closo-Carboranes as dual CH⋯π and BH⋯π donors: theoretical study and biological significance

In this manuscript the ability ofcloso-carboranes to establish CH⋯π and BH⋯π interactions with several aromatic moieties exhibiting different electronic natures has been evaluated at the PBE0-D3/def2-TZVP level of theory.

Solid-state supramolecular architectures of a series of Hg(ii) halide coordination compounds based on hydroxyl-substituted Schiff base ligands

Herein, six Hg(ii) coordination compounds containing Schiff base ligands were synthesized, characterized and studied using geometrical and Hirshfeld analyses as well as theoretical calculations.

H-Bonded anion-anion complexes in fentanyl citrate polymorphs and solvates

Herein we report the experimental observation (X-ray characterization) of two different binding modes in H-bonded anion-anion complexes (anion = citrate) in N-(1-(2-phenylethyl)-4-piperidinylium)-N-phenyl-propanamide-citrate (fentanyl citrate). High level DFT calculations indicate that both types of anion-anion complexes (one with two and the other with four H-bonds) are thermodynamically unstable but kinetically stable with respect to the isolated anions with activation barriers as high as 14 kcal mol^-1.

S⋅⋅⋅Sn Tetrel Bonds in the Activation of Peroxisome Proliferator-Activated Receptors (PPARs) by Organotin Molecules

In this study, a PDB (Protein Data Bank) analysis and theoretical calculations (PBE0-D3/def2-TZVP level of theory) were combined to analyze the impact of S⋅⋅⋅Sn tetrel-bonding interactions in the activation mechanism of peroxisome proliferator-activated receptors (PPARs) by two organotin derivatives, triphenyltin (TPT) and tributyltin (TBT). The presence of a covalently bonded CYS285 to the organotin molecule was found to be key to enhance the σ-hole-donor ability of the tin atom, thus strengthening the tetrel-bonding interaction with a sulfur atom belonging to a vicinal methionine residue (MET364).

Surface-grafted lanthanoid complexes of the tungstosilicate polyanion [SiW12O40]4−: a synthetic, structural and computational investigation

As an extension of our continued interest in the preparation of inorganic–organic hybrids, we report the successful hydrothermal synthesis of sodium tris[triaqua(μ-1,10-phenanthroline-2,9-dicarboxylato)dysprosium(III)] silicododecatungstate dodecahydrate, {[DyNa(C14H6N2O4)3(H2O)9(SiW12O40)]·12H2O}nor Na[Dy(PDA)(H2O)3]3[SiW12O40]·12H2O (1), and sodium aqua tris[tetraaqua(μ-4-hydroxypyridine-2,6-dicarboxylato)praseodymium(III)] silicododecatungstate dodecahydrate, {[NaPr(C7H3NO5)3(H2O)13(SiW12O40)]·12H2O}nor Na(H2O)[Pr(pydc-OH)(H2O)4]3[SiW12O40]·12H2O (2) (in which H2PDA is 1,10-phenanthroline-2,9-dicarboxylic acid and H2pydc-OH is 4-hydroxypyridine-2,6-dicarboxylic acid or chelidamic acid). Both compounds have been characterized using elemental analysis, IR spectroscopy and X-ray diffraction methods. Structural characterization by single-crystal X-ray diffraction reveals that these compounds consist of [SiW12O40]4−Keggin-type polyoxometalates (POMs), where a single {W3O13} triad is decorated with a trinuclear Ln complex. Moreover, the decorated polyanions are involved in a series of intermolecular interactions, such as hydrogen bonds and anion–π interactions, resulting in three-dimensional supramolecular architectures. Density functional theory (DFT) studies were conducted to support these intermolecular interactions in both1and2, and have been rationalized using molecular electrostatic potential (MEP) surface calculations.

Intramolecular Noncovalent Carbon Bonding Interaction Stabilizes the cis Conformation in Acylhydrazones

Noncovalent carbon bonding, a recently explored σ-hole interaction, was hitherto supposed to be a weak and structure-guided interaction. Here, its role in the intramolecular stabilization of the cis conformation of the amide moiety in acylhydrazones is described. The calculations reveal an electron donation from the lone pair of the nitrogen atom to the empty antibonding C-N orbital [LP(N)→BD*(C-N)] with a concomitant stabilization energy of E⁽²⁾ =1.2 kcal mol^-1 .

Boron triel bonding: a weak electrostatic interaction lacking electron-density descriptors

In an effort to describe π-hole interactions, we undertook accurate high-resolution X-ray diffraction analyses of single crystals of 1,4-dinitrobenzene, a co-crystal of cis-tartaric acid and bis-pyridine N-oxide and the hydrochloride of B-4-pyridinylboronic acid. We selected these three compounds owing to the π-hole accessibility features that the sp² hybridized B, C and N atoms provide, thus allowing us to compare the fundamental characteristics of π-hole interactions using Bader's Atom in Molecules (AIM) theory. This particular study required extremely accurate experimental diffraction data, because the interaction of interest is weak. As shown by the experimental charge density maps of the -YO₂ (Y = B, C, N) units, we assign the depletion of electron-density present in the central boron, carbon and nitrogen atoms (electrophilic π-holes) as the main origin for the establishment of intermolecular Lewis acid-Lewis base attractive interaction with complementary electron-rich regions. Unexpectedly, the Bader's analyses of both experimentally and theoretically calculated charge distribution maps for the solid involving the - BO₂H₂ group do not show the presence of bond paths, neither of the bond critical points, between the interacting electron rich sites and the boron or carbon atoms featuring the electron hole. In contrast, these topological descriptors of chemical interactions for the AIM theory were easily located in the solid-state structures of the compounds involving the carboxylic and the nitro groups.

