Reference compounds, diamagnetic

The ligand dependence of the downfield shift as compared with diamagnetic reference compounds follows the order ... 

Fig. 31. Background corrected neutron inelastic scattering spectrum of CePdj and its diamagnetic reference compound YPdj at 7 =145K. The hatched area is due to the nuclear incoherent elastic scattering. (From Holland-Moritz et al. 1982.)...

Another interesting point is to be presented in relation to chemical shift evaluations. From the directly-measured spin-rotation constant of POF3, diamagnetic and paramagnetic contributions to phosphorus chemical shifts were estimated (ca. +1000 and —640 p.p.m.). Extended to H3P04, which is the commonly accepted reference compound, this gives about 320 p.p.m. for the absolute 31P chemical shift.a999,9)... 

First it should be pointed out that the agreement between R. Ditch-field s theoretical results (private communication and ref. 25, 26) and the experimental results has been extremely good for the isotropic chemical shift.27 Normally, both the experimental and theoretical shifts are taken with respect to a reference compound, such as CH4, and the relative shifts compared. It is also possible-through the use of experimental spin-rotation constants or anisotropies in conjunction with accurate theoretical diamagnetic quantities—to place the experimental quantities on an absolute scale (B. R. Appleman, C. W. Kern, T. Toku-hiro, and G. Fraenkel, unpublished data, and ref. 20) and compare them directly with the theoretical quantities. 

The temperature dependence of the unsubstituted ring proton resonances are linear functions of T 1 and the slopes of shift vs. T-- - are identical within experimental error to that of uranocene (fig. 7, Table V). The slight difference in intercepts at T-1=0 undoubtedly result from using the proton resonance of cycloocta-tetraene dianion as a diamagnetic reference for all the compounds. 

In solutions, nuclear magnetic resonance is of use from the H paramagnetic shift (AAv) of a reference compound, corrected for the diamagnetic contribution of the ligands, the paramagnetic susceptibility is evaluable using the Evans method [10]... 

It is less obvious in these charts why the alkenes, alkynes, aldehydes and ketones, and aromatic compounds show up where they do. Although the isotropic diamagnetic term is usually the major contributor to the overall shielding ctq of the nucleus, the reference compound shares much of that same contribution, which is subtracted out when we calculate 8. Therefore, other terms may be more significant when it comes to the chemical shift, which is a smaller number than (Tq. 

Monomer-oligomer equilibria. [Ni(Me-sal)2], mentioned above as a typical planar complex, is a much studied compound. In pyridine it is converted to the octahedral bispyridine adduct (/zsoo = 3.1 BM), while in chloroform or benzene the value of is intermediate but increases with concentration. This is ascribed to an equilibrium between the diamagnetic monomer and a paramagnetic dimer, which must involve a coordination number of the nickel of at least 5 a similar explanation is acceptable also for the paramagnetism of the solid when heated above 180°C. The trimerization of Ni(acac)2 to attain octahedral coordination has already been referred to but it may also be noted that it is reported to be monomeric and planar in dilute chloroform solutions. 

With respect to the physical properties mentioned, band-structure calculations have attracted considerable interest, e.g., for SbSBr, SbSI, and SbSel (234). For the compounds having reference 22i in column 4 of Table XXIX, a temperature-independent diamagnetism has been found, with values of about 10 cm" g between 77 and 340 K. A small temperature-dependence is exhibited by BiTel, a narrow-gap semiconductor (41). The anisotropy of the magnetic susceptibility has been studied for SbSI, BiSel, and BiTel (41, 420). 

Dalton s law Dalton s law states that in a mixture of gases (A + B + C. . . ) the total pressure is simply the sum of the partial pressures (the pressures associated with each individual gas), decomposition reactions Decomposition reactions are reactions in which a compound breaks down into two or more simpler substances, diamagnetism Diamagnetism is the repulsion of a molecule from a magnetic field due to the presence of all electrons in pairs, dilute Dilute is a qualitative term that refers to a solution that has a relatively small amount of solute in comparison to the amount of solvent, dimensional analysis Dimensional analysis, sometimes called the factor label method, is a method for generating a correct setup for a mathematical problem. 

The motion of the protons in the proximity of Gd-based CAs contributes to the relaxivity, which is defined as the relaxation rate at a 1 mM concentration. Paramagnetic compounds, such as Gd complexes, increase the 1/Ti and I/T2 of solvent nuclei. The observed relaxivity (l/TlOobs is composed of the diamagnetic relaxation (1/U)d and the paramagnetic relaxation (l/TOp, which refer to the solvent relaxation in the absence and presence of paramagnetic compounds, respectively, as shown in Equation 10.1. 

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