Competitive photoinduced electron transfer by the complex formation of porphyrin with cyclodextrin bearing viologen

Photoinduced Electron Transfer in Encapsulated Heterocycles by Cavitands

Host-guest complexation of small heterocyclic (guest) and macrocyclic cavitands (hosts) organic molecules is still to date a very popular, inexpensive approach that bypasses the burdens of conventional covalent synthesis. Understanding the selection criteria of these chemicals is crucial to the design and potential applications of their supramolecular assemblies. This review surveys examples within the last 15 years (2005-2020) of supramolecular complexes in which the interacting photoinduced electron transfer (PET)-based chromophore and quencher fragments are commonly used in the market with reported CAS numbers. It appears from this survey that the supramolecular effects can be directed to specifically disrupt PET when the nonemissive macrocycles separately encapsulate the fluorescent acceptor or donor molecules, among other specific factors, such as when inducing conformational changes or pK_a shift of the donor. On the contrary, synergetic encapsulation of both donor and acceptor molecules, formation of ternary self-assembly at the rim or encapsulation of one component while grafting the other onto the macrocycle, among other specific factors such as the modulation of the excited-state structure of donor, will lead to the enhancement of PET process. In the event the donor or acceptor molecules have multitopic structures, the PET process can repeatedly be switched on and off. It is generally concluded that understanding the criteria for the combination of these available products for the purpose of manipulating their PET efficiency should pave the way for the facile alternative generation of new noncovalently bonded host-guest supramolecular assemblies with a more specific design tailored for more advanced, diverse and economic applications such as chemical sensing, molecular gates, drug delivery and biolabeling.

Porphyrinoid biohybrid materials as an emerging toolbox for biomedical light management

The present article reviews the most important developing strategies in light-induced nanomedicine, based on the combination of porphyrinoid photosensitizers with a wide variety of biomolecules and biomolecular assemblies.

Syntheses and self-assembly behaviors of the azobenzenyl modified beta-cyclodextrins isomers

A couple of analogues of azobenzenyl beta-cyclodextrins 1 and 2 with self-locked and self-unlocked conformations have been synthesized via the Huisgen cycloaddition from the same reactants, but in distinct reaction conditions (i.e., the hydrothermal synthesis and the "click" reaction, respectively), their conformations were sufficiently proved by X-ray crystal structural analysis, molecular modeling study, and 2D NMR spectroscopy, and their self-assembly behaviors in aqueous solution were also investigated by NMR spectroscopy. Interestingly, the self-locked conformer 1, which could be regarded as a new type of [1]rotaxane, self-assembled to a novel bimolecular capsule, where its azobenzene substituent was included in both its own cavity and the counterpart's cavity, in aqueous solution and in the solid state. In contrast, by adjusting the conformation of 1 to a self-unlocked one, the resulting conformer 2 was found to self-assemble to a linear supramolecule. These studies have shown the stronger impact of the reaction condition changing in cyclodextrin's modification products and will provide a new access to control the structure of supramolecular assemblies by tuning the conformation of building blocks.