Al-Kahtani AA, Al-Jallal NA, El-Azhary AA. Conformational and vibrational analysis of 18-crown-6-alkali metal cation complexes.
SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014;
132:70-83. [PMID:
24858348 DOI:
10.1016/j.saa.2014.04.170]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 04/20/2014] [Accepted: 04/23/2014] [Indexed: 05/27/2023]
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.
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