Upgrade of Weak σ-hole Bond Donors via Cr(CO)3 Complexation.

Molecular recognition mediated by s-hole interactions is enhanced as the electrostatic potential at the σ-hole becomes increasingly positive. Traditional methods to strengthen σ-hole donor ability of atoms such as halogens often involve covalent modifications, such as, introducing electron-withdrawing substituents (neutral or positively charged) or electrochemical oxidation. Metal coordination, a relatively underexplored approach, offers a promising alternative.

Tetrel Bond Affects the Self-Assembly of Acetylcholine and its Analogues and is an Ancillary Interaction in Protein Binding.

The -N(CH) residue is present in acetylcholine (ACh) and in many of its analogues which are used as selective ACh agonist or antagonists for human therapy. The X-ray structures of four ACh derivatives show the presence of short and linear contacts between the C atoms of -N(CH) groups and lone pair possessing atoms. These contacts can be rationalized as tetrel bonds (TtBs) thanks to their geometric features.

Anion⋯anion self-assembly under the control of σ- and π-hole bonds.

The electrostatic attraction between charges of opposite signs and the repulsion between charges of the same sign are ubiquitous and influential phenomena in recognition and self-assembly processes. However, it has been recently revealed that specific attractive forces between ions with the same sign are relatively common. These forces can be strong enough to overcome the Coulomb repulsion between ions with the same sign, leading to the formation of stable anion⋯anion and cation⋯cation adducts.

Osme Bond: Geometric and Energetic Features in the Adducts between OsO and Lewis Bases.

Adducts between OsO and Lewis bases exert a role in important oxidation processes such as epoxidation and dihydroxylation. It has been shown that the attractive interaction driving the formation of these adducts is a σ-hole bond involving the metal as the electrophilic species; the term Osme Bond (OmB) was proposed for designating it. Here some new adducts between OsO and various bases have been characterized through single crystal x-ray diffraction (XRD) and computational studies (density functional theory, DFT), confirming the existence of a robust correlation between σ-hole interaction energy and deformation of the tetrahedral geometry of OsO.

Chalcogen and Hydrogen Bond Team up in Driving Anion⋅⋅⋅Anion Self-Assembly.

H-selenite anions (HSeO ) form in the solid unprecedented anionic supramolecular chains wherein single units are assembled via alternating short Se⋅⋅⋅O and H⋅⋅⋅O contacts. Crystallographic analyses and computational studies (the quantum theory of "atoms-in-molecules", QTAIM, and the noncovalent interaction plot, NCIPlot) consistently prove the attractive nature of these chalcogen bonds (ChBs) and hydrogen honds (HBs), the Janus-type character of HSeO anions which act as both donors and acceptors of ChB and HB, and the possible stability of anion dimers in solution. The effectiveness of the ChBs herein described may lead to consider the HSeO moiety as a new entry in the toolbox of crystal engineering based on ChB.