1 research outputs found
Reversible Valence Photoisomerization between Closed-Shell Quinoidal and Open-Shell Biradical Forms
We
report here a kinetic study on the thermal equilibrium process
between the biradical form and the quinoidal form starting from the
singlet biradical form alone. A photochromic phenoxyl–imidazolyl
radical complex repeatedly generates biradical species upon UV light
irradiation, and the following thermal equilibrium process responsible
for valence isomerization from the open-shell singlet biradical to
the closed-shell quinoidal form is observed in the microsecond time
region. The thermodynamic parameters for the equilibrium process were
determined for the first time by nanosecond laser flash photolysis.
We also found that visible-light excitation to the equilibrium state
causes valence photoisomerization from the quinoidal to the biradical
form, which returns thermally to the quinoidal form