13C, 13C coupling constants in anthracene, 9,10-dihydroanthracene and phthalic acid derivatives. Determination of signs by the symmetrical double labelling (SDL) method V

Carbon-13, carbon-13 one-bound and long-range coupling constants are determined for anthracene and 9,10-dihydroanthracene labelled in the 9,10-positions, and for thiophthalic anhydride and phthalimide, labelled in both carbonyl groups. Relative signs are determined by the SDL method. Signs in naphthalene, anthracene and pyrene derivatives are discussed. The general trends observed in many aromatic compounds, ³J|>|²J|>|⁴J| and ²J positive, ³J positive, ⁴J negative are mostly confirmed. However, evidence suggests that two-bond couplings between carbon atoms in the same ring in aromatic hydrocarbons are negative.     

13C,13C coupling constants from a mixture of isotopomers (13C) of substituted aromatic compounds; 1-nitronaphthalenes

¹³C Homonuclear decoupling experiments led to the assignment of the carbon-carbon coupling constants of ¹³C-enriched 1-nitronaphthalene obtained by nitration of [1-¹³C]naphthalene. The effects of substituents on coupling constants can be explained on the basis of the electronegativity of the first atom of the substituent, and the observed substituent effects are shown to be parallel to previous data for oxygen containing substituents.     

13C?13C coupling constants in derivatives of trans-stilbene and tetraphenylethylene. Determination of relative signs II

Magnitudes and signs of ¹³C? ¹³C coupling constants in compounds of the type Ph¹³CR¹R²? ¹³CR¹R²Ph have been determined and the results are discussed in a broader context. Two types of coupling constants, J(C-i, C-α) and J(C-i, C-β), between aromatic carbon atoms and the benzylic carbons, probably with different coupling mechanisms, are considered. Whereas ²J(C-2, C-α) are always found positive, ²J(C-1, C-β) in the present compounds are found to be negative or about zero. ³J(C-3, C-α) has the same sign as ²J(C-2, C-α). A ⁴J and a ⁵J were observed in trans-stilbene.     

Pulsed fourier transform NMR of substituted aryltrimethyltin derivatives : II. (119Sn-13C) coupling constants and 13C chemical shifts of meta- and para-derivatives

Carbon-13 NMR data are reported for thirteen para- and meta-substituted phenyltrimethyltin compounds, RC₆H₄Sn(CH₃)₃, where R = para-N(CH₃)₂, para-OCH₃, para-OC₂H₅, para-CH₃, meta-CH₃, -H, para-F, meta-OCH₃, para-Cl, para-Br, meta-F, meta-Cl and para-Sn(CH₃)₃. In the para-derivatives, correlation coefficients with Hammet σ-constants of greater than ca. 0.9 are obtained with the tin-carbon couplings to methyl, C₁ and C₄ carbons, and with the carbon-13 chemical shifts δ(C(1)). In the meta-derivatives, the couplings |J(Sn-CH₃)|:, |:J(Sn-C(1))|:, |:J(Sn-C(3))|: and |:J(Sn-C(6))|:, and the shifts δ(C(1)) and δ(C(5)) correlate well with Hammett σ. In the para-derivatives, sensitivity to change in substituent falls off C(4) > C(3, 5) > C(1) > C(2, 6) > CH₃ as registered by the δ(C), while in the meta-derivatives δ(C) changes decrease C(3) > C(2), C(4) > C(1) > C(5), C(6) > CH₃. The magnitudes of the tin coupling constants decrease C(1) > CH₃ > C(3, 5) > C(2, 6) > C(4) in the para-derivatives, while in the meta-series the order is C(1) > CH₃ > C(3), C(5) > C(2) > C(6) > C(4). The two sets of one-bond |:J(Sn-CH₃)|: and |:J(Sn-C(1)|: values correspond closely to the 0.25/0.33 ratio of coefficients in the LCAO approach, and are interpreted in terms of s-electron redistributions at the tin atom with change in substituent.     

