Theoretical Studies on Selectivity of Dibenzo-18-Crown-6-Ether for Alkaline Earth Divalent Cations

Abstract

Crown ether is one of well-known host molecules and able to selectively sequester metal cation. We employed M06-2X density functional theory with IEFPCM and SMD continuum solvation models to study selectivity of dibenzo-18-crown-6-ether (DB18C6) for alkaline earth dications, Ba, and Mg 2+ in the gas phase and in aqueous solution. Mg 2+ showed predominantly strong binding affinity in the gas phase because of strong polarization of CO bonds by cation. In aqueous solution, binding free energy differences became smaller among these dications. However, Mg 2+ had the best binding, being incompatible with experimental observations in aqueous solution. The enthalpies of the dication exchange reaction between DB18C6 and water cluster molecules were computed as another estimation of selectivity in aqueous solution. These results also demonstrated that Mg 2+ bound to DB18C6 better than Ba 2+. We speculated that the species determining selectivity in water could be 2:1 complexes of two DB18C6s and one dication.

A combined experimental and quantum mechanical investigation on some selected metal complexes of l-serine with first row transition metal cations

“…The MP2 level negative values of interaction enthalpies (À97.27 to À31.01 kcal/mol in gas phase and À85.71 to À23.20 kcal/mol in aqueous phase) and Gibbs energies (À92.32 to À30.18 kcal/mol in gas phase and À70.62 to À23.45 kcal/mol in aqueous phase) for all the three complexes indicate that the interactions of metal ions with L-Ser lowers the total electronic energies of the metal complexes, and that the complexes are thermodynamically stable. On the other hand, L-Ser shows consistently higher values of binding affinity towards the doubly charged metal ions in the isolated gas phase environment than those in the aqueous phase which is also in good agreement with earlier theoretical results where Mg 2+ ion was found to possess noticeably large binding affinity to DB18C6 in gas phase [56]. In view of the MP2 predicted data Table 4 Fluorescence parameters of L-Ser and its complexes in DMSO (intensities are given in parentheses).…”

The low temperature radiolysis of cis-syn-cis- dicyclohexano-18-crown-6 complexes with alkaline earth metal nitrates: An evidence for energy transfer to the macrocyclic ligand

“…However, during reprocessing the nuclear waste, at least, some fraction of the CE is actually present in the form of complex with metal salt (e.g., Me n þ (CE)A n À , wherein Me n þ is a metal cation and A À is a monovalent anion). The incorporation of the metal cation into the cavity of 18-membered crown ethers results in essential conformational rearrangement of the polyether ring (Heo, 2012), which may lead to some peculiarities in the radiolysis mechanism and radiation resistance of the macrocyclic complex. Recently, we have revealed such an effect upon investigation of the low temperature radiolysis of a cis-syn-cis-DCH18C6 Á BaCl 2 complex (Zakurdaeva et al, 2013).…”

Theoretical Study on the Extraction of Alkaline Earth Salts by 18-Crown-6: Roles of Counterions, Solvent Types and Extraction Temperatures

“…However, very few theoretical studies have attempted to study the role of counterion, solvent types and extraction temperatures on the alkaline earth crown ether complexes. Recently, the DFT B3LYP/6-31+G(d) level of theory have also been performed on ion-pair receptor of calixarene derivative and its interactions with the halide anions F within the cavity of dibenzo-18-crown-6 has been reported using B3LYP/LanL2DZ and 6-31+G(d) level of theory in gas and solvent phase [17]. The extraction properties of 12-crown-4 derivates toward Li + with Cl -as counterion in biphasic solvent phase has been studied at B3LYP and MP2/6-311+G(d,p) level of theory [18].…”