Experimental and theoretical study on interaction of the silver cation with nonactin

• Published in: Molecular physics Vol. 113; no. 23; pp. 3712 - 3716
• Main Authors: Makrlík, Emanuel, Vanura, Petr
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02.12.2015; Taylor & Francis Ltd
• Subjects: Bonding; Cationic; Cations; complexation; Constants; Extraction; extraction and stability constants; Ligands; Mathematical analysis; Nitrobenzenes; nonactin; quantum mechanical calculations; silver cation; structures
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2015.1054326

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium occurring in the two-phase water-nitrobenzene system (1 = nonactin, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K ex (Ag + , 1 ⋅ Na + ) = 0.6 ± 0.1. Furthermore, the stability constant of the 1 ⋅ Ag + complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β nb (1 ⋅ Ag + ) = 6.6 ± 0.2. Finally, employing quantum mechanical calculations, the most probable structure of the cationic complex species 1 ⋅ Ag + was derived. In the resulting complex, having a tennis-ball-seam conformation with the C 2 symmetry, the 'central' cation Ag + is bound by eight relatively strong bonding interactions to eight oxygen atoms of the parent nonactin ligand. The interaction energy of the considered 1 ⋅ Ag + complex was found to be -468.5 kJ/mol, confirming also the formation of this cationic species.