Two-Factor Rule for Distinguishing the Covalent and Tetrel Bonds.

Understanding and exploring the existence of a recognizable boundary between the noncovalent tetrel bond (TtB) and the coordination or weakened covalent bond are important for the bonding characterization. We have developed a simple methodology for analysing the type of bonds based on comparison of the electrostatic and total static potentials along the bond line. For the typical σ-hole noncovalent bond formed by a Tt atom in a tetrahedral molecule, we have found that the space gap between positions of the maxima of the total static potential and the negative quantity of electrostatic potential is much wider than that for the coordination bonds in a trigonal bipyramid molecular system for the Cl-Tt/Cl⋅⋅⋅Tt and N-Tt/N⋅⋅⋅Tt (Tt=C, Si, Ge) bonds in molecules and molecular complexes.

Covalent Organic Frameworks in Computational Design of Second-Harmonic Generation Materials: Role of Tetrel Atoms and Their Interactions.

Modern approaches to the design of nonlinear optical materials often rely on computational techniques. Here, we discuss the effects of the variation in the center tetrel atoms, Tt = C, Si, or Ge, in a series of covalent organic frameworks of the COF-102 family. The effects of halogen substitution, Hal = Cl, Br, or I on intramolecular tetrel bonding are also discussed.

Noncovalent Interactions of Silatranes and Germatranes with the Surface of Stoichiometric and Hydroxylated 2D Silica.

Analysis of noncovalent interactions formed by the surface of a 2D silica bilayer and atrane molecules, as precursors of functional layers immobilized on a surface of silicatene, was performed. For this purpose, the systems of substituted silatranes and germatranes adsorbed on silicatene surfaces with different amounts of hydroxyl groups (0, 2, 4, and 30 per cell) were simulated by using quantum chemical modeling with periodic boundary conditions and full-electron basis sets. The observation results for interaction energy changes in the systems "atrane molecule-silicatene surface" with increasing silanol number of the silicatene surface can be used to predict the optimal degree of silicatene hydroxylation in order to control the effective progress of atrane deprotection on activated 2D silica materials.

Electron delocalization in defect-containing graphene and its influence on tetrel bond formation.

Using the advanced analyses of electron density and fermionic potential, we show how electron delocalization influences the ability of defect-containing graphene to form tetrel bonds. The C atoms of a vacancy defect can produce one nonpolar interaction, alongside a peculiar polar C⋯C bond. The latter stems from the presence of a localized electron pair on a vacancy defect C atom and the local depletion of electron localization on another C atom.