Successive Photoswitching and Derivatization Effects in Photochromic Dithienylethene‐Based Coordination Cages

Abstract

Abstract A new series of [Pd 2 ( L ) 4 ] cages based on photochromic dithienylethene (DTE) ligands allowed us to gain insight into the successive photoswitching of multiple DTE moieties in a confined metallo‐supramolecular assembly. Three new X‐ray structures of [Pd 2 ( o‐ L 4 ) 4 ], [Pd 2 ( o‐ L 1 ) 2 ( c‐ L 1 ) 2 ] and [Pd 2 ( c‐ L 1 ) 4 ] ( o‐ L and c‐ L = open and closed forms of DTE ligands, respectively) were obtained. The structures deliver snapshots of three different combinations of DTE photoisomeric states within the cage, facilitating a comparison of the all‐open with the all‐closed, and most notably, an intermediate form where open and closed switches co‐exist in the same cage. Moreover, a series of spherical anionic borate clusters was introduced in order to study their roles in the light‐controllable host–guest chemistry. The binding guests show higher affinities with the flexible open cage [Pd 2 ( o‐ L 1 ) 4 ] than with the rigid closed cage [Pd 2 ( c‐ L 1 ) 4 ]. For the [B 12 F 12 ] 2− guest, thermodynamic data obtained from NMR experiments was compared to results from isothermal titration calorimetry (ITC).