Photochemical reaction of dimethylarsinous iodide in aerated methanol: A contribution to arsenic radical chemistry

Continuous and laser photolysis studies of (CH3)2As(III)I were carried out in methanol solutions. The photoproduct obtained with the continuous photolysis of the aerated solutions was identified as {(CH3)2As(V)(OH)2}+{(CH3)2As(V)O(OH)}2][I3−] by X-ray crystallography. The laser flash photolysis of (CH3)2As(III) I in a degassed methanol gives a transient spectrum of dimethylarsine radical, (CH3)2As(III), with a broad peak centered around 560 nm. The arsinous radical, (CH3)2As(III), decays according to second order kinetics to regenerate (CH3)2As(III)I. In the presence of oxygen, (CH3)2As(III) reacts with oxygen to yield the peroxy radicals, [(CH3)2As(III) (O2)] with the bimolecular rate constant, 2.0 × 109 M−1 s−1. The peroxy radical having weak and broad absorption in the wavelength region λ > 500 nm decays according to first order kinetics with a rate constant 5.0 × 105 s−1. It is suggested that the peroxy radical unimolecularly converts to (CH3)2As(V) (O)O, which eventually turns to the product {(CH3)2As(V)(OH)2}+{(CH3)2As(V)O(OH)}2][I3−].