Conformational behaviour and alkali metal cation binding selectivity of 5,11,17,23-tetra- tert-butyl[25,26,27,28-tetrakis(2-pyridylmethyl)oxy]-calix[4]arene: a molecular dynamics study

• Published in: Chemical physics 2000-12, Vol.262 (2), p.359-368
• Main Authors: Fantoni, A.C, Marañón, J
• Format: Article
• Language: English
• ISSN: 0301-0104
• DOI: 10.1016/S0301-0104(00)00333-5

A series of molecular dynamics simulations have been performed on the title ligand (L) and its complex with Na + (LNa +), in the gas phase and in acetonitrile solution. Indirect evidences suggest that the solvent molecule hosted by each monomer in the crystal does not play any role in the complexation of the cation, but is included once the LNa + complex is already formed. The selectivity of the ligand in binding alkali metal cations in acetonitrile solution has been analysed using the concept of thermodynamic cycle to calculate free energy differences for binding of different ions from the free energy changes due to ion mutations. Both, the slow-growth and multi-configurational thermodynamic integration methods were used. Although ligand partial charges determined by different methods were tried, parametrization was necessary to reproduce the right trend in binding selectivity. The best agreement with experiment was obtained with a scaled MKS set of charges.