129Xe NMR chemical shift in Xe@C60 calculated at experimental conditions: essential role of the relativity, dynamics, and explicit solvent.

The isotropic (129)Xe nuclear magnetic resonance (NMR) chemical shift (CS) in Xe@C60 dissolved in liquid benzene was calculated by piecewise approximation to faithfully simulate the experimental conditions and to evaluate the role of different physical factors influencing the (129)Xe NMR CS. The (129)Xe shielding constant was obtained by averaging the (129)Xe nuclear magnetic shieldings calculated for snapshots obtained from the molecular dynamics trajectory of the Xe@C60 system embedded in a periodic box of benzene molecules. Relativistic corrections were added at the Breit-Pauli perturbation theory (BPPT) level, included the solvent, and were dynamically averaged.

Exploring new 129Xe chemical shift ranges in HXeY compounds: hydrogen more relativistic than xenon.

Among rare gases, xenon features an unusually broad nuclear magnetic resonance (NMR) chemical shift range in its compounds and as a non-bonded Xe atom introduced into different environments. In this work we show that (129)Xe NMR chemical shifts in the recently prepared, matrix-isolated xenon compounds appear in new, so far unexplored (129)Xe chemical shift ranges. State-of-the-art theoretical predictions of NMR chemical shifts in compounds of general formula HXeY (Y = H, F, Cl, Br, I, -CN, -NC, -CCH, -CCCCH, -CCCN, -CCXeH, -OXeH, -OH, -SH) as well as in the recently prepared ClXeCN and ClXeNC species are reported.

Interpretation of substituent effects on 13C and 15N NMR chemical shifts in 6-substituted purines.

A range of purine derivatives modified at position 6 of the basic purine skeleton exhibit a variety of biological activities. Several derivatives are used or tested nowadays for pharmacological treatments. The present work aims to analyze the effects of substituents on the electron distribution in the purine core as reflected by NMR chemical shifts.

Understanding the NMR chemical shifts for 6-halopurines: role of structure, solvent and relativistic effects.

A prototypical study of NMR chemical shifts in biologically relevant heteroaromatic compounds containing a heavy halogen atom is presented for two isomers of halogen-substituted purines. Complete sets of (1)H-, (13)C- and (15)N-NMR chemical shifts are determined experimentally in solution. Experimental results are complemented by quantum-chemical calculations that provide understanding of the trends in the chemical shifts for the studied compounds and which show how different physical effects influence the NMR parameters.

Covalent bonding of azoles to quaternary protoberberine alkaloids.

Adducts of the quaternary protoberberine alkaloids (QPA) berberine, palmatine, and coptisine were prepared with nucleophiles derived from pyrrole, pyrazole, imidazole, and 1,2,4-triazole. The products, 8-substituted 7,8-dihydroprotoberberines, were identified by mass spectrometry and 1D and 2D NMR spectroscopy, including (1)H--(15)N shift correlations at natural abundance. In addition, two adducts of QPA with chloroform and methanethiolate were characterized by using NMR data.