N-Salicylideneanilines are interesting model compounds for understanding solid-state photochromism. The introduction of bulky substituents (trityl or tert-butyl groups) by chemical modification of the N-salicylideneaniline derivative is an effective method to build up photochromic solids. Alternatively, we propose, herein, a supramolecular approach to design photochromic materials which involves the introduction of a bulky anion in the structure. In this context, this is the first report on N-salicylideneamino-1-alkylpyridinium salts (iodide and tetraphenylboride salts). Iodide salts were obtained by alkylation of the parent N-salicylideneaminopyridine with the appropriate iodoalkane (iodomethane or iodoethane) in acetone. The iodide salts were used as the starting material for the production of tetraphenylborate salts by anion-exchange in methanol. All solids were characterized by means of X-ray diffraction and absorption spectroscopy. The effect of different counterions as well as the effect of the crystal structure on the solid-state photochromism is investigated.
Phthalimides have been successfully synthesized in the solid state by grinding (or kneading) of substituted phthalic anhydride and aniline derivatives. Selected products and intermediates were crystallized and characterized by crystallography leading to a potential rationale for the solid-state reactivity that involves co-crystals as intermediates.
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