1417158-14-5Relevant articles and documents
Photochromism of a merocyanine dye bound to sulfonatocalixarenes: Effect of ph and the size of macrocycle on the kinetics
Miskolczy, Zsombor,Biczók, László
, p. 648 - 653 (2013/03/14)
The effect of 1:1 complex formation on the photochromic behavior of the merocyanine isomer of a nitro-substituted spirobenzopyran dye was studied in aqueous solution using 4-sulfonatocalixarene (SCXn) cavitands possessing four or eight phenol units. The binding constants were independent of the size of the macrocycle, and about 7-fold more stable associates were produced at pH 2.3 than in slightly alkaline solution. The complexation with SCXn diminished the acidity of protonated merocyanine (trans-MCH+) and precluded its photoinitiated transition to spirobenzopyran form, but did not affect the reactions in basic media. Upon exposure to light, the complexed trans-MCH + was converted to cis isomer. The association with 4-sulfonatocalix[4]arene slowed down the thermal back reaction in the dark to a larger extent than the confinement to 4-sulfonatocalix[8]arene. Both the activation energy and the Arrhenius A factor were significantly larger when the smaller, more rigid macrocycle served as a host.