Role of electronic polarization on the liquid phase affinity of calixarene–crown-ethers towards alkali cations: a QM/MM molecular dynamics simulation

Quantum mechanical calculations of the interactions between diazacrowns and the sodium cation: an insight into Na+ complexation in diazacrown-based synthetic ion channels

Quantum mechanical calculations were performed to study the conformational behavior and complexation between a sodium cation and a diazacrown (diaza-18-crown-6) using density functional theory (DFT), Møller–Plesset (MP2) and molecular mechanics methods.

Computational study of small molecule binding for both tethered and free conditions

Using a calix[4]arene-benzene complex as a test system, we compare the potential of mean force for when the calix[4]arene is tethered versus free. When the complex is in vacuum, our results show that the difference between tethered and free is primarily due to the entropic contribution to the potential of mean force resulting in a significant binding free energy difference of 6.6 kJ/mol. By contrast, when the complex is in water, our results suggest that there is no appreciable difference between tethered and free. This study elucidates the roles of entropy and enthalpy for this small molecule system and emphasizes the point that tethering the receptor has the potential to dramatically impact the binding properties. These findings should be taken into consideration when using calixarene molecules in nanosensor design.

Rb(+)/Cs(+) selectivity of benzo and tribenzo derivatives of the 21C7 crown ether. A density functional study

A density functional study has been performed on Rb(+) and Cs(+) complexes of mono and tribenzo derivatives of the 21Crown7 crown ether. Calculations have been carried out using the B3LYP functional together with a split valence basis set with additional polarization and diffuse functions. The cations have been described with effective core potentials. Structures of the tribenzo-21Crown7 are compared to X-ray data. The Rb(+)/Cs(+) affinity of the benzo and tribenzo derivatives in gas phase is discussed on the basis of binding energies, strain energies, and electrostatic contributions. For the first time, a detailed description of the effect arising from the presence of benzo groups is described. On one hand, the benzo groups decrease the electronic density on the ether oxygen atoms. On the other hand, they confer a stronger electronic polarizability to the ligand. The energetic analysis shows that the polarization contributions play a crucial role and reach up to 29% of the total electrostatic energy.