Abstract
The alkali cation (Li+, Na+, K+, Rb+, and Cs+) binding properties of cryptands [2.1.1], [2.2.1], and [2.2.2] were investigated under solvent-free, gas-phase conditions using Fourier transform ion cyclotron resonance mass spectrometry. The alkali cations serve as size probes for the cryptand cavities. All three cryptands readily form 1:1 alkali cation complexes. Ligand−metal (2:1) complexes of [2.1.1] with K+, Rb+, and Cs+, and of [2.2.1] with Rb+ and Cs+ were observed, but no 2:1 complexes of [2.2.2] were seen, consistent with formation of “inclusive” rather than “exclusive” complexes when the binding cavity of the ligand is large enough to accommodate the metal cation. Kinetics for 2:1 ligand−metal complexation, as well as molecular mechanics calculations and cation transfer equilibrium constant measurements, lead to estimates of the radii of the cation binding cavities of the cryptands under gas-phase conditions: [2.1.1], 1.25 A; [2.2.1], 1.50 A; [2.2.2], 1.65 A. Cation transfer equilibrium studies com...
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.