241128-48-3Relevant academic research and scientific papers
Quercetin 2,3-dioxygenase mimicking ring cleavage of the flavonolate ligand assisted by copper. Synthesis and characterization of copper(I) complexes [Cu(PPh3)2(fla)] (fla = flavonolate) and [Cu(PPh3)2(O-bs)] (O-bs = O-benzoylsalicylate)
Balogh-Hergovich, éva,Kaizer, József,Speier, Gábor,Fül?p, Vilmos,Párkányi, László
, p. 3787 - 3795 (1999)
Cu(PPh3)2(fla) has been prepared by reacting copper(I) chloride with sodium flavonolate in tetrahydrofuran solution. Crystallographic characterization of the complex (orthorhombic, P212121, a = 9.588(1) ?, b= 17.364(3) ?, c = 24.378(3) ?, V = 4058.6(10) ?3, Z = 4, R = 0.049) has shown that the coordination geometry of the molecule is tetrahedral. Oxygenation of Cu(PPh3)2(fla) in a methylene chloride solution at ambient conditions gives the O-benzoylsalicylato copper complex Cu(PPh3)2(O-bs) and carbon monoxide. Labeling experiments with an 18O216O2 mixture (1:4) evidenced the incorporation of both 18O atoms of 18O2 into the O-bs ligand. IR and MS studies of labeled O-bs confirmed the incorporation of 18O2 while the released CO remained unlabeled. Crystallographic characterization of Cu(PPh3)2(O-bs) on crystals obtained as the acetone solvate (triclinic, P1?, a = 13.154(1) ?, b = 17.991(1) ?, c = 20.495(1) ?, a = 80.01(1)°, β= 88.02(1)°, γ = 71.83(1)°, V = 4537.5(5) ?3, Z = 4, R = 0.0403) shows that the molecule has a distorted tetrahedral structure. The oxygenolysis was followed by spectrophotometry, and the rate constants were determined according to the rate law - d[Cu(PPh3)2(fla)]/dt = fa[Cu(PPh3)2(fla)][O2]. The rate constant, activation enthalpy, and entropy at 363.16 K are as follows: k2/M-1 s-1 = 4.16 ± 0.48, ΔH?/kJ mol-1 = 102 ±7, ΔS?/J mol-1 K-1 = -13.0 ± 21. The reaction fits a Hammett linear free energy relationship for 4′-substituted flavonolates, and an increase of the electron density on copper makes the oxygenation reaction faster.
