Inorganic Bergman Cyclization: An Appeal From Theory.

The scope of Bergman cyclization is expanded computationally by exploring the cyclization in inorganic B, N substituted derivative. This substitution has introduced polarity into the transition state, which resulted in dramatic lowering of the activation barrier. Natural charge distribution throughout the reaction profile has ascertained this hypothesis. Single B and N atom substitution at 1 and 6 terminal positions lowers the activation barrier by almost half of the original value which becomes even lower in the complete B, N analogue. The parent Bergman and single B, N substituted products were characterized by significant biradical character while the complete B, N substituted analogue was characterized by significant zwitterionic character. Reduction in electron delocalization is also observed in the complete B, N substituted analogue.

Insights into the Interaction between Polyphenols and ß-Lactoglobulin through Molecular Docking, MD Simulation, and QM/MM Approaches.

In this work, we have explored the interaction of three different polyphenols with the food protein ß-lactoglobulin. Antioxidant activities of polyphenols are influenced by complexation with the protein. However, studies have shown that polyphenols after complexation with the protein can be more beneficial due to enhanced antioxidant activities. We have carried out molecular docking, molecular dynamics (MD) simulation, and quantum mechanics/molecular mechanics (QM/MM) studies on the three different protein-polyphenol complexes. We have found from molecular docking studies that apigenin binds in the internal cavity, luteolin binds at the mouth of the cavity, and eriodictyol binds outside the cavity of the protein. Docking studies have also provided binding free energy and inhibition constant values that showed that eriodictyol and apigenin exhibit better binding interactions with the protein than luteolin. For eriodictyol and luteolin, van der Waals, hydrophobic, and hydrogen bonding interactions are the main interacting forces, whereas for apigenin, hydrophobic and van der Waals interactions play major roles. We have calculated the root mean square deviation (RMSD), root mean square fluctuations (RMSF), solvent-accessible surface area (SASA), interaction energies, and hydrogen bonds of the protein-polyphenol complexes. Results show that the protein-eriodictyol complex is more stable than the other complexes. We have performed ONIOM calculations to study the antioxidant properties of the polyphenols. We have found that apigenin and luteolin act as better antioxidants than eriodictyol does on complexation with the protein, which is consistent with the results obtained from MD simulations.

Boron-boron quadruple bond in Li3B2- and Li4B2 clusters.

Homopolar quadruple bonding in first row p-block elements is expected due to the presence of four valence orbitals accessible for bonding. Although quadruple bonding in C2 has been proposed, no such proposal exists for B2. Here we report the unprecedented B-B quadruple bonding in Li3B2- and Li4B2 clusters based on high level theoretical calculations. The quadruple bonding is omnipresent in the global minimum, its nearest energy isomer and the transition states connecting them. Various bonding analyses reveal the unprecedented nature of the BB quadruple bonding interaction.

Unsupported Donor-Acceptor Complexes of Noble Gases with Group 13 Elements.

Unsupported donor-acceptor complexes of noble gases (Ng) with group 13 elements have been theoretically studied using density functional theory. Calculations reveal that heavier noble gases form thermodynamically stable compounds. The present study reveals that no rigid framework is necessary to stabilize the donor-acceptor complexes. Rather, prepyramidalization at the Lewis acid center may be an interesting alternative to stabilize these complexes. Detailed bonding analyses reveal the formation of two-center-two-electron dative bonding, where Ng atoms act as a donor.

Is a transition metal-silicon quadruple bond viable?

Quadruple bonding in heavier main group elements is not known albeit having four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between a silicon atom and a transition metal fragment in the 1A1 electronic ground state of C3v symmetric SiRu(CO)3 based on high level theoretical calculations. Various bonding analyses reveal the nature of the Si[quadruple bond, length as m-dash]Ru quadruple bonding interaction, which involves one usual Si-Ru σ bond, two usual Si-Ru π bonds and one additional Si → Ru dative σ bond.

Planar Pentacoordinate Nitrogen in a Pseudo-Double-Aromatic NBe5H4+ Cluster.

High-level quantum-chemical calculations have been used to predict a cationic ternary NBe5H4+ cluster containing a planar pentacoordinate nitrogen atom. The proposed cluster has pseudo dual aromaticity and is kinetically and thermodynamically very stable.

Transition metal carbon quadruple bond: viability through single electron transmutation.

Quadruple bonding to main group elements is extremely rare although they have four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between a carbon atom and a transition metal fragment Fe(CO)3 based on high level theoretical calculations. Various bonding analyses reveal the unprecedented nature of the C[quadruple bond, length as m-dash]Fe quadruple bonding interaction. The validity of the single electron transmutation concept has been tested which fruitfully reproduces the structural and bonding similarities between the two neighbours in the periodic table.

Double aromaticity in a BBe6H6+ cluster with a planar hexacoordinate boron structure.

Aromaticity is one of the central concepts in chemistry and stabilizes many clusters that have interesting structural motifs. Herein, a cationic BBe6H6 cluster featuring a planar hexacoordinate boron structure stabilized by 2π/6σ double aromaticity was predicted theoretically. The cluster was predicted to be dynamically stable well above room temperature.

Ultra-Weak Metal-Metal Bonding: Is There a Beryllium-Beryllium Triple Bond?

Metal-metal triple bonds featuring s-block element have not been reported until now. Only Be-Be double bonds between have been predicted theoretically based on the intuitive electron donation from four s1 type electron-donating ligands. Herein, we theoretically predicted a novel species featuring a Be-Be triple bond in the Li6 Be2 molecule. The molecule was found to be thermodynamically stable. The presence of the triple bond was confirmed by adaptive natural density partitioning (AdNDP), electron localization function (ELF), and atoms in molecules (AIM) analyses. Moreover, the mechanical strength of the Be-Be triple bond was analyzed by using compliance matrix, pointing towards its ultra-weak nature.