scholarly journals Predicting Pt-195 NMR Chemical Shift and 1J(195Pt-31P) Coupling Constant for Pt(0) Complexes Using the NMR-DKH Basis Sets

2021 ◽  
Vol 7 (11) ◽  
pp. 148
Author(s):  
Joyce H. C. e Silva ◽  
Hélio F. Dos Santos ◽  
Diego F. S. Paschoal
Keyword(s):  
Chemical Shift ◽  
Geometry Optimization ◽  
Coupling Constants ◽  
Basis Sets ◽  
Coupling Constant ◽  
Nmr Chemical Shift ◽  
Absolute Deviation ◽  
Ligand Type ◽  
Original Group ◽  
Linear Correlations

Pt(0) complexes have been widely used as catalysts for important reactions, such as the hydrosilylation of olefins. In this context, nuclear magnetic resonance (NMR) spectroscopy plays an important role in characterising of new structures and elucidating reaction mechanisms. In particular, the Pt-195 NMR is fundamental, as it is very sensitive to the ligand type and the oxidation state of the metal. In the present study, quantum mechanics computational schemes are proposed for the theoretical prediction of the Pt-195 NMR chemical shift and 1J(195Pt–31P) in Pt(0) complexes. The protocols were constructed using the B3LYP/LANL2DZ/def2-SVP/IEF-PCM(UFF) level for geometry optimization and the GIAO-PBE/NMR-DKH/IEF-PCM(UFF) level for NMR calculation. The NMR fundamental quantities were then scaled by empirical procedures using linear correlations. For a set of 30 Pt(0) complexes, the results showed a mean absolute deviation (MAD) and mean relative deviation (MRD) of only 107 ppm and 2.3%, respectively, for the Pt-195 NMR chemical shift. When the coupling constant is taken into account, the MAD and MRD for a set of 33 coupling constants in 26 Pt(0) complexes were of 127 Hz and 3.3%, respectively. In addition, the models were validated for a group of 17 Pt(0) complexes not included in the original group that had MAD/MRD of 92 ppm/1.7% for the Pt-195 NMR chemical shift and 146 Hz/3.6% for the 1J(195Pt–31P).

scholarly journals Predicting Co-59 NMR Chemical Shit using the NMR-DKH Basis Sets

2020 ◽  
Author(s):  
Matheus G. R. Gomes ◽  
Hélio F. dos Santos ◽  
Diego F. S. Paschoal
Keyword(s):  
Chemical Shift ◽  
Model Systems ◽  
Basis Set ◽  
Basis Sets ◽  
Active Nucleus ◽  
Relative Deviation ◽  
Nmr Chemical Shift ◽  
Absolute Deviation ◽  
Nmr Signals ◽  
Computational Protocol

The cobalt-59 nucleus is an NMR active nucleus with the nuclear spin I = 7/2 and has a natural abundance of 100 %. It is an important nucleus because it has ease of detectable NMR signals both liquid and solid-state. The Co-59 NMR chemical shift range is one of the largest known in NMR spectroscopy, spanning some 18,000 ppm or more. However, Co-59 NMR is an extremely sensitive technique to external factors such as pressure, temperature, and others. Therefore, predicting Co-59 NMR chemical shift might be useful to assist experimentalists in the structural characterization. In the present study, we propose a new NMR-DKH basis set for Co atom to predict NMR chemical shift in Co complexes. Besides, we proposed a computational protocol (Functional DFT/Co basis set/Ligands basis set) for the prediction of the structure and, later, for the prediction of the Co-59 NMR chemical shift using 6 Co complexes as model systems. The results show that the computational protocol (NMR/structure) GIAO-B3LYP/NMR-DKH/IEF-PCM(UFF)//CAM-B3LYP/LANL2DZ/jorge-DZP/IEF-PCM(UFF) presents a mean relative deviation (DRM) of 1.48% for the structure, a mean absolute deviation (MAD) of 101 ppm and a DRM of 1.2% for the Co-59 chemical shift. Finally, the protocol was corrected by a linear regression model giving a MAD and MRD of 57 ppm and 0.7%, respectively.

scholarly journals Relativistic prediction of Pt-195 NMR chemical shift using the NMR- DKH basis sets.

2020 ◽  
Author(s):  
Diego F. S. Paschoal ◽  
Joyce H. C. e Silva
Keyword(s):  
Chemical Shift ◽  
Energy Surface ◽  
Relativistic Effects ◽  
New Drugs ◽  
Basis Sets ◽  
Hybrid Functional ◽  
Relative Deviation ◽  
Nmr Chemical Shift ◽  
Absolute Deviation ◽  
Antitumor Potential

