TY - JOUR
T1 - Binding Energies of the pi-Stacked Anisole Dimer: New Molecular Beam-Laser Spectroscopy Experiments and CCSD(T) Calculations
AU - Muller-Dethlefs, Klaus
AU - Rezac, Jan
AU - Nachtigallova, Dana
AU - Mazzoni, Federico
AU - Pasquini, Massimiliano
AU - Pietraperzia, Giangaetano
AU - Becucci, Maurizio
AU - Mueller-Dethlefs, Klaus
AU - Hobza, Pavel
N1 - Times Cited: 1 Rezac, Jan/A-9107-2010; Becucci, Maurizio/J-1616-2012; Hobza, Pavel/G-8060-2014 Rezac, Jan/0000-0001-6849-7314; Becucci, Maurizio/0000-0002-2428-471X; 0 1 1521-3765
PY - 2015
Y1 - 2015
N2 - Among noncovalent interactions, pi-pi stacking is a very important binding motif governed mainly by London dispersion. Despite its importance, for instance, for the structure of bio-macromolecules, the direct experimental measurement of binding energies in pi-pi stacked complexes has been elusive for a long time. Only recently, an experimental value for the binding energy of the anisole dimer was presented, determined by velocity mapping ion imaging in a two-photon resonant ionisation molecular beam experiment. However, in that paper, a discrepancy was already noted between the obtained experimental value and a theoretical estimate. Here, we present an accurate recalculation of the binding energy based on the combination of the CCSD(T)/CBS interaction energy and a DFT-D3 vibrational analysis. This proves unambiguously that the previously reported experimental value is too high and a new series of measurements with a different, more sensitive apparatus was performed. The new experimental value of 1800 +/- 100 cm(-1) (5.15 +/- 0.29 kcal mol(-1)) is close to the present theoretical prediction of 5.04 +/- 0.40 kcal mol(-1). Additional calculations of the properties of the cationic and excited states involved in the photodissociation of the dimer were used to identify and rationalise the difficulties encountered in the experimental work.
AB - Among noncovalent interactions, pi-pi stacking is a very important binding motif governed mainly by London dispersion. Despite its importance, for instance, for the structure of bio-macromolecules, the direct experimental measurement of binding energies in pi-pi stacked complexes has been elusive for a long time. Only recently, an experimental value for the binding energy of the anisole dimer was presented, determined by velocity mapping ion imaging in a two-photon resonant ionisation molecular beam experiment. However, in that paper, a discrepancy was already noted between the obtained experimental value and a theoretical estimate. Here, we present an accurate recalculation of the binding energy based on the combination of the CCSD(T)/CBS interaction energy and a DFT-D3 vibrational analysis. This proves unambiguously that the previously reported experimental value is too high and a new series of measurements with a different, more sensitive apparatus was performed. The new experimental value of 1800 +/- 100 cm(-1) (5.15 +/- 0.29 kcal mol(-1)) is close to the present theoretical prediction of 5.04 +/- 0.40 kcal mol(-1). Additional calculations of the properties of the cationic and excited states involved in the photodissociation of the dimer were used to identify and rationalise the difficulties encountered in the experimental work.
U2 - 10.1002/chem.201406134
DO - 10.1002/chem.201406134
M3 - Article
SN - 0947-6539
VL - 21
SP - 6740
EP - 6746
JO - Chemistry: A European Journal
JF - Chemistry: A European Journal
IS - 18
ER -