We have quantum chemically analyzed element−element bonds of archetypal HnX−YHn molecules (X, Y=C, N, O, F, Si, P, S, Cl, Br, I), using density functional theory. One purpose is to obtain a set of consistent homolytic bond dissociation energies (BDE) for establishing accurate trends across the periodic table. The main objective is to elucidate the underlying physical factors behind these chemical bonding trends. On one hand, we confirm that, along a period (e. g., from C−C to C−F), bonds strengthen because the electronegativity difference across the bond increases. But, down a period, our findings constitute a paradigm shift. From C−F to C−I, for example, bonds do become weaker, however, not because of the decreasing electronegativity difference. Instead, we show that the effective atom size (via steric Pauli repulsion) is the causal factor behind bond weakening in this series, and behind the weakening in orbital interactions at the equilibrium distance. We discuss the actual bonding mechanism and the importance of analyzing this mechanism as a function of the bond distance.
Bibliographical noteFunding Information:
We thank the Advanced Research Center Chemical Building Blocks Consortium (ARC CBBC; grant 2018.019.B), the Netherlands Organization for Scientific Research (NWO) and the Spanish MINECO (PID2019‐106830GB‐I00 and MDM‐2017‐0767) for financial support.
We thank the Advanced Research Center Chemical Building Blocks Consortium (ARC CBBC; grant 2018.019.B), the Netherlands Organization for Scientific Research (NWO) and the Spanish MINECO (PID2019-106830GB-I00 and MDM-2017-0767) for financial support.
© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
- Bond energy
- Bond theory
- Density functional calculations
- Main group elements