Hierarchical self-assembly of triangular metallodendrimers into the ordered nanostructures

A chromatography-free total synthesis of a ferrocene-containing dendrimer exhibiting the property of recognizing 9,10-diphenylanthracene

Molecules comprising several ferrocene residues constitute an intriguing group of compounds for various applications. Here, the total synthesis of a new example of a ferrocene-containing dendrimer is presented. The target compound was obtained in excellent combined yield (65%) employing facile, chromatography-free methods at each step. Interesting findings, meeting the dynamic covalent chemistry concept, are reported. Cyclic voltammetry analyses revealed one pair of current signals for the ferrocene moieties. Ultimately, the synthesized ferrocene-containing dendrimer has been used as an innovative recognition material for 9,10-diphenylanthracene, a polycyclic aromatic hydrocarbon, with the limit of detection value equal to 0.06 μM.

Soft Materials with Diverse Suprastructures via the Self-Assembly of Metal-Organic Complexes

Inspired by assemblies in the natural world, researchers have prepared diverse suprastructures with distinct spatial arrangements by artificial self-assembly, including micelles, vesicles, ribbons, films, fibers, and tubes. The field of assembly is undergoing a transition from single-component to multicomponent assembly and single-step to multistep processing. Control over the size, shape, and composition of these building blocks has enabled the formation of suprastructures with substantial structural diversity. More importantly, harnessing noncovalent interactions to create suprastructures in a controlled manner will lead to a better understanding of the formation of complex self-organized patterns. However, for the construction of multiscale self-assemblies with controllable shapes and functions, the selection of a suitable protocol remains challenging. Coordination-driven self-assembly provides a bottom-up approach to construct various metal-organic complexes (MOCs), which could be further used as building blocks with controllable shapes and sizes. Despite the tremendous progress made in the design of MOC-based supramolecular materials, most of these MOCs have dimensions of only several nanometers, and investigations of these structures rely on the characterization of their crystal structure. However, most of the functional suprastructures in living organisms have dimensions ranging from microns to centimeters and have the form of soft materials. Thus, obtaining MOC-based highly ordered materials of larger size remains a challenge. This Account focuses on our recent advances in the construction of soft suprastructure materials with MOCs. A series of functionalized MOCs was first constructed through coordination-driven self-assembly. Then, further self-assembly of the as-prepared MOCs gave rise to the formation of higher-order structures. By changing the functional groups in the acceptors and donors in the MOCs, different suprastructures, including nanospheres, nanodiamonds, nanorods, nanofibers, membranes, films, and gels, were prepared. These studies suggest that using MOCs as building blocks is a highly efficient strategy to achieve complex architectures and functional materials for the development of desired MOC-based soft materials with high precision and fidelity.

Porphyrin-functionalized coordination star polymers and their potential applications in photodynamic therapy

We present a new family of porphyrin-functionalized coordination star polymers prepared through combination of coordination-driven self-assembly and post-assembly polymerization. Their self-assembly behaviour in water and potential for photodynamic therapy were demonstrated.

Construction of Stimuli-Responsive Functional Materials via Hierarchical Self-Assembly Involving Coordination Interactions

Supramolecular self-assembly, which creates the ordered structures as a result of spontaneous organization of building blocks driven by noncovalent interactions (NCIs), is ubiquitous in nature. Recently, it has become increasingly clear that nature often builds up complex structures by employing a hierarchical self-assembly (HSA) strategy, in which the components are brought together in a stepwise process via multiple NCIs. Inspired by the dedicated biological structures in nature, HSA has been widely explored to construct well-defined assemblies with increasing complexity. The employment of direct metal-ligand bonds to drive the formation of discrete metallosupramolecular architectures has proven to be a highly efficient strategy to prepare structurally diverse architectures like two-dimensional (2-D) polygons and three-dimensional (3-D) polyhedra with well-defined shapes, sizes, and geometries. Such well-defined organometallic assemblies provide an ideal platform for designing novel artificial supramolecular systems with the increasing complexity though HSA. The presence of a well-defined organometallic scaffold brings an additional dimension to the final nanoscale structures. Moreover, the multilevel dynamic nature of hierarchical self-assemblies brings more structural and functional possibilities of resultant supramolecular systems. This Account will focus on our recent advance on construction of stimuli-responsive functional materials through HSA involving coordination interactions. In our study, a series of functionalized metallacycles were first constructed through coordination-driven self-assembly (CDSA). Then, the secondary noncovalent interaction sites were integrated within the functionalized metallacycle system via either preassembly or postassembly approach. Different segments, such as alkyl chains, dendrimers, cholesteryl moiety, covalent macrocycles, and even polymeric fragments, which could provide hydrophobic and hydrophilic interactions, van der Waals forces, hydrogen bonding, CH-π and π-π interactions, and host-guest interactions, have been utilized to provide the secondary NCIs. Further self-assembly of functionalized metallacycles gives rise to the formation of complex higher-order structures driven by other NCIs by taking advantages of orthogonal property of coordination bonds with other NCIs. By changing the type of additional NCIs embodied in building blocks, different supramolecular architectures, such as the ordered nanostructures, supramolecular polymers and gels, fluorescent materials and sensors, have been successfully prepared with the tailored chemical and physical properties. In particular, the dynamic nature of coordination bonds as well as other NCIs endows final assemblies with stimuli-responsive functions. Collectively, our studies suggest that combining coordination and other NCIs in a well-defined and precise manner is a highly efficient strategy to achieve the complex architectures and functional materials. Therefore, it is very promising to develop the desired functional materials with high precision and fidelity by employing HSA involving coordination interactions.

Coordination-driven self-assembly of discrete Ru6-Pt6 prismatic cages

The coordination-driven self-assembly of two new Ru6-Pt6 hexanuclear trigonal prismatic cages comprising arene-ruthenium(II) clips (1a(NO3)2 and 1b(NO3)2 ) and a tritopic platinum(II) metalloligand 2 has been performed in methanol at room temperature. The [3 + 2] hexanuclear cages 3a and 3b were isolated in good yields and characterized by well-known spectroscopic techniques including multinuclear NMR, mass spectrometry, UV-vis and infrared studies. Geometry optimization revealed the shapes and sizes of these hexanuclear prismatic cages. The combination of ruthenium and platinum metal center in a one-pot self-assembly reaction showcases the construction of aesthetically elegant heterometallic structures in supramolecular chemistry leading to the formation of a single major product.

Construction of Porphyrin-Containing Metallacycle with Improved Stability and Activity within Mesoporous Carbon

The successful construction of porphyrin functionalized metallacycle in the confined cavity of mesoporous carbon FDU-16 (3⊂C) is presented in this study. Because of high dispersity of metallacycles within the mesoporous cavities, the stability and activity of porphyrin-containing metallacycles were obviously improved. For example, ¹O₂ generation efficiency of 3⊂C is ca. 6-fold faster than that of free metallaycles in solution. Thus, the resultant hybrid material has been successfully employed as a heterogeneous catalyst for photooxidation of sulfides.

Facile construction of organometallic rotaxane-terminated dendrimers using neutral platinum-acetylides as the main scaffold

We present the successful construction of a new family of organometallic rotaxane-terminated dendrimers using neutral platinum-acetylides as the main scaffold. The fourth generation dendrimer has 24 rotaxane moieties on the surface termini in a monodisperse manner.

Cross-linked AIE supramolecular polymer gels with multiple stimuli-responsive behaviours constructed by hierarchical self-assembly

Cross-linked AIE supramolecular polymer gels were successfully constructed by hierarchical self-assembly.