Ligand effect on reversible conversion between copper(I) and bis(mu-oxo)dicopper(III) complex with a sterically hindered tetradentate tripodal ligand and monooxygenase activity of bis(mu-oxo)dicopper(III) complex.
A new sterically hindered tetradentate tripodal ligand (Me2-etpy) and its labeled analogue having deuterated methylene groups (d4-Me2-etpy) were synthesized, where Me2-etpy is bis(6-methyl-2-pyridylmethyl)(2-pyridylethyl)amine. Copper(I) complexes [Cu(Me2-etpy or d4-Me2-etpy)]+ (1 and 1-d4, respectively) reacted with dioxygen at -80 degrees C in acetone to give bis(mu-oxo)dicopper(III) complexes [Cu2(O)2(Me2-etpy or d4-Me2-etpy)2](2+) (1-oxo and 1-d4-oxo, respectively), the latter of which was crystallographically characterized. Unlike a bis(mu-oxo)dicopper(III) complex with a closely related Me2-tpa ligand having a 2-pyridylmethyl pendant, 1-oxo possessing a 2-pyridylethyl pendant is not fully formed even under 1 atm of O2 at -80 degrees C and is very reactive toward the oxidation of the supporting ligand. Thermal decomposition of 1-oxo gave an N-dealkylated ligand in yield approximately 80% based on a dimer and a corresponding aldehyde. The deuterated ligand d4-Me2-etpy greatly stabilizes the bis(mu-oxo)dicopper(III) complex 1-d4-oxo, indicating that the rate determining step of the N-dealkylation is the C-H bond cleavage from the methylene group. The reversible conversion between 1-d4 and 1-d4-oxo in acetone is dependent on the temperature, and the thermodynamic parameters (DeltaH and DeltaS) of the equilibrium were determined to be -53 +/- 2 kJ mol(-1) and -187 +/- 10 J mol(-1) K(-1), respectively. The effect of the 2-pyridylethyl pendant in comparison with the 2-pyridylmethyl and 6-methyl-2-pyridylmethyl pendants on the physicochemical properties of the copper(I) and bis(mu-oxo)dicopper(III) species is discussed.
Mizuno
Masayasu
M
Department of Chemistry, Faculty of Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Hayashi
Hideki
H
Fujinami
Shuhei
S
Furutachi
Hideki
H
Nagatomo
Shigenori
S
Otake
Shigenori
S
Uozumi
Kounosuke
K
Suzuki
Masatatsu
M
Kitagawa
Teizo
T
D000465:Algorithms; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D008024:Ligands; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics
D007202:Indicators and Reagents; D008024:Ligands; D009942:Organometallic Compounds; D003300:Copper; D006899:Mixed Function Oxygenases; D010100:Oxygen