1 .3 ,3 -Trimethyl-5 -nitrospiro benzopyran

Figure 4. Dependence of log(D7 /Dri) (i.e., the ratio of the optical density DT after n flashes to the optical density DTl after the first flash) on n for l, 3, 3 -trimethyl-8-methoxy-6-nitrospiro[2//-l-benzopyran-2,2 -indoline] (11). Deviation ftom linearity is more pronounced for aerated toluene or benzene solutions than for the corresponding deaerated solutions. (Reprinted from Ref. 28 with permission of Editions Scientifiques et Medicales Elsevier.)...

Labsky et have studied the photochromic behaviour of spiropyrans. For example, r,3, 3 -trimethyl-6-nitrospiro(2/f-l-benzopyran-2,2 -indoline) undergoes the configurational change shown in Scheme 12. 

The photo-, thermo- and solvatochromic properties of 2,3-dihydro-1 ,3 ,3 -trimethyl-6-nitrospiro[l-benzopyran-2,2 -17/-indole] (BSP) and its photo-induced merocyanine isomer (MC) were investigated in phosphonium based ILs by UV-vis absorption spectroscopy and the kinetics and thermodynamics of the BSPMC equilibrium were found to be sensitive to the nature of the anion. For example, the MC Xmax shifted from 560 nm to 578 nm in solutions of [Me(C4H9)3P][tos] and [Ci4H29(C6Hi3)3P][dca], respectively. The BSP isomer was highly favoured at equilibrium in the ILs studied. 

Seki and Ichimura have investigated the thermal isomerization kinetics of photoinduced merocyanine (MC) to spiropyran (SP) in solid films having multibilayer structures, which consists of ion complexes between ammonium bilayers forming amphiphiles (2Ci82CiN ) and polyanions (montmorillonite and poly(-styrene sulfonate), abbreviated as PSS) (210). l,3,3-Trimethyl-6 -nitrospiro[indo-line-2,2 -2 /f-benzopyran](SP) was incorporated into thin films of the polyion complexes, which were prepared by casting the chloroform solution or suspension of the polyion complexes. 

Kiebwetter R, Pustet N, Brandi F, Mannschreck A (1999) 1, 3, 3 -Trimethyl-6-nitrospiro[2H-l-benzopyran-2,2 -lndoline] its thermal enantiomerlzation and the equilibration with its mero-cyanine. Tetrahedron Asymmetry 10 4677—4687... 

Abe, Y., Nakao, R., Horii, T., Okada, S., and Irie, M., MNDO-PM3 MO studies on the thermal isomerization of photochromic l, 3, 3 -trimethyl-6-nitrospiro[2H-l-benzopyran-2,2 -indo-line], /. Photochem. Photobiol. A Chem., 95, 209,1996. 

---