N-Salicylidene aniline

A series of N-salicylidene aniline (SA) derivatives (Figure 10.10) have been investigated for their photochromic and NLO properties. For many years, scientists have known of the photochromism of some of these molecules in the crystalline state. Among them, those that crystallize in a nonGentro-symmetric space group were selected, and the NL[Pg.322]

The majority of reversible photoinduced PT reactions takes place between a donor and an acceptor that are chemically different, being either different atoms or identical atoms in inequivalent positions of a molecule or a molecular assembly [12,13], Examples are systems in which the phenomenon was first discovered and which (sometimes in the form of related compounds and derivatives) continue to be the object of present work methyl-salicylate [6,7], n-salicylidene aniline [8], 3-hydroxyflavone [10], and dimers of 7-aza-indole [9], Other molecules include 2-(2 -hydro-xyphenyl)benzothiazole [163,164] and 2-(2 hydroxyphenyl)benzoxazole, which has been studied in detail by Grellmann and co-workers [165,166], and where in addition to the fast transfer in the excited singlet state, the slower transfer in the triplet manifold could be characterized by transient absorption measurements in solution at temperatures down to 55 K. 

Thompson BC, Abboud KA, Reynolds JR, Nakatani K, Audebert P (2005) Electrochromic conjugated N-salicylidene-aniline (anil) functionalized pyrrole and 2,5-dithienylpyrrole-based polymers. New J Chem 29 1128-1134... 

Jacquemin, P.-L., Robeyns, K., Devillers, M., and Garcia, Y. (2014) Reversible photochromism of an N-salicylidene aniline anion. Chem. Commun.,... 

N-saltcylidene 2-chloro-aniline (2-CI, X=H,Y=Cl). N-salicylidene 2-bromo-aniline (2-Br, X=H,Y=Br), N-salicylidene 4-bromo-aniline (4-Br, X=Br, Y=H), and N-salicylidene 2-methyl-4-nitro-aniline (2-Me-4-N02,X=N02,Y=CH3). ... 

In the cases of the Af-salicylidene (46) and N-benzylidene (47) anilines (15a and 15b), there is less ambiguity arising from thermal motion. For both series of compounds it is believed, on spectroscopic grounds, that the molecules are nonplanar in solution. While there are some crystal phases known in which the molecules retain this conformation (the dihedral angle between the anilino and salicylidenimino planes being of the order of 40°), in others the molecules are definitely planar. In the case of 15a it has been found that there are marked differences in densities and in photochemical and spectroscopic properties between crystals of the two types. 

Lewis, J.W. and Sandorfy, J.W., A spectroscopic study of proton transfer and photochromism in N-(2-hydroxybenzylidene)aniline, Can. J. Chem., 60, 1738, 1982 Becker, R.S., Lenoble, C., and Zein, A., A comprehensive investigation of the photophysics and photochemistry of salicylidene-anihne and derivatives of phenylbenzothiazole including solvent effects, /. Phys. Chem., 91, 3509, 1987 PistoHs, G., Gegiou, D., and Hadjoudis, E., Effect of cyclodextrin complexation on thermo-chromic Schiff bases, /. Photochem. Photohiol, A Chem., 93, 179, 1996. 

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