74487-99-3Relevant academic research and scientific papers
Triplet Ground-State Benzoylphenylmethylene and Its Quintet Ground-State Triplet-Triplet Radical Pair
Murai, H.,Safarik, I.,Torres, M.,Strausz, O. P.
, p. 1025 - 1032 (2007/10/02)
Photolysis of crystalline azibenzil powder at 77 K and λ >/= 345 nm generates a complex ESR spectrum consisting of four components, namely a strong triplet, a weak triplet, a quintet, and a doublet.The strong triplet has been previously assigned to ground-state benzoylphenylmethylene and the quintet to the ground state of a radical pair formed between two triplet benzoylphenylmethylenes.On the basis of the similar values exhibited by the zero-field splitting parameters, the strong and weak triplet signals are assigned here to the s-Z and s-E isomers of the ground state of benzoylphenylmethylene, respectively.The s-Z conformer is more abundant and less stable than the s-E, and on annealing, the decay of both signals follows first-order kinetics.Above 90 K the quintet radical pair also decays with first-order kinetics to yield a new triplet diradical, which is stable at T 120 K but disappears with first-order kinetics above 120 K.The Arrhenius parameters have been determined for all decay reactions and utilized in their mechanistic interpretation.The carrier of the structureless, broad doublet signal observed appears to be generated from the secondary photolysis of the tiplet benzoylphenylmethylene.The assignment of the quintet spectrum to a radical pair is also supported by the absence of this spectrum in the photolysate of dilute azibenzil solutions in glassy matrices.Under such conditions, in addition to the spectrum of benzoylphenylmethylene and its doublet photolysis products, a new triplet diradical appears wiht a kinetics of formation suggesting that it is formed by the decay of the quintet.However, its identity has not been established.
