title: Conformational and vibrational analysis of 18-crown-6-alkali metal cation complexes.
abstract: Conformational analysis was performed for the 18-crown-6-alkali metal cation complexes, 18c6-AMCCs, using the CONFLEX method. The number of predicted conformations of the 18c6-Li+, Na+, K+, Rb+ and Cs+ complexes was 10, 24, 15, 9 and 4 conformations, respectively. Electronic and geometrical structures were calculated for the predicted conformations at the HF, B3LYP, CAM-B3LYP, M06 and MP2 levels. Binding energies and enthalpies of the ground state conformations were also calculated. Vibrational, IR and Raman, spectra of free 18c6 and 18c6-AMCCs were measured. Comparison between the calculated vibrational frequencies using multi-scale-factor scaling of the B3LYP force field and the experimental vibrational frequencies predicted that the 18c6-K+, Rb+ and Cs+ complexes exist in the D3d, C3v and C3v conformations, respectively. It was also predicted that the 18c6-Na+ complex exists in a D3d-like conformation. It was not possible to identify in what conformation the 18c6-Li+ complex exists.
authors.affiliation: Chemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: A A
authors.initials: AA
authors.lastname: Al-Kahtani
authors.affiliation: Chemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: N A
authors.initials: NA
authors.lastname: Al-Jallal
authors.affiliation: Chemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia. Electronic address: azhary60@hotmail.com.
authors.forename: A A
authors.initials: AA
authors.lastname: El-Azhary
mesh_terms: D002412:Cations; D056831:Coordination Complexes / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D008672:Metals, Alkali / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014732:Vibration
chemical_list: D002412:Cations; D056831:Coordination Complexes; D043844:Crown Ethers; D008672:Metals, Alkali; C015762:18-crown-6
keywords: 18-Crown-6; 18-Crown-6–alkali metal cation complexes; Conformational analysis; Crown ethers; Vibrational analysis