Influence of the Solvent on the Thermal Back Reaction of One Spiropyran

Abstract

The solvent influence on the absorption spectra and the kinetics of the back reaction of the 1′,3′-dihydro-1′,3′,3′-trimethyl-6-nitrospiro­(2H-1-benzopyran-2,2′-2H-indole) (6-NO2-BIPS) has been investigated by means of temperature-controlled, UV–visible spectroscopic measurements. The back reaction process was proved to follow first-order kinetics for five different solvents (toluene, THF, acetonitrile, DMSO, and ethanol) at several temperatures. Kinetics parameters (E a, A, τ, ΔH #, ΔS #, and ΔG #) were extracted from absorbance decay profiles for all solvents, and a simple model based on solvation mechanism was proposed in good agreement with experimental results. Such a photochromic compound also exhibits strong solvatochromism in its merocyanine form. All these experiments were performed to illustrate solvent effects on kinetic processes and optical properties for students with an undergraduate physical chemistry theoretical background. All the experiments described could be performed in a physical chemistry undergraduate laboratory.

Noncovalent Spiropyran Coatings for Photoinduced Wettability Switching

“…For red light illumination no effect is observed. This is consistent with the behavior of spiropyran in solutions [11,21].…”

“…Backswitching to spiropyran is achieved by visible light or thermal relaxation, which also means that merocyanine is often not a stable molecule at room temperature. This switching has only been demonstrated for spiropyran mixed into solvents [11], host polymers [12][13][14][15], or single molecule layers [16,17], where steric hindrances are reduced. In its solid crystalline form switching has not been reported.…”

Microreactors as a Tool for Acquiring Kinetic Data on Photochemical Reactions

“…Indeed, Roxburgh et al 15 have experimentally obtained an identical rate of reaction at 21 °C in methanol. Görner 14, Wojtyk et al 16, and Piard 17 reported the following values in ethanol at 25 °C, respectively: 10 −3 s −1 , 6.9 × 10 −4 s −1 , and 6.0 × 10 −4 s −1 .…”

Direct Access by Mechanochemistry or Sonochemistry to Protonated Merocyanines: Components of a Four‐State Molecular Switch

“…[8,9] Depending on the nature of the substituents and the medium, the electronic distribution of ME varies from az witterionic form to an onionic quinoidal structure. ME can be stabilized by highly polar solvents [10,11] and solid matrices [12][13][14] or through coordination to metal ions. [15][16][17] Encapsulation can selectively stabilize one of the isomeric forms, which enablest he direct synthesiso ff unctional and tunable solid materials.…”