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In the present paper, we report the quantitative evaluation of the electron density shift (EDS) maps within different complexes. Values associated with the total EDS maps exhibited good correlation with different quantities such as interaction energies, Eint, intermolecular distances, bond critical points, and LMOEDA energy decomposition terms. Besides, EDS maps at different cutoffs were also evaluated and related with the interaction energies values. Finally, EDS maps and their corresponding values are found to correlate with Eint within systems with cooperative effects. To our knowledge, this is the first time that the EDS has been quanitatively evaluated., The research was financially supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades (Projects PGC2018-094644-B-C2), Dirección General de Investigación e Innovación de la Comunidad de Madrid (PS2018/EMT4329 AIRTEC-CM), and Science Foundation of Ireland (SFI), grant number 18/SIRG/5517. The authors thank CTI (CSIC) and the Irish Centre for High-End Computing (ICHEC) for their continued computational support, as well as Dr. Lee O’Riordan for his careful reading and suggestion. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.

A theoretical study of a variety of cyclohexane-based anion transporters interacting with the chloride anion has been conducted using density functional theory. The calculations have been performed in the gas phase but also, in order to describe the solvation effects on the interaction, two different solvents-chloroform and dimethylsulfoxide-have been taken into account. Gas-phase interaction energies within the complexes are found to be up to 400 kJ/mol, while, when solvent effects are considered, the interaction energy values decreased drastically concomitantly with an elongation in the interatomic distances. Atoms in molecules and natural bond analysis corroborate the trends found for the intermolecular energies and Cl···H distances, suggesting strong donations from the Cl- anion into the σ*H-N antibonding orbitals, as well as with noncovalent interaction plots showing large areas of electron density overlap within the chloride anion surroundings.

A theoretical study has been carried out at the M062X/6-311++G(d,p) computational level to search for a rationale on ligands' affinity toward α2-adrenoceptors by estimating the nature and strength of intramolecular hydrogen bonds potentially formed (by means of the QTAIM and NBO approaches) as well as the degree of deviation from planarity that could be observed in some of the compounds. Four different families have been studied: thiophen-2-yl, 3-carboxylatethiophen-2-yl esters, 3-cyanothiophen-2-yl, and 2-thiazolyl guanidinium derivatives. In the case of the thiophen-2-yl guanidines not substituted in the 3 position, nonplanarity was always observed, whereas in the thiazole series, intramolecular hydrogen bonds were identified between the guanidinium and the thiazole ring forcing the systems to planarity. Regarding the carboxylic esters, two different rotamers were found: quasi-planar and quasi-perpendicular systems with very similar energy. Both of these isomers can form different nets of intramolecular hydrogen bonds and other types of noncovalent interactions. Different physicochemical properties such as basicity, solubility, or lipophilicity were calculated for these systems, but no correlation to the degree of planarity was found. However, when comparing the α2-ARs affinity with the planarity of the molecules, a trend appears in the thiophen-2-yl guanidinium series indicating that lack of planarity seems to be optimal for α2-ARs engagement.

The geometry, energy and electron density properties of the 1:1, 1:2 and 1:3 complexes between cyclic (Py-M)3 (M = Au, Ag and Cu) and halide ions (F&minus, Cl&minus, and Br&minus, ) were studied using M&oslash, ller Plesset (MP2) computational methods. Three different configurations were explored. In two of them, the anions interact with the metal atoms in planar and apical dispositions, while in the last configuration, the anions interact with the CH(4) group of the pyrazole. The energetic results for the 1:2 and 1:3 complexes are a combination of the specific strength of the interaction plus a repulsive component due to the charge:charge coulombic term. However, stable minima structures with dissociation barriers for the anions indicate that those complexes are stable and (Py-M)3 can hold up to three anions simultaneously. A search in the CSD confirmed the presence of (Pyrazole-Cu)3 systems with two anions interacting in apical disposition.

A theoretical study of the complexes formed by Ag and Cu with different molecules, XH (FH, ClH, OH, SH, HCN, HNC, HCCH, NH and PH) that can act as hydrogen-bond donors (Lewis acids) or regium-bond acceptors (Lewis bases) was carried out at the CCSD(T)/CBS computational level. The heteronuclear diatomic coinage molecules (AuAg, AuCu, and AgCu) have also been considered. With the exception of some of the hydrogen-bonded complexes with FH, the regium-bonded binary complexes are more stable. The AuAg and AuCu molecules show large dipole moments that weaken the regium bond (RB) with Au and favour those through the Ag and Cu atoms, respectively., The research was financially supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (Projects PGC2018-094644- B-C2) and Dirección General de Investigación e Innovación de la Comunidad de Madrid (PS2018/EMT-4329 AIRTEC-CM). This research was funded by Science Foundation of Ireland (SFI), grant number 18/SIRG/5517. Thanks are also given to the CTI (CSIC) and the Irish Centre for High-End Computing for their continued computational support.

