The isotropic nuclear magnetic shielding constants of acetone in supercritical water: A sequential Monte Carlo/quantum mechanics study including solute polarization

Abstract

Monte Carlo simulation strategies for computing the wetting properties of fluids at geometrically rough surfaces J. Chem. Phys. 135, 184702 (2011) Semi-bottom-up coarse graining of water based on microscopic simulations J. Chem. Phys. 135, 184101 (2011) Hydrophobic interactions in presence of osmolytes urea and trimethylamine-N-oxide J. Chem. Phys. 135, 174501 (2011) Potential of mean force between identical charged nanoparticles immersed in a size-asymmetric monovalent electrolyte J. Chem. Phys. 135, 164705 (2011) Additional information on J. Chem. Phys. The nuclear isotropic shielding constants ͑ 17 O͒ and ͑ 13 C͒ of the carbonyl bond of acetone in water at supercritical ͑P = 340.2 atm and T = 673 K͒ and normal water conditions have been studied theoretically using Monte Carlo simulation and quantum mechanics calculations based on the B3LYP/ 6-311+ + G͑2d ,2p͒ method. Statistically uncorrelated configurations have been obtained from Monte Carlo simulations with unpolarized and in-solution polarized solute. The results show that solvent effects on the shielding constants have a significant contribution of the electrostatic interactions and that quantitative estimates for solvent shifts of shielding constants can be obtained modeling the water molecules by point charges ͑electrostatic embedding͒. In supercritical water, there is a decrease in the magnitude of ͑ 13 C͒ but a sizable increase in the magnitude of ͑ 17 O͒ when compared with the results obtained in normal water. It is found that the influence of the solute polarization is mild in the supercritical regime but it is particularly important for ͑ 17 O͒ in normal water and its shielding effect reflects the increase in the average number of hydrogen bonds between acetone and water. Changing the solvent environment from normal to supercritical water condition, the B3LYP/ 6-311+ + G͑2d ,2p͒ calculations on the statistically uncorrelated configurations sampled from the Monte Carlo simulation give a 13 C chemical shift of 11.7Ϯ 0.6 ppm for polarized acetone in good agreement with the experimentally inferred result of 9 -11 ppm.

Quantum Chemistry with Thermodynamic Condition. A Journey into the Supercritical Region and Approaching the Critical Point

“…In SCW, there is a decrease in the magnitude of σ( 13 C) but a sizable increase in the magnitude of σ( 17 O) when compared with the results obtained in NW. Changing from NW to SCW, the calculations 26 give a 13 C chemical shift of 11.7 AE 0.6 ppm for acetone in good agreement with the experimentally inferred result of 9-11 ppm. 33 One interesting case is para-nitroaniline (p-NA) in SCW that has been reported 34 to suffer a red shift of 17 nm, corresponding to 0.24 eV (or 1935 cm À1 ), in the intense charge transfer transition.…”

“…Additional studies including NMR parameters have also been made. 26 For instance, the nuclear isotropic shielding constants σ( 17 O) and σ( 13 C) of the carbonyl bond of acetone in water again at the same supercritical (P ¼ 340.2 atm and T ¼ 673 K) and NW conditions have been studied theoretically using MC simulation and quantum mechanics calculations based on the B3LYP/6-311++G(2d,2p) method. In SCW, there is a decrease in the magnitude of σ( 13 C) but a sizable increase in the magnitude of σ( 17 O) when compared with the results obtained in NW.…”

“…We briefly review some of the results obtained in our laboratory discussing some specific cases. [24][25][26][27][28][29][30] The UV-vis absorption spectrum of benzophenone has been obtained experimentally 31,32 in normal (NW) and supercritical water (SCW). The intense π À π* transition is seen to suffer a blue shift of 1700 cm À1 upon change from NW (P ¼ 1 atm and T ¼ 298 K; for simulation in the NVT ensemble we use ρ ¼ 0.997 g/cm 3 ) to SCW (in the condition of P ¼ 340.2 atm and T ¼ 673 K).…”

Isomerization effects on chemical shifts and spin‐spin coupling constants of polyacetylene chains: A GIAO‐DFT study

“…Nuclear chemical shifts and indirect spin‐spin coupling constants are magnetic molecular properties that can be obtained from NMR spectroscopy. In recent years, substantial methodological efforts have been made to estimate such magnetic properties with high accuracy3–21. In particular, an efficient way to include the solvent effects on the shielding constants of solute molecules has been reported by Coutinho et al17.…”

13C chemical shifts of polyacetylene chains with charged conformational defects: A GIAO–DFT study

“…Closed-shell polyacetylene chains containing odd [even] numbers of carbon atoms are employed to model charged solitons [bipolarons]. There have been extensive theoretical studies to estimate such magnetic properties with high accuracy [22][23][24][25][26][27][28][29][30][31][32]. Highly correlated schemes provide accurate descriptions for the magnetic shielding constants [22,23] but their applicability is still nowadays restricted to small compounds.…”