Analysis of the paramagnetic spin–orbit transmission mechanism for NMR spin–spin coupling constants using the paramagnetic spin–orbit density distribution

Gräfenstein, Jürgen; Cremer, Dieter

doi:10.1016/j.cplett.2003.10.147

Cited by 32 publications

(16 citation statements)

References 18 publications

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“…The Fermi contact is directly related to the relative s contribution in the observed atom and is therefore related to the σ bonding scheme of the Tmp ligand. On the other hand, the paramagnetic spin–orbit contribution is related to the π orbitals. , The increase of the 1 J Yb–P value is therefore related to the bonding mode of the phosphorus atom in the Tmp ligand. The NMR of 2-L Et and 2-L Cy is then of high importance to test this conjecture because of the observed η 1 coordination mode, as described above in the X-ray structures.…”

Section: Resultsmentioning

confidence: 99%

η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

2015

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This paper reports the synthesis of a series of complexes based on the bis(pentamethylcyclopentadienyl)ytterbium(II) (1; Cp*2Yb) and bis(tetramethylphospholyl)ytterbium(II) (2; Tmp2Yb) fragments bearing an additional neutral bis(methyliminophosphoranyl)pyridine ligand (L) on which the steric demand is modulated at the phosphorus position (triethyl, L Et ; triphenyl, L Ph ; tricyclohexyl, L Cy ) to yield the original complexes Cp*2YbL Et (1-L Et ), Cp*2YbL Ph (1-L Ph ), Tmp2YbL Et (2-L Et ), Tmp2YbL Ph (2-L Ph ), and Tmp2YbL Cy (2-L Cy ), while no reaction occurs between 1 and L Cy . The crystal structures of these sterically crowded complexes are reported as well as room-temperature NMR data for all the complexes. The solid-state coordination mode of L R differs depending on the nature of the fragments 1 and 2 and on the steric bulk of L R . The crystal structure of the divalent Tmp2Yb(py)2 (3) is also reported for structural and spectroscopic comparisons. Interestingly, in both 2-L Et and 2-L Cy , one of the two Tmp ligands coordinates in an η1 rather than in an η5 fashion, a relevant coordination mode for the study of sterically induced reductions. The behavior of those complexes in solution varies with the sterics and electronics of the ligands, as demonstrated by variable-temperature NMR experiments. In solution, the 1 J Yb–P coupling is used to track the coordination mode of the Tmp ligand and a large difference in the 1 J Yb–P coupling constant allows the distinction between an η5 coordination mode and a dynamic η5–η1 switch.

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Section: Resultsmentioning

confidence: 99%

η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

2015

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“…According to the theory, in π-systems, 13 C shielding effects are dominated by the paramagnetic term, which mainly results from the coupling of occupied and vacant molecular orbitals close in energy under the effect of the external magnetic field. ,,− The strength of the coupling is inversely proportional to the energy difference between the orbitals involved. If, for instance, we take the HOMO–LUMO gap as a measure for these energy differences, then due to the GGA HOMO–LUMO, eigenvalue differences are less than those of hybrid functionals, and the paramagnetic component of the shielding constant for π-donating carbons is increased.…”

Section: Discussionmentioning

confidence: 99%

“…For the sp 3 carbons, the diamagnetic term in the CS is dominant. ,,− This term is mostly associated with the shielding caused by core orbitals and originates from the ground state of the molecule, which is less sensitive to the approximations used in its calculation. Therefore, no explicit artifacts are observed for such carbons.…”

Section: Discussionmentioning

confidence: 99%

DFT Approach for Predicting ¹³C NMR Shifts of Atoms Directly Coordinated to Nickel

et al. 2021

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The aim of this work is to develop a simple density functional theory (DFT) method that can be safely applied to calculate 13C NMR shifts in diamagnetic Ni complexes. A comparative analysis of calculated vs experimental 13C NMR shifts for a wide range of nickel complexes (157 in total) was carried out. A number of functional–basis set combinations were tested. On the whole, the NMR shifts of carbon atoms directly bonded to nickel can be calculated within the framework of the Kohn–Sham theory level using a number of hybrid functionals. The linear scaling procedure significantly improves results (root-mean-square error (RMSE) = 4.0–4.6 ppm). In the complexes coordinated with solvent and/or counterions, the predictions are less accurate (RMSE = 6.4 ppm). In the Ni–diimine alkyne complexes, calculations underestimate the NMR shielding (by 7–10 ppm) possibly due to the influence of high-spin states. At the same time, pure generalized gradient approximation (GGA) functionals show limits in their predictive power, particularly for the N-heterocyclic carbenes (NHCs) and π-donating carbons. Care has to be taken when interpreting 13C NMR spectra of Ni complexes using empirical dependencies, which may be misleading.

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“…[21][22][23][24][25][26] Recently such an approach has also been devised for response functions at the level of the second order polarization propagator approximation (SOPPA) [27][28][29] and for relativistic DFT calculations at the level of the zeroth-order regular approximation (ZORA). 30 The third class of approaches proposed by Cremer and co-workers [31][32][33][34][35][36][37] essentially obtains the contribution of a given orbital indirectly by removing the contribution of this orbital in the coupled perturbed DFT calculations.…”

Section: Introductionmentioning

confidence: 99%

On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

Zarycz

Provasi

Sauer

2015

The Journal of Chemical Physics

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It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

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Analysis of the paramagnetic spin–orbit transmission mechanism for NMR spin–spin coupling constants using the paramagnetic spin–orbit density distribution

Cited by 32 publications

References 18 publications

η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

DFT Approach for Predicting ¹³C NMR Shifts of Atoms Directly Coordinated to Nickel

On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

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Analysis of the paramagnetic spin–orbit transmission mechanism for NMR spin–spin coupling constants using the paramagnetic spin–orbit density distribution

Cited by 32 publications

References 18 publications

η5–η1 Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR 1JYb–P Coupling Constants

η5–η1 Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR 1JYb–P Coupling Constants

DFT Approach for Predicting 13C NMR Shifts of Atoms Directly Coordinated to Nickel

On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

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η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

η⁵–η¹ Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR ¹J_Yb–P Coupling Constants

DFT Approach for Predicting ¹³C NMR Shifts of Atoms Directly Coordinated to Nickel