Prediction of magnesium tetraethynylporphyrin’s solubility by theoretical calculation

To investigate the solubility of porphyrin derivatives, their intermolecular interaction energies were calculated by the counterpoise method at the B97D3/6-31G(d) level. It was found that the calculated intermolecular interaction energies corresponded to the solubility measured by UV-vis spectroscopy. This correlation was consistent with differences in substituents and in the metals in the porphyrin core.

A DFT study on the interaction of small molecules with alkali metal ion-exchanged ETS-10

In this paper, we present a systematic quantum-mechanical density functional theory (DFT) study of adsorption of small gas molecules in cation-exchanged Engelhard titanosilicate ETS-10 crystalline materials. Adsorbates with a range of polarities were considered, ranging from polar (H2O), quadrupolar (CO2 and N2), to apolar (CH4) atmospheric gases. Starting from the base-case of Na-ETS-10, other extra framework cations such as Li+, K+, Rb+ and Cs+ were considered. The DFT calculations were performed with the M06-L functional and were corrected for basis set superposition error with the counterpoise method in order to provide accurate and robust geometries and adsorption energies. For all adsorbates, the adsorption enthalpies decrease in the order Li+>Na+>K+>Rb+>Cs+, while adsorbate – cation interaction distances increase along the same order. For the two extreme cases, the enthalpies calculated at the M06-L/6-31++G** level of theory for CH4, N2, CO2, and H2O interaction with Li+(Cs+) exchanged materials are −21.8 (−1.7) kJ·mol−1, −19.0 (−10.7) kJ·mol−1, −34.4 (−21.3) kJ·mol−1, and −70.5 (−36.1) kJ·mol−1, respectively. Additionally, the calculated vibrational frequencies are found to be in quite good agreement with the characteristic vibrational modes of alkali metal cation-exchanged ETS-10 and also with the available experimental frequencies for CH4, N2, CO2, and H2O interactions with alkali metal cations in the 12-membered channel of ETS-10.

Intermolecular Interaction in Methylene Halide (CH2F2, CH2Cl2, CH2Br2 and CH2I2) Dimers

The intermolecular interaction in difluoromethane, dichloromethane, dibromomethane, and diiodomethane dimers has been investigated using high level quantum chemical methods. The potential energy curve of intermolecular interaction along the C⋯C bond distance obtained using the coupled-cluster theory with singles, doubles, and perturbative triples excitations CCSD(T) were compared with values given by the same method, but applying the local (LCCSD(T)) and the explicitly correlated (CCSD(T)-F12) approximations. The accuracy of other theoretical methods—Hartree–Fock (HF), second order Møller–Plesset perturbation (MP2), and dispersion corrected DFT theory—were also presented. In the case of MP2 level, the canonical and the local-correlation cases combined with the density-fitting technique (DF-LMP2)theories were considered, while for the dispersion-corrected DFT, the empirically-corrected BLYP-D and the M06-2Xexchange-correlation functionals were applied. In all cases, the aug-cc-pVTZ basis set was used, and the results were corrected for the basis set superposition error (BSSE) using the counterpoise method. For each molecular system, several dimer geometries were found, and their mutual orientations were compared with the nearest neighbor orientations obtained in recent neutron scattering studies. The nature of the intermolecular interaction energy was discussed.

On the effects of the basis set superposition error on the change of QTAIM charges in adduct formation. Application to complexes between morphine and cocaine and their main metabolites

QTAIM atomic properties variation upon interaction is analyzed by: (i) deformation; (ii) BSSE estimated by counterpoise method; and (iii) binding.