13C-labeled platinum(IV)-carbohydrate complexes: structure determination based on (1)H-(1)H, (13)C-(1)H, and (13)C-(13)C spin-spin coupling constants

The reaction of D-mannose and D-allose with [PtMe(3)(Me(2)CO)(3)]BF(4) 1 in acetone affords complexes [PtMe(3)L]BF(4) 5 and 6 (5, L = alpha-D-mannofuranose; 6, L = beta-D-allofuranose). The coordination mode and conformation of the carbohydrate ligands in 5 and 6 in acetone-d(6) have been determined from an analysis of J(HH), J(CH), and J(CC) in complexes formed using site-specific (13)C-labeled D-mannose and D-allose. These coupling data are compared to those measured in (13)C-labeled complex [PtMe(3)L]BF(4) 2 (L = 1, 2-O-isopropylidene-alpha-D-glucofuranose) and 1, 2-O-isopropylidene-alpha-D-glucofuranose 3, whose solid-state structures are known, and in (13)C-labeled 1,2;5, 6-di-O-isopropylidene-alpha-D-glucofuranose 4. The preferred furanose ring conformations in 2 and 5 are very similar ((3)E/E(4) and E(4)/(o)E/E(1), respectively; eastern hemisphere of the pseudorotational itinerary), with platinum coordination involving O3, O5, and O6 of the saccharide. In contrast, the furanose ring of 6 prefers an (4)E/E(o)/(1)E geometry (western hemisphere of the pseudorotational itinerary) resulting from altered complexation involving O1, O5, and O6. Couplings within the exocyclic fragments of 2, 5, and 6 also support the existence of two different platinum coordination modes. In addition to establishing the structures and conformations of 2, 5, and 6 in solution, one-, two-, and three-bond J(CH) and J(CC) observed in these complexes provide new insights into the effect of structure and conformation on the magnitudes of these couplings in saccharides. Weak platinum(IV) complexation with the carbohydrate conformationally restricts the furanose and exocyclic fragment without introducing undesirable structural strain, thereby allowing more reliable correlations between structure and coupling magnitude.     

DFT calculation of 1J(119Sn,13C) and 2J(119Sn,1H) coupling constants in di- and trimethyltin(IV) compounds

We have tested several computational protocols, at the nonrelativistic DFT level of theory, for the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) spin-spin coupling constants in di- and trimethyltin(IV) derivatives with various ligands. Quite a good agreement with experimental data has been found with several hybrid functionals and a double-zeta basis set for a set of molecules comprising tetra-, penta-, and hexa-coordinated tin(IV). Then, some of the protocols have been applied to the calculation of the 2J(119Sn, 1H) of the aquodimethyltin(IV) ion and dimethyltin(IV) complex with D-ribonic acid and to the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) of the dimethyltin(IV)-glycylglycine and glycylhistidine complexes in water solutions. Solvent effects have been considered in these cases by including explicit water molecules and/or the solvent reaction field, resulting in a good agreement with experimental data. The proposed protocols constitute a helpful tool for the structural determination of di- and triorganotin(IV) derivatives.     

Determination of 3J(31P31P) and 13C31P coupling constants in 1,6-diphosphatriptycene from carbon-13 n.m.r. lone pairs effects on 13C31P couplings

The ³¹P? ³¹P and ¹³C? ³¹P coupling constants in 1,6-diphosphatriptycene have been obtained from analysis of its proton decoupled ¹³C n.m.r. spectra. More accurate data, however, resulted from simultaneous analysis of the proton decoupled ¹³C spectra and ³¹P(¹³C) satellite spectra. The ¹³C? ³¹P couplings are strongly influenced by the proximity and orientation of the phosphorus lone pair electrons. The first ³¹P? ³¹P coupling in an aromatic diphosphine is reported.     

