THERMOCHROMISM AND PHOTOCHROMISM OF N-SALICYLIDENEBENZYLAMINES AND N-SALICYLIDENE-2-AMINOMETHYLPYRIDINE

N-salicylidenebenzylamine (II), N-salicylidene-2-phenylethylamine (III ), their mono- and di-substituted derivatives, N-salicyclidene-2-amino methylpyridine (XIV) and N-salicylidene-2-aminoethyl-pyridine (XV) wer e investigated for their thermochromic and photochromic properties in the solid state and in solution, in the temperature range 298 K-77 K. II, III, XV, some of the monosubstituted derivatives of II and all the monosubstituted derivatives of III studied presented both properties, i.e they were both thermochromic and photochromic. The di-substituted derivatives were, practically, photochemically inactive. All the comp ounds investigated and found to be thermochromic, presented negative t hermochromism in non-polar solvents and some in polar solvents also. N egative thermochromism in non-polar solvents was due to aggregation as it was mainly shown by the concentration dependence on the electronic spectra. The same also seemed true in polar proton donating solvents but the picture was diversified by solubility.