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. The characteristics of the calculated electron density have been implemented to describe the features of the electron distribution around the central fragment involving a tetrahedral tetrel atom. The effect of the central Tt atom leads to a dramatic change in the character of electron delocalization on the Tt-C