Subat, Michael and Woinaroschy, Kristina and Gerstl, Corinna and Sarkar, Biprajit and Kairn, Wolfgang and Koenig, Burkhard (2008) 1,4,7,10-tetraazacyclododecane metal complexes as potent promoters of phosphodiester hydrolysis under physiological conditions. INORGANIC CHEMISTRY, 47 (11). pp. 4661-4668. ISSN 0020-1669, 1520-510X
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Previously reported mono- and dinuclear Zn(II), Cu(II), and Ni(II) complexes of 1,4,7,10-tetrazacyclododecane ([12]aneN(4) or cyclen) with different heterocyclic spacers (triazine, pyridine) of various lengths (bi- and tripyridine) or an azacrown-pendant have been tested for the hydrolysis of bis(4-nitrophenyl)phosphate (BNPP) under physiological conditions (pH 7-9, 25 degrees C). All Zn(II) complexes promote the hydrolysis of BNPP under physiological conditions, while those of Cu(II) and Ni(II) do not have a significant effect on the hydrolysis reaction. The hydrolysis kinetics in buffered solutions (0.05 M Bis/Tris, TRIS, HEPES, or CHES, I = 0.1 M, NaCl) at 25 degrees C were determined by the initial slope method (product conversion <5%). Comparison of the second-order pH-independent rate constants (k(BNPP), M-1 s(-1)) for the mononuclear complexes ZnL1, ZnL3, and ZnL6, which are 6.1 x 10(-5), 5.1 x 10(-5), and 5.7 x 10-5, respectively, indicate that the heterocyclic moiety improves the rate of hydrolysis up to six times over the parent Zn([12]aneN(4)) complex (k(BNPP) = 1.1 x 10(-5) M-1 s(-1)). The reactive specie's is the Zn(II)-OH- complex, in which the Zn(II)-bound OH- acts as a nucleophile. For dinuclear complexes Zn2L.2, Zn(2)L4, and Zn(2)L5, the rate of reaction is defined by the degree of cooperation between the metal centers, which is determined by the spacer length. Zn2L2 and Zn2L4 possessing shorter spacers are able to hydrolyze BNPP 1 to 2 orders of magnitudes faster than Zn(2)L5. The second-order rate constants k of Zn(2)L4 and Zn(2)L2 at pH 7, 8, and 9 are significantly higher than those of previously reported related complexes. The high BNPP hydrolytic activity may be related to pi-siacking and hydrophobic interactions between the aromatic spacer moieties and the substrate. Complexes Zn(2)L4 and Zn(2)L2 show hydrolytic activity at pH 7 and 8, which allows for the hydrolysis of activated phosphate esters under physiological conditions.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PHOSPHATE DIESTER HYDROLYSIS; MACROCYCLIC TETRAAMINE COMPLEX; HIGHLY SELECTIVE RECOGNITION; AQUEOUS-SOLUTION; ZINC(II) COMPLEX; PHOSPHORYL-TRANSFER; ESTER HYDROLYSIS; CARBOXYESTER HYDROLYSIS; COPPER(II) COMPLEXES; ALKALINE-PHOSPHATASE; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Burkhard König |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 29 Oct 2020 11:48 |
| Last Modified: | 29 Oct 2020 11:48 |
| URI: | https://pred.uni-regensburg.de/id/eprint/30751 |
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