Mesitylcopper reacts with flavonol (flaH) in the presence of 1,3-bis(2-pyridylimino)isoindoline (indH) to yield the diamagnetic complex Cu-I(fla)(indH), which on reaction with molecular oxygen undergoes oxidative splitting of the C2-C3 bond of the pyranone ring of the flavonolate ligand to give Cu-I(indH)(O-bs) (O-bs = O-benzoylsalicylate) (orthorhombic, P (1) over bar, a = 8.048(7) Angstrom, b = 8.969(9) Angstrom, c = 19.240(2) Angstrom, alpha = 85.69 degrees, beta 80.24(7)degrees, gamma = 77.87(7)degrees, V = 1337(2) Angstrom(3), Z = 2) and carbon monoxide. The reaction of [Cu-I(CH3CN)(4)]ClO4, flaH, and indH with dioxygen at room temperature affords the paramagnetic complex [Cu-II(Ra)(indH)]ClO4 (mu = 2.10 mu(B)), and after elimination of HClO4, Cu-II(fla)(ind) (orthorhombic, P-bca. a = 8.888(2) Angstrom, b = 19.169(7) Angstrom, c = 33.614(10) Angstrom, alpha = beta = gamma = 90 degrees, V = 5727(3) Angstrom(3), Z = 8) With mu = 1.86 mu(B) is formed. The latter undergoes cleavage of the pyranone ring on oxygenation at 80 degrees C to give Cu-II(ind)(O-bs) (mu = 1.87 mu(B), nu(CO) = 1742 cm(-1), and nu(CO2) = 1581, 1387 cm(-1)) and carbon monoxide. Cu-II(fla)(ind) and [Cu-II(fla)(indH)]ClO4 serve as good catalysts for the oxygenation of flavonol to O-benzoylsalicylic acid.