Photochromism, spiropyrans

Photoinduced transformations of photochromes (spiropyrans, furan-derived fulgides, dithienylethenes) in polymers 98PAC2157. 

M. B. Gordin, and M. A. Gal bershtam, Kinetics of the darkening [Note fading is meant] of several photochromic spiropyrans, Kinet. Catal, 12, 688-689 (1971). 

E. Ando, J. Miyazaki, and K. Morimoto, J-aggregation of photochromic spiropyran in Langmuir-Blodgett films, Thin Solid Films, 133, 21-28 (1985). 

M. Melzig and H. Zinner, Photochromic spiropyran compounds, World Pat. Appl. WO 95/00504 (1995). 

The previously mentioned photochromic spiropyrans also exhibit thermochromic activity upon melting [56-58], The melts are usually purple, red, or blue [19] and the color change is reversible however, the stability of the spiropyran/merocyanine composition is low at the thermochromic temperature transition range. As a consequence, the useful thermochromic lifetime of the spiropyrans is relatively short. Other molecular types that exhibit both photochromic and thermochromic activity are the indenone oxides, anils, spirooxazines, and chromemes. 

In this experiment students create their own indicator of ultraviolet (UV) light exposure, a photochromic spiropyran, and evaluate different sunscreen products to determine their effectiveness in blocking UV light. 

The combination of photochromic spiropyrans with enzymes could lead to enzymatic systems with photoswitchable catalytic behavior (Chapter 9). 

E. Goldburt, F. Shvartsman, S. Fishman, and V Krongauz, Intramolecular interactions in photochromic spiropyran-merocyanine polymers, Macromolecules 17, 1225-1230 (1984). 

M. Kryszewski, B. Nadolski, R. E. Imhof, A. North, and R. A. Pethrick, Effect of photoselection on the kinetics of colour decay in a photochromic spiropyran/poly(alkyl methacrylate) matrix, Macromol. Chem. 183, 1257-1267(1982). 

K. Ichimura, Y. Hayashi, and N. Ishizuki, Photocontrol of in-plane alignment of a nematic liquid crystal by a photochromic spiropyran monolayer absorbing linearly polarized hght, Chem. Lett. 1992,1063-1066. 

A. Samat, D. De Keukeleire, and R. Guglielmetti, Synthesis and spectrokinetic properties of photochromic spiropyrans, Bull. Soc. Chim. Belg. 100, 679-700 (1991). 

P. Appriou, R. Guglielmetti, and F. Gamier, Study of the photochemical processes in the benzopyranic ring opening reaction of photochromic spiropyrans, 7. Photochem. 8, 145-165 (1978). 

As distinct from photochromic spiropyrans and spirooxazines, [2//J-chro-menes do not contain a heterocyclic fragment such as an indoline nucleus. Consequently, in such compounds there are no specific n-a orbital interactions that elongate and weaken the C, iro—O bond, the ruptures of this bond in the excited and ground states being responsible for the photo- or thermochromic properties of spiropyrans and spirooxazines as well as [2// -chromcncs. 

P. Shibaeva, L. P. Rozenberg, A. S. Kholmanskii, and A. V. Zubkov, Crystalline and molecular structure of photochromic spiropyrane, C24N2O3H20, Dokl, Akad. Nauk SSSR 226, 1374-1377 1976). 

Sh. Karaev, N. G. Furmanova, and N. V. Belov, On crystal and molecular structure of a photochromic spiropyran, C H,8N203, Dokl. Akad. Nauk SSSR 262, 877-880 (1982). 

S. M. Aldoshin and L. O. Atovmyan, Structure of the new photochromic spiropyran of indoline series CI9H,8N203, Izv. Akad. NaukSSSR, Ser. Khim. 1985, 191-194. 

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