Studies on chiral spiropyran derivatives

Şentürk, Bengi
Spiropyrans are a class of organic molecules that possess photochromic characteristics. Their isomerization to the merocyanine form can be induced by light, heat, polarity, and pH of the environment. The merocyanine form is obtained from the heterolytic cleavage of the bond between spiro carbon and the oxygen, which results in a transformation of the optically active spiropyrans into an achiral form. The back conversion of the achiral merocyanine to the spiropyrans leads to racemization. In this study, D and L forms of alanine and phenylalanine derivatives were incorporated into a spiropyran with alcohol fuctionality to obtain optically active spiroyprans. Their photochemical and photophysical properties were studied in methanol, isopropanol, dichloromethane and hexane. The results showed that these spiropyrans display different characteristics in their spectroscopic analyses. The effect of the benzyl and methyl units on the ring closure rate of the merocyanines was also investigated. For this purpose, ring closure kinetics of different merocyanines containing hydroxy group as well as D-alanine and D-phenylalanine derivatives were compared. The results reveal that the ring closure rate of the merocyanine with benzyl group attached is faster than the rate of the structures with methyl or hydroxy groups.


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Amino Acid Conjugated Spiropyrans: Synthesis and Photoisomerization Studies
Şentürk, Bengi; Akdağ, Akın (2022-09-01)
Among photo-switchable compounds, spiropyrans have attracted significant attention owing to their multi-responsiveness towards a change in the pH, solvent polarity, and temperature, along with light. Upon exposure to the external stimulants, the merocyanine form is obtained due to bond cleavage between spiro carbon and oxygen, which transforms the optically active spiropyrans into an achiral form. The back conversion of the resulting achiral merocyanine form to the spiropyrans brings about a racemic mixture...
Citation Formats
B. Şentürk, “Studies on chiral spiropyran derivatives,” M.S. - Master of Science, Middle East Technical University, 2021.