Transition metal compounds

Many transition metal ions are bearing unpaired electrons. They can be observed by the MS5000 ESR spectrometer down to nanomolar concentrations. The exact spin states („high-spin“ or „low spin“) of compounds with different ligands can be distinguished easily for one and the same central ion. This is especially useful for protein characterization in bioinorganic chemistry.

Detection of copper compounds with ESR spectrometer MS5000

ESR spectrometry provides key information to compare coordination geometries of active metal centres in enzymes and their model complexes of low molecular weight. An example is shown on the right, displaying the ESR-spectra of the active Cu2+ centre of Cu(II)2Zn2 superoxide dismutase and Cu(II)PuPy, a superoxide dismutase mimic. Most of the enzymes and model complexes examined in bioinorganic research are copper and iron bearing compounds.

Vanadium

Vanadium is a common encounter in petrochemistry & catalytic applications. ESR can detect the VO2+ and V2+ ions sensitively, making vanadium a useful indicator for crude oil quality control & research in hetero-catalysis. Even though vanadium is 470 times more rare than iron.

Manganese

Manganese is essential for all life forms since it participates in enzyme formation and redox reactions. It is also abundant on the earth where it occurs as an impurity, for instance in ZnS (see below).

Useful Add-ons

The signal-to-noise ration of transition metals can be improved by low-temperature measurements. Usage of liquid nitrogen or helium for MS5000 allows to record spectra in frozen solutions. A 1:1 mixture of ethylene glycol and water for instance provides information about the coordination geometry. The hyperfine splitting of these anisotropic signals reveal if the coordination is tetragonal planar or tetrahedrally distorted.