Hi All,
I have three solutions, which contain Pd extracted by using different extraction media, i.e., (1) HCl-H2O2, (2) HCl, and (3) Aqua regia. The UV Vis spectra of each solution show peaks at different wavelengths. Clearly speaking, Pd extracted with HCl-H2O2 shows peaks at 277 and 231 nm, while Pd extracted with HCl shows three peaks at 211 nm, 231 nm and 277 nm. Similarly, for aqua regia extracted sample, 218 nm, 231 nm and 277 nm. What could be the reason for the appearance of an additional peak in the case of HCl and aqua regia extracted samples?
Thanks in advance.
ANSARI
I think, there were many factors like as; the acidity of the media, Temperature dependence, ligand-to-metal charge transfer, and concentrations ...etc.
There may be several reasons for the appearance of spectra with different maxima in solutions of palladium salts and complexes. Firstly, this metal has up to six oxidation states, although the main one is 2+, and this may be one reason. Second, it forms complex compounds with many anions, and neutral molecules in which a charge transfer from an ion to metal occurs, and the degree of transfer is different - and this may be the second reason. The third reason may be the tendency towards isomerism of palladium complexes, and the content of isomers depends on the medium. Fourth, although this also applies to complex compounds, it forms solvates with molecules of electron-donor solvents, in which the degree of charge transfer is also different, and it can also occur to solvent molecules. All this gives rise to a wide variety of colors of its salts and their solutions. It needs to find special literature data for explaining every case.
Dear Ansari,
Concerning extraction: Which material has been extracted and how exactly? Maybe you extracted something, differing in its absorption from Pd as a complex.
Concerning UV-Vis: The coordination of your central atom Pd is crucial for the as-mentioned LMCT. If you know the coordination, you can assume/look up the difference in absorption wavelength.
Hope this helps
Best regards
Lucas Warmuth
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