Photochromic and thermochromic anils

Polymorphism inN-Salicylideneaniline Reconsidered

“…The packings of the R 1 and -polymorphs are indeed quite similar but clearly different from that of the R 2 -polymorph 15 (see Figures 2 and 8), which is, as expected, relatively open. It is worth stressing this point, since it was categorically stated 3,10,35,48 that the structure of nonplanar polymorphs is relatively open and planar polymorphs have closed structures. Since the packing of the R 1 -polymorph is closer to that of the planar -polymorph, we conclude that the previous statement needs amendment and that some other polymorphs, with different chromic behavior, related by a phase transition, should be investigated.…”

“…Because of this electronic redistribution, a subsequent geometrical rearrangement occurs in the excited state; different proportions of the cis-keto and trans-keto forms (with respect to the C1-C7 bond) were found by various authors. [10][11][12] These proportions furthermore seem to depend on the sample history (equilibrium between enol and cis-keto form in the ground state) and crystal quality (all glassy systems are photochromic). The colored species can be reversibly bleached either by irradiation with visible light or by heating the crystals.…”

Specific Features of Intramolecular Proton Transfer Reaction in Schiff Bases

“…Schiff bases are of special interest in the literature; they show thermochromic and photochromic properties, which can be a basis for numerous practical applications [8][9][10]. The features responsible for such properties are directly connected with ground state and excited state proton transfer.…”

Synthesis, Characterization and Study of the Biological activity of Some Aldimines Derivatives

“…[3][4][5] Aldimines have been generelly used as substrates in the formation of a large number of industrial compounds via cycloaddition , ring closure , replacement reaction , etc. 6,7 .…”