Rotational Spectroscopy Meets Quantum Chemistry for Analyzing Substituent Effects on Non-Covalent Interactions: The Case of the Trifluoroacetophenone-Water Complex

Abstract

The most stable isomer of the 1:1 complex formed by 2,2,2-trifluoroacetophenone and water has been characterized by combining rotational spectroscopy in supersonic expansion and state-of-the-art quantum-chemical computations. In the observed isomer, water plays the double role of proton donor and acceptor, thus forming a seven-membered ring with 2,2,2-trifluoroacetophenone. Accurate intermolecular parameters featuring one classical O-H···O hydrogen bond and one weak C-H···O hydrogen bond have been determined by means of a semi-experimental approach for equilibrium structure. Furthermore, insights on the nature of the established non-covalent interactions have been unveiled by means of different bond analyses. The comparison with the analogous complex formed by acetophenone with water points out the remarkable role played by fluorine atoms in tuning non-covalent interactions.

Importance of water and intramolecular interaction governs substantial blue shift of Csp2–H stretching frequency in complexes between chalcogenoaldehydes and water

“…This evidences the larger strength of O–H⋯Z versus C sp 2 –H⋯O in H/CH 3 Z- n , in accordance with the trend reported by Lei et al in trifluoroacetophenone·H 2 O complex. 72 …”

Setting up the HyDRA blind challenge for the microhydration of organic molecules

“…TPH is an unsymmetric ketone, in which the water molecule is strongly directed to one of the CO lone electron pairs. Its monohydrate was recently accurately characterised by rotational spectroscopy and theory 72 but we are not aware of a published gas phase vibrational study. Comparison to the well-studied non-fluorinated parent compound APH from the training set will reveal the influence of fluorination through space and through several bonds.…”

Unveiling Bifunctional Hydrogen Bonding with the Help of Quantum Chemistry: The Imidazole-Water Adduct as Test Case

“…Whenever some SE equilibrium intermolecular parameters cannot be determined, they can be obtained from partial geometry optimizations at an accurate QC level. On the basis of recent works, − the so-called jun-“cheap” composite scheme (hereafter jun-ChS) provides, for noncovalent complexes, interaction energies on par with the most sophisticated composite methods at a significantly reduced computational cost. It is, therefore, natural to investigate if this computational approach is able to also deliver accurate geometrical parameters to be employed in the interpretation and prediction of equilibrium rotational constants.…”