Associated dimeric structures of molecular tweezers bearing naphthalimide and adamantane units in the solid state

Abstract

The crystallization of molecular tweezer (1), which is composed of two 1,8-naphthalimide units and a diphenyladamantane spacer, resulted in the formation of two inclusion crystals (1a, 1b) depending on the crystallization solvent used. X-ray crystallographic analysis of the two crystals revealed that 1 had a U-shaped conformation and its dimerization produced naphthalimide quadruple π stacks in an antiparallel fashion. The overlapping of the four naphthalimide units in the non-covalently associated dimeric structures of crystal 1a was larger than that of crystal 1b. The dimeric structures were assembled into network architectures through intermolecular interactions. In inclusion crystal (2a) of compound 2 containing 2,3-naphthalimide units, 2 adopted a Z-shaped conformation in contrast to 1, indicating that discrete dimeric structures of quadruple π stacks were not generated.