In this study, we examined the conformation and intermolecular interactions of benzo-12-crown-4 (B12C4) complexes with NH4 +, CH3NH3 + (MeNH3 +), CH3CH2NH3 + (EtNH3 +), and CH3CH2CH2NH3 + (PrNH3 +) using cold gas-phase spectroscopy. All of the B12C4 complexes showed sharp vibronic features in the UV photodissociation spectra, and the position of the 0-0 band was close to that of the B12C4 complex with an isotropic K+ guest. This result suggests that the conformation of B12C4 is maintained despite oriented interactions with ammonium guests via anisotropic N–H···O interactions. Further, we measured the IR–UV double-resonance spectra of these complexes in the NH stretching region. In the IR–UV spectra of the EtNH3 + and PrNH3 + complexes, two distinct IR fingerprints were observed depending on the UV probe wavelength selected, indicating the existence of another (second) conformer for these complexes. Quantum chemical calculations clarified that the second conformer of the EtNH3 + and PrNH3 + complexes was partially stabilized by the C–H···π hydrogen bond. The conformation of B12C4 complexes with ammonium ions is strongly affected by the interaction between the alkyl chain of the ion guest and the benzene ring of the B12C4 host, although the main intermolecular interaction occurs between the NH3 + group and crown cavity through the N–H···O hydrogen bonds.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.