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What is the difference between the terms photochemical and photophysical properties? What are some examples from each category?

Hazinga
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    Reminds me about Differences between chemical physics and physical chemistry? – Martin - マーチン May 10 '21 at 20:57
  • So is it bonkers when I see a paper describing the photochemical and photophysical properties of X? – Hazinga May 11 '21 at 01:07
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    Just a guess: photophysical can mean anything relating to the interaction of light and matter, simple absorption for instance. Photochemical implies a chemical reaction results from the interaction due to formation of excited species. – Buck Thorn May 11 '21 at 06:03
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    In photochemistry light is used to break a bond e.g. $\ce{I_2 +light -> 2I\cdot}$ or trans stilbene + light $\to$ cis stilbene, photophysics is the study of how this happens. – porphyrin May 11 '21 at 07:09
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    Photophysics digs a lot into details. They can be or not associated to a following reaction. While absorption can be a analytical chemistry tool, and might be relevant to conduct photochemical reactions, doing time resolved spectroscopy is certainly photophysics. I think that the comment by Buck Thorn helps in a sort of definition, but the point made by Martin is valid, too. In all cases, recording Absorption spectra, to give an example, certainly isn't photochemistry. Though is likely the most familiar physical technique among chemists. – Alchimista May 11 '21 at 08:19
  • @porphyrin the stilbene example is relevant. If we consider thermal isomerisation is that photophysical? But if we consider the cyclisation of Z-stilbene to the phenanthrene, would that be photochemical? Finally, if I characterise the pi-pi* transitions of a photochromic ligand + its thermal isomerisation kinetics could I accurately describe that as 'photophysical characteristics'? – Hazinga May 11 '21 at 17:00
  • Thermal by definition is definitely neither photochemical nor photophysical. The photo-induced events have to occur from an excited state produced by absorbing a photon. – porphyrin May 11 '21 at 17:18

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