Study of conjugation effects by NMR spectroscopy. XXIV. Determination of the conformational composition of alkyl phenyl ethers with branched alkyl radicals from the13C-1H and13C-13C spin-spin coupling constants

Conclusions During analysis of the¹³C-¹-H and¹³C-¹³C spin-spin coupling constants of the phenyl group in alkyl phenyl ethers it was established that the steric inhibition of the conjugation due to increase in the branching of the alkyl group partial in nature and is strongest in 2-methyl-2-phenoxypropane, whereas further increase in the effective volume of the alkyl group leads to some decrease in the population of the orthogonal conformer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2463–2467, November, 1985.     

Determination of stability constants of outer sphere adducts between CCl4 and Cr(acac)3 by the13C NMR method

Conclusions The equilibrium constant for the formation of an outer sphere adduct between CCl₄ and Cr(acac)₃, which leads to the delocalization of a noticeable spin density from the paramagnetic center to CCl₄, was determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1918–1920, August, 1983.     

1H and 13C NMR spectra, structure and physicochemical features of phenyl acridine-9-carboxylates and 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulphonates--alkyl substituted in the phenyl fragment

The 1H and 13C NMR spectra of twelve phenyl acridine-9-carboxylates--alkyl-substituted in the phenyl fragment--and their 10-methyl-9-(phenoxycarbonyl)acridinium salts dissolved in CD3CN, CD3OD, CDCl3 and DMSO-d6 were recorded in order to examine the influence of the structure of these compounds and the properties of the solvents on chemical shifts and 1H-(1)H coupling constants. Experimental data were compared with 1H and 13C chemical shifts predicted at the GIAO/DFT level of theory for DFT(B3LYP)/6-31G** optimised geometries of molecules, as well as with values of 1H chemical shifts and 1H-(1)H coupling constants, estimated using ACD/HNMR database software to ensure that the assignment was correct. To investigate the relations between chemical shifts and selected structural or physicochemical characteristics of the target compounds, the values of several of these parameters were determined at the DFT or HF levels of theory. The HOMO and LUMO energies obtained at the HF level yielded the ionisation potentials and electron affinities of molecules. The DFT method provided atomic partial charges, dipole moments, LCAO coefficients of pz LUMO of selected C atoms, and angles reflecting characteristic structural features of the compounds. It was found that the experimentally determined 1H and 13C chemical shifts of certain atoms relate to the predicted dipole moments, the angles between the acridine and phenyl moieties, and the LCAO coefficients of the pz LUMO of the C atoms believed to participate in the initial step of the oxidation of the target compounds. The spectral and physicochemical characteristics of the target compounds were investigated in the context of their chemiluminogenic ability.     

13C and19F NMR study of α,β-difluorostyryl derivatives of transition metal carbonylates. A method of signal assignment based on the carbon—fluorine spin-spin coupling constants

The¹³C and¹⁹F NMR spectra ofZ- andE-isomers of β-X-substituted α,β-difluorostyrenes (X=F, Cl, CpFe(CO)₂, Re(CO)₅, Re₂(CO)₉Na) were studied. Direct and long-range (across 1–5 bonds) spin-spin coupling constants and the (¹³C−¹²C) isotope shifts in the¹⁹F NMR spectra were determined. The study of the¹³C satellites in the¹⁹F NMR spectra of substituted difluorostyrenes permitted assignment of the¹³C NMR signals of the vinylic carbon atoms. Similarly, the signals in¹⁹F NMR spectra were assigned based on coupling constants of fluorine withipso-carbon. These assignments were found to be in good agreement with the data available from the literature (X=F, Cl). The developed approach was applied to the elucidation of the structure ofZ−PhCF=CClFe(CO)₂Cp. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya. No. 8, pp. 1575–1579, August, 1998.     

