NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method
The NMR spin coupling parameters, 1J(N1H) and 2J(H,H), and the chemical shielding, σ(15N), of liquid ammonia are studied from a combined and sequential QM/MM methodology. Monte Carlo simulations are performed to generate statistically uncorrelated configurations that are submitted to density functio...
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2009
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10895639_v113_n52_p14936_Gester http://hdl.handle.net/20.500.12110/paper_10895639_v113_n52_p14936_Gester |
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paper:paper_10895639_v113_n52_p14936_Gester2023-06-08T16:06:26Z NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method Ammonia Chemical shift Computer simulation Density functional theory Deuterium Molecules Monte Carlo methods Nuclear magnetic resonance Shielding Spin dynamics Time varying systems Vapors Ammonia molecules Chemical shielding Density functional theory calculations Deuterated liquids Electronic polarization Experimental values Geometry relaxation Hydrogen bonded molecules Iterative procedures Lennard-Jones potential Liquid ammonia Liquid chemicals Monte Carlo Simulation Pure solvents QM/MM method Solvent molecules Spin couplings Spin-spin coupling constants Systematic investigations Theoretical models Theoretical result Liquids The NMR spin coupling parameters, 1J(N1H) and 2J(H,H), and the chemical shielding, σ(15N), of liquid ammonia are studied from a combined and sequential QM/MM methodology. Monte Carlo simulations are performed to generate statistically uncorrelated configurations that are submitted to density functional theory calculations. Two different Lennard-Jones potentials are used in the liquid simulations. Electronic polarization is included in these two potentials via an iterative procedure with and without geometry relaxation, and the influence on the calculated properties are analyzed. B3LYP/aug-cc-pVTZ-J calculations were used to compute the 1J(N,H) constants in the interval of -67.8 to -63.9 Hz, depending on the theoretical model used. These can be compared with the experimental results of -61.6 Hz. For the 2J(H,H) coupling the theoretical results vary between -10.6 to -13.01 Hz. The indirect experimental result derived from partially deuterated liquid is - 11.1 Hz. Inclusion of explicit hydrogen bonded molecules gives a small but important contribution. The vapor-to-liquid shifts are also considered. This shift is calculated to be negligible for 1J(N,H) in agreement with experiment. This is rationalized as a cancellation of the geometry relaxation and pure solvent effects. For the chemical shielding, σ(15N) calculations at the B3LYP/aug-pcS-3 show that the vapor-to-liquid chemical shift requires the explicit use of solvent molecules. Considering only one ammonia molecule in an electrostatic embedding gives a wrong sign for the chemical shift that is corrected only with the use of explicit additional molecules. The best result calculated for the vapor to liquid chemical shift △σ(15N) is -25.2 ppm, in good agreement with the experimental value of -22.6 ppm © 2009 American Chemical Society. 2009 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10895639_v113_n52_p14936_Gester http://hdl.handle.net/20.500.12110/paper_10895639_v113_n52_p14936_Gester |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Ammonia Chemical shift Computer simulation Density functional theory Deuterium Molecules Monte Carlo methods Nuclear magnetic resonance Shielding Spin dynamics Time varying systems Vapors Ammonia molecules Chemical shielding Density functional theory calculations Deuterated liquids Electronic polarization Experimental values Geometry relaxation Hydrogen bonded molecules Iterative procedures Lennard-Jones potential Liquid ammonia Liquid chemicals Monte Carlo Simulation Pure solvents QM/MM method Solvent molecules Spin couplings Spin-spin coupling constants Systematic investigations Theoretical models Theoretical result Liquids |
| spellingShingle |
Ammonia Chemical shift Computer simulation Density functional theory Deuterium Molecules Monte Carlo methods Nuclear magnetic resonance Shielding Spin dynamics Time varying systems Vapors Ammonia molecules Chemical shielding Density functional theory calculations Deuterated liquids Electronic polarization Experimental values Geometry relaxation Hydrogen bonded molecules Iterative procedures Lennard-Jones potential Liquid ammonia Liquid chemicals Monte Carlo Simulation Pure solvents QM/MM method Solvent molecules Spin couplings Spin-spin coupling constants Systematic investigations Theoretical models Theoretical result Liquids NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| topic_facet |
Ammonia Chemical shift Computer simulation Density functional theory Deuterium Molecules Monte Carlo methods Nuclear magnetic resonance Shielding Spin dynamics Time varying systems Vapors Ammonia molecules Chemical shielding Density functional theory calculations Deuterated liquids Electronic polarization Experimental values Geometry relaxation Hydrogen bonded molecules Iterative procedures Lennard-Jones potential Liquid ammonia Liquid chemicals Monte Carlo Simulation Pure solvents QM/MM method Solvent molecules Spin couplings Spin-spin coupling constants Systematic investigations Theoretical models Theoretical result Liquids |
| description |
The NMR spin coupling parameters, 1J(N1H) and 2J(H,H), and the chemical shielding, σ(15N), of liquid ammonia are studied from a combined and sequential QM/MM methodology. Monte Carlo simulations are performed to generate statistically uncorrelated configurations that are submitted to density functional theory calculations. Two different Lennard-Jones potentials are used in the liquid simulations. Electronic polarization is included in these two potentials via an iterative procedure with and without geometry relaxation, and the influence on the calculated properties are analyzed. B3LYP/aug-cc-pVTZ-J calculations were used to compute the 1J(N,H) constants in the interval of -67.8 to -63.9 Hz, depending on the theoretical model used. These can be compared with the experimental results of -61.6 Hz. For the 2J(H,H) coupling the theoretical results vary between -10.6 to -13.01 Hz. The indirect experimental result derived from partially deuterated liquid is - 11.1 Hz. Inclusion of explicit hydrogen bonded molecules gives a small but important contribution. The vapor-to-liquid shifts are also considered. This shift is calculated to be negligible for 1J(N,H) in agreement with experiment. This is rationalized as a cancellation of the geometry relaxation and pure solvent effects. For the chemical shielding, σ(15N) calculations at the B3LYP/aug-pcS-3 show that the vapor-to-liquid chemical shift requires the explicit use of solvent molecules. Considering only one ammonia molecule in an electrostatic embedding gives a wrong sign for the chemical shift that is corrected only with the use of explicit additional molecules. The best result calculated for the vapor to liquid chemical shift △σ(15N) is -25.2 ppm, in good agreement with the experimental value of -22.6 ppm © 2009 American Chemical Society. |
| title |
NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| title_short |
NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| title_full |
NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| title_fullStr |
NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| title_full_unstemmed |
NMR chemical shielding and spin-spin coupling constants of liquid NH 3: A systematic investigation using the sequential QM/MM method |
| title_sort |
nmr chemical shielding and spin-spin coupling constants of liquid nh 3: a systematic investigation using the sequential qm/mm method |
| publishDate |
2009 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10895639_v113_n52_p14936_Gester http://hdl.handle.net/20.500.12110/paper_10895639_v113_n52_p14936_Gester |
| _version_ |
1768542517954871296 |