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J. Dybal, E. Makrlík, P. Vanura, J. Lang
A Combined Experimental and Theoretical Study on the Complexation of H3O+ with Hexaethyl Calix[6]arene Hexaacetate
Keywords: hydroxonium cation, calixarene compound, Water–Nitrobenzene System, DFT study, structure of protonated calixarene
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H3O+(aq) + 1•Na + (nb)⇔ 1•H3O + (nb) + Na + (aq) taking place in the two-phase water–nitrobenzene system (1 = hexaethyl calix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(H3O+,1•Na + ) = 0.0± 0.1. Further, the stability constant of the 1•H3O + complex in water saturated nitrobenzene was calculated for a temperature of 25ºC as log β nb(1•H3O + ) = 4.8± 0.1. By using quantum mechanical DFT calculations, the most probable structure of the 1•H3O + complex species was predicted. In this complex, the hydroxonium ion H3O + is bound partly to three carbonyl oxygen atoms by strong hydrogen bonds and partly to three alternate phenoxy oxygens by somewhat weaker hydrogen bonds.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 221, 04/2007
Pages: 519 - 525