title: Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism.
abstract: We have analyzed the structure and bonding of gas-phase Cl-X and [HCl-X](+) complexes for X(+)= H(+), CH3 (+), Li(+), and Na(+), using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl(-) and HCl for the various cations. The Cl-X bond becomes longer and weaker along X(+) = H(+), CH3 (+), Li(+), and Na(+). Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn-Sham molecular orbital (KS-MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities.
authors.affiliation: Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM) VU University Amsterdam De Boelelaan 1083 1081 HV Amsterdam The Netherlands.
authors.forename: Zakaria
authors.initials: Z
authors.lastname: Boughlala
authors.affiliation: Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM) VU University Amsterdam De Boelelaan 1083 1081 HV Amsterdam The Netherlands.
authors.forename: Célia
authors.identifier: 0000-0002-2973-5321
authors.initials: C
authors.lastname: Fonseca Guerra
authors.affiliation: Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM) VU University Amsterdam De Boelelaan 1083 1081 HV Amsterdam The Netherlands; Institute of Molecules and Materials Radboud University Nijmegen Heyendaalseweg 1356525 AJ Nijmegen The Netherlands.
authors.forename: F Matthias
authors.identifier: 0000-0003-4655-7747
authors.initials: FM
authors.lastname: Bickelhaupt
keywords: alkali metal cation affinities; bond theory; density functional calculations; methyl cation affinities; proton affinities; thermochemistry