Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have evolved as the most common techniques in metabolomics studies, and each brings its own advantages and limitations. Unlike MS spectrometry, NMR spectroscopy is quantitative and does not require extra steps for sample preparation, such as separation or derivatization. Although the sensitivity of NMR spectroscopy has increased enormously and improvements continue to emerge steadily, this remains a weak point for NMR compared with MS. MS-based metabolomics provides an excellent approach that can offer a combined sensitivity and selectivity platform for metabolomics research. Moreover, different MS approaches such as different ionization techniques and mass analyzer technology can be used in order to increase the number of metabolites that can be detected. In this chapter, the advantages, limitations, strengths, and weaknesses of NMR and MS as tools applicable to metabolomics research are highlighted.

The strengths and weaknesses of NMR spectroscopy and mass spectrometry with particular focus on metabolomics research.

Anion recognition based on halogen, chalcogen, pnictogen and tetrel bonding

https://iopscience.iop.org/article/10.1070/RCR4795/pdf

Organofluorine chemistry: promising growth areas and challenges

This review discusses the various aspects of the bio-geochemistry of germanium, and of its technological, economical and environmental importance. Despite the relatively low annual production and consumption of this semi-metal (ca. 80 metric tons/a) there are important technological applications of this element in the semiconductor, infrared optics and fibre optics/telecommunication industries. A small, but not insignificant fraction of this element is used for the production of pharmaceuticals and nutritional supplements, although its actual merits have not been fully demonstrated yet, while they are opposed to chronic toxicity of the element when being administrated at relatively high doses for an extended period of time. Neither the exact mechanism of action in the case of cancer treatment or the treatment of infectious diseases is known, nor the reason for the toxicity of inorganic species of this element. In plants, Ge can partially substitute for B in the case of boron deficiency, although deficiency symptoms are still seen with a lag period of ca. one to three weeks. In biogeochemical respect, germanium and silicon react very similar, as if Ge were a very heavy isotope of Si. Their molar ratio is typically in the order of 0.6 × 10−6, with significant deviations only where germanium is complexed and transported, e.g., by humic-rich waters. Germanium is a very conservative element in biogeochemical terms: It hardly shows involvement in any biogeochemical reaction cycles and is mainly present in the form of complexes or hydroxo-compounds of the tetravalent germanium. The only naturally occurring organogermanium compounds are mono- and dimethylgermanium which are believed to be formed by microbiological activity in continental zones containing Ge-rich minerals, and then are leached into rivers, and finally into the open sea. It becomes evident that, although very sophisticated technological uses of germanium exist, a better understanding of its biogeochemical importance, cycling and reactivity must still be developed.

Germanium: environmental occurrence, importance and speciation

This review is devoted to the scientific achievements of the departments of organic chemistry in higher schools of Russia within the past decade.

Modern Trends of Organic Chemistry in Russian Universities

Published data on stereodynamic processes in the coordination units of di- and tetravalent silicon, germanium, tin and lead compounds are summarized and analyzed.

Stereochemical non-rigidity of complexes of hypercoordinate Group 14 elements

1
Introduction and Outline

2
Self-Associates

3
Pentacoordinate Anionic Compounds

4
Pentacoordinate Intermolecular Neutral Compounds

5
Pentacoordinate Intramolecular Neutral Germanium Compounds

6
Pentacoordinate Intramolecular Neutral Tin and Lead Compounds

7
Pentacoordinate Cationic Compounds

8
Hexacoordinate Anionic Compounds

9
Hexacoordinate Neutral Compounds

10
Hexacoordinate Cationic Tin Compounds

11
Acknowledgments



Keywords:

pentacoordinate anionic compounds;
hypervalent germanium reactivity;
stoichiometry of complexes and nature of organometallic halides;
pentacoordinate intermolecular neutral compounds;
pentacoordinate intramolecular germanium complexes;
hypervalent compounds of organic germanium, tin and lead;
AMPAC and HyperChem software;
Quantum-chemical calculations of trichloroorganogermanes

Hypervalent Compounds of Organic Germanium, Tin and Lead Derivatives

Stereochemical Flexibility of Bis(amidomethyl)dichlorogermanes. A Novel Dissociative Mechanism of Ligand Exchange in Neutral Hexacoordinated Bischelate Complexes

The signals in the13C NMR spectra of 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes (R1=R2=H, Me,cyclo-C3H5, SiMe3, SnMe3, R1=Me, R2=H, Cl) were completely assigned using 2D NMR spectroscopy. The pattern of the variation of the chemical shifts in the13C NMR spectra indicates that the effects of substituents R1 and R2 on the heterocycle and on the phenyl groups are of inductive rather than mesomeric origin and include the direct through-space polarization of bonds (field effect).

S. N. Tandura

Papers

Stereochemical non-rigidity of complexes of hypercoordinate Group 14 elements

Hypervalent Compounds of Organic Germanium, Tin and Lead Derivatives

Stereochemical Flexibility of Bis(amidomethyl)dichlorogermanes. A Novel Dissociative Mechanism of Ligand Exchange in Neutral Hexacoordinated Bischelate Complexes

Hypervalent Compounds of Organic Germanium, Tin and Lead Derivatives

Electron density distributions in substituted 2,3,4,5-tetraphenyl- 1-germacyclopenta-2,4-dienes studied by NMR spectroscopy