Arrangement of σ-holes at the halogen atom in halonium cations.

Halonium cations are key entities that can stabilize transition states in organocatalysis. The distribution of the electrostatic potential on the crystal structures and theoretical models was investigated in the current study. The Cambridge Structural Database (CSD) survey revealed 478 structures of the [L⋯X⋯L] (X - halogen atom, L - ligands attached to the halogen) structural motif, which were divided by the values of the L⋯X⋯L angles.

Unusually short Au(III)⋯Au(III) aurophilic contacts between anions. Necessity of counterions.

Certain crystals contain unusually short contacts between Au(III) species, sometimes interpreted as unsupported aurophilic interactions. Calculations at various levels of theory, including CCSD(T)/CBS, demonstrate the potentials between anions containing these Au(III) centers are purely repulsive, despite the presence of noncovalent bonding between the Au centers. The occurrence of these anion⋯anion dimers in the crystal structure are dependent on the presence of counterions.

Ability of strained C atoms to act as an electron donor.

There is a great deal of strain within the propellane and pyramidane hydrocarbon molecules. Quantum chemical calculations evaluate how this strain affects the ability of the bridgehead C atom to act as an electron donor in hydrogen, halogen, chalcogen, pnicogen, and tetrel bonds, despite the absence of a formal C lone pair or C[double bond, length as m-dash]C multiple bond. The strain induces the formation of a substantial region of negative electrostatic potential on this C atom which can attract the σ-hole of an electrophile.

Proton Changes the Rules of the Game: Insight into the Nature of "Proton Sponges".

There are cases when a small change, such as capture of a simple particle, has a significant impact on the molecular properties. This indeed happens with the "proton sponges". It is shown how the substituent effect (SE) and the presence of an intramolecular hydrogen bond modulate the properties of 1,8-bis(dimethylamino)naphthalene (DMAN), its protonated form (DMANH) and their 4-X substituted derivatives, based on the geometric, electronic structure and energetic parameters.

Ability of the Spectroscopic Properties of the P═Se Bond of a Base to Assess Noncovalent Bond Strength.

The viability of the P═Se bond to serve as a monitor of the strength of a noncovalent bond was tested in the context of the (CH)PSe molecule. Density functional theory (DFT) computations paired this base with a collection of Lewis acids that spanned hydrogen, halogen, chalcogen, pnicogen, and tetrel bonding interactions and covered a wide range of bond strengths. A very strong linear correlation was observed between the interaction energy and the nuclear magnetic resonance (NMR) J(PSe) coupling constant, which could serve as an accurate indicator of bond strength.

Interactions Between [PdX] (X=Cl, Br) Dianions in Presence of Counterions.

The interaction between two square palladium (II) dianions PdX (X=Cl, Br) is evaluated by crystal study and analyzed by quantum chemical means. The arrangement within the crystal between each pair of PdX neighbors is suggestive of a Pd⋅⋅⋅X noncovalent bond, which is verified by a battery of computational protocols. While the potential between these two bare dianions is computed to be highly repulsive, the introduction of even just two counterions makes this interaction attractive, as does the presence of a constellation of point charges.

Attraction versus Repulsion between Methyl and Related Groups: (CHNHCH) and (CHSeBrCH).

The starting point for this work was a set of crystal structures containing the motif of interaction between methyl groups in homodimers. Two structures were selected for which QTAIM, NCI and NBO analyses suggested an attractive interaction. However, the calculated interaction energy was negative for only one of these systems.

Structural subtleties and catalytic activity of sodium aminophenolate complexes in polylactide degradation: towards sustainable waste management solutions.

This study explores the intricate coordination chemistry of sodium aminophenolate species and their significant role in the depolymerization of polylactide (PLA), offering novel insights into catalytic degradation processes. By examining sodium coordination entities, including dimers and larger aggregates such as tetramers, we reveal how structural modifications, particularly the manipulation of steric hindrances, influence the formation and stability of these complexes. The dimers, characterized by a unique four-center core (Na-O-Na-O), serve as a foundational motif, which is further elaborated to obtain complexes with varied coordination environments through strategic ligand design.

Wolfium bonds in homodimers of MXY (M = Mo, W; X = F, Cl, Br; Y = O, S, Se).

The term "wolfium bond" has been recently introduced to describe the noncovalent attraction between an atom of group 6 and a nucleophile a σ-hole binding site. Crystal structures commonly contain a motif wherein two MXY units are arranged in close proximity, where M represents either Mo or W, and X and Y refer to halogen and chalcogen atoms respectively. DFT calculations were thus applied to a wide range of homodimers of these molecules so as to assess their preferred arrangements, and to characterize the types of bonding that are present in each in a systematic manner.

What do we know about bifunctional cage-like T silsesquioxanes? Theory lab routine.

In this article, we explore theoretical validations of experimental findings pertaining to the classical corner-capping reactions of a commercially available heptaisobutyltrisilanol cage to mono-substituted phenylhepta(isobutyl)-POSS cages. Additionally, the process of opening a fully condensed cage is tracked to assess the possibility of isolating and separating the resulting isomers. The corner-capping reactions of potential silanotriols, both as monomers and dimers, and the impact of these structural motifs on their closing to bifunctional POSS cages are also investigated.

Pd and Pt metal atoms as electron donors in σ-hole bonded complexes.

