Guest-Induced Assembly of Tetracarboxyl-Cavitand and Tetra(3-pyridyl)-Cavitand into a Heterodimeric Capsule via Hydrogen Bonds and CH−Halogen and/or CH−π Interaction: Control of the Orientation of the Encapsulated Guest

The guest- or solvent-induced assembly of a tetracarboxyl-cavitand 1 and a tetra(3-pyridyl)-cavitand 2 into a heterodimeric capsule 1.2 in a rim-to-rim fashion via four intermolecular CO 2 H...N hydrogen bonds has been investigated both in solution and in the solid state. In the 1 H NMR study, a 1:1 mixture of 1a and 2a (R = (CH 2 ) 6 CH 3 ) in CDCl 3 gave a mixture of various complicated aggregates, whereas this mixture in CDCl 2 CDCl 2 or p-xylene-d 10 exclusively produced the heterodimeric capsule 1a.2a. It was found that an appropriate 1,4-disubstituted-benzene is a suitable guest for inducing the exclusive formation of 1a.2a in CDCl 3 . The ability of a guest to induce the formation of guest-encapsulating heterodimeric capsule, guest@(1a.2a), increased in the order p-ethyltoluene < 1-ethyl-4-methoxybenzene s 1-ethyl-4-iodobenzene ≤ 1,4-dibromobenzene < 1-iodo-4-methoxybenzene ≤ 1,4-dimethoxybenzene ≤ 1,4-diiodobenzene. The 1 H NMR study revealed that a CH-halogen interaction between the inner protons of the methylene-bridge rims (-O-H out CH in -O-) of the 1a and 2a units and the halogen atoms of 1,4-dihalobenzenes and a CH-π interaction between the methoxy protons of 1,4-dimethoxybenzene and the aromatic cavities of the 1a and 2a units play important roles in the formation of 1,4-dihalobenzene@(1a.2a) and 1,4-dimethoxybenzene@-(1a.2a), respectively. A preliminary single-crystal X-ray diffraction analysis of guest@(1b.2b) (R = (CH 2 ) 2 -Ph; guest = 1-iodo-4-methoxybenzene or p-xylene) confirmed that the guest encapsulated in 1b.2b is oriented with the long axis of the guest along the long axis of 1b-2b and that the iodo and the methoxy groups of the encapsulated 1-iodo-4-methoxybenzene are specifically oriented with respect to the cavities of the 2b and 1b units, respectively.