摘要:

Abstract129Xe gas to solution shifts, which generally do not correlate well with solvent parameters, are shown to be linearly related to the13C gas to solution shifts of methane in the same solvents. Since the shifts are attributed exclusively to van der Waals effects, and129Xe is 27.1 times more sensitive to these effects than13C,129Xe is suggested as a reference for van der Waals shifts induced in different nuclei.

ISSN:0749-1581    

DOI:10.1002/mrc.1260291202

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe complete assignment of the proton and carbon spectra for two new 2‐pyridylquinoline ligands, 4‐phenyl‐2‐(2′‐pyridyl)quinoline (Ph‐pq) and 2,6‐di(4′‐phenylquinol‐2′‐yl)pyridine (Ph‐dqp), and their ruthenium(II) complexes [Ru(bpy)2(Ph‐pq)](PF6)2and [Ru(Ph‐dqp)2](PF6)2has been accomplished using a combination of one‐ and two‐dimensional NMR techniques, including COSY, NOESY, one‐bond and long‐range HETCOR and selective INEPT spectra. TheJ(H,H) andJ(C,H) values have been determ

ISSN:0749-1581    

DOI:10.1002/mrc.1260291203

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe magnetic moment of a micro‐sized solid sample can be semi‐quantitatively determined by proton magnetic resonance spectral measurement with the sample in a capillary cell coaxially placed within an NMR tube containing a suitable diamagnetic solvent with a standard such as TMS. Small signals appearing on the low‐frequency side of the main peaks can be assigned to the protons in the layer of the solution surrounding the outer surface of the coaxially placed capillary. The molar chemical shift difference of this signal splitting is proportional to the square of the magnetic moment (μ) orn(n+ 2), wherenis equal to the number of unpaired electrons in the

ISSN:0749-1581    

DOI:10.1002/mrc.1260291204

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

Abstract13C nuclear magnetic relaxation rates were measured as a function of temperature for methyl fluorene‐3‐carboxylate and used to describe the dynamics of this molecule. The easiest reorientation is about thexprincipal diffusion axis, which is situated close to that inertial principal axis corresponding to the smallest moment of inertia. The reorientation of this planar asymmetric rotor is found to be anisotropic about the in‐planexandyaxes, as expected from unequal moments of inertia. The reorientation about the out‐of‐plane axiszis faster at the lowest temperature measured and it becomes comparable to the in‐plane motion at the remaining temperatures, showing decreased frictional forces for rotation in the molecular plane. Total assignment of the1H and13C NMR spectra of the fluorene derivative was achieved by employing 1D and 2D NMR

ISSN:0749-1581    

DOI:10.1002/mrc.1260291205

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractYttrium(III) oxoisopropoxide, Y5O(OiPr)13, was synthesized via a new synthetic route and characterized by mass spectrometry and multinuclear magnetic resonance spectroscopic techniques. Extensive1H,13C and89Y NMR studies with full assignments are reported.

ISSN:0749-1581    

DOI:10.1002/mrc.1260291206

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe chemical structure of a plant growth substance, calonyctin A, was determined by NMR spectroscopy. The13C and1H spectral assignments were obtained using a combination of DEPT, heteronuclear chemical shift correlation,1H–1H COSY,1H–1H NOESY and inverse long‐range1H–13C correlation. Calonyctin A was found to be a mixture of two homologous glycosides, each containing four rhamnoses and two aglycones. The configuration of the rhamnoses and the structural linkage between the six molecular fragments are r

ISSN:0749-1581    

DOI:10.1002/mrc.1260291207

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractPotassium naphthalenide solutions in tetrahydrofuran were studied by means of39K NMR spectroscopy. The effect of temperature, concentration and potassium cation complexation on paramagnetic shift and relaxation behaviour was demonstrated and is discussed. An attempt was made to assess the contributions due to the various relaxation mechanisms operating at different temperatures in the systems studied.

ISSN:0749-1581    

DOI:10.1002/mrc.1260291208

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo‐dimensional H,C‐COSY spectra of some tetra‐, penta‐ and hexa‐coordinated organotin(IV) compounds were measured. The relative signs ofnJ(119Sn,13C) and (n+1J(119Sn,1H) coupling constants were determined after analysis of the orientation of the appropriate119/117Sn satellites in the H,C–COSY spectra. The relative signs in BunSn and BznSn (n= 2 or 3) derivatives are opposite, whereas in Ph3Sn derivatives these signs are the same for carbon atoms in theorthoandmetapositions and opposite for carbon atoms in theparapositions. The same sign was found for2J(119Sn,13C‐2)vs.2J(119SnC1H2) in tribenzyltin(IV) chloride from the C

ISSN:0749-1581    

DOI:10.1002/mrc.1260291209

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

Abstract13C13C spin–spin coupling constants have been measured for a series of variously substituted ethenes. The largest1J(CC) value, 172 Hz, was found in chlorotrifluoroethene and the smallest, 45.3 Hz, in tris(trimethylsilyl)ethene, which covers a range of 127 Hz for the1J(CC) values. An analysis of the data revealed a large discrepancy between the experimental1Jvalues and those estimated by the commonly used additive increment scheme. Good agreement was found, however, between the experimental values and those calculated by means of a multiplicative

ISSN:0749-1581    

DOI:10.1002/mrc.1260291210

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spin–lattice relaxation times,T1, and nuclear Overhauser effect data were obtained for neat tetra‐n‐octyltin at 22.5 and 100.6 MHz over a wide temperature range.T1values were also measured at 25.16 MHz at pressures up to 211 MPa. The ambient‐pressure data were fitted to the ‘model‐free’ two‐correlation time spectral density with a temperature‐dependent order parameter,S2. The pressure data were interpreted by assuming that internal motions of the octyl chain are independent of pressure while the overall (tumbling) motion andS2are pressure dependent. The values of the motional parameters for tetra‐n‐octyltin lie in the ranges expected for compounds containing longn‐alkyl chains. The results show that this approach is applicable to complex liquids such as synthetic lubrican

ISSN:0749-1581    

DOI:10.1002/mrc.1260291211

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY