Thermodynamic driving forces of guest confinement in a photoswitchable cage

Abstract

Photoswitchable cages that confine small guest molecules inside their cavities offer a way to control the binding/unbinding process through irradiation with light of different wavelengths. However, a detailed characterization of...

Increasing structural and functional complexity in self-assembled coordination cages

“… 122 Apparently, the guest is already ejected after switching of the first ligand, pointing to a situation in which the rigid, closed ligand photosiomer dictates the conformational preference of the remaining open ligands. This assumption was further supported by comparing X-ray structures of cage isomers with four open, two open/two closed and four closed switches 123 and recently supported through MD simulations and detailed binding enthalpy/entropy calculations by Schäfer et al 124 …”

Coordination of a Potentially Tritopic Ligand via Phosphorus, Nitrogen and Oxygen: From Ligand Design to Heterobimetallic Metal–Organic Frameworks and Supramolecules

“…The alternating occupancy of the vertices by different cations and the disposition of the 12 ditopic ligands along the edges are in agreement with tetrahedral symmetry and lead to the overall formula [(AlL 3 ) 4 Cu 4 ]­(PF 6 ) 4 . Similar to the situation encountered for extended structures, the vast field of discrete coordination cages is dominated by monometallic species. − Heterobimetallic coordination cages, albeit less common, are well represented nonetheless, − and many of them resemble cube-like architectures. − Most of them do, however, feature metal centers on their faces. Our example is rather reminiscent of the heterocubane motif − and its slightly elongated relatives, the cubic cyanometalates. , Compound 7 thus belongs to the family of octanuclear cubic coordination polyhedra , and is one of the very few heterometallic examples. , It crystallizes in the noncentrosymmetric cubic space group P 4̅3 n with Z = 2.…”

Computational Modeling of Supramolecular Metallo-organic Cages–Challenges and Opportunities

“…Schäfer and co-workers have also studied the controllable uptake and release of [B 12 F 12 ] 2– in a [Pd 2 L 4 ] 4+ cage with photoswitchable ligands . They calculated binding affinity using US with explicit solvent, which compared well to the value obtained from experiments (computed −6.7 kcal mol –1 vs −6.4 and −5.9 kcal mol –1 from ITC and NMR, respectively).…”

“…Complementary to experimental characterization, detailed computational studies have enabled the study of the mechanisms of guest encapsulation and release and the flexibility of the cage during these processes. Such studies have been performed, for example, to study the binding of fullerenes inside [Pd 4 L 8 ] 8+ , − charged guests inside [Ga 4 L p 6 ] 12– , photoswitchable [Pd 2 L 4 ] 4+ cages, and photoswitchable guests inside the [Pd 6 L 4 ] 12+ cage . Since binding occurs on the millisecond to second time scale, which is practically impossible to reach using conventional MD simulations, rare event sampling methods such as US, accelerated MD (aMD), the attach–pull–release (APR) method, and metadynamics , are employed.…”