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Resorcin[4]arene-based container hosts such as carcerand, hemicarcerand, velcrand, polyvelcraplex, and selfassembled molecular capsule have been characterized with the potential applications as molecular reactors, selective storage, delivery and controlled-releasing systems. Recently, the research fields of supramolecular systems are being expanded from single host-guest systems to high ordered macromolecular systems such as polymeric nanostructure or self-assembly monolayer. Dimeric container system could duplex the function of monomeric container molecule and a well-controlled manipulation of dimeric container system would result in a new highly accumulated information storage system. By Cram group, various heterobridged hemicarcerplexes were synthesized from diol 1, in which the fourth bridging unit differs from the other three bridging units. And a fourth bridging unit has been used to connect with another hemicarcerand to give various dimeric hemicarceplexes. Metal coordination to promote the self-assembly of highordered and well-defined supramolecular architectures has become an important synthetic strategy because it allows well defined geometry, coordination number, and a range of binding strengths. Here we report on the synthesis and binding properties of hemicarcerand 2 which has a metal coordinating cyanophenyl unit and its preliminary characteristics as a dimeric self-assembly by metal coordination. Diol 1 was synthesized in 44% yield from tetrol using Sherman's templating procedure (NMP, Cs2CO3, 3 equiv of TsO(CH2)4OTs, 25 C, 12 h). Under the dilution condition, diol 1 was reacted with 3,5-bis(bromomethyl)-benzonitrile in a mixture of Cs2CO3 and NMP at 60 C to afford hemicarcerand 2@CHCl3 in 38% yield after chromatographic purification (hexane : CHCl3 = 2 : 1) and recrystallization (CH3OH). The initial product 2@NMP seems to be changed to 2@CHCl3 by mass-driven exchange. Heterobridged hemicarcerand 2@CHCl3 was characterized by H NMR, FT-IR and FAB+ Mass spectra. Hemicarceplexes 2a-g were obtained by heating a mixture of 2@CHCl3 and an excess of guests. To a round bottom flask equipped with an argon gas inlet were added hemicarcerand 2@CHCl3 and various guests as solvents (> 1000 fold). The mixture was heated at 130-160 C for 36-64 hours. The cooled reaction mixtures were flooded with CH3OH and the precipitates were filtered and dried in vacuo. Table 1 shows the conditions and results for thermally induced complexation, and chemical shifts of H NMR spectra for complexed guest in CDCl3 at 25 C. The sizes and shapes of guest candidates must be complementary enough to the host's portals and interiors so that constrictive and intrinsic binding taken together allow isolable and manipulable hemicarceplexes. The chemical shift changes of guest protons illustrate the relative orientation of guest in the interior of hemicarcerand. Due to the shielding effect of aromatic units, protons close to aromatic π-cloud shift to upfield. In general the upfield-shift of protons on metaor para-substituent is larger than that of ortho-substituent. Trisubstitued benzenes enter slowly than disubstitued ones do. From the complexation ratio of disubstitued benzenes the complexation efficiency decreases in the order of para> meta>> ortho-disubstituted benzene. Interestingly methoxy group favors complextion than methyl group does. Table 2 shows the half-lives for decomplexation. It is assumed that decomplexation exhibits the first order behavior in large excess of solvent over several half-lives. Decomplexation half-life for hemicarceplex 2a is about 2.5 times longer than that for hemicarceplex 2b whose half-life is about 17 times longer than that of hemicarceplex 2e. Clearly the steric hindrance of guest imposes a large activation energy barrier to escape the portal of host.

Molecular Engineering. Part 12. Hemicarcerand Having a Metal Coordinating Ligand at a Hetero-Bridge