Quantum calculations provide a systematic assessment of the ability of Group 10 transition metals M = Pd and Pt to act as an electron donor within the context of pnicogen, chalcogen, and halogen bonds. These M atoms are coordinated in a square planar geometry, attached to two N atoms of a modified phenanthrene unit, as well as two ligand atoms Cl, Br, or I. As the Lewis acid, a series of AF molecules were chosen, which could form a pnicogen bond (A = P, As, Sb), chalcogen bond (A = S, Se, Te) or halogen bond (A = Cl, Br, I) with M.

Static and Dynamical Quantum Studies of CX-AlX and CSiX-BX (X = F, Cl, Br) Complexes with Hydrocyanic Acid: Unusual Behavior of Strong π-Hole at Triel Center.

The set of TX-TrX (T = C, Si, Ge; Tr = B, Al, Ga; X = F, Cl, Br) molecules offers a rather unique opportunity to study both σ-hole and π-hole dimerization on the tetrel and triel ends, respectively. According to the molecular electrostatic potential (MEP) distribution, the π-hole extrema (acidic sites) were more intense than their σ-hole counterparts. The molecules owning the most (CX-AlX) and least (SiX-BX) intense π-holes were chosen to evaluate their capacities to attract one and two HCN molecules (Lewis bases).

Unraveling the Nature of Hydrogen Bonds of "Proton Sponges" Based on Car-Parrinello and Metadynamics Approaches.

The nature of intra- and intermolecular non-covalent interactions was studied in four naphthalene derivatives commonly referred to as "proton sponges". Special attention was paid to an intramolecular hydrogen bond present in the protonated form of the compounds. The unsubstituted "proton sponge" served as a reference structure to study the substituent influence on the hydrogen bond (HB) properties.

Factors contributing to halogen bond strength and stretch or contraction of internal covalent bond.

The halogen bond formed by a series of Lewis acids TFX (T = C, Si, Ge, Sn, Pb; X = Cl, Br, I) with NH is studied by quantum chemical calculations. The interaction energy is closely mimicked by the depth of the σ-hole on the X atom as well as the full electrostatic energy. There is a first trend by which the hole is deepened if the T atom to which X is attached becomes more electron-withdrawing: C > Si > Ge > Sn > Pb.

Chalcogen Bond as a Factor Stabilizing Ligand Conformation in the Binding Pocket of Carbonic Anhydrase IX Receptor Mimic.

It is postulated that the overexpression of Carbonic Anhydrase isozyme IX in some cancers contributes to the acidification of the extracellular matrix. It was proved that this promotes the growth and metastasis of the tumor. These observations have made Carbonic Anhydrase IX an attractive drug target.

Involvement of Arsenic Atom of AsF in Five Pnicogen Bonds: Differences between X-ray Structure and Theoretical Models.

Bonding within the AsF crystal is analyzed via quantum chemical methods so as to identify and quantify the pnicogen bonds that are present. The structure of a finite crystal segment containing nine molecules is compared with that of a fully optimized cluster of the same size. The geometries are qualitatively different, with a much larger binding energy within the optimized nonamer.

Experimental and Theoretical Evidence of a Pb⋅⋅⋅Pb Ditetrel Bond Without a σ-Hole.

The crystal structure of a newly synthesized compound, [PbL(Ac)] , (where L=2 (amino(pyrazin-2-yl) methylene) hydrazinecarbothioamide, Ac=acetate anion) exhibits a close contact between pairs of Pb atoms, suggesting a ditetrel bond, in addition to two Pb⋅⋅⋅O tetrel bonds, and two C-H⋅⋅⋅O H-bonds. The presence of this ditetrel bond as an attractive component is confirmed by various quantum chemical methods. This novelty of this particular bond is its existence even in the absence of a σ-hole on the Pb atom, which is typically considered a prerequisite for a bond of this type.

The Role of Hydrogen Bonds in Interactions between [PdCl] Dianions in Crystal.

[PdCl] dianions are oriented within a crystal in such a way that a Cl of one unit approaches the Pd of another from directly above. Quantum calculations find this interaction to be highly repulsive with a large positive interaction energy. The placement of neutral ligands in their vicinity reduces the repulsion, but the interaction remains highly endothermic.

Competition between Intra and Intermolecular Pnicogen Bonds: Complexes between Naphthalene Derivatives and Neutral or Anionic Bases.

The PnF (Pn=P,As,Sb,Bi) on a naphthalene scaffold can engage in an internal pnicogen Pn⋅⋅⋅N bond (PnB) with an NH group placed close to it on the adjoining ring. An approaching neutral NH molecule can engage in a second PnB with the central Pn, which tends to weaken the intramolecular bond. The presence of the latter in turn weakens the intermolecular PnB with respect to that formed in its absence.

Physicochemical Characterization of the Loganic Acid-IR, Raman, UV-Vis and Luminescence Spectra Analyzed in Terms of Quantum Chemical DFT Approach.

The molecular structure and vibrational spectra of loganic acid (LA) were calculated using B3LYP density functional theory, the 6-311G(2d,2p) basis set, and the GAUSSIAN 03W program. The solid-phase FTIR and FT-Raman spectra of LA were recorded in the 100-4000 cm range. The assignment of the observed bands to the respective normal modes was proposed on the basis of the PED approach.