Abstract
The specific host-guest interactions in the corresponding complexes of K+ and NH4+ with typical crown ethers were investigated by using FTIR and ultrafast IR spectroscopies. The counteranions, i.e., SCN-, were employed as a local vibrational probe to report the structural dynamics of the complexation. It was found that the vibrational relaxation dynamics of the SCN- was strongly affected by the cations confined in the cavities of the crown ethers. The time constant of the vibrational population decay of SCN- in the complex of NH4+ with the 18-crown-6 was determined to be 6 ± 2 ps, which is ∼30 times faster than that in the complex of K+ with the crown ethers. Control experiments showed that the vibrational population decay of SCN- depended on the size of the cavities of the crown ethers. A theoretical calculation further indicated that the nitrogen atom of SCN- showed preferential coordination to the K+ ions hosted by the crown ethers, while the NH4+ can form hydrogen bonds with the oxygen atoms in the studied crown ethers. The geometric constraints formed in the complex of crown ethers can cause a specific interaction between the NH4+ and SCN-, which can facilitate the intermolecular vibrational energy redistribution of the SCN-.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
