A stabilization rule for metal carbido cluster bearing µ3-carbido single-atom-ligand encapsulated in carbon cage.

Metal carbido complexes bearing single-carbon-atom ligand such as nitrogenase provide ideal models of adsorbed carbon atoms in heterogeneous catalysis. Trimetallic µ3-carbido clusterfullerenes found recently represent the simplest metal carbido complexes with the ligands being only carbon atoms, but only few are crystallographically characterized, and its formation prerequisite is unclear. Herein, we synthesize and isolate three vanadium-based µ3-CCFs featuring V = C double bonds and high valence state of V (+4), including VSc2C@Ih(7)-C80, VSc2C@D5h(6)-C80 and VSc2C@D3h(5)-C78. Based on a systematic theoretical study of all reported µ3-carbido clusterfullerenes, we further propose a supplemental Octet Rule, i.e., an eight-electron configuration of the µ3-carbido ligand is needed for stabilization of metal carbido clusters within µ3-carbido clusterfullerenes. Distinct from the classic Effective Atomic Number rule based on valence electron count of metal proposed in the 1920s, this rule counts the valence electrons of the single-carbon-atom ligand, and offers a general rule governing the stabilities of µ3-carbido clusterfullerenes.

Fullerene Covalent Passivation of Black Phosphorus Nanosheets toward Enhanced Near-Infrared-II Photothermal Therapy.

Photothermal therapy (PTT) triggered by near-infrared-II (NIR-II, 1000-1700 nm) light is developed as a potential tumor therapy technique with deeper tissue penetration capacity and higher allowable laser power density of the skin than NIR-I (750-1000 nm) biowindow. Black phosphorus (BP) with excellent biocompatibility and favorable biodegradability demonstrates promising applications in PTT but suffers from low ambient stability and limited photothermal conversion efficiency (PCE), and utilization of BP in NIR-II PTT is scarcely reported. Herein, we develop novel fullerene covalently modified few-layer BP nanosheets (BPNSs) with ∼9-layer thickness through an easy one-step esterification process (abbreviated BP-ester-C60), bringing about the dramatically enhanced ambient stability of BPNSs due to bonding of the hydrophobic C60 with high stability and the lone electron pair on the phosphorus atom. BP-ester-C60 is then applied as a photosensitizer in NIR-II PTT, delivering a much higher PCE than the pristine BPNSs. Under 1064 nm NIR-II laser irradiation, in vitro and in vivