Molecular design of a "molecular syringe" mimic for metal cations using a 1,3-alternate calix[4]arene cavity.

The chemically switchable actions well imitate the function of a "molecular syringe," has been studied in theory using the 1,3-alternate calix [4]arene bearing a nitrogen-containing crown cap at one side and a bis(ethoxyethoxy) group at another side by the pi-basic calixtube as a pipette and the crown ring as a rubber cap. The model is characterized by geometry optimization using density functional theory (DFT) at B3LYP/6-31G level. The obtained optimized structures are used to perform natural bond orbital (NBO) and frequency analysis.

Density functional theory study of calix[4]arene-N-azacrown-5, calix[4]arene-N-phenyl-azacrown-5, and their complexes with alkali-metal cations: Na+, K+, and Rb+.

Theoretical studies of 1,3-alternate-25,27-bis(1-methoxyethyl)calix[4]arene-azacrown-5 (L(1)), 1,3-alternate-25,27-bis(1-methoxyethyl)calix[4]arene-N-phenyl-azacrown-5 (L(2)), and the corresponding complexes M(+)/ L of L(1) and L(2) with the alkali-metal cations: Na(+), K(+), and Rb(+) have been performed using density functional theory (DFT) at B3LYP/6-31G* level. The optimized geometric structures obtained from DFT calculations are used to perform natural bond orbital (NBO) analysis. The two main types of driving force metal-ligand and cation-pi interactions are investigated.

Density functional theory study of the free and tetraprotonated spheroidal macrotricyclic ligands and the complexes with halide anions: F(-), Cl(-), Br(-).

Theoretical studies of the macrotricyclic tetramine hexaether (SC), its tetraprotonated form SC-4H(+), and the corresponding complexes X(-) subsetSC-4H(+) (This expression represents the structural properties of the halide inclusion complex formed though the free ligand SC-4H(+) and the halide anion X(-): the spherical halide anion X(-) is held by a tetrahedral array of (+)N--H...

DFT study of the carbon- and nitrogen-pivot lariat crown ethers and their complexes with alkali metal cations: Na(+), K(+).

In this work, a quantum mechanical research of five lariat crown ethers(LCEs), 2-methoxy-15-crown-5(A), N-methoxy-4-aza-15-crown-5(B), N-methoxy-4-aza-18-crown-6(C), N-methoxyethyl-4-aza-18-crown-6(D), N,N'-bis(2-metho xyethyl)-4,13-diaza-18-crown-6(E), which are based on either 15-crown-5 or 18-crown-6 frameworks and contain various pendant arms extending from either carbon or nitrogen atoms on the crown frameworks, had been done using density functional theory with B3LYP/6-31G* method to obtain the electronic and geometrical structures of the LCEs and their complexes with alkali metal ions: Na(+) and K(+). The nucleophilicity of LCEs had been investigated by the Fukui functions. For complexes, the match between the cation and cavity size, the status of interaction between alkali metal ions and donor atoms in the LCEs, and the sidearm effect of the LCEs had been analyzed through the other calculated parameters, such as, highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, and energy gaps.