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The counterpoise (CP) correction by Boys and Bernardi has been well accepted as a reliable strategy to account for basis set superposition error (BSSE) in intermolecular complexes. The behavior of the CP correction was thoroughly studied in individual molecules of molecular complexes. This work studies the performance of the CP correction in many‐body clusters including three‐body clusters of organic compounds in the 3B‐69 dataset. Additionally, we used crystal structures of polymorphs of benzene, aspirin, and oxalyl dihydrazide (ODH) to construct a many‐body cluster dataset, abbreviated as the MBC‐36 dataset, consisting of two, four and eight molecules, and 16 molecules in the case of benzene. A series of Dunning's basis sets—cc‐pXZ and aug‐cc‐pXZ (X = D and T)—were used to predict CP‐corrected Hartree–Fock (HF) interaction energies of the 3B‐69 and MBC‐36 datasets. The CP‐corrected interaction energies were found to be basis‐set independent, whereas the non‐CP corrected interaction energies were found not to a follow a smooth exponential fitting as previously found for electronic energies of individual molecules. This observation was attributed to the presence of non‐additive induction forces in some clusters. Two 2 × 2 × 2 supercells of benzene polymorphs were constructed to explore the local nature of BSSE effects. A cut‐off radius of 10 Å was demonstrated to be sufficient to fully recover these effects. Although the behavior of CP correction was found to be non‐conventional in many‐body clusters of organic compounds, the use of a small basis set such as cc‐pVDZ showed excellent performance in the prediction of HF interaction energies. [ABSTRACT FROM AUTHOR]

A frustrated Lewis pair of dititanoxycarbene [(Ti(N[tBu]Ar)3)2(μ-CO2)] (Ar = 3,5-Me2C6H3) and B(C6F5)3 cleaved dihydrogen under ambient conditions to give the zwitterionic formate [(Ti(N[tBu]Ar)3)2(μ-OCHO-ηO:ηO′)(B(C6F5)3)] and the hydrido borate [Ti(N[tBu]Ar)3][HB(C6F5)3]. [ABSTRACT FROM AUTHOR]

We present an inexpensive and robust theoretical approach based on the fragment molecular orbital methodology and the spin‐ratio scaled second‐order Møller–Plesset perturbation theory to predict the lattice energy of benzene crystals within 2 kJ⋅mol−1. Inspired by the Harrison method to estimate the Madelung constant, the proposed approach calculates the lattice energy as a sum of two‐ and three‐body interaction energies between a reference molecule and the surrounding molecules arranged in a sphere. The lattice energy converges rapidly at a radius of 13 Å. Adding the corrections to account for a higher correlated level of theory and basis set superposition for the Hartree Fock (HF) level produced a lattice energy of −57.5 kJ⋅mol−1 for the benzene crystal structure at 138 K. This estimate is within 1.6 kJ⋅mol−1 off the best theoretical prediction of −55.9 kJ⋅mol−1. We applied this approach to calculate lattice energies of the crystal structures of phase I and phase II—polymorphs of benzene—observed at a higher temperature of 295 K. The stability of these polymorphs was correctly predicted, with phase II being energetically preferred by 3.7 kJ⋅mol−1 over phase I. The proposed approach gives a tremendous potential to predict stability of other molecular crystal polymorphs. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) such as choline dihydrogen phosphate exhibit an extraordinary solubilizing ability for proteins such as cytochrome C when mixed with 20 wt % water. Most widely used imidazolium-based ionic liquids coupled with dihydrogen phosphate do not exhibit the same solubilizing properties, suggesting that a multifunctional cation such as choline might play a key role in enhancing these properties of ionic liquid mixtures with water. In this theoretical work, we compare intermolecular interactions between the water molecule and ionic liquid ions in two ion-paired clusters of choline- and 1-butyl-3-methyl-imidazolium-based ionic liquids coupled with acetate, dihydrogen phosphate, and mesylate. Gibbs free energy (GFE) of solvation of water in these ionic liquids was calculated. Incorporation of a water molecule into ionic liquid clusters was accompanied by negative GFEs of solvation in both types of cations. These results were in good agreement with previously reported experimental GFEs of solvation of water in ILs. Compared to imidazolium-based clusters, strong interionic interactions of choline ionic liquids resulted in more negative GFEs due to their smaller deformation upon the addition of a water molecule, with dihydrogen phosphate and mesylate predicting the lowest GFEs of -30.1 and -43.5 kJ/mol -1 , respectively. Lower GFEs of solvation of water in choline-based clusters were also accompanied with smaller entropic penalties, suggesting that water easily incorporates itself into the existing ionic network. Analysis of the intramolecular bonds within the water molecule showed that the choline hydroxyl group donates electron density to the neighboring water molecule, leading to additional polarization. The predicted infrared spectra of clusters of ionic liquids with water showed a pronounced red shift due to strongly polarized O-H bonds, in excellent agreement with the experimentally measured infrared spectra of ionic liquid mixtures with water. Increased polarization of water in choline-based ionic liquids undoubtedly creates more effective solvents for stabilizing biological molecules such as proteins.