Synthesis, Characterization And Reactivity Of Model Complexes For The β-diketone Dioxygenase

β-diketone dioxygenase (Dkel) can activate molecular oxygen to catalyze the oxygenative reaction of acetylacetone to acetic acid and2-oxopropanal.(1) One new model ligand LH (3-{[(6-Methyl-pyridin-2-ylmethyl)-pyridin-2-ylmethyl-amino]-methyl}-benzoic acid) for the active site of Dkel has been synthesized and characterized by IR,1H NMR and API/MS.(2) Ten new corresponding model complexes [MⅡLSR](M:Fe, Ni) have been designed and synthesized as the structural and functional models for the active site of Dkel, which also have been characterized by IR, UV-vis, API/MS and CV.(3) Their spectroscopic features and reactivity toward dioxygen have been investigated in detail.(4) We analyze the products of ternary model complexes reacting with molecular oxygen and obtain the degradation product benzoic acid and keto acid compounds of native enzyme.The conclusions of our study are as follows:①Metal ion effects:With the same substrates and different metal ion, the reactivity of Fe(Ⅱ) model complexes are higher than Ni(Ⅱ) model complexes.②Electronic effects of substrates:With the different substrates and same metal ion, the reactivity is in the order of [MⅡLSOMe]>[MⅡLSMe]>[MⅡLSH]>[MⅡLSBr]>[MⅡLSNO2]. The substrates with electron donating group can increase the reaction rate, so the oxygenation reaction is a electrophilic reaction.③According to the spectrum, dynamic data and the theoretical calculation results derives the proposed reaction mechanism.