Nano Cavity Induced Isotope Separation of Zinc: Density Functional Theoretical Modeling

Density functional theoretical calculation was performed to understand the isotopic fraction of zinc in the nano cavity of different crown ethers and crown ethers anchored on solid resin matrix. The structure, energetic, thermodynamics, and vibration IR spectra were also evaluated. The gas phase binding energy of Zn2+ with crown ether of varied cavity can be correlated with NPA charge transfer but no such correlation is obtained with the fraction of electron transfer, ΔN. The reduced partition function ratio (RPFR) of complexes of Zn2+ ion with different solvents, crown ethers, and grafted crown ethers was also computed to predict the isotope separation factor of the Zn2+ ion. The present study reveals that with increasing cavity size of the crown ether the RPFR was found to be decreased leading to a high value of isotope separation factor as observed in the experiments. An attempt was made to correlate the calculated RPFR and separation factor with binding energy of different zinc-crown ether systems. Further, it is shown that the smaller the solvation energy of the metal ion the higher will be distribution constant of Zn2+ ion as confirmed by experiments indicating solvents with low dielectric constant should be used for chromatographic separation process. The present study should be useful in screening the nano cavity based grafted resin and for future development of new grafted materials for Zn and other isotope separation.