CLOPPA-IPPP analysis of cooperative effects in hydrogen-bonded molecular complexes. Application to intermolecular 2hJ(N,C) spin-spin coupling constants in linear (CNH)n complexes

The cooperative effects on NMR indirect nuclear coupling constants are analyzed by means of the IPPP-CLOPPA approach (where CLOPPA is the Contributions from Localized Orbitals within the Polarization Propagator Approach and IPPP is the Inner Projections of the Polarization Propagator). The decomposition of the J coupling allows one to classify these effects as those due to changes in the geometric structure and those that directly involve the transmission mechanisms. This latter contribution admits a further classification, taking into account its electronic origin. As an example, the cooperative effects on intermolecular 2hJ(N,C) couplings of the linear complexes (CNH)n (n = 2, 3, 4) are discussed.     

Nitrogen-containing organosilicon compounds. 150. Synthesis and chromatographic and 1H, 13C, 15N,and 29Si NMR spectroscopic investigation of substituted (piperidinoalkyl)silanes

Substituted (piperidinoalkyl)silanes were synthesized and investigated by means of multinuclear NMR spectroscopy and GLC. The data obtained indicate an additional N-Si interaction in -aminomethylsilanes that depends substantially on the properties of the substituents attached to the silicon atom. The effect of the R¹R²R³Si substituent on the capacity of the nitrogen atom for intermolecular interactions is not restricted to steric effects but also has electronic character.See [1] for communication 149.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1644–1652, December, 1991.     

Structural studies on aryl‐substituted enaminoketones and their thio analogues. Part II. Experimental and DFT calculated carbon–carbon coupling constants,nJ(CC)'s (n = 1–3)

Spin–spin carbon–carbon coupling constants across one, two and three bonds, J(CC), have been measured for a series of aryl‐substituted Z‐s‐Z‐s‐E enaminoketones and their thio analogues. As a result, a large set, altogether 178, of J(CC)s has been obtained. It consists of 82 couplings across one bond, 31 couplings across two bonds and 65 couplings across three bonds. Independently, the DFT calculations at the B3PW91/6‐311++G(d,p)//B3PW91/6‐311++G(d,p) level yielded a set of theoretical J(CC) values. A comparison of these two sets of data gave an excellent linear correlation with parameters a and b close to ideal; a = 0.9978 which is not far from unity and b = 0.22 Hz which is close to zero. The ¹J(CC) couplings determined for the crucial fragment of the molecules, i.e. ? C?C? C?O (or ? C?C? C?S), are: ¹J(C?C) ≈ 68 Hz (67 Hz) and ¹J(C? C) = 60.5 Hz (60.0 Hz). The corresponding couplings found for the Z‐s‐Z‐s‐E isomer of the parent enaminoketone, 4‐methylamino‐but‐3‐en‐2‐one are 64.1 and 59.3 Hz, respectively. The most sensitive towards substitution of the oxygen atom by sulfur are two‐bond couplings between the α‐vinylic and aromatic C_ipso carbon atoms, which attain 12 Hz in the enaminoketone derivatives and decrease to 5 Hz in their thio analogues. Copyright © 2009 John Wiley & Sons, Ltd.     

The 13C,H coupling constants in structural and conformational analysis: II The correlation of 3J(HCCH) and 3J(CH3CCH) in ethylenes and their methyl derivatives

The vicinal ³J(C H₃C?CH ) coupling constants were determined for a number of propylene derivatives and compared with the ³J(H C?CH ) couplings of the corresponding ethylenes. A linear regression analysis yielded the correlation ³J(CH) = 0.46 ׳ J(HH)+1.58 Hz, the correlation coefficient being 0.956.     

The use of one-bond,heteronuclear coupling constants (1J —C,H) as structure reporters in 13 C-N.M.R. of oligosaccharides containing 3-deoxy-(=D)-manno-2-octulosonic acid

In proton-coupled, ¹³ C-n.m.r.-spectra of 3-deoxy-(=D)-$\text{manno}$-2-octulopyranosylono (KDO$\text{p}$-)derivatives, the ¹$\text{J}$-C-5,H-5 is significantly larger (148 Hz) than the respective coupling constants of the other carbon signals, and the chemical shift of the signal displaying this spacing indicates whether position 5 is glycosidated or unsubstituted.