Benchmark calculations of 29Si–1H spin–spin coupling constants across double bond

Benchmark calculations of geminal and vicinal ²⁹Si–¹H spin–spin coupling constants across double bond in three reference alkenylsilanes have been carried out at both DFT and SOPPA levels in comparison with experiment. At the former, four density functionals, B3LYP, B3PW91, PBE0 and KT3, were tested in combination with five representative basis sets. At the latter, three main SOPPA‐based methods, SOPPA, SOPPA(CC2) and SOPPA(CCSD), were examined in combination with the same series of basis sets. On the whole, the wavefunction methods showed much better results as compared to DFT, with the most efficient combination of SOPPA/cc‐pVTZ‐su2 characterized by a mean absolute error of only 0.4 Hz calculated for a set of nine coupling constants in three compounds with a sample span of around 40 Hz. Copyright © 2012 John Wiley & Sons, Ltd.     

Open‐chain unsaturated selanyl sulfides: stereochemical structure and stereochemical behavior of their 77Se–1H spin–spin coupling constants

Stereochemical structure of nine Z‐2‐(vinylsulfanyl)ethenylselanyl organyl sulfides has been investigated by means of experimental measurements and second‐order polarization propagator approach calculations of their ¹H–¹H, ¹³C–¹H, and ⁷⁷Se–¹H spin–spin coupling constants together with a theoretical conformational analysis performed at the MP2/6‐311G** level. All nine compounds were shown to adopt the preferable skewed s‐cis conformation of their terminal vinylsulfanyl group, whereas the favorable rotational conformations with respect to the internal rotations around the C–S and C–Se bonds of the internal ethenyl group are both skewed s‐trans. Stereochemical trends of ⁷⁷Se–¹H spin–spin coupling constants originating in the geometry of their coupling pathways and the selenium lone pair effect were rationalized in terms of the natural J‐coupling analysis within the framework of the natural bond orbital approach. Copyright © 2012 John Wiley & Sons, Ltd.     

Nonempirical calculations of the one‐bond 29Si–13C spin–spin coupling constants taking into account relativistic and solvent corrections

The computational study of the one‐bond ²⁹Si–¹³C spin–spin coupling constants has been performed at the second‐order polarization propagator approximation (SOPPA) level in the series of 60 diverse silanes with a special focus on the main factors affecting the accuracy of the calculation including the level of theory, the quality of the basis set, and the contribution of solvent and relativistic effects. Among three SOPPA‐based methods, SOPPA(MP2), SOPPA(CC2), and SOPPA(CCSD), the best result was achieved with SOPPA(CCSD) when used in combination with Sauer's basis set aug‐cc‐pVTZ‐J characterized by the mean absolute error of calculated coupling constants against the experiment of ca 2 Hz in the range of ca 200 Hz. The SOPPA(CCSD)/aug‐cc‐pVTZ‐J method is recommended as the most accurate and effective computational scheme for the calculation of ¹J(Si,C). The slightly less accurate but essentially more economical SOPPA(MP2)/aug‐cc‐pVTZ‐J and/or SOPPA(CC2)/aug‐cc‐pVTZ‐J methods are recommended for larger molecular systems. It was shown that solvent and relativistic corrections do not play a major role in the computation of the total values of ¹J(Si,C); however, taking them into account noticeably improves agreement with the experiment. The rovibrational corrections are estimated to be of about 1 Hz or 1–1.5% of the total value of ¹J(Si,C). Copyright © 2014 John Wiley & Sons, Ltd.     

Conformational analysis and stereochemical dependences of 31P–1H spin–spin coupling constants of bis(2‐phenethyl)vinylphosphine and related phosphine chalcogenides

Theoretical energy‐based conformational analysis of bis(2‐phenethyl)vinylphosphine and related phosphine oxide, sulfide and selenide synthesized from available secondary phosphine chalcogenides and vinyl sulfoxides is performed at the MP2/6‐311G** level to study stereochemical behavior of their ³¹P–¹H spin–spin coupling constants measured experimentally and calculated at different levels of theory. All four title compounds are shown to exist in the equilibrium mixture of two conformers: major planar s‐cis and minor orthogonal ones, while ³¹P–¹ H spin–spin coupling constants under study are found to demonstrate marked stereochemical dependences with respect to the geometry of the coupling pathways, and to the internal rotation of the vinyl group around the P(X)‐C bonds (X = LP, O, S and Se), opening a new guide in the conformational studies of unsaturated phosphines and phosphine chalcogenides. Copyright © 2009 John Wiley & Sons, Ltd.     

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

One‐bond spin–spin coupling constants involving selenium of seven different types, ¹ J(Se,X), X = ¹H, ¹³C, ¹⁵ N, ¹⁹ F, ²⁹Si, ³¹P, and ⁷⁷Se, 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. Copyright © 2014 John Wiley & Sons, Ltd.     