Nuclear magnetic resonance (NMR) spectroscopy has played an important role in the discovery and design of new drugs with antitumor potential and the Pt-195 NMR has a fundamental role since the Pt-195 nucleus is very sensitive to the nature of the ligands in the coordination sphere and the oxidation state of the metal. The theoretical prediction of the Pt-195 NMR chemical shift is an extremely difficult task in which several factors must be taken into accounts, such as basis sets, electronic correlation, solvent, and relativistic effects. In an earlier study, Paschoal et al. developed the NMR-DKH basis sets and a nonrelativistic protocol for predicting the Pt-195 NMR chemical shift. The authors studied a set of 258 Pt(II) complexes and obtained a mean absolute deviation (MAD) of 168 ppm and a mean relative deviation (MRD) of 5%. However, relativistic calculations with the NMR-DKH basis sets have not been performed. Thus, the present work aims to apply the NMR-DKH in predicting the Pt-195 NMR chemical shift including the relativistic effects. The cisplatin was used as a model and its geometry was optimized and characterized as a minimum point on the potential energy surface at the B3LYP/LANL2DZ/def2-SVP/COSMO level. The Pt-195 NMR chemical shift was calculated at the DFT-Functional-DKFull/NMR-DKH/COSMO, where the functionals BP86, PBE, BLYP, PBE0, and B3LYP were tested. All calculations were carried out in NWCHEM 7.0.0 program. From the calculated results, it can be observed that the pure GGA functionals showing a better performance when compared to the hybrid functional. The best result was obtained at the BLYP-DKFull/NMR-DKH/COSMO level, where a DAM and DRM of only 34 ppm and 1.6% was found.

Carbon magnetic resonance studies of some phenyl, furyl and thienyl organometallics. Some comments on carbon-metal scalar coupling

1974 ◽  
Vol 27 (2) ◽  
pp. 417 ◽  
Author(s):  
D Doddrell ◽  
KG Lewis ◽  
CE Mulquiney ◽  
W Adcock ◽  
W Kitching ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Coupling Constant ◽  
Aryl Substituent ◽  
Magnetic Resonance Studies ◽  
Thienyl Group ◽  
13C Chemical Shift

13C chemical shift variations within a series of phenyl, furyl and thienyl Group IVB organometallics appear to be best understood in terms of the usual alkyl and aryl substituent effects on 13C chemical shifts and not variations in dπ ?pπ metal-aryl interactions. Large changes in 13C-metal scalar coupling constants have been observed suggesting that other factors besides the s-character of the carbon-metal bond is responsible in determining the coupling constant.

Quantum chemical B3LYP/cc-pvqz computation of ground-state structures and properties of small molecules with atoms of Z ≤ 18 (hydrogen to argon)(IUPAC Technical Report)

2001 ◽  
Vol 73 (9) ◽  
pp. 1521-1553 ◽  
Author(s):  
Rudolf Janoschek
Keyword(s):  
Small Molecules ◽  
Ground State ◽  
Quantum Chemical ◽  
Density Functional ◽  
Spectroscopic Properties ◽  
Computational Method ◽  
Coupling Constants ◽  
Basis Sets ◽  
General Question ◽  
Absolute Deviation

Since density functional theory (DFT) achieved a remarkable break-through in computational chemistry, the important general question "How reliable are quantum chemical calculations for spectroscopic properties?" should be answered anew. In this project, the most successful density functionals, namely the Becke B3LYP functionals, and the correlation-consistent polarized valence quadruple zeta basis sets (cc-pvqz) are applied to small molecules. In particular, the complete set of experimentally known diatomic molecules formed by the atoms H to Ar (these are 214 species) is uniformly calculated, and calculated spectroscopic properties are compared with experimental ones. Computationally demanding molecules, such as open-shell systems, anions, or noble gas compounds, are included in this study. Investigated spectroscopic properties are spectroscopic ground state, equilibrium internuclear distance, harmonic vibrational wavenumber, anharmonicity, vibrational absolute absorption intensity, electric dipole moment, ionization potential, and dissociation energy. The same computational method has also been applied to the ground-state geometries of 56 polyatomic molecules up to the size of benzene. Special sections are dedicated to nuclear magnetic resonance (NMR) chemical shifts and isotropic hyperfine coupling constants. Each set of systems for a chosen property is statistically analyzed, and the above important question "How reliable...?" is mathematically answered by the mean absolute deviation between calculated and experimental data, as well as by the worst agreement. In addition to presentation of numerous quantum chemically calculated spectroscopic properties, a corresponding updated list of references for experimentally determined properties is presented.

NMR Spectroscopic Studies of Thialene (Cyclopenta[b]thiapyran) and Isothialene (Cyclopenta[c]thiapyran)

1993 ◽  
Vol 58 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Robert F. X. Klein ◽  
Václav Horák ◽  
Arthur G. Anderson
Keyword(s):  
Chemical Shift ◽  
Bond Order ◽  
Spectroscopic Studies ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Vicinal Coupling Constant ◽  
Spectral Parameters ◽  
First Order ◽  
Nmr Techniques ◽  
C Nmr

1H and 13C NMR spectral parameters are reported for the S-pseudoazulenes thialene (cyclopenta[b]thiapyran) (I) and isothialene (cyclopenta[c]thiapyran) (II). Both compounds display complex first order spectra, with thialene having 10 and isothialene 14 of 15 possible coupling constants. Complete unambiguous assignments of all protons and non-quaternary carbons were made via 2-dimensional NMR techniques and PPP-SCF π-electron density/chemical shift and π-bond order/vicinal coupling constant correlations.

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