A Quantitative Molecular Orbital Perspective of the Chalcogen Bond
Lucas de Azevedo Santos, Stephanie C. C. van der Lubbe, Trevor A. Hamlin, Teodorico C. Ramalho, F. Matthias Bickelhaupt
Abstract
Abstract We have quantum chemically analyzed the structure and stability of archetypal chalcogen‐bonded model complexes D 2 Ch⋅⋅⋅A − (Ch = O, S, Se, Te; D, A = F, Cl, Br) using relativistic density functional theory at ZORA‐M06/QZ4P. Our purpose is twofold: (i) to compute accurate trends in chalcogen‐bond strength based on a set of consistent data; and (ii) to rationalize these trends in terms of detailed analyses of the bonding mechanism based on quantitative Kohn‐Sham molecular orbital (KS‐MO) theory in combination with a canonical energy decomposition analysis (EDA). At odds with the commonly accepted view of chalcogen bonding as a predominantly electrostatic phenomenon, we find that chalcogen bonds, just as hydrogen and halogen bonds, have a significant covalent character stemming from strong HOMO−LUMO interactions. Besides providing significantly to the bond strength, these orbital interactions are also manifested by the structural distortions they induce as well as the associated charge transfer from A − to D 2 Ch.