Remote Control of Anion-π Catalysis on Fullerene-Centered Catalytic Triads

The design, synthesis and evaluation of catalytic triads composed of a central C60 fullerene with an amine base on one side and polarizability enhancers on the other side are reported. According to an enolate addition benchmark reaction, fullerene-fullerene-amine triads display the highest selectivity in anion-π catalysis observed so far, whereas NDI-fullerene-amine triads are not much better than fullerene-amine controls (NDI=naphthalenediimide). These large differences in activity are in conflict with the small differences in intrinsic π acidity, that is, LUMO energy levels and π holes on the central fullerene. However, they are in agreement with the high polarizability of fullerene-fullerene-amine triads. Activation and deactivation of the fullerene-centered triads by intercalators and computational data on anion binding further indicate that for functional relevance, intrinsic π acidity is less important than induced π acidity, that is, the size of the oriented macrodipole of polarizable π systems that emerges only in response to the interaction with anions and anionic transition states. The resulting transformation is thus self-induced, the anionic intermediates and transition states create their own anion-π catalyst.

Tetrel Bonding Interactions in Perchlorinated Cyclopenta- and Cyclohexatetrelanes: A Combined DFT and CSD Study

In this manuscript, we combined DFT calculations (PBE0-D3/def2-TZVP level of theory) and a Cambridge Structural Database (CSD) survey to evaluate the ability of perchlorinated cyclopenta- and cyclohexatetrelanes in establishing tetrel bonding interactions. For this purpose, we used Tr₅Cl₁₀ and Tr₆Cl₁₂ (Tr = Si and Ge) and HCN, HF, OH⁻ and Cl⁻ as electron donor entities. Furthermore, we performed an Atoms in Molecules (AIM) analysis to further describe and characterize the interactions studied herein. A survey of crystal structures in the CSD reveals that close contacts between Si and lone-pair-possessing atoms are quite common and oriented along the extension of the covalent bond formed by the silicon with the halogen atom.

A comparative experimental and theoretical investigation of hydrogen-bond, halogen-bond and π–π interactions in the solid-state supramolecular assembly of 2- and 4-formylphenyl arylsulfonates

To explore the operational role of noncovalent interactions in supramolecular architectures with designed topologies, a series of solid-state structures of 2- and 4-formylphenyl 4-substituted benzenesulfonates was investigated. The compounds are 2-formylphenyl 4-methylbenzenesulfonate, C14H12O4S, 3a, 2-formylphenyl 4-chlorobenzenesulfonate, C13H9ClO4S, 3b, 2-formylphenyl 4-bromobenzenesulfonate, C13H9BrO4S, 3c, 4-formylphenyl 4-methylbenzenesulfonate, C14H12O4S, 4a, 4-formylphenyl 4-chlorobenzenesulfonate, 4b, C13H9ClO4S, and 4-formylphenyl 4-bromobenzenesulfonate, C13H9BrO4S, 4c. The title compounds were synthesized under basic conditions from salicylaldehyde/4-hydroxybenzaldehydes and various aryl sulfonyl chlorides. Remarkably, halogen-bonding interactions are found to be important to rationalize the solid-state crystal structures. In particular, the formation of O...X (X = Cl and Br) and type I X...X halogen-bonding interactions have been analyzed by means of density functional theory (DFT) calculations and characterized using Bader's theory of `atoms in molecules' and molecular electrostatic potential (MEP) surfaces, confirming the relevance and stabilizing nature of these interactions. They have been compared to antiparallel π-stacking interactions that are formed between the arylsulfonates.

Regium-π bonds: An Unexplored Link between Noble Metal Nanoparticles and Aromatic Surfaces

The ability of metal clusters involving elements from group 11 (Ag, Cu, Au) to favorably interact with π systems of different size and electronic nature was evaluated at the PBE0-D3/def2-TZVPP//PBE0-D3/def2-TZVP level of theory. The M₉ clusters (M=Cu, Ag, Au) were used as σ-hole and σ-lump donors, and benzene, trifluorobenzene, and hexafluorobenzene as aromatic rings. In addition, the study was expanded to the analysis of extended π systems by using naphthalene and anthracene as well as their corresponding perfluorinated derivatives. Furthermore, Bader's theory of Atoms in Molecules as well as natural bonding orbital and spin-density calculations were used to further investigate and characterize the regium-π and σ-lump complexes described herein. Apparently, regium-π bonds have not previously been described in the literature and may be of great importance in the understanding of organocatalytic processes involving aromatic substrates as well as in the design of new materials based on this novel subclass of σ-hole bonding.

Chalcogen 'like-like' Interactions Involving Trisulphide and Triselenide Compounds: A Combined CSD and Ab Initio Study

In this manuscript, we combined a search in the Cambridge Structural Database (CSD) and ab initio calculations (RI-MP2/def2-TZVPD level of theory) to analyze the ability of trisulphide and triselenide moieties to establish chalcogen ‘like-like’ interactions. A preliminary CSD inspection revealed two predominant structural patterns, depending on the anti or syn conformation adopted by the substituents of the S₃/Se₃ bridge, leading to bifurcated or double chalcogen bonding interactions, respectively. In order to analyze these two relevant structural motifs we have used a series of S and Se derivatives Ch₃X₂ (Ch = S and Se and X = H, F, CN, and CF₃) which act as both electron donor (using the lone pairs) and acceptor (using the σ-holes) entities. Besides, we have carried out “atoms in molecules” (AIM) and natural bonding orbital (NBO) analyses to further describe and characterize the chalcogen bonding interactions described herein. As far as we know, chalcogen···chalcogen interactions involving trichalconides (S₃/Se₃) have not been previously described in literature a may be of great importance in the preparation and characterization of new solids based on this subclass of σ-hole bonding.