Light-Driven Purification of Progesterone from Steroid Mixtures Using a Photoresponsive Metal-Organic Capsule.

Chemical separations are expensive, consuming 10-15% of humanity's global energy budget. Many current separation methods employ thermal energy for distillation, often through the combustion of carbon-containing fuels, or extractions and crystallizations from organic solvents, which must then be discarded or redistilled, with a substantial energetic cost. The direct use of renewable energy sources, such as light, could enable the development of novel separations processes, as is required for the transition away from fossil fuel use. Metal-organic capsules, which can selectively bind molecules from mixtures, can provide the foundation for these novel separations processes. Here we report a tetrahedral metal-organic capsule bearing light-responsive diazo moieties around its metal-ion vertices. This capsule can be used to selectively separate progesterone from a mixture of steroids in a process driven by visible light energy. Our process combines biphasic extraction and selective binding of progesterone with the light-driven release of this molecule in purified form. Ultimately, our process might be adapted to the purifications of the many other fine chemical products that are bound selectively by capsules.

A three-shell supramolecular complex enables the symmetry-mismatched chemo- and regioselective bis-functionalization of C60.

Molecular Russian dolls (matryoshkas) have proven useful for testing the limits of preparative supramolecular chemistry but applications of these architectures to problems in other fields are elusive. Here we report a three-shell, matryoshka-like complex-in which C60 sits inside a cycloparaphenylene nanohoop, which in turn is encapsulated inside a self-assembled nanocapsule-that can be used to address a long-standing challenge in fullerene chemistry, namely the selective formation of a particular fullerene bis-adduct. Spectroscopic evidence indicates that the ternary complex is sufficiently stable in solution for the two outer shells to affect the addition chemistry of the fullerene guest. When the complex is subjected to Bingel cyclopropanation conditions, the exclusive formation of a single trans-3 fullerene bis-adduct was observed in a reaction that typically yields more than a dozen products. The selectivity facilitated by this matryoshka-like approach appears to be a general phenomenon and could be useful for applications where regioisomerically pure C60 bis-adducts have been shown to have superior properties compared with isomer mixtures.

Complete Dynamic Reconstruction of C60, C70, and (C59N)2 Encapsulation into an Adaptable Supramolecular Nanocapsule.

The dynamic adaptability of tetragonal prismatic nanocapsule 18+ in the selective separation of fullerenes and endohedral metallofullerenes (EMFs) remains unexplored. Therefore, the essential molecular details of the fullerene recognition and binding process into the coordination capsule and the origins of fullerene selectivity remain elusive. In this work, the key steps of fullerene recognition and binding processes have been deciphered by designing a protocol which combines 1H-1H exchange spectroscopy (2D-EXSY) NMR experiments, long time-scale Molecular Dynamics (MD) and accelerated Molecular Dynamics (aMD) simulations, which are combined to completely reconstruct the spontaneous binding and unbinding pathways from nanosecond to second time-range. On one hand, binding (k'on) and unbinding (koff) rate constants were extracted from 1H-1H exchange spectroscopy (EXSY) NMR experiments for both C60 and C70. On the other hand, MD and aMD allowed monitoring the molecular basis of the encapsulation and guest competition processes at a very early stage under nonequilibrium conditions. The receptor capsule displays dynamical adaptability features similar to those observed in the process of biomolecular recognition in proteins. In addition, the encapsulation of bis-aza[60]fullerene (C59N)2 within a supramolecular coordination capsule has been studied for the first time, showcasing the pros and cons of the dumbbell-shaped guest in the dynamics of the encapsulation process and in the stability of the final bound adduct. The powerful combination of NMR, MD, and aMD methodologies allows to obtain a precise picture of the subtle events directing the encapsulation and is thus a predictive tool for understanding host-guest encapsulation and interactions in numerous supramolecular systems.

Highly selective encapsulation and purification of U-based C78-EMFs within a supramolecular nanocapsule.

The ability of the tetragonal prismatic nanocapsule 1·(BArF)8 to selectively encapsulate U-based C78 EMFs from a soot mixture is reported, showing enhanced affinity for C78-based EMFs over C80-based EMFs. Molecular recognition driven by the electrostatic interactions between the host and guest is at the basis of the high selectivity observed for ellipsoidal C78-based EMFs compared to spherical C80-based EMFs. In addition, DFT analysis points towards an enhanced breathing adaptability of nanocapsule 1·(BArF)8 to C78-based EMFs to further explain the selectivity observed when the host is used in the solid phase.

Purification of Uranium-based Endohedral Metallofullerenes (EMFs) by Selective Supramolecular Encapsulation and Release.

Supramolecular nanocapsule 1⋅(BArF)8 is able to sequentially and selectively entrap recently discovered U2 @C80 and unprecedented Sc2 CU@C80 , simply by soaking crystals of 1⋅(BArF)8 in a toluene solution of arc-produced soot. These species, selectively and stepwise absorbed by 1⋅(BArF)8 , are easily released, obtaining highly pure fractions of U2 @C80 and Sc2 CU@C80 in one step. Sc2 CU@C80 represents the first example of a mixed metal actinide-based endohedral metallofullerene (EMF). Remarkably, the host-guest studies revealed that 1⋅(BArF)8 is able to discriminate EMFs with the same carbon cage but with different encapsulated cluster and computational studies provide support for these observations.

Self-Assembled Cofacial Zinc-Porphyrin Supramolecular Nanocapsules as Tuneable 1 O2 Photosensitizers.

We demonstrate the benefits of using cofacial Zn-porphyrins as structural synthons in coordination-driven self-assembled prisms to produce cage-like singlet oxygen (1 O2 ) photosensitizers with tunable properties. In particular, we describe the photosensitizing and emission properties of palladium- and copper-based supramolecular capsules, and demonstrate that the nature of the bridging metal nodes in these discrete self-assembled prisms strongly influences 1 O2 generation at the Zn-porphyrin centers. The PdII -based prism is a particularly robust photosensitizer, whereas the CuII self-assembled prism is a dormant photosensitizer that could be switched to a ON state upon disassembly of the suprastructure. Furthermore, the well-defined cavity within the prisms allowed encapsulation of pyridine-based ligands and fullerene derivatives, which led to a remarkable guest tuning of the 1 O2 production.

A Copper-based Supramolecular Nanocapsule that Enables Straightforward Purification of Sc3 N-based Endohedral Metallofullerene Soots.

A self-assembled CuII -based nanocapsule enables efficient and straightforward isolation of Sc3 N@C80 from arc-processed raw soot. The newly designed CuII -based supramolecular nanocapsule 5⋅(OTf)8 was used to effectively entrap fullerenes and endohedral metallofullerenes (EMFs) with different affinities depending on their size and shape. Moreover, we took advantage of the sharply different entrapment abilities of the 5⋅(OTf)8 cage in the solid state versus in solution to encapsulate all the species with the exception of Sc3 N@C80 (both Ih and D5h isomers), which remains pure in solution. HPLC quantification determined that up to 85 % of the total Sc3 N@C80 content in the initial mixture was recovered in very high purity (>99.5 %). The complete release of the encapsulated species with an orthogonal solvent-washing strategy regenerates 5⋅(OTf)8 ready to be re-used. This approach opens new opportunities for EMFs purification.