TY - JOUR
T1 - Coordination modes of bridge carboxylates in dinuclear manganese compounds determine their catalase-like activities
AU - Jiang, Xiaojun
AU - Liu, Hui
AU - Zheng, Bing
AU - Zhang, Jingyan
PY - 2009/10/28
Y1 - 2009/10/28
N2 - To explore the role of bridge carboxylate coordination modes on the catalase-like activities of dinuclear manganese compounds, [MnII 2(bpmapa)2(H2O)2](ClO 4)2 (1), [MnII2(pbpmapa) 2(H2O)2](ClO4)2 (2), and [MnII2(bpmaa)2(H2O) 3](ClO4)2 (3) (bpmapa = [bis(2-pyridylmethyl) amino]propionic acid, pbpmapa = α-phenyl-β-[bis(2-pyridylmethyl) amino]propionic acid, and bpmaa = [bis(2-pyridylmethyl)amino]acetic acid), in which MnII-MnII centers have a similar coordination sphere but different carboxylate-Mn bridging modes have been synthesized and structurally characterized by single X-ray diffraction, UV-visible, IR, and EPR spectroscopies, and their catalase-like activities were investigated. Studies of their catalytic activities and the influence of the nitrogenous bases on their catalytic activities indicated that the carboxylate-Mn coordination mode was crucial in H2O2 deprotonation, and eventually in H 2O2 disproportionation. Compound 1 with a bidentate carboxylate bridge showed higher catalase-like activity than 2 and 3, in which the carboxylate groups have a monodentate bridging mode. The deprotonation ability of the carboxylate anion was determined by the O-C-O angle and the distance between the weakly bound oxygen of the bridging carboxylate to the manganese ion. The smaller the angle, and the shorter the distance, the stronger the basicity that the carboxylate anion exhibits. The bidentate μ-1,1 bridging coordination mode functionally mimicked the glutamate residues at the manganese catalase active site. Our results suggested that increasing the basicity of the bridging carboxylate ligand of the catalase model compounds will increase their deprotonation ability and lead to more active catalase mimics.
AB - To explore the role of bridge carboxylate coordination modes on the catalase-like activities of dinuclear manganese compounds, [MnII 2(bpmapa)2(H2O)2](ClO 4)2 (1), [MnII2(pbpmapa) 2(H2O)2](ClO4)2 (2), and [MnII2(bpmaa)2(H2O) 3](ClO4)2 (3) (bpmapa = [bis(2-pyridylmethyl) amino]propionic acid, pbpmapa = α-phenyl-β-[bis(2-pyridylmethyl) amino]propionic acid, and bpmaa = [bis(2-pyridylmethyl)amino]acetic acid), in which MnII-MnII centers have a similar coordination sphere but different carboxylate-Mn bridging modes have been synthesized and structurally characterized by single X-ray diffraction, UV-visible, IR, and EPR spectroscopies, and their catalase-like activities were investigated. Studies of their catalytic activities and the influence of the nitrogenous bases on their catalytic activities indicated that the carboxylate-Mn coordination mode was crucial in H2O2 deprotonation, and eventually in H 2O2 disproportionation. Compound 1 with a bidentate carboxylate bridge showed higher catalase-like activity than 2 and 3, in which the carboxylate groups have a monodentate bridging mode. The deprotonation ability of the carboxylate anion was determined by the O-C-O angle and the distance between the weakly bound oxygen of the bridging carboxylate to the manganese ion. The smaller the angle, and the shorter the distance, the stronger the basicity that the carboxylate anion exhibits. The bidentate μ-1,1 bridging coordination mode functionally mimicked the glutamate residues at the manganese catalase active site. Our results suggested that increasing the basicity of the bridging carboxylate ligand of the catalase model compounds will increase their deprotonation ability and lead to more active catalase mimics.
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U2 - 10.1039/b907687e
DO - 10.1039/b907687e
M3 - Article
C2 - 19809747
AN - SCOPUS:74249102903
SN - 1477-9226
SP - 8714
EP - 8723
JO - Dalton Transactions
JF - Dalton Transactions
IS - 40
ER -