ABSTRACT
A steady stream of material transport based on carriers and channels in living systems plays an extremely important role in normal life activities. Inspired by nature, researchers have extensively applied supramolecular cages in cargo transport because of their unique three-dimensional structures and excellent physicochemical properties. In this review, we will focus on the development of supramolecular cages as carriers and channels for cargo transport in abiotic and biological systems over the past fifteen years. In addition, we will discuss future challenges and potential applications of supramolecular cages in substance transport.
ABSTRACT
Developing synthetic molecular devices for controlling ion transmembrane transport is a promising research field in supramolecular chemistry. These artificial ion channels provide models to study ion channel diseases and have huge potential for therapeutic applications. Compared with self-assembled ion channels constructed by intermolecular weak interactions between smaller molecules or cyclic compounds, metallacage-based ion channels have well-defined structures and can exist as single components in the phospholipid bilayer. A naphthalene diimide-based artificial chloride ion channel is constructed through efficient subcomponent self-assembly and its selective ion transport activity in large unilamellar vesicles and the planar lipid bilayer membrane by fluorescence and ion-current measurements is investigated. Molecular dynamics simulations and density functional theory calculations show that the metallacage spans the entire phospholipid bilayer as an unimolecular ion transport channel. This channel transports chloride ions across the cell membrane, which disturbs the ion balance of cancer cells and inhibits the growth of cancer cells at low concentrations.
ABSTRACT
A series of covalent organic cages built from fluorophores capable of aggregation-induced emission (AIE) were elegantly prepared through the reduction of preorganized M2 (LA )3 (LB )2 -type metallacages, simultaneously taking advantage of the synthetic accessibility and well-defined shapes and sizes of metallacages, the good chemical stability of the covalent cages as well as the bright emission of AIE fluorophores. Moreover, the covalent cages could be further post-synthetically modified into an amide-functionalized cage with a higher quantum yield. Furthermore, these presented covalent cages proved to be good energy donors and were used to construct light-harvesting systems employing Nile Red as an energy acceptor. These light-harvesting systems displayed efficient energy transfer and relatively high antenna effect, which enabled their use as efficient photocatalysts for a dehalogenation reaction. This research provides a new avenue for the development of luminescent covalent cages for light-harvesting and photocatalysis.
ABSTRACT
Over the past few decades, the design and construction of high-efficiency artificial light-harvesting systems (LHSs) involving multistep fluorescence-resonance energy transfer (FRET) processes have gradually received considerable attention within wide fields ranging from supramolecular chemistry to chemical biology and even materials science. Herein, through coordination-driven self-assembly, a novel tetragonal prismatic metallacage featuring a FRET process using tetraphenylethene (TPE) units as donors and BODIPY units as acceptors has been conveniently synthesized. Subsequently, taking advantage of supramolecular hydrophobic interactions, a promising artificial LHS involving two-step FRET processes from TPE to BODIPY and then to Nile Red (NiR) has been successfully fabricated in an aqueous solution using the FRET-featuring metallacage, NiR, and an amphiphilic polymer (mPEG-DSPE). Notably, this obtained aqueous LHS exhibits highly efficient photocatalytic activity in the dehalogenation of a bromoacetophenone derivate. This study provides a unique strategy for fabricating artificial LHSs in aqueous solutions with multistep FRET processes and further promotes the future development of mimicking the photosynthesis process.
ABSTRACT
During the past few decades, fabrication of multistep fluorescence-resonance energy transfer (FRET) systems has become one of the most attractive topics within supramolecular chemistry, chemical biology, and materials science. However, it is challenging to efficiently prepare multistep FRET systems with precise control of the distances between locations and the numbers of fluorophores. Herein we present the successful fabrication of a two-step FRET system bearing specific numbers of anthracene, coumarin, and BODIPY moieties at precise distances and locations through an efficient and controllable orthogonal self-assembly approach based on metal-ligand coordination and host-guest interactions. Notably, the photosensitization efficiency and photooxidation activity of the two-step FRET system gradually increased with the number of energy transfer steps. For example, the two-step FRET system exhibited 1.5-fold higher 1O2 generation efficiency and 1.2-fold higher photooxidation activity than that of its corresponding one-step FRET system. This research not only provides the first successful example of the efficient preparation of multistep FRET systems through orthogonal self-assembly involving coordination and host-guest interactions but also pushes multistep FRET systems toward the application of photosensitized oxidation of a sulfur mustard simulant.
ABSTRACT
In the past few decades, the construction of discrete supramolecular double-metallacycles has attracted wide interest because of their unique structures and their potential applications in photoelectric materials. Since some progress has been made in this area, it is time to summarize the progress of discrete supramolecular double-metallacycles. In this review, we will briefly introduce the synthetic strategy of discrete supramolecular double-metallacycles. In addition, we will discuss the design principles, preparation methods, optical properties, and functions of these discrete supramolecular double-metallacycles.
