Interaction of acetonitrile with alkaline metal cations: A density functional, coupled‐cluster, and quadratic configuration interaction study

Abstract

ABSTRACT:A systematic quantum chemical study of CH 3 CN and its CH 3 CN· · ·M + 1:1 model adducts (M + ∈ {Li + , Na + }) is presented, with respect to binding energetics, structural and vibrational force field changes. Several gradient-corrected density functional levels of theory were employed (of both "pure" and "hybrid" character), together with the coupled cluster including double substitutions from the Hartree-Fock determinant (CCD) and quadratic configuration interaction including single and double substitutions (QCISD) methods [with the rather large 6-311G(d,p) basis set], and their performances compared. The binding energy decompositions according to the Kitaura-Morokuma scheme and the reduced variational space self-consistent field (RVS-SCF) method have shown that the electrostatic plus polarization interaction terms are primarily responsible for overall stabilization, while the charge-transfer term is negligibly small and virtually identical for both adducts. The computed harmonic vibrational frequencies for acetonitrile correlate excellently with the experimental ones (r 2 > 0.9998 for almost all cases, while for the BLYP level, r 2 = 1). It is shown for the first time that the experimentally observed blue shifts of the ν CN mode are caused even by formation of 1:1 adducts, contrary to the previously accepted opinions. The CCD and QCISD, as well as the BPW91 and BP86 levels of theory predict almost excellently the ν CN mode blue shift upon adduct formation, while the BLYP and B3LYP levels perform significantly poorer.

Gas-Phase Lithium Cation Basicity: Revisiting the High Basicity Range by Experiment and Theory

“…Another explanation is the lower polarizing power of Li + compared with the proton. Nevertheless, the covalent contribution to the bonding of neutral ligands with Li + is significant [31,32]. Quite interestingly, the lithium cation binds relatively strongly to aromatic systems [33][34][35][36][37][38][39][40] that are weakly polar or nonpolar, providing evidence that bonding mechanisms other than pure ion/dipole are acting.…”

Microsolvation of sodium ion in acetonitrile clusters: Structure and energetic trend by first principle study

“…Studies of the solvation of alkali metal ions in acetonitrile solvents are not as common as studies of water systems, however good numbers of reports are available in literature [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Using mass spectrometry, Megyes et al [21] found up to six acetonitrile molecules surrounding the Li + ion in the gas phase.…”

“…The clusters of an alkali metal ion solvated with acetonitrile molecules have also been studied by many theoretical calculations in the past decades [30][31][32][33][34][35][36][37][38][39][40]. Various theoretical simulations have been made to describe the solvation of cations in acetonitrile molecules with, usually employing empirical/semi-empirical/realistic potential functions [30][31][32][33][34][35][36][37][38].…”

“…Apart from molecular dynamics and Monte Carlo simulation, all electron ab-initio calculations have also been carried out on solvation of alkali metal ions in small size acetonitrile clusters [29,39,40]. A variety of correlated methods were used by Pejov [39] to study the interaction of Li + and Na + with single CH 3 CN molecule.…”

“…A variety of correlated methods were used by Pejov [39] to study the interaction of Li + and Na + with single CH 3 CN molecule. Cabaleiro-Lago and Rios reported the gas phase structure of Li + , Na + , and Mg 2+ (CH 3 CN) n clusters using HF, B3LYP and MP2/6-31+G(d) calculations [40].…”