Oxathiirane (XHCSO) homodimers bonded by hydrogen bonds (HB) and chalcogen bonds (YB) were studied at the Moller-Plesset (MP2) computational level. Binding energies obtained at the Coupled-Cluster level up to the Complete Basis Set limit [CCSD(T)/CBS] indicate that HB complexes present stronger binding modes than the YB complexes. In terms of chiral discrimination energy, R , S complexes are favored over R , R complexes with the exceptions of SiCl 3 and SiF 3 derivatives. Natural Bond Orbital (NBO) results are in agreement with the interaction energies in the case of the HB complexes, but could not discriminate between R , R and R , S in the YB complexes. The lack of correlation between molecular electrostatic values on the 0.001 a.u. and binding energies, in addition to the discrepancies between Atoms in Molecules (AIM) and NBO results may suggest that the electrostatics is not the dominant term in the interaction energy. This was corroborated by the Localized Molecular Orbital Energy Decomposition Analysis (LMOEDA) calculations which showed that the exchange and dispersion terms are the most important attractive components for all the complexes studied, contributing up to 50.6% and 42.5% to the total attractive forces respectively.

In this manuscript the different noncovalent interactions established between (HYCN)2 dimers (Y = S, Se and Te) have been studied at the MP2 and CCSD(T) level of theory. Several homodimers have been taken into account, highlighting the capacity of these compounds to act both as electron donor and acceptor. The main properties studied were geometries, binding energy (Eb), and molecular electrostatic potential (MEP). Given the wide application of chalcogen bonds, and more specifically of cyano‐chalcogen moieties in molecular recognition, natural bond orbital (NBO), “atoms‐in‐molecules” (AIM), and electron density shift (EDS) analysis were also used to analyse the different noncovalent interactions upon complexation. The presence of hydrogen, chalcogen and dipole‐dipole interactions was confirmed and their implications on molecular recognition were analysed.

The stationary points for the reaction between the CO and nine different phosphatranes molecules have been characterized by means of MP2 computational methods. Two minima structures have been located: a pnicogen bonded complex where one of the oxygen atoms of CO acts as electron donor and an adduct that presents a covalent P−C linkage. The corresponding transition state structure linking the two minima has also been characterized. In gas phase, the pnicogen bonded complex is more stable than the corresponding adduct except in one case. In contrast, the inclusion of the solvent effect (toluene and THF), reverts the stability, being in all cases the different adducts more stable than the pnicogen bonded complexes. The electronic properties of the systems have been analysed with the Quantum Theory of Atoms in Molecules (QTAIM) and Electron Density Shift (EDS) methods., This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades of Spain (Project No. PGC2018-094644-B-C22) and Comunidad Autónoma de Madrid (P2018/EMT-4329 AIRTEC-CM). Thanks are also given to the Irish Centre for High-End Computing (ICHEC), and CTI (CSIC) for their continued computational support

We analysed the interactions and aromaticity electron-density delocalisation observed in π-π complexes between the phenalenyl radical and acenaphthylene, and the DNA and RNA nucleobases (adenine, guanine, cytosine, thymine and uracil). Interaction energies are obtained at the M06-2X/6-311++G(2df,p) computational level for gas phase and PCM-water conditions. For both the phenalenyl radical and acenaphthylene, the complexes formed with guanine are the most stable ones. Atoms in molecules and natural bond orbital results reveal weak π-π interactions between both interacting moieties, characterized by bond critical points between C⋅⋅⋅C and C⋅⋅⋅N atoms. Nucleus independent chemical shifts (NICS) indicate the retention of the aromatic character of the monomers in the outer region of the complex. The fluctuation indexes reveal a loss of electron delocalisation upon complexation for all cases except guanine complexes. Nevertheless, the interface region shows large negative NICS values, which is not associated with an increase of the aromaticity or electron-density delocalisation, but with magnetic couplings of both molecules, leading to an unrealistic description of the aromatic behaviour in that region.

Cyanophosphine derivative dimers, [HXP(CN)]2 with X=H, F and Cl, have been characterized by means of CCSD(T)/aug'-cc-pVTZ//MP2/aug'-cc-pVTZ computational level calculations. Different interactions have been found upon complexation, such as hydrogen bonds, pnicogen bonds and dipole···dipole interactions. The intermolecular distances range between 2.84 and 3.53Å and the binding energies between -34.7 and -3.6kJmol-1. Compounds with dipole···dipole interactions present shorter contact distances and larger (more negative) binding energies than those with pure P···P pnicogen bonds. Electron density shift maps show larger variations in compounds with dipole···dipole interactions than in those with pure pnicogen ones, in line with the energetic results. However, NBO analysis suggests that the complexes with P···P pnicogen bonds, in special those with XP···PX (X=F, Cl) show E(2) orbital interaction energies much larger than the dipole···dipole ones.

Considering that guanidine-based derivatives are good DNA minor groove binders, we have theoretically studied, using the Polarizable Continuum model mimicking water solvation, the complexes formed by the biologically relevant guanidinium cation and the DNA and RNA nucleobases (adenine, guanine, cytosine, thymine, and uracil). The interactions established within these complexes both by hydrogen bonds and by cation-π interactions have been analyzed by means of the Atoms in Molecules and Natural Bond Orbital approaches. Moreover, maps of electron density difference have been produced to understand the cation-π complexes. Finally, the NICS and three-dimensional NICS maps of the cation-π complexes have been studied to understand the effect of the guanidinium cation on the aromaticity of the nucleobases. © 2013 American Chemical Society.