Discrete Pt(II) metallacycles have potential applications in biomedicine. Herein, we engineered a dual-modal imaging and chemo-photothermal therapeutic nano-agent 1 that incorporates discrete Pt(II) metallacycle 2 and fluorescent dye 3 (emission wavelength in the second near-infrared channel [NIR-II]) into multifunctional melanin dots with photoacoustic signal and photothermal features. Nano-agent 1 has a good solubility, biocompatibility, and stability in vivo. Both photoacoustic imaging and NIR-II imaging in vivo confirmed that 1 can effectively accumulate at tumor sites with good signal-to-background ratio and favorable distribution. Guided by precise dual-modal imaging, nano-agent 1 exhibits a superior antitumor performance and less severe side effects compared with a single treatment because of the high efficiency of the chemo-photothermal synergistic therapy. This study shows that nano-agent 1 provides a promising multifunctional theranostic platform for potential applications in biomedicine.

Here, we present a method for the building of new bicyclic heterometallic cross-linked supramolecular polymers by hierarchical unification of three types of orthogonal noncovalent interactions, including platinum(II)−pyridine coordination-driven self-assembly, zinc−terpyridine complex, and host−guest interactions. The platinum−pyridine coordination provides the primary driving force to form discrete rhomboidal metallacycles. The assembly does not interfere with the zinc−terpyridine complexes, which link the discrete metallacycles into linear supramolecular polymers, and the conjugation length is extended upon the formation of the zinc−terpyridine complexes, which red-shifts the absorption and emission spectra. Finally, host−guest interactions via bis-ammonium salt binding to the benzo-21-crown-7 (B21C7) groups on the platinum acceptors afford the cross-linked supramolecular polymers. By continuous increase of the concentration of the supramolecular polymer to a relatively high level, supramolecular polymer gel is obtained, which exhibits self-healing properties and reversible gel−sol transitions stimulated by various external stimuli, including temperature, K + , and cyclen. Moreover, the photophysical properties of the supramolecular polymers could be effectively tuned by varying the substituents of the precursor ligands.

Hierarchical self-assembly of discrete organo­platinum­(II) metalla­cycles has attracted considerable attention. However, the exact assembly mechanism involving non-covalent interactions has limited the formation and application of self-assembly due to the dynamics of platinum metalla­cycles. Herein, we report the hierarchical self-assembly of a pyrene-based discrete organo­platinum­(II) double-metalla­cycle that takes advantage of hetero­ligation-coordination-driven self-assembly and triflate anions’ hydrogen bonding, which is extended into a 3-D supra­molecular framework by the hydrogen-bonding interactions involving triflate anions. Furthermore, the assembled system displays tunable fluorescence emission and enhanced solid emission. The studies herein disclosed pave the way to prepare platinum­(II) metalla­cycle-based supra­molecular functional materials.

Two trigonal prismatic metallacages 1 and 2 bearing triphenylamine and anthracene moieties are designed and synthesized to fabricate artificial light-harvesting systems (LHSs). These two cages are prepared via the coordination-driven self-assembly of two anthracene–triphenylamine-based tripyridyl ligand 3, three dicarboxylates, and six 90° Pt­(II) acceptors. The design of the anthracene–triphenylamine chromophore makes possible the tunable excited-state property (like the emissive transition energy and lifetime) as a function of the solvent polarity, temperature, and concentration. The synergistic photophysical footprint of these metallacages, defined by their high absorptivity and emission quantum yield (QY) relative to the free ligand 3, signifies them as a superior light sensitizer component in an LHS. In the presence of the fluorescent dye Nile Red (NR) as an energy acceptor, the metallacages display efficient (>93%) excited energy transfer to NR through an apparent static quenching mechanism in viscous dimethyl sulfoxide solvent.

The recent progress in platinum(II) coordination driven supramolecular polymers has had a substantial effect on the design of functional soft materials. However, the prospect of realizing platinum(II) metallacycle-based host-guest interactions induced polymerization has received little attention until recently. Here we report the realization of supramolecular polymerization driven by platinum(II) metallacycle-based host-guest interactions both in the solid state and in solution. On the basis of the disclosed polymerization mechanism, we present a new strategy for the preparation of platinum(II) metallacycle-based supramolecular polymers.