title: The rate of O2 and CO binding to a copper complex, determined by a "flash-and-trap" technique, exceeds that for hemes.
abstract: The observation and fast time-scale kinetic determination of a primary dioxygen-copper interaction have been studied. The ability to photorelease carbon monoxide from [Cu(I)(tmpa)(CO)](+) in mixtures of CO and O(2) in tetrahydrofuran (THF) between 188 and 218 K results in the observable formation of a copper-superoxide species, [Cu(II)(tmpa)(O(2)(-))](+) lambda(max) = 425 nm. Via this "flash-and-trap" technique, temperature-dependent kinetic studies on the forward reaction between dioxygen and [Cu(I)(tmpa)(thf)](+) afford activation parameters DeltaH = 7.62 kJ/mol and DeltaS = -45.1 J/mol K. The corresponding reverse reaction proceeds with DeltaH = 58.0 kJ/mol and DeltaS = 105 J/mol K. Overall thermodynamic parameters are DeltaH degrees = -48.5 kJ/mol and DeltaS degrees = -140 J/mol K. The temperature-dependent data allowed us to determine the room-temperature second-order rate constant, k(O2) = 1.3 x 10(9) M(-1) s(-1). Comparisons to copper and heme proteins and synthetic complexes are discussed.
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry*; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010782:Photolysis; D011725:Pyridines / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D009942:Organometallic Compounds; D011725:Pyridines; C431843:tris(2-pyridylmethyl)amine; D006418:Heme; D003300:Copper; D002248:Carbon Monoxide; D010100:Oxygen