,6-dimethoxy naphthalene presents vertical stacks of alternating pi-rich and pi-def icient subunits with the long axes of the respective components approx imately parallel. Investigation of the packing in the cocrystal also r eveals a stabilizing array of hydrogen bonds between the components of adjacent stacks. Cocrystallization with 1,5-[2-(2-hydroxyethoxy)ethox y]naphthalene, a derivative bearing hydroxy terminated ethyleneoxy cha ins, gives rise to an altered structural arrangement. Alternating dono r-acceptor stacks once again dominate the structure but adopt a geomet ry where the long axes of the constituents are essentially perpendicul ar. Hydrogen-bonding interactions result in the formation of continuou s non-covalently linked columns of donor and acceptor subunits by link ing the terminal hydroxy functions of the naphthalene component to the imide protons. The structural preferences revealed by these solid-sta te analyses indicate that these complexes are useful prototypes of mor e complex neutral supramolecular assemblies.