Structure determination of three furan-substituted benzimidazoles and calculation of π–π and C—H...π interaction energies

The synthesis and structural characterization of 2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazole [C16H12N2O2, (I)], 2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazol-3-ium chloride monohydrate [C16H13N2O2+·Cl−·H2O, (II)] and the hydrobromide salt 5,6-dimethyl-2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazol-3-ium bromide [C18H17N2O2+·Br−, (III)] are described. Benzimidazole (I) displays two sets of aromatic interactions, each of which involves pairs of molecules in a head-to-tail arrangement. The first, denoted set (Ia), exhibits both intermolecular C—H...π interactions between the 2-(furan-2-yl) (abbreviated as Fn) and 1-(furan-2-ylmethyl) (abbreviated as MeFn) substituents, and π–π interactions involving the Fn substituents between inversion-center-related molecules. The second, denoted set (Ib), involves π–π interactions involving both the benzene ring (Bz) and the imidazole ring (Im) of benzimidazole. Hydrated salt (II) exhibits N—H...OH2...Cl hydrogen bonding that results in chains of molecules parallel to theaaxis. There is also a head-to-head aromatic stacking of the protonated benzimidazole cations in which the Bz and Im rings of one molecule interact with the Im and Fn rings of adjacent molecules in the chain. Salt (III) displays N—H...Br hydrogen bonding and π–π interactions involving inversion-center-related benzimidazole rings in a head-to-tail arrangement. In all of the π–π interactions observed, the interacting moieties are shifted with respect to each other along the major molecular axis. Basis set superposition energy-corrected (counterpoise method) interaction energies were calculated for each interaction [DFT, M06-2X/6-31+G(d)] employing atomic coordinates obtained in the crystallographic analyses for heavy atoms and optimized H-atom coordinates. The calculated interaction energies are −43.0, −39.8, −48.5, and −55.0 kJ mol−1for (Ia), (Ib), (II), and (III), respectively. For (Ia), the analysis was used to partition the interaction energies into the C—H...π and π–π components, which are 9.4 and 24.1 kJ mol−1, respectively. Energy-minimized structures were used to determine the optimal interplanar spacing, the slip distance along the major molecular axis, and the slip distance along the minor molecular axis for 2-(furan-2-yl)-1H-benzimidazole.

DFT STUDY OF HYDROGEN STORAGE ON Li- AND Na-DOPED C59B HETEROFULLERENE

Effect of light alkali metal ( Li and Na ) decorated on the C 59 B heterofullerene for hydrogen storage is considered using DFT-MPW1PW91 method. Results show that Li and Na atoms strongly prefer to adsorb on top of five-member and six-member ring where a carbon atom is replaced by a boron atom. Significant charge transfer from the alkali metal to the C 59 B compensates for the electron deficiency of C 59 B and makes the latter aromatic in nature. Corrected binding energies of hydrogen molecule on the alkali-doped C 59 B using counterpoise method, structural properties and NBO analysis indicate that first hydrogen molecule is adsorbed physically and does not support minimal conditions of DOE requirement. Finally, positive values of binding energies for the adsorption of a second hydrogen molecule show that alkali doped C 59 B are capable of storing a maximum of one hydrogen molecule.

Modeling of the Three-Body Effects in the Neutral Trimers in the Quartet State by ab initio Calculations. H3, Na3, and Na2B

The Na2B, Na3, and H3 trimers in the lowest quartet states were studied by ab initio methods, using both the supermolecular approach and the intermolecular Møller-Plesset perturbation theory. Partitioning of the nonadditive contribution into the orientational two-body part and the genuine three-body part was proposed. The lowest quartet state of the Na3 trimer and all the three lowest quartet states of the Na2B trimer are bound, and the forms of these clusters are essentially determined by two-body forces. In the case of the Na2B trimer the orientational two-body nonadditivity proved to be crucial. In addition, in the title metal trimers, in the region of the van der Waals minima, the genuine nonadditivity is very important, and amounts to 30% in Na2B and up to 70% in Na3. The leading nonadditive term is the triple-exchange Heitler-London exchange term. For triangular arrangements it considerably enhances the total stabilization. The single-exchange term and the SCF deformation play only a secondary role. The dispersion nonadditivity is negligible. The isotropic part of the basis set superposition error (BSSE) is large and must be corrected by the counterpoise method. The anisotropic contribution to BSSE is practically negligible.