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. In addition, the enthalpies of complexation reaction had been studied by the calculated thermodynamic data (298 K). The calculated results are all in a good agreement with the experimental data for the complexes.

β-Cyclodextrin (β-CD) has a hydrophilic exterior and a hydrophobic internal cavity, which allows it to form host-guest complexes with a wide range of guests, such as organics, inorganics, and biomolecules. The aforementioned features lead to an extensive range of applications of β-CD, as the properties of β-CD mean that it is environmentally friendly and can be recovered and reused without mass loss. Here, the β-CD-catalyzed anti-Markovnikov addition of styrene to thiophenol in the presence of aerial oxygen and in aqueous solution to give 1-phenyl-2-(phenylsulfanyl)-1-ethanol was studied using density functional theory (DFT) and the Hartree-Fock (HF) method. The optimal configuration of the inclusion complex of styrene and thiophenol within β-CD was obtained, which indicated that styrene and thiophenol enter from the secondary and primary hydroxyl ends of β-CD, respectively. Moreover, hydrogen bonding of β-CD with styrene and thiophenol contributes to the stability of the inclusion complex. An investigation of the charges from electrostatic potentials using a grid-based method (CHELPG) highlighted the distribution of atomic charges upon complexation. The reaction sites of styrene and thiophenol were determined based on electrostatic potentials (ESPs) and condensed dual descriptors. The calculated H nuclear magnetic resonance (H NMR) spectrum of β-CD implied that the chemical shifts of its protons change and H3 and H5 move to higher fields upon complexation, while the calculated C nuclear magnetic resonance (C NMR) spectrum of styrene suggested that this molecule is electrophilic. Graphical abstract ᅟ.

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...X(-) hydrogen bonds inside the intramolecular cavity of the tetraprotonated form SC-4H(+)) of SC-4H(+) with the halide anions: F(-), Cl(-), and Br(-) have been performed using density functional theory (DFT) with B3LYP/6-31G method implemented in the Gaussian 03 program package. The optimized geometric structures obtained from DFT calculations are used to perform Natural Bond Orbital (NBO) analysis. The three main types of hydrogen bonds (+)N--H...F(-), (+)N--H...Cl(-), and (+)N--H...Br(-) are investigated. The results indicate that hydrogen bonding interactions are dominant and the halide anions: F(-), Cl(-), and Br(-) offer lone pair electrons to the contacting sigma* (N--H) antibond orbital of SC-4H(+). For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the proton-donor molecule. The intermolecular interaction energies are predicted by using B3LYP/6-31G methods with basis set superposition error (BSSE) and zero-point energy (ZPE) correction.

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. The results indicate that intermolecular electrostatic interactions are dominant and the electron-donating oxygen offer lone pair electrons to the contacting RY* (1-center Rydberg) or LP* (1-center valence antibond lone pair) orbitals of M(+) (Na(+), K(+), and Rb(+)). What's more, the cation-pi interactions between the metal ion and pi-orbitals of the two rotated benzene rings play a minor role. For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the calix[4]arene molecule. In addition, an extra pendant phenyl group attached to nitrogen can promote metal complexation by 3D encapsulation greatly. In addition, the enthalpies of complexation reaction and hydrated cation exchange reaction had been studied by the calculated thermodynamic data. The calculated results of hydrated cation exchange reaction are in a good agreement with the experimental data for the complexes.