Self-Assembly of N,N‘-Bis(2-tert-Butylphenyl)pyromellitic Diimide and Phenols or Indoles into a Piled Sandwich Structure. Networks Constructed by Weak Host−Host and Strong Host−Guest Interaction in the Clathrate Compounds

A novel clathrate host, N,N‘-bis(2-tert-butylphenyl)pyromellitic diimide (1), was designed to create a sandwich structure without using cyclophanes nor the acyclic compounds. In the host−guest crystal, the host molecule is sandwiched between two aromatic guest molecules. The inclusion experiment was performed by recrystallization of 1 from chloroform in the presence of the guest at room temperature to give the clathrate compounds. Phenols (phenol, p-cresol, α-naphthol, β-naphthol, catechol) and indoles (indole, 3-methylindole, 4-methylindole, 5-methylindole) were included in the clathrate compounds, and the host/guest ratio 1:2 was observed in all cases. To explain the mechanism of the self-assembly to the piled sandwich structure, X-ray analysis of the single crystals was performed in all cases. Further, charge-transfer complexation, hydrogen bonding and dipole−dipole interaction were investigated using UV, IR, differential scanning calorimertry (DSC), and AM1 calculation. The order of the decomposition temperature related well with the order of the guest insertion. During the crystallization process, the packing of a guest with a small dipole moment smoothly proceeds and forms a stable clathrate compound. However, a guest which has a large dipole moment generates large electrostatic repulsion in the networks and forms an unstable clathrate compound.