Water Solvent Effect on Theoretical Evaluation of1H NMR Chemical Shifts: o-Methyl-Inositol Isomer.
In this paper, density functional theory calculations of nuclear magnetic resonance (NMR) chemical shifts for l-quebrachitol isomer, previously studied in our group, are reported with the aim of investigating in more detail the water solvent effect on the prediction of1H NMR spectra. In order to include explicit water molecules, 20 water-l-quebrachitol configurations obtained from Monte Carlo simulation were selected to perform geometry optimizations using the effective fragment potential method encompassing 60 water molecules around the solute. The solvated solute optimized geometries were then used in B3LYP/6-311+G(2d,p) NMR calculations with PCM-water. The inclusion of explicit solvent in the B3LYP NMR calculations resulted in large changes in the1H NMR profiles. We found a remarkable improvement in the agreement with experimental NMR profiles when the explicit hydrated l-quebrachitol structure is used in B3LYP1H NMR calculations, yielding a mean absolute error (MAE) of only 0.07 ppm, much lower than reported previously for the gas phase optimized structure (MAE = 0.11 ppm). In addition, a very improved match between theoretical and experimental1H NMR spectrum measured in D2O was achieved with the new hydrated optimized l-quebrachitol structure, showing that a fine-tuning of the theoretical NMR spectra can be accomplished once solvent effects are properly considered.
Hélio F
HF
Dos Santos
Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais , Campus Pampulha, 31270-901 Belo Horizonte, MG, Brazil.
Marcelo A
MA
Chagas
Laboratório de Química Computacional (LQC), Departamento de Química Inorgânica, Instituto de Química, Universidade Federal Fluminense (UFF) , 24020-150 Niterói, RJ, Brazil.
Leonardo A
LA
De Souza
Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais , Campus Pampulha, 31270-901 Belo Horizonte, MG, Brazil.
Willian R
WR
Rocha
Mauro V
MV
De Almeida
Laboratório de Química Fundamental (LQF), Departamento de Química, Universidade Federal de Lavras , 37200-000 Lavras, MG, Brazil.
Cleber P A
CP
Anconi
Laboratório de Química Computacional (LQC), Departamento de Química Inorgânica, Instituto de Química, Universidade Federal Fluminense (UFF) , 24020-150 Niterói, RJ, Brazil.
Wagner B
http://orcid.org/0000-0003-0785-2284
WB
De Almeida