engleski

Cucurbit[8]uril Forms Tight Complexes with Cationic Triamantanes

We report the synthesis of quaternary (di)cationic triamantane derivatives G1 and G3 by the permethylation of the corresponding primary ammonium ions G2 and G4. The complexation behaviors of G1 – G4 toward CB[7] and CB[8] were examined by 1H NMR spectroscopy, which reveals that CB[8] is capable of fully encapsulating G1 – G4 whereas CB[7] forms inclusions complexes with G1, G2, and G4 but cannot fully encapsulate the central hydrophobic core of bis-quaternary ammonium ion G3. The geometry of the CB[n]•guest complexes were determined by analyzing the complexation induced changes in chemical shifts and were further confirmed by molecular modelling using the Conformer-Rotamer Ensemble Sampling Tool (CREST) based on the GFN methods. Finally, the complexation thermodynamics were determined by a combination of 1H NMR competition experiments, direct isothermal titration calorimetry (ITC) measurements, and competitive ITC titrations using a tight binding ternary complex as competitor.

Diamondoids ; Host-guest complexes ; Cucurbit[n]urils ; Triamantane ; Titrations

We thank the National Science Foundation (CHE-1807486 to L.I.) and the Croatian Science Foundation (project UIP-2017-05-9653 to M.Sˇ.) for financial support. S.M. thanks the Department of Education for a GAANN fellowship (P200A150033) and the University of Maryland for summer research and Wylie dissertation fellowships. The computations were performed using the resources of the computer cluster Isabella based in SRCE – the University of Zagreb, University Computing Centre.