Acid-base and UV behavior of 3-(3,4-dihydroxyphenyl)-propenoic acid (caffeic acid) and complexing ability towards different divalent metal cations in aqueous solution

作者：De Stefano Concetta; Foti Claudia; Giuffre Ottavia^*; Sammartano Silvio

来源：Journal of Molecular Liquids, 2014, 195: 9-16.

DOI：10.1016/j.molliq.2014.01.027

• Caffeic acid
• Zn2+ Cu2+, Cd2+, (CH3)(2)Sn2+ complexes
• Spectrophotometry
• Potentiometry
• Acid-base properties
• UV properties

The acid-base and the UV behavior of 3-(3,4-dihydroxyphenyl)-propenoic acid (caffeic acid) was studied by potentiometry and UV spectrophotometry at T = 298.15 K and 0.1 %26lt;= I/mol L-1 in NaCl aqueous solution. The complex formation with Zn2+, Cu2+, Cd2+, (CH3)(2)Sn2+ at I = 0.1 mol L-1 in NaCl has been also determined by using potentiometric and spectrophotometric titration techniques. The results obtained by the spectrophotometric measurements fully confirm those obtained by potentiometry, with a particularly good agreement for the system containing Cu2+. The results showed that, for the ML species, at I = 0.1 mol L-1 in NaCl and T = 298.15 K, the stability of the caffeate-(CH3)(2)Sn2+, and -Cu2+ species is high, with log beta(ML) = 16.577 and 13.05, respectively, while that of the caffeate-Zn2+ and -Cd2+ species is considerably lower, with log beta(ML) = 8.526 and 7272, respectively. Speciation profiles for all the systems under study were also calculated and sequestering ability of the caffeate towards the different metal cations considered in this investigation was also evaluated. For example, at physiological pH, I = 0.1 mol L-1 in NaCl and T = 298.15 K, the order of sequestering ability is Cu2+ %26gt; (CH3)(2)Sn2+ %26gt; Zn2+ %26gt; Cd2+.

• 出版日期2014-7