Pyridine-2,6-dicarboxylate , transition

Pyridine, methyltrioxorhenium hgands, 460-1 Pyridine-2,6-dicarboxylate (dipic), transition metal peroxides, 1060, 1061 Pyridinium dichromate, alcohol oxidation, 787-8... 

For the determination of lanthanides in geological samples, a problem arises regarding the co-elution with excess amounts of heavy and transition metals. For an improved separation between both classes of compounds, one capitalizes on the different com-plexing behavior of heavy metals and rare-earth elements with pyridine-2,6-dicarboxylic acid. Heavy and transition metals form stable monovalent and divalent complexes with PDCA, while the complexes of lanthanides with PDCA are trivalent ... 

Hydrogen bonding between carboxylic acid and pyridine has been widely applied for the formation of a variety of mesogenic structures [43-54]. Components of dicarboxylic acid have been used for the complexation [43-45]. A twin mesogenic structure shows an odd-even effect on transition... 

To illustrate the tuning aspects of the MLCT transitions in ruthenium polypyridyl complexes, the well known [RuLs] (L = 4,4 dicarboxylic acid-2,2 -bi-pyridine) type of complex can be considered. This complex shows strong visible band at 466 nm, because of CT transition from metal t2g highest occupied molecular orbitals (HOMO) to jr -lowest unoccupied molecular orbitals (LUMO) of the ligand (Fig. 3). The Ru(II)/(III) oxidation potential is at 1.3 V, and the ligand based reduction potential is at —1.5V... 

Chromium(ii) reductions of Co(NH3)g complexes of various dicarboxylic acid derivatives of pyridine have been studied in order to determine the effect of placing the cobalt centre at different positions relative to the ring nitrogen. It is found that in general complexes with cobalt attached to carboxyl in the 2-position react 10—10 times faster than those with cobalt attached at a more remote position. This is attributed to chelation in the transition state. 

Figure 4.66 illustrates the separation of eight different transition metals with pyridine-2,6-dicarboxylic acid as a complexing agent. In comparison to the corresponding separation on lonPac CSS, the resolution between metal ions was... 

Other common transition metal corrosion products typically monitored at various sites within the plant include iron, copper, nickel, zinc, and chromium. More than 80% of BWR plants analyze for iron, nickel, copper, and zinc in reactor water, and nearly all of the BWR plants determine these metals in feed water. In addition, zinc is also an additive used in many plants to control the shutdown radiation dose rate. Nickel and chromium are corrosion products in BWR plants fi-om stainless-steel piping. The best selectivity and sensitivity for achieving low to submicrogram/Liter detection limits for transition metals can be obtained by separating transition metal complexes using pyridine-2, 6-dicarboxylic acid (PDCA) or oxalic acid as chelators in the eluent, followed by postcolumn derivatization with 4-(2-pyridylazo)resorcinol (PAR) and absorbance detection at 520 nm (see Section 8.2.1.2). This approach was successfully used to determine trace concentrations of iron, copper, nickel, and zinc in BWR and PWR matrices [197]. Figure 10.113 compares the chromatograms from the... 

Figure 10.355 Analysis of transition metals in 50% sodium hydroxide. Separator column lonPac CS5A eluent 6 mmol/L pyridine-2,6-dicarboxylic acid -i- lOmmol/L NaOH -1-40 mmol/L NaOAc-l-50mmol/L HOAc flow rate 1 mL/min detection photometry at 520nm...

Fig. 4-53. Simultaneous analysis of nine different transition metals. — Separator column lonPac CSS eluant 4 mmol/L pyridine-2,6-dicarboxylic acid +...

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