Solution Speciation of the Dinuclear ZrIV‐Substituted Keggin Polyoxometalate [{α‐PW11O39Zr(μ‐OH)(H2O)}2]8– and Its Reactivity towards DNA‐Model Phosphodiester Hydrolysis. Issue 31 (29th September 2014)

• Record Type: Journal Article
• Authors: Luong, Thi Kim Nga; Absillis, Gregory; Shestakova, Pavletta; Parac‐Vogt, Tatjana N.
• Is Part Of: European journal of inorganic chemistry. Issue 31(2014)
• Page Start: 5276
• Page End: 5284
• Publication Date: 2014-09-29
• Subjects: Polyoxometalates -- Zirconium -- Hydrolysis -- Kinetics -- NMR spectroscopy; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201402735
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: The solution speciation of the Zr IV ‐substituted Keggin polyoxometalate (Et2 NH2 )8 [{α‐PW11 O39 Zr(μ‐OH)(H2 O)}2 ]· 7H2 O (ZrK 2:2) was fully determined under different pD, temperature, and concentration conditions. Subsequently, phosphodiester bond hydrolysis of the DNA model substrate bis(4‐nitrophenyl) phosphate (BNPP) promoted by ZrK 2:2 was studied in detail. In the presence of ZrK 2:2, phosphoester bond hydrolysis in BNPP proceeded with a rate constant of k obs = (4.75 ± 0.25) × 10 –6 s –1 at pD 6.4 and 60 °C, which represented a 320‐fold rate enhancement relative to the spontaneous hydrolysis of BNPP. The pD dependence of k obs exhibits a bell‐shaped profile, with the fastest rate observed at pD 6.4. An activation energy ( E a ) of 60.16 kJ mol –1, enthalpy of activation (Δ H # ) of 57.44 kJ mol –1, entropy of activation (Δ S # ) of –173.16 J mol –1 K –1, and Gibbs activation energy (Δ G # ) of 111.12 kJ mol –1 at 37 °C were calculated. The influence of the concentration of ZrK 2:2 on the reaction rate constant was studied in the concentration range 0.5 to 6.0 mM . The results showed that ZrK 2:2 is able to hydrolyze an excess amount of BNPP, thus demonstrating that ZrK 2:2 acts as a catalyst for phospho(di)ester bond hydrolysis. In addition, the influence of ionic strength and the inhibitor diphenyl phosphate on BNPP hydrolysis were examined. Abstract : A detailed 31 P NMR spectroscopic aqueous solution study on the Zr IV ‐substituted Keggin‐type polyoxometalate (Et2 NH2 )8 [{α‐PW11 O39 Zr(μ‐OH)(H2 O)}2 ]· 7H2 O (ZrK 2:2) describes the influence of pD, temperature, reaction time, ionic strength, and ZrK 2:2 or substrate concentration, which allowed for a full characterization of the speciation equilibria.