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REFLECTANCE SPECTROSCOPY FOR THE CHARACTERIZATION OF PHOTOCHROMISM IN THE CRYSTALLINE STATE
Author(s) -
Wettermark Gunnar,
King Abram
Publication year - 1965
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1965.tb09754.x
Subject(s) - photochromism , arrhenius equation , benzaldehyde , activation energy , chemistry , cinnamaldehyde , photochemistry , diffuse reflectance infrared fourier transform , analytical chemistry (journal) , pyridine , fading , medicinal chemistry , organic chemistry , catalysis , telecommunications , decoding methods , photocatalysis , computer science
— The Kubelka‐Munk theory for diffuse reflectance has been applied to a quantitative study of photochromism in the crystalline state. For three systems investigated it was found possible to assign first order rate constants to the thermal relaxation process and estimate the pre‐exponential factor A and the activation energy E a in Arrhenius equation. For the fading of the red photocolored form, Λ max =490 mμ, of benzaldehyde phenylhydrazone A = 1.4×10 8 min ‐1 and E a = 15.7 kcal mole ‐1 . For the fading of the blue photocolored form, Λ max =590 mμ, of 2–(2,4‐dinitrobenzyl)pyridine A= 5×10 14 min ‐1 E a =23.3 kcal mole ‐1 , Cinnamaldehyde semicarbazone showing ‘reversed phototropy’ has a photoactivated state, Λ max =400 mμ, which in dark is transformed into a strongly absorbing yellow species, Λ max = 430 mμ with A = 14 × 10 10 min ‐1 and E a = 18.7 kcal mole‐ 1 .