Phosphodiester Cleavage Promoted by an Asymmetric Dinuclear Zinc Complex: Synthesis,Structure, and Catalytic Activity |
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| Authors: | Ai‐Zhi Wu Long Chen Tao Wang |
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| Affiliation: | School of Chinese Materia Medica, Guangzhou University of Chinese Medicine, Guangzhou, 510006, P. R. China |
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| Abstract: | The dinuclear ZnII complex Zn2L(DNBA)2]BPh4 · EtOH ( 1 ) (DNBA = 3,5‐dinitrobenzonic acid) with an asymmetric dinuclear ligand, N‐4‐methyl‐homopiperazine‐N′‐N‐(2‐pyridylmethyl)‐N‐2‐(2‐pyridylethyl)amine]‐1,3‐diamino‐propan‐2‐ol (HL), was synthesized and characterized. Single crystal X‐ray crystallographic analysis shows that the coordination around the two ZnII ions in 1 is significantly asymmetric, and the distance between both atoms is 3.426 Å, which is close to the Zn···Zn distance in related natural dinuclear metalloenzymes. Phosphodiesterase activity of Zn2L in situ formed from a 2:1 mixture of Zn2+ ion and HL was investigated using bis(4‐nitrophenyl) phosphate (BNPP) as substrate. The pH dependence of the BNPP cleavage in aqueous buffer media reveals a bell‐shaped pH‐kobs profile with an optimum at about pH 7.9, which is parallel to the formation of the dinuclear species Zn2L‐OH obtained from the potentiometric titration. The catalytic rate constant (kcat) is 6.30 × 10–4 s–1 at pH 7.9 and 25 °C, which is approx. 108‐fold higher than that of the uncatalyzed reaction. The homopiperazine bound deprotonated Zn‐OH group is responsible for the hydrolysis reaction. The possible mechanism for the BNPP cleavage promoted by Zn2L is proposed on the basis of kinetic and spectral analysis. |
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| Keywords: | Asymmetric dinuclear zinc complex Crystal structure Phosphodiester cleavage Catalytic activity Zinc Hydrolysis |
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