Relativistic effects in the one‐bond spin–spin coupling constants involving selenium

Abstract

One-bond spin-spin coupling constants involving selenium of seven different types, (1) J(Se,X), X = (1) H, (13) C, (15) N, (19) F, (29) Si, (31) P, and (77) Se, were calculated in the series of 14 representative compounds at the SOPPA(CCSD) level taking into account relativistic corrections evaluated both at the RPA and DFT levels of theory in comparison with experiment. Relativistic corrections were found to play a major role in the calculation of (1) J(Se,X) reaching as much as almost 170% of the total value of (1) J(Se,Se) and up to 60-70% for the rest of (1) J(Se,X). Scalar relativistic effects (Darwin and mass-velocity corrections) by far dominate over spin-orbit coupling in the total relativistic effects for all (1) J(Se,X). Taking into account relativistic corrections at both random phase approximation and density functional theory levels essentially improves the agreement of theoretical results with experiment. The most 'relativistic' (1) J(Se,Se) demonstrates a marked Karplus-type dihedral angle dependence with respect to the mutual orientation of the selenium lone pairs providing a powerful tool for stereochemical analysis of selenoorganic compounds.

Relativistic heavy atom effect on the 31P NMR parameters of phosphine chalcogenides. Part 1. Chemical shifts

“…In other words, a good agreement between the experimental chemical shifts and total calculated values, obtained within the high accuracy ab initio nonrelativistic approach with taking into account solvent, vibrational, and relativistic corrections (with the latter being obtained within relativistic DFT framework), means the adequacy of the relativistic DFT approach for the relativistic corrections to chemical shifts. This way of examination of the suitability of four‐component relativistic DFT approach for calculation of the relativistic corrections has already been used in our previous paper dealing with the HALA effect on 13 C NMR chemical shifts, initiated by the adjacent chalcogens …”

Indirect NMR spin–spin coupling constants in diatomic alkali halides

“…The first is that a proper treatment of electron correlation effects is required, and second one has to take into account relativistic effects. The latter problem becomes more pronounced when heavy atoms are present in the molecular systems, as documented by several groups in research articles [3][4][5][6][7][8][9][10][11][12] and reviews. 13,14 The relativistic effects can be interpreted by applying perturbation theory; 15 for example, the effects caused by the interplay between the Fermi-contact (FC) interaction of nucleus K with the spinorbit (SO) interaction generated by the magnetic moment of nucleus L can be analyzed.…”

Stereochemical behavior of geminal and vicinal 77Se–13C spin–spin coupling constants studied at the SOPPA(CC2) level taking into account relativistic corrections

“…Collected in Table are the results of the present calculations of geminal and vicinal 77 Se– 13 C spin–spin coupling constants performed in the series of diverse organoselenium compounds 1–9 in comparison with available experimental data for 1 and 2 , 3 , 4 , 5 , 6 , 7 , 8 and 9 . In our earlier publication we have studied one‐bond 77 Se– 13 C coupling constants in a series of 13 organoselenium compounds including two compounds of the present series (compounds 7 and 9 ) at the nonrelativistic level using the second‐order polarization propagator approach, SOPPA, in combination with the second‐order approximate coupled cluster model, SOPPA(CC2), one from the most accurate pure nonempirical family of SOPPA‐based methods used to calculate spin–spin coupling constants . The same level of theory is used herewith for the nonrelativistic calculations of geminal and vicinal 77 Se– 13 C spin–spin coupling constants in the present series of 1–9 .…”

“…Also, it was a challenging task to perform the full four‐component relativistic calculations of ‘real’ organoselenium compounds of up to 23 atoms including the fourth‐period selenium and to reveal the importance of relativistic corrections for geminal and vicinal 77 Se– 13 C coupling constants. Relativistic effects play a major role in the mechanism of the nucleus spin–spin coupling involving at least one ‘heavy’ nuclei, and we expected that relativistic corrections to 2 J(Se,C) and 3 J(Se,C) should be far from negligible based on our recent study of the relativistic effects in the one‐bond 77 Se– 13 C coupling constants that could result in a contribution of as much as 15–20% of the total values of 1 J(Se,C) noticeably improving an agreement of the calculated couplings with their experimental values …”