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Abstract
25,26,27,28-Tetramethoxycalix[4] arene selectively captures cations by changing the conformation. In this study, a hybrid approach of ab initio molecular orbital calculation and statistical mechanics for molecular liquid was utilised to understand the capture mechanism in electrolyte solution phase at molecular level. The association free energy and solvation structure were evaluated on the basis of statistical mechanics for molecular liquids. The selectivity is correctly reproduced by the computation, namely cone conformer captures Na+ while K+ is recognised by the partial-cone conformer.
Acknowledgements
The work is financially supported in part by Grant-in-Aid for Scientific Research on Innovative Areas ‘Molecular Science of Fluctuations’ (2006-21107511) and ‘Dynamical ordering of biomolecular systems for creation of integrated functions’ (2501-25102002) as well as by Grant-in-Aid for Scientific Research (C) (20550013, 25410011). The Strategic Programs for Innovative Research (SPIRE), the Computational Materials Science Initiative (CMSI), and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan are also acknowledged. Theoretical computations were partly performed using Research Center for Computational Science, Okazaki, Japan.
Notes
1. The computations were carried out by using GAUSSIAN03 package. The universal force field (UFF) was employed as the atomic radii and the solvent type was chloroform. The option ‘surface = VDW’ was also used.
2. From Ref. [2], Table 3, corresponding to the measured log K = 4.6 in 9:1 chloroform–acetonitrile.
3. The positions were determined based on the procedure described in [41] so as to minimise the root mean square deviations from the set of RDF peaks on oxygen–cation, terminus carbon–cation and methoxy carbon–cation.