A supramolecular engineering approach has been developed for a novel family of N-salicylidene aniline derivatives to control their thermo-and photochromic behaviours. Hsaltrz, Habs, Hsalphen, Hsaltz and Ksaltz are versatile molecules built from N-heterocycles, which drive the molecular arrangement to form a controlled crystal packing with predesigned optical properties. A complete structural, optical and computational study of powders of these new molecular nanoswitches is presented. An N-salicylidene aniline derivative possessing no thermo-or photoinduced chromic properties thanks to a specific molecular geometry was sought, and Habs and Hsalphen were designed to enhance π-π stacking

The cover picture shows a panel of functional N‐salicylidene derivatives that can be rationally designed and assembled by crystal engineering. The amplitude of their thermochromism and/or photochromism can be finely tuned as shown by the central needle. This study is supported by a multidisciplinary approach (syntheses, physical and structural studies, calculations). Details are discussed in the article by Y. Garcia et al. on p. 621 ff.