Novel octanuclear NHC complexes of gold(I) and silver(I) form metallocavitand structures with very defined tubular cavities and are able to selectively host linear molecules. These pillarplexes exhibit numerous advantages compared to current organic benchmark systems. The solubility of the host-complexes can easily be adjusted by simple anion exchange reactions so that the compounds can be made soluble in water wherein they show a high longtime stability. The complexes furthermore are highly shape selective, that is, linear molecules can access the cavity, whereas six-membered aromatic moieties, such as phenyl or pyridyl, are size-excluded.<br/>The pillarplexes’ host-guest behavior was studied in depth with 1,8-diaminooctane as model guest substrate by means of NMR and emission spectroscopy, isothermal titration calorimetry and X-ray crystallography. From the molecular structure of the supramolecular assembly, the dimensions of the pillar-shaped host were determined. The height of the metallocavitand amounts to approximately 11.7 Å, its inner diameter to 4.3 Å. Thus, the penetrable cavity is significantly longer, but narrower than that of pillar[5]arene (height 7.8 Å, inner diameter 4.7 Å) suggesting a higher selectivity and affinity toward linear molecules. The geometrical prerequisite of the cavity forces the guest into an unfavorable all-anti conformation. As the gold(I) complex is intrinsically emissive in aqueous solutions, a determination of the binding constant to the diamine via luminescence quenching was enabled. The results obtained by this technique were confirmed by ITC measurements revealing a K<sub>d</sub> of 8 μM suggesting a stronger binding to the guest molecule than that of the structurally comparable pillararene family.

Pillarplexes: A metal-organic class of supramolecular hosts

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.