Alkali metal mediated resorcarene capsules: an ESI-FTICRMS study on gas-phase structure and cation binding of tetraethyl resorcarene and its per-methylated derivative.
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) with additional ab initio calculations were used to examine the alkali metal cation binding selectivity (i.e., molecular recognition) and host properties of tetraethyl resorcarene (1) and its per-methylated derivative (2). The significance of intramolecular hydrogen bonding for the crown conformation was demonstrated. The presence of intramolecular flip-flop hydrogen bonding in 1 was confirmed both with calculations and in ND3-exchange experiments. All the alkali metal cations formed host-guest complexes by docking inside the cavity of the host. Complexation with the larger cations, especially Cs+, was favored. All the alkali metal cations also formed dimeric resorcarene capsules with 1. The capsules were directly H-bonded species, with no linking solvent molecules. ND3-exchange experiments and molecular modeling revealed the significance of direct intermolecular H-bonding for the crown conformation of 1 and stability of the capsule structure.
Mäkinen
Marko
M
Department of Chemistry, University of Joensuu, Finland.
Vainiotalo
Pirjo
P
Rissanen
Kari
K
D000468:Alkalies / Q000737:chemistry*; D005583:Fourier Analysis; D006860:Hydrogen Bonding; D008670:Metals / Q000737:chemistry; D008745:Methylation; D008958:Models, Molecular; D008968:Molecular Conformation; D011083:Polycyclic Compounds / Q000138:chemical synthesis*; D021241:Spectrometry, Mass, Electrospray Ionization
D000468:Alkalies; D008670:Metals; D011083:Polycyclic Compounds