Mesitylene guest molecules

Fig. 4 Neutral mesitylene and cationic l,F-dimethyl-4,4 -bipyridicium [MV] " guest molecules contained within a [Cd3(CN)6Cl2] framework—from the x-ray structure of [MV] [Cd3(CN)6Cl2]. C6H3(CH3)3. Diagram adapted from Ref. [29].

Br)PP -3C,HxN and ZnlT(p-Br)PP -4C,ll,> mesitylene). In (he p-bromo compounds, ligation of two pyridines to the Zn(ll) ion was observed. The remaining uncoordinated guest molecules were ob.served to occupy voids between the [Torphyrin moieties. 

All force-distance experiments were conducted in mesitylene (1,3,5-trimethylbenzene) solution. Mesitylene is a good solvent for calixarenes and has a high boiling point, which is desirable for single-molecule experiments. The dimeric calixarene capsules have a cavity size suitable for the inclusion of solvent molecules such as mesitylene. Because hydrogen bridges inside the capsules can be influenced by the dielectric permittivity of the guest molecules, it is important to test whether impurities of the solvent may affect the experimental result. Toluene is probably the most likely contamination. Control experiments were conducted with 5 vol% toluene as an... 

Trithiocyanuric acid (TCA) and 4,4 -bipyridyl (BP) form hydrogen-bonded co-crystals with aromatic compounds such as benzene, toluene, /7-xylene and anthracene. The TCA-BP co-crystal is composed of cavities formed by the N-H - N hydrogen bonds between the two molecules, and the three-dimensional structure contains channels of approximately 10 A where aromatic molecules are accommodated. The molar ratios of TCA, BP and the aromatic compound in the co-crystals are 2 1 1 or 2 1 0.5. Benzene, toluene and /7-xylene are removed from the channels around 190, 183 and 170 °C respectively, and these aromatic guests can be reintroduced into the empty channels of the apo-hosts. The apo-hosts with empty channels have reasonable thermal stability and exhibit shape selectivity in that the empty channels accommodate /7-xylene but not m- or o-xylene or mesitylene. 

A cap molecule of suitable size and symmetry could effectively close off the interior of trimer 7 to create a very large molecular container. Such a feat has recently been accomplished in our laboratories, where trimer carceplex 9 -3 DMF was synthesized in 37% yield, by reaction of trimer 7 with 2,4,6-tris(bromomethyl)mesitylene under basic conditions (Scheme 4-4) [21]. No empty trimer carcerand has yet been isolated, which implies that a template (or templates) is required for formation. Can a large single template molecule form trimer carceplex 9-guest We are currently investigating this possibility. Such an investigation begs the question when does a template effect become a solvent effect ... 

---