Stereochemical behavior of 2 J(Se,H) and 3 J(Se,H) spin‐spin coupling constants across sp3 carbons: a theoretical scrutiny

A theoretical study of geminal and vicinal ⁷⁷Se‐¹ H coupling constants in the benchmark dimethyl and diethyl selenides has been performed at the SOPPA level followed by the NJC analysis within the NBO approach to reveal their stereochemical behavior in respect with the three main structural factors, namely, (i) the dihedral angle dependences, (ii) the bond angle dependences and (iii) the lone pair effects. It has been demonstrated that both geminal and vicinal couplings provide a unique stereospecificity in respect with the orientational lone pair effect together with the geometry of a coupling pathway, which is of prime importance for the stereochemical studies of organoselenium compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

NMR spin–spin coupling constants in hydrogen‐bonded glycine clusters

The influence of the hydrogen bond formation on the NMR spin–spin coupling constants (SSCC), including the Fermi contact (FC), the diamagnetic spin‐orbit, the paramagnetic spin‐orbit, and the spin dipole term, has been investigated systematically for the homogeneous glycine cluster, in gas phase, containing up to three monomers. The one‐bond and two‐bond SSCCs for several intramolecular (through covalent bond) and intermolecular (across the hydrogen‐bond) atomic pairs are calculated employing the density functional theory with B3LYP and KT3 functionals and different types of extended basis sets. The ab initio SOPPA(CCSD) is used as benchmark for the SSCCs of the glycine monomer. The hydrogen bonding is found to cause significant variations in the one‐bond SSCCs, mostly due to contribution from electronic interactions. However, the nature of variation depends on the type of oxygen atom (proton‐acceptor or proton‐donor) present in the interaction. Two‐bond intermolecular coupling constants vary more than the corresponding one‐bond constants when the size of the cluster increases. Among the four Ramsey terms that constitute the total SSCC, the FC term is the most dominant contributor followed by the paramagnetic spin‐orbit term in all one‐bond interaction.     

One‐bond 29Si‐1H spin‐spin coupling constants in the series of halosilanes: benchmark SOPPA and DFT calculations,relativistic effects,and vibrational corrections

A number of most representative second order polarization propagator approach (SOPPA) based wavefunction methods, SOPPA, SOPPA(CC2) and SOPPA(CCSD), and density functional theory (DFT) based methods, B3LYP, PBE0, KT2, and KT3, have been benchmarked in the calculation of the one‐bond ²⁹Si‐¹H spin‐spin coupling constants in the series of halosilanes SiH_nX_4?n (X = F, Cl, Br, I), both at the non‐relativistic and full four‐parameter Dirac's relativistic levels taking into account vibrational corrections. At the non‐relativistic level, the wavefunction methods showed much better results as compared with those of DFT. At the DFT level, out of four tested functionals, the Perdew, Burke, and Ernzerhof's PBE0 showed best performance. Taking into account, relativistic effects and vibrational corrections noticeably improves wavefunction methods results, but generally worsens DFT results. Copyright © 2013 John Wiley & Sons, Ltd.     

Stereochemical behavior of 77Se‐1H spin‐spin coupling constants in pyrazolyl‐1,3‐diselenanes and 1,2‐diselenolane

Conformational study of five derivatives of 2‐(pyrazol‐4‐yl)‐1,3‐diselenane together with related 1,2‐diselenolane in respect to the stereochemical trends of geminal and vicinal ⁷⁷Se‐¹H spin‐spin coupling constants has been carried out by means of high‐level theoretical calculations in combination with experiment. The marked dihedral angle dependences for both types of couplings accounted for the lone pair effect in the case of geminal coupling constants and the Karplus‐type relationship for vicinal couplings have been established, which is of major importance for the stereochemical analysis of saturated selenium containing heterocycles. Copyright © 2012 John Wiley & Sons, Ltd.     

First example of the correlated calculation of the one‐bond tellurium–carbon spin–spin coupling constants: Relativistic effects,vibrational corrections,and solvent effects

This work reports on the comprehensive calculation of the NMR one‐bond spin–spin coupling constants (SSCCs) involving carbon and tellurium, ¹J(¹²⁵Te,¹³C), in four representative compounds: Te(CH₃)₂, Te(CF₃)₂, Te(C?CH)₂, and tellurophene. A high‐level computational treatment of ¹J(¹²⁵Te,¹³C) included calculations at the SOPPA level taking into account relativistic effects evaluated at the 4‐component RPA and DFT levels of theory, vibrational corrections, and solvent effects. The consistency of different computational approaches including the level of theory of the geometry optimization of tellurium‐containing compounds, basis sets, and methods used for obtainig spin–spin coupling values have also been discussed in view of reproducing the experimental values of the tellurium–carbon SSCCs. Relativistic corrections were found to play a major role in the calculation of ¹J(¹²⁵Te,¹³C) reaching as much as almost 50% of the total value of ¹J(¹²⁵Te,¹³C) while relativistic geometrical effects are of minor importance. The vibrational and solvent corrections account for accordingly about 3–6% and 0–4% of the total value. It is shown that taking into account relativistic corrections, vibrational corrections and solvent effects at the DFT level essentially improves the agreement of the non‐relativistic theoretical SOPPA results with experiment. © 2016 Wiley Periodicals, Inc.     

Indirect relativistic bridge and substituent effects from the ‘heavy’ environment on the one‐bond and two‐bond 13C1H spin–spin coupling constants

Indirect relativistic bridge effect (IRBE) and indirect relativistic substituent effect (IRSE) induced by the ‘heavy’ environment of the IV‐th, V‐th and VI‐th main group elements on the one‐bond and geminal ¹³C? ¹H spin–spin coupling constants are observed, and spin‐orbit parts of these two effects were interpreted in terms of the third‐order Rayleigh–Schrödinger perturbation theory. Both effects, IRBE and IRSE, rapidly increase with the total atomic charge of the substituents at the coupled carbon. The accumulation of IRSE for geminal coupling constants is not linear with respect to the number of substituents in contrast to the one‐bond couplings where IRSE is an essentially additive quantity. Copyright © 2015 John Wiley & Sons, Ltd.     

Prediction of water's isotropic nuclear shieldings and indirect nuclear spin–spin coupling constants (SSCCs) using correlation‐consistent and polarization‐consistent basis sets in the Kohn–Sham basis set limit

Density functional theory (DFT) was used to estimate water's isotropic nuclear shieldings and indirect nuclear spin–spin coupling constants (SSCCs) in the Kohn–Sham (KS) complete basis set (CBS) limit. Correlation‐consistent cc‐pVxZ and cc‐pCVxZ (x = D, T, Q, 5, and 6), and their modified versions (ccJ‐pVxZ, unc‐ccJ‐pVxZ, and aug‐cc‐pVTZ‐J) and polarization‐consistent pc‐n and pcJ‐n (n = 0, 1, 2, 3, and 4) basis sets were used, and the results fitted with a simple mathematical formula. The performance of over 20 studied density functionals was assessed from comparison with the experiment. The agreement between the CBS DFT‐predicted isotropic shieldings, spin–spin values, and the experimental values was good and similar for the modified correlation‐consistent and polarization‐consistent basis sets. The BHandH method predicted the most accurate ¹H, ¹⁷O isotropic shieldings and ¹J(OH) coupling constant (deviations from experiment of about ? 0.2 and ? 1 ppm and 0.6 Hz, respectively). The performance of BHandH for predicting water isotropic shieldings and ¹J(OH) is similar to the more advanced methods, second‐order polarization propagator approximation (SOPPA) and SOPPA(CCSD), in the basis set limit. Copyright © 2008 John Wiley & Sons, Ltd.     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes

A systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of ?14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and ?5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd.     

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

A systematic theoretical study of geminal and vicinal ⁷⁷Se–¹³C spin–spin coupling constants in the series of the open‐chain selenides and selenium‐containing heterocycles revealed that relativistic effects play an essential role in the selenium–carbon coupling mechanism, especially when the coupling pathway includes a triple bond, contributing to about 10–15% of their total values and noticeably improving the agreement of the calculated couplings with experiment. Both geminal and vicinal ⁷⁷Se–¹³C spin–spin coupling constants show marked stereochemical behavior as documented by their calculated dihedral angle dependence that could be used as a practical guide in stereochemical studies of organoselenium compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Resonance assignments of diastereotopic CH2 protons in the anomeric side chain of selenoglycosides by means of 2J(Se,H) spin‐spin coupling constants

Unambiguous resonance assignments of diastereotopic CH₂ protons in the anomeric side chain of nine alkyl‐ and aralkylselenoglycosides have been carried out on the basis of experimental CPMG‐HSQMBC measurements and theoretical second order polarization propagator approach (SOPPA) calculations of geminal ⁷⁷Se‐¹H spin‐spin coupling constants involving diastereotopic pro‐R and pro‐S protons. Theoretical conformational analyses have been performed at the MP2/6‐311G** level. The conformational space of each of the selenoglycosides under study could be adequately described as a mixture of six interconverting conformers with the molar fractions depending on the nature of the side chain substituent at the selenium atom. The good agreement observed between measured and the weighted conformational averaged values of the calculated coupling constants provides a basis for reliable diastereotopic assignments in this type of carbohydrate structures. Copyright © 2012 John Wiley & Sons, Ltd.     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 2. Strained polycarbocycles

High‐level non‐empirical calculations of carbon–carbon spin–spin coupling constants in a series of strained polycarbocycles have been carried out, in excellent agreement with available experimental data. The utmost importance of electronic correlation effects in this case has been demonstrated and it has been shown that the Second‐Order Polarization Propagator Approach (SOPPA) is an adequate method to account for those effects. It has been demonstrated that the most reliable basis sets to calculate J(C,C) at the SOPPA level are the correlation‐consistent basis sets of Dunning and co‐workers augmented with inner core s‐functions or decontracted in their s‐parts. The nature of the unusual bridgehead–bridgehead bonds in bicyclobutane and propellane in terms of s‐characters of bonding hybrids and also the hybridization effects in spiropentane are discussed based on the arguments derived from the current calculations of J(C,C) in the title compounds. The values of the unknown J(C,C) in propellane and spiropentane are predicted with high reliability. Copyright © 2003 John Wiley & Sons, Ltd.     

Temperature dependence of the 1J(11B19F) spin–spin coupling in BF3 molecule

The ¹J(¹¹B¹⁹F) spin–spin coupling of gaseous BF₃ was observed in ¹¹B NMR spectra as a function of density in a wide range of temperatures. Following the extrapolation of the measured values to the zero‐density limit, the coupling constant free from intermolecular effects ¹J₀(¹¹B¹⁹F) was obtained for each temperature. In contrast to previous investigations, the final results indicate a nonlinear dependence of ¹J₀(¹¹B¹⁹F) on temperature. In the corresponding ab initio calculations of spin–spin coupling constants performed at the coupled cluster singles and doubles (CCSD) level to obtain a reliable result for this coupling constant we had to take into account large vibrational corrections. Copyright © 2009 John Wiley & Sons, Ltd.     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes

High‐level ab initio calculations of carbon–carbon coupling constants were carried out in tetrahedrane, prismane and cubane using the SOPPA (Second‐Order Polarization Propagator Approach) computational scheme, in good agreement with available experimental data. It was found that SOPPA performs perfectly well in combination with Dunning's correlation‐consistent basis sets augmented with inner core functions; however, no improvement was observed on adding tight s‐functions. The utmost importance of electronic correlation effects decreasing the total values of computed J(C,C) in the title compounds by a factor of ～2.0–2.5 was found. Unknown values of J(C,C) in the title polyhedranes were predicted with high reliability and the latter were treated in terms of s‐characters of carbon–carbon bonds based on the additive scheme of coupling pathways. All three compounds under study showed decreased s‐characters of their carbon–carbon bonds, which is the result of their remarkable steric strain. Copyright © 2003 John Wiley & Sons, Ltd.     

H2O,H2, HF,F2 and F2O nuclear magnetic shielding constants and indirect nuclear spin–spin coupling constants (SSCCs) in the BHandH/pcJ‐n and BHandH/XZP Kohn–Sham limits

Good performance of segmented contracted basis sets XZP, where X = D, T, Q and 5, for obtaining H₂O, H₂, HF, F₂ and F₂O nuclear isotropic shielding constants in the BHandH Kohn–Sham basis set limit was shown. The results of two‐ and three‐parameter complete basis set limit extrapolation schemes were compared with experimental results, earlier literature data and benchmark ab initio results. Similar convergence patterns of shieldings obtained from calculations using general purpose XZP basis sets and from polarization‐consistent basis sets pcS‐n and pcJ‐n, where n = 0, 1, 2, 3 and 4, designed to accurately predict magnetic properties were observed. On the contrary, the SSCCs were more sensitive to the XZP basis set size and generally less accurate than those estimated using pcJ‐n basis set family. The BHandH density functional markedly outperforms B3LYP method in predicting heavy atom shieldings and SSCCs values in the studied systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 1. Three‐membered rings

The carbon–carbon indirect nuclear spin–spin coupling constants in cyclopropane, aziridine and oxirane were investigated by means of ab initio calculations at the RPA, SOPPA and DFT/B3LYP levels. We found that the carbon–carbon couplings are by far dominated by the Fermi contact term. Our best SOPPA and DFT results are in a very good agreement with each other and with the experimental values, whereas calculations at the RPA level of theory strongly overestimate the carbon–carbon couplings. Significant differences in the basis set dependence of the calculated carbon–carbon coupling constants obtained with either wavefunction method, RPA or SOPPA, or the density functional method, DFT/B3LYP, are observed. The SOPPA results depend much more strongly on the quality of the basis set than the results of DFT/B3LYP calculations. The medium‐sized core‐valence basis sets cc‐pCVTZ and even cc‐pCVDZ were found to perform fairly well at the SOPPA level for the one‐bond carbon–carbon couplings investigated here. Copyright © 2002 John Wiley & Sons, Ltd.