 ISSN 0235-7216 ISSN 2424-4538 (online) |
2009 m. Nr. 2 Spectrophotometric investigation of the formation of Cu(II)–maleic acid complexes
Spectrophotometric investigations of Cu(II) and maleic acid solutions containing 0.3 M K2SO4 as a supporting electrolyte were carried out over the pH range from 2 to 6. Addition of maleic acid (LH2) into Cu(II) solutions results in a significant rise of the absorption maximum and its shift from 806 to 722 nm. Similar effects were also observed when the pH of the solutions was increased at a constant ligand concentration. Experimental absorption spectra can be described quantitatively on the assumption that two species, viz. Cu2+ and CuL, are responsible for absorption in the region of visible light. Then, a modified Lorentz distribution, which follows from the description of a driven harmonic oscillator, is applicable to each partial spectrum. The stability constant (β1) of CuL species, expressed in terms of concentration, was determined. Using the recently obtained cumulative stability constants of protonated ligands LH– and LH2 (105.75 and 107.3, respectively), we found that log β1 = 2.2 ± 0.07. Keywords: copper, maleic acid, stability constants, spectrophotometry |
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