Extraordinary acceleration of phosphodiester hydrolyses by thorium cations

Moss, Robert A.; Zhang, Jing; Bracken, Kathryn

doi:10.1039/a703568c

Cited by 30 publications

(31 citation statements)

References 17 publications

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“…Assuming an average dissociation constant of K d $ 0.5 mm for the complexation of the phosphates in a dinuclear complex, [48] an apparent k cat for the reactivity of the supramolecular zirconium-phosphate complex can be estimated and compared with the background reaction. [49] The rate accelerations determined this way are in the range of 9 Â 10 6 to 3.1 Â 10 9 , and are comparable to those observed for Th IV salts [51] and for dinuclear Co III complexes. [2e] The production of 16 from 2 cannot be compared with a background reaction since this reaction did not take place without 4, neither under basic or acidic, nor under thermal conditions.…”

Section: Resultssupporting

confidence: 53%

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

Stulz¹,

Bürgi²,

Leumann³

2000

Chem. Eur. J.

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The Zr IV -tetraphenylporphyrinates Zr(TPP)(X,X'), (X,X' À OAc, À OMe, Cl À ) 4 ± 6, 8 were prepared and their complexing properties as well as catalytic properties towards solvolysis of the phosphate diesters hpp (2), dmp (3) and pmp (16) characterised. The diesters 2 and 16, representing model phosphates for RNA and DNA, were substrates for the catalyst Zr(TPP)Cl 2 (4), and rate accelerations over background by 6 ± 9 orders of magnitude were measured. These accelerations are comparable to those of dinuclear transition metal catalysts and lanthanide ions. Catalytic turnover was observed. Kinetic studies revealed that the catalytically active species of 4 in the solvolysis of 2 and 16 in methanolcontaining solvents are dinuclear complexes containing either one or two phosphate esters depending upon the phosphate concentration. Besides the usual solvolysis pathway of the RNA model hpp (2), which proceeds via the cyclophosphate 20, a second, unusual pathway via direct substitution of the hydroxypropyl substituent was found. X-ray analysis of the Zr(TPP)(dmp) complex 19 revealed a dinuclear structure with two bridging dmp ligands and one monomethyl phosphate unit. In 19 one of the two dmp residues occurs in a very unusual high energy ac,ap conformation. Based on this structure and on the kinetic data, mechanistic models for the two solvolysis reaction pathways were developed. From an extensive CSD search on phosphodiester structures no correlation between P À O ester bond lengths and diester conformations could be found. However, PÀO ester bonds decrease in length with increasing formal charge of the complexing metal ions. This underlines the higher importance of electrostatic activation relative to stereoelectronic effects in phosphodiester hydrolysis.

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Section: Resultssupporting

confidence: 53%

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

Stulz¹,

Bürgi²,

Leumann³

2000

Chem. Eur. J.

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“…[49] The rate accelerations determined this way are in the range of 9 Â 10 6 to 3.1 Â 10 9 , and are comparable to those observed for Th IV salts [51] and for dinuclear Co III complexes.…”

supporting

confidence: 65%

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

Stulz

Bürgi

Leumann³

2000

Chem. Eur. J.

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The Zr(IV)-tetraphenylpor-phyrinates Zr(TPP)(X,X'), (X,X' = -OAc, -OMe, Cl ) 4-6, 8 were prepared and their complexing properties as well as catalytic properties towards solvolysis of the phosphate diesters hpp (2), dmp (3) and pmp (16) characterised. The diesters 2 and 16, representing model phosphates for RNA and DNA, were substrates for the catalyst Zr(TPP)Cl2 (4), and rate accelerations over background by 6-9 orders of magnitude were measured. These accelerations are comparable to those of dinuclear transition metal catalysts and lanthanide ions. Catalytic turnover was observed. Kinetic studies revealed that the catalytically active species of 4 in the solvolysis of 2 and 16 in methanol-containing solvents are dinuclear complexes containing either one or two phosphate esters depending upon the phosphate concentration. Besides the usual solvolysis pathway of the RNA model hpp (2), which proceeds via the cyclophosphate 20, a second, unusual pathway via direct substitution of the hydroxypropyl substituent was found. X-ray analysis of the Zr(TPP)(dmp) complex 19 revealed a dinuclear structure with two bridging dmp ligands and one monomethyl phosphate unit. In 19 one of the two dmp residues occurs in a very unusual high energy ac,ap conformation. Based on this structure and on the kinetic data, mechanistic models for the two solvolysis reaction pathways were developed. From an extensive CSD search on phosphodiester structures no correlation between P-O ester bond lengths and diester conformations could be found. However, P-O ester bonds decrease in length with increasing formal charge of the complexing metal ions. This underlines the higher importance of electrostatic activation relative to stereoelectronic effects in phosphodiester hydrolysis.

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“…4 Among the metal ions studies, the lanthanide ions have attracted great attention owing their excellent catalytic effects in hydrolysis and nucleophilic substitution reactions at phosphoric esters. [5][6][7][8] Lanthanides can either act as free ions or associate with nucleophilic species, resulting in large incremental increases in reaction rate. 9,10 The total charge of the metal ion and its ability to polarize P-O bonds are important factors in the study of the mechanisms of reactions promoted by metals.…”

Section: Introductionmentioning

confidence: 99%

Bis(2,4‐dinitrophenyl) phosphate hydrolysis mediated by lanthanide ions

Longhinotti

Domingos

Silva

et al. 2004

J of Physical Organic Chem

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The kinetics of the hydrolysis of bis(2,4-dinitrophenyl) phosphate (BDNPP) were studied in basic solutions in the presence of La 3þ , Sm 3þ , Tb 3þ and Er 3þ . Bis-Tris propane (BTP) buffer was used to stabilize the Ln 3þ hydroxide complexes in solution. Two equivalents of the 2,4-dinitrophenolate ion (DNP) were liberated for each equivalent of BDNPP and the reaction showed first-order kinetics. Potentiometric titrations showed the formation of dinuclear complexes such as [Ln 2 (BTP) 2 (OH) n ] (6 À n) , with values of n varying as a function of pH, for all studied metals. Hence the catalytic effect depends on the formation of dinuclear lanthanide ion complexes with several hydroxo ligands.

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Extraordinary acceleration of phosphodiester hydrolyses by thorium cations

Abstract: Th IV cations in aqueous Brij micelles strongly promote the hydrolyses of several phosphodiester substrates; in the case of bis(p-nitrophenyl)phosphate 1, the observed rate constant (0.028 s 21 ) represents an acceleration of ca 2.8 billion.

Cited by 30 publications

References 17 publications

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

ZrIV-tetraphenylporphyrinates as Nuclease Mimics: Structural, Kinetic and Mechanistic Studies on Phosphate Diester Transesterification

Bis(2,4‐dinitrophenyl) phosphate hydrolysis mediated by lanthanide ions

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