Continuing studies based on measurements of the nuclear spin relaxation rates running via the SC2 mechanism (scalar relaxation of the second kind), we present in this work the results obtained for three bromo compounds: CBrCl3, (CH3)3CBr, and CBr4. A careful separation of saturation-recovery curves, measured for signals of (13)C nuclei at 7.05 and 11.7 T on two components, has provided the longitudinal SC2 relaxation rates of carbon signals in (79)Br and (81)Br containing isotopomers of the investigated compounds. These data have enabled experimental determination of spin-spin coupling constants and relaxation rates of quadrupole bromine nuclei, both types of parameters being hardly accessible by direct measurements. Investigation of the relaxation behavior of these molecules, being of similar size and shape, has provided quite different practical and interpretational problems which are likely to be encountered in relaxation studies of many other carbon-bromine systems. In order to evaluate the quality of the obtained experimental results, advanced theoretical calculations of the indirect (1)J((13)C,(79)Br) coupling constants, magnetic shielding of carbon nuclei, and quadrupole coupling constants of bromines in the investigated compounds have been performed and compared with the experimental values. Relatively small divergences between experiment and theory have been found. The contributions of the relativistic effects to the values of the discussed parameters have been tentatively estimated.

Magnetic shielding and indirect spin-spin coupling phenomena are tensorial properties and both their isotropic and anisotropic parts do affect NMR spectra. The involved interaction tensors, σ and J, can nowadays be theoretically calculated, although the reliability of such methods in the case of anisotropic parameters, Δσ and ΔJ, in systems involving heavy nuclei, yet demands testing. In this communication the results of the experimental and theoretical investigations of bis(phenylethynyl)mercury (I) labeled with (13)C isotope at positions neighboring Hg are reported. The theoretical calculations of molecular geometry and values of NMR parameters for I have been performed by the ZORA/DFT method, including the relativistic scalar and spin-orbit coupling contributions, using the PBE0 functional and TZP (or jcpl) basis set. These values have been confronted with the experimentally measured ones. The isotropic parameters have been measured by the standard (13)C and (199)Hg NMR spectra. The shielding anisotropies for the atoms in the central part of molecule I have been determined in a liquid sample using magnetic relaxation measurements. The relaxation data have been interpreted within the rotational diffusion theory, assuming the symmetrical top reorientation model. The anisotropies of one-bond (13)C-(199)Hg and two-bond (13)C-Hg-(13)C spin-spin couplings have been determined exploiting the temperature-dependent (13)C NMR spectra of I in the ZLI1167 liquid-crystal phase. We have found that our theoretical calculations reproduce experimental values of both isotropic and anisotropic NMR parameters very well.

The enolization degrees of succinylacetone, an important heme biosynthesis inhibitor, have been determined in CDCl(3) and water solutions using (1)H NMR. The solution structures of SA have been investigated using a combined NMR/theoretical [GIAO DFT PBE1PBE/6-311++G(2d, p) PCM] approach. The populations of both enolic forms undergoing enol-enol equilibriums for SA and a series of unsymmetrical beta-diketones have been established by a quantitative comparison of the experimental (13)C NMR chemical shifts and calculated shielding constants. Moreover, using the same method and considering various trial structures differing in conformation and/or hydration of neutral SA molecule as well as its monoanion and dianion the structures of the most abundant species being present in the investigated water solutions have been deduced.

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High-resolution (1)H NMR spectroscopy of body fluids has proved to be very useful in diagnostics of inherited metabolic diseases, whereas (13)C NMR remains almost unexploited. In this paper the application of (13)C NMR spectroscopy of fivefold concentrated urine samples for diagnosis of selected metabolic diseases is reported. Various marker metabolites were identified in test urine samples from 33 patients suffering from 10 different diseases, providing information which could be crucial for their diagnoses. Spectra were accumulated for 2 h or overnight when using spectrometers operating at 9.4 or 4.7 T magnetic fields, respectively. Interpretation of the measurement results was based on a comparison of the peak positions in the measured spectrum with reference data. The paper contains a table with (13)C NMR chemical shifts of 73 standard compounds. The method can be applied individually or as an auxiliary technique to (1)H NMR or any other analytical method.