Laser Flash Photolysis of Pyridine N-Oxide: Kinetic Studies of Atomic Oxygen [O(3P)] in Solution

Preparation, Characterization, and Aquation Kinetics of Pyridine N‐Oxide Complexes of Chromium(III)

“…[22] By analogy to that work, the blue paste-like material generated from CrO 3 , X-pyO and H 2 O 2 is assigned the formula CrO(O 2 ) 2 (X-pyO). Reduction with Fe aq 2+ produces the desired (H 2 O) 5 Cr(X-pyO) 3+ , Equation (1).…”

“…Pyridine N-oxides (X-pyO) are important reagents in thermal [1,2] and photochemical [3][4][5] oxidations. Often, although not always, [6] such reactions involve oxygen-atom transfer [7][8][9] with pyridine N-oxide playing a role of either oxygen-atom donor [2,[7][8][9][10][11][12] or a promoter of oxygen transfer from active donors to the substrate.…”

“…There are, however, few reports available on the kinetics and mechanisms of the reactions of such complexes, [18][19][20] especially in aqueous solutions. [21,22] Several pentaamminecobalt(III) ions, (NH 3 ) 5 Co(X-pyO) 3+ have been prepared [21,22] and found to be reasonably stable at room temperature, provided there are no cyano substituents on the pyridine ring, in which case facile hydrolysis to a bound amide takes place. [21] The reduction of the parent (H 2 O) 5 Co(pyO) 3+ by chromium(II) is believed to take place by an inner-sphere mechanism whereby Cr aq 2+ attacks at the coordinated pyO oxygen, [21] although the expected product, (H 2 O) 5 was not observed, possibly because of its decomposition on ion-exchange resin.…”

“…[23] These studies have now been extended to a series of chromium complexes, (H 2 O) 5 Cr(X-pyO) 3+ (X = H, 3-CH 3 , 4-CH 3 , 4-OCH 3 , 4-NO 2 ). In this first report, we focus on the preparation and spectral and kinetic characterization of these complexes.…”

“…In this first report, we focus on the preparation and spectral and kinetic characterization of these complexes. Prior to this work, only the parent ion, (H 2 O) 5 Cr(pyO) 3+ , was known. [24] It was generated by thermal equilibration of Cr(H 2 O) 6 3+ with an excess of pyO in slightly acidic aqueous solutions at elevated temperatures, followed by ion exchange.…”