Reversible chromism of spiropyran in the cavity of a flexible coordination cage

• Published in: Nature communications Vol. 9; no. 1; pp. 641 - 9
• Main Authors: Samanta, Dipak, Galaktionova, Daria, Gemen, Julius, Shimon, Linda J. W., Diskin-Posner, Yael, Avram, Liat, Král, Petr, Klajn, Rafal
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-02-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/131; 639/638/541/965; 639/638/541/966; 639/925/357/339; Aqueous solutions; Cages; Confined spaces; Confining; Conformation; Crystal structure; Flexibility; Humanities and Social Sciences; Information storage; Ligands; Molecular machines; multidisciplinary; NMR; Nuclear magnetic resonance; Science; Science (multidisciplinary); Switches
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-02715-6

Confining molecules to volumes only slightly larger than the molecules themselves can profoundly alter their properties. Molecular switches—entities that can be toggled between two or more forms upon exposure to an external stimulus—often require conformational freedom to isomerize. Therefore, placing these switches in confined spaces can render them non-operational. To preserve the switchability of these species under confinement, we work with a water-soluble coordination cage that is flexible enough to adapt its shape to the conformation of the encapsulated guest. We show that owing to its flexibility, the cage is not only capable of accommodating—and solubilizing in water—several light-responsive spiropyran-based molecular switches, but, more importantly, it also provides an environment suitable for the efficient, reversible photoisomerization of the bound guests. Our findings pave the way towards studying various molecular switching processes in confined environments.
Under confinement, molecular switches lose the conformational freedom often needed to isomerize. Here, the authors show that a flexible coordination cage can adapt its shape to guide the photoisomerization of encapsulated spiropyrans, rendering them reversibly photochromic even within the confines of the cavity.