Ionic recognition by thiacalixarenes: binding of alkali and heavy metal ions by thiacalix[4]arene-bis-crown[n] ethers

Extraction equilibrium and thermodynamics of cesium with a new derivative of calix[4]biscrown

“…Due to their superior recognition ability toward alkali metal cations and other ions [1][2][3][4][5][6], calix [4]crowns have received increasing attention. Calix [4]crowns have been found to show the potential application in the fields of molecular sensors [7], ion selective electrodes [8], artificial allosteric systems [9], separation and purification [10][11][12]. According to the number of polyether bridging on the lower rim of a calix [4]arene molecule, calix [4]crowns can be divided into two types.…”

Molecular Dynamics Simulation and Density Functional Theory Investigation for Thiacalix[4]biscrown and its Complexes with Alkali-Metal Cations

“…11,14,15 Moreover, this weak metal binding character of 3 was confirmed by the observation of the metal ion shuttling through the thiacalix [4]biscrown tube. 11,12 This intrigued us to perform the detailed DFT calculations on the metal ion complexes of 3 to understand the thermodynamic stability of the complexes of 3 and the driving force for the cation recognition.…”

“…11,14,15 For the 3+K + complex, the distances between crown ether oxygens and K + ion are 2.89, 2.88, 2.87, 2.88, and 2.87 Å (average = 2.88 Å) Also, the distances between two phenolic oxygens in the upward and the downward cavities are 5.08 and 5.03 Å, respectively. The atomic charge distributions for 3 and its metal ion complexes are summarized in Table 2.…”

“…Although Na + is too small for the crown-5 ring to coordinate tightly regarding the key-and-lock rule 32 , Na + is enough to attract the ether oxygens located inside the cavity. 15 Since LANL2DZ basis set is not available for the Na + ion, we couldn't compute the binding energy for 3+Na + complex and compare it with other complexes.…”

“…11,12 It was reported that metal ion extractabilities of several thiacalix [4]biscrown compounds were not as efficient as those of conventional calix [4]biscrowns. [11][12][13][14][15][16][17] Nevertheless, only limited studies have been reported on the metal ion shuttling experimentally and theoretically. 11,12,18 Conformational characteristics and thermodynamics stability order among different conformers of 2 were previously reported by us in comparison with those of 1 by using density functional theory (DFT) calculations.…”