Abstract
Photochromes have proven to be attractive molecules for potential applications not necessary based on their spectacular colour change (such as biomimetic chemistry and photoswitchable nucleosides). Their development was incited by the versatility of compounds that could be prepared, but their applications also depended on their photobehaviour. The latter, conceptually requires a comprehensive description of their kinetics. A field which is somewhat still to be developed since, thus far, a single integrated rate-law (c = f(t), expressing the variation of the concentration with irradiation time) has been analytically established for samples exposed to monochromatic light. Similar integrated rate-law equations have yet to be analytically developed for polychromatic light irradiation.
The present paper investigates the facets of photokinetics of a photochromic closed-form diarylethene derivative (c-DAE) and its variability with the light type impinging on the sample. An integrated rate-law equation has been derived, to describe kinetics under polychromatic light. The findings have then been applied to establish robust methodologies for both monochromatic and polychromatic light actinometries for the visible range. c-DAE is been shown to be a reliable, easily manipulated, actinometer for the 400-600 nm range for both light types. It is an exemplar of a new generation of actinometers that are easy-to-handle, regenerated, reliable, do not require to have a wavelength-invariant quantum yield, useful for both monochromatic and polychromatic light set-ups, and their procedures are based on integrated rate-law equations.