Single-crystal UV-vis spectroscopic examination of a striking odd-even effect on structure and chromic behaviour of salicylidene alkylamines.

We have found that a series of N-(5-bromosalicylidene) alkylamines exhibited distinct chromic behaviour depending on the parity of their alkyl chain length. A group with an even number of carbon atoms in the alkyl chain showed photochromism, while another group with odd number showed thermochromism.