Preparation of a Multicarbazole-Based Nanocapsule Capable of Largely Modulating Guest Spectroscopic Properties in Water

Transformation of Highly Hydrophobic Triarylphosphines into Amphiphiles via Staudinger Reaction with Hydrophilic Trichlorophenyl Azide

Owing to its hydrophobic properties and reactivity, triarylphosphines (PAr3 ) are promising precursors for the development of new amphiphiles. However, an efficient and reliable synthetic method for amphiphiles based on highly hydrophobic PAr3 is still required. Herein, a straightforward transformation of highly hydrophobic PAr3 into amphiphiles via the Staudinger reaction is reported. By simply mixing PAr3 and a hydrophilic trichlorophenyl azide containing two hydrophilic chains, amphiphiles bearing a N=P bond (i. e., an azaylide moiety) were quantitatively formed. The obtained azaylide-based amphiphiles were remarkably water-soluble, enabling their spontaneous self-assembly into 2 nm-sized micelles composed of 4-5 molecules in water with a low critical micelle concentration (up to 0.05 mM or less) due to the effective intermolecular interactions among the hydrophobic surfaces. Although the azaylide moiety is easily hydrolyzed in the presence of water, the azaylide in the amphiphiles displayed notable stability in water even at 60 h, which stems from the LUMO modulation induced by the presence of three electron-withdrawing chloro groups and two twisted alkoxycarbonyl groups, according to DFT calculations. An amphiphile having a large hydrophobic surface solubilized various hydrophobic organic dyes through efficient intermolecular interactions, resulting in the dyes exhibiting either monomer or excimer emissions in water.

Aromatic micelles: toward a third-generation of micelles

Micelles are useful and widely applied molecular assemblies, formed from amphiphilic molecules, in water. The majority of amphiphiles possess an alkyl chain as the hydrophobic part. Amphiphiles bearing hydrophilic and hydrophobic polymer chains generate so-called polymeric micelles in water. This review focuses on the recent progress of "aromatic micelles", formed from bent polyaromatic/aromatic amphiphiles, for the development of third-generation micelles. Thanks to multiple host-guest interactions, e.g., the hydrophobic effect and π-π/CH-π interactions, the present micelles display wide-ranging uptake abilities toward various hydrophobic compounds in water. In addition to such host functions, new stimuli-responsive aromatic micelles with pH, light, and redox switches, aromatic oligomer micelles, saccharide-coated aromatic micelles, and related cycloalkane-based micelles were recently developed by our group.

Morpholine-Functionalized Multicomponent Metallacage as a Vector for Lysosome-Targeted Cell Imaging

Metallacages with suitable cavities and specific functions are promising delivery vectors in biological systems. Herein, we report a morpholine-functionalized metallacage for lysosome-targeted cell imaging. The efficient host-guest interactions between the metallacage and dyes prevent them from aggregation, so their emission in aqueous solutions is well maintained. The fluorescence quantum yield of these host-guest complexes reaches 74.40%. Therefore, the metallacage is further employed as a vector to deliver dyes with different emission colors (blue, green, and red) into lysosomes for targeted imaging. This research affords a type of vector for the delivery of various cargos toward biological applications, which will enrich the usage of metallacages in biomedical engineering.

An Adamantane Capsule and its Efficient Uptake of Spherical Guests up to 3 nm in Water

Efficient uptake of small to large guests, with a large difference in relative size, is quite rare for synthetic host compounds. Herein we designed and prepared a micellar capsule, composed of bent amphiphiles bearing two adamantyl groups, as a new host with a well-defined nanostructure. Unlike previous covalent, coordination, and hydrogen-bonding hosts, the adamantane-based capsule displays unusual uptake abilities toward spherical molecules with small (∼0.6 nm in diameter; e.g., adamantane) to medium size (∼1 nm; e.g., fullerene) as well as large size (∼3 nm; i.e., metal-organic polyhedra (MOP)), where the size differences are up to 5-fold, in water. Moreover, the resultant MOP-uptaking capsule incorporates medium-sized molecules (e.g., perylene and eosin Y) into the polyhedral cavity to generate ternary core-shell structures.

Synthesis of Azaylide-Based Amphiphiles by the Staudinger Reaction

Catalyst- and reagent-free reactions are powerful tools creating various functional molecules and materials. However, such chemical bonds are usually hydrolysable or require specific functional groups, which limits their use in aqueous media. Herein, we report the development of new amphiphiles through the Staudinger reaction. Simple mixing of chlorinated aryl azide with a hydrophilic moiety and various triarylphosphines (PAr3) gave rise to azaylide-based amphiphiles NPAr3, rapidly and quantitatively. The obtained NPAr3 formed ca. 2 nm-sized spherical aggregates (NPAr3)_n in water. The hydrolysis of NPAr3 was significantly suppressed as compared with those of non-chlorinated amphiphiles nNPAr3. Computational studies revealed that the stability is mainly governed by the decrease in LUMO around the phosphorus atom owing to the o-substituted halogen groups. Furthermore, hydrophobic dyes such as Nile red and BODIPY were encapsulated by the spherical aggregates (NPAr3)_n in water.

Supramolecular Singlet Fission of Pentacene Dimers within Polyaromatic Capsules

We herein report a new set of supramolecular nanotools for the generation and modulation of singlet fission (SF) of noncovalent/covalent pentacene dimers. Two molecules of a pentacene monomer with bulky substituents are facilely encapsulated by a polyaromatic capsule, composed of naphthalene-based bent amphiphiles, in water. The encapsulated noncovalent dimer converts to otherwise undetectable triplet pairs and an individual triplet in high quantum yields (179% and 53%, respectively) even under high dilution conditions. Within the capsule, a covalently linked pentacene dimer with bulky groups generates two triplet pair intermediates in parallel, which are hardly distinguished in bulk solution, in excellent total quantum yield (196%). The yield of the individual triplet is enhanced by 1.6 times upon encapsulation. For both types of pentacene dimers, the SF features can be readily tuned by changing the polyaromatic panels of the capsule (i.e., anthracene and phenanthrene).