The Different Story of π Bonds.

Marco Cappelletti,Davide M Proserpio,Matteo Cococcioni,Rocco Martinazzo,Mirko Leccese

doi:10.3390/molecules26133805

Abstract

We revisit “classical” issues in multiply bonded systems between main groups elements, namely the structural distortions that may occur at the multiple bonds and that lead, e.g., to trans-bent and bond-length alternated structures. The focus is on the role that orbital hybridization and electron correlation play in this context, here analyzed with the help of simple models for - and -bonds, numerically exact solutions of Hubbard Hamiltonians and first principles (density functional theory) investigations of an extended set of systems.

Highlights

If one asks a chemist which is the most important element of the periodic table, chances are that his choice will be carbon
Together with its incredible versatility, with it being able to form all sorts of structures from simple molecules to proteins, and from 0D to 3D materials, carbon compounds are capable of displaying extraordinary transport properties [1,2]
First principle results presented below were obtained with Density Functional Theory (DFT)

Summary

Introduction

If one asks a chemist which is the most important element of the periodic table, chances are that his choice will be carbon. The difference between carbon and silicon was shown to be due to atomic-like properties, albeit in a counter-intuitive way: It is the larger interaction between valence orbitals in C—which in turns arises from the similar size of its s and p valence shells—that determines a larger π bending stiffness This occurs because a destructive interference between s and p orbitals arises when forming a distorted π bond and establishes a direct link between the unusual atomic properties of second-row elements (related to the presence of poorly screened p valence orbitals [36,37]) and their unique chemistry.

Methods

Trans-Bending

Bond-Length Alternation

Conclusions