Guang-Qiang Yin

Construction of Smart Supramolecular Polymeric Hydrogels Cross-linked by Discrete Organoplatinum(II) Metallacycles via Post-Assembly Polymerization

Postassembly modification strategy has been successfully employed in the construction of discrete metallosupramolecular assemblies. However, the most known reports have been limited to the simple structural conversion through the easy covalent reactions, thus hindering the development of organometallic functional materials. In this study, we first combined coordination-driven self-assembly and postassembly reversible addition-fragmentation chain-transfer (RAFT) polymerization to produce a new family of star supramolecular polymers containing well-defined metallacycles as cores, which featured typical lower critical solution temperature (LCST) behavior in water because of the existence of poly(N-isopropylacrylamide) (PNIPAAM) moieties. Moreover, the obtained star polymers could further form supramolecular hydrogels cross-linked by discrete hexagonal metallacycles at room temperature without heating-cooling process. Interestingly, the resultant polymeric hydrogels exhibited stimuli-responsive behavior toward temperature and bromide anion as well as self-healing property. We demonstrated that the dynamic nature of Pt-N bonds in the hexagonal metallacycles played an important role in determining the stimuli-responsive and self-healing property of the final soft matters. Thus, merging coordination-driven self-assembly and postassembly polymerization provided a new avenue to the preparation of functional materials containing well-defined, discrete metal-organic assemblies as main scaffolds.

Multiphase transition of supramolecular metallogels triggered by temperature

We present a new family of supramolecular metallogels undergoing reversible multiphase transition triggered by temperature from amphiphilic alkynylplatinum(ii) complexes. Further investigation revealed that intermolecular PtPt and π-π stacking interactions facilitate such phase transitions upon increasing the temperature.

Self-assembly of emissive supramolecular rosettes with increasing complexity using multitopic terpyridine ligands

Coordination-driven self-assembly has emerged as a powerful bottom-up approach to construct various supramolecular architectures with increasing complexity and functionality. Tetraphenylethylene (TPE) has been incorporated into metallo-supramolecules to build luminescent materials based on aggregation-induced emission. We herein report three generations of ligands with full conjugation of TPE with 2,2′:6′,2″-terpyridine (TPY) to construct emissive materials. Due to the bulky size of TPY substituents, the intramolecular rotations of ligands are partially restricted even in dilute solution, thus leading to emission in both solution and aggregation states. Furthermore, TPE-TPY ligands are assembled with Cd(II) to introduce additional restriction of intramolecular rotation and immobilize fluorophores into rosette-like metallo-supramolecules ranging from generation 1–3 (G1−G3). More importantly, the fluorescent behavior of TPE-TPY ligands is preserved in these rosettes, which display tunable emissive properties with respect to different generations, particularly, pure white-light emission for G2.Metal coordination of multitopic ligands is a powerful approach to building complex, functional architectures. Here, the authors construct three generations of fluorescent supramolecular rosettes by coordination of aggregation-induced emissive ligands, including a 2nd-generation macrocycle that emits pure white light.

A tetraphenylethylene (TPE)-based supra-amphiphilic organoplatinum(II) metallacycle and its self-assembly behaviour

In recent years, fluorescent functional materials with aggregation-induced emission (AIE) properties have evolved to be one of the most attractive topics within chemistry and materials science. In particular, discrete TPE-based metallacycles or metallacages through coordination-driven self-assembly have proven to be novel scaffolds to construct various fluorescent materials with light-emitting characteristics. Herein, we report the preparation of a new family of discrete, TPE-based supra-amphiphilic metallacycles decorated with three PNIPAAM arms through combination of an exo-functionalization strategy and post-assembly polymerization. The obtained supra-amphiphilic organometallic species could spontaneously self-assemble into fluorescent nanoparticles in water. Moreover, by taking advantages of both AIE property and good biocompatibility of the obtained TPE-based supra-amphiphilic metallosupramolecular structure, its potential application in cell imaging was investigated.

Direct Self‐Assembly of a 2D and 3D Star of David

Two- and three-dimensional metallosupramolecules shaped like a Star of David were synthesized by the self-assembly of a tetratopic pyridyl ligand with a 180° diplatinum(II) motif and PdII ions, respectively. In contrast to other strategies, such as template-directed synthesis and stepwise self-assembly, this design enables the formation of 2D and 3D structures in one step and high yield. The structures were characterized by both one-dimensional (1 H, 13 C, 31 P) and two-dimensional (COSY, NOESY, DOSY) NMR spectroscopy, ESI-MS, ion-mobility mass spectrometry (IM-MS), AFM, and TEM. The stabilities of the 2D and 3D structures were measured and compared by gradient tandem mass spectrometry (gMS2 ). The high stability of the 3D Star of David was correlated to its high density of coordination sites (DOCS).

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

Herein, we present the successful construction of a new family of cross-linked AIE supramolecular polymer gels with multiple stimuli-responsive behaviours through hierarchical self-assembly involving coordination and host–guest interactions. Firstly, by decorating the tetraphenylethylene (TPE) core with two dipyridyl moieties and two pillar[5]arene units, a new dipyridyl donor H1 was successfully prepared. Then, a rhomboidal metallacycle H2 with four pillar[5]arene units and a hexagonal metallacycle H3 with six pillar[5]arene units were constructed through coordination-driven self-assembly. Subsequently, cross-linked supramolecular polymers H2⊃G2 and H3⊃G3 were formed through host–guest interactions. The obtained supramolecular polymers were able to transform into supramolecular polymer gels under higher concentration, which displayed AIE properties due to the restriction of TPE intramolecular motions within three-dimensional polymeric networks. More interestingly, by taking advantages of dynamic nature of both coordination bonds and host–guest interactions, the resultant supramolecular polymer gels displayed multiple stimuli-responsive gel–sol transitions under different stimuli, such as temperature, competitive guest molecules, halides, etc., along with the “on–off” of fluorescence.

Facile Construction of Structurally Defined Porous Membranes from Supramolecular Hexakistriphenylamine Metallacycles through Electropolymerization.

The construction of well-controlled porous materials is very challenging. Herein, we report the successful preparation of structurally defined porous membranes based on hexakistriphenylamine metallacycles through electropolymerization. The newly designed porous materials were characterized by the typical cyclic voltammograms, XPS, SEM, and TEM investigations. Further investigations revealed that the metallacycle-based polymer films displayed a good size-selective molecular-sieving behavior.

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.

Dual stimuli-responsive rotaxane-branched dendrimers with reversible dimension modulation

With the aim of mimicking biological machines, in which the delicate arrangement of nanomechanical units lead to the output of specific functions upon the external stimulus, the construction of dual stimuli-responsive rotaxane-branched dendrimers was realized in this study. Starting from a switchable organometallic [2]rotaxane precursor, the employment of a controllable divergent approach allowed for the successful synthesis of a family of rotaxane-branched dendrimers up to the third generation with 21 switchable rotaxane moieties located on each branch. More importantly, upon the addition and removal of dimethylsulfoxide (DMSO) molecule or acetate anion as the external stimulus, the amplified responsiveness of the switchable rotaxane units endowed the resultant rotaxane-branched dendrimers the solvent- or anion-controlled molecular motions, thus leading to the dimension modulation. Therefore, we successfully constructed a family of rotaxane-branched dendrimers with dual stimuli-responsiveness that will be a privileged platform for the construction of dynamic supramolecular materials.Mechanically interlocked molecules are extensively applied as artificial molecular machines but rotaxane-branched dendrimers are rarely explored because of synthetic challenges. Here the authors present the construction of dual stimuli-responsive rotaxane-branched dendrimer which can be stimulated by DMSO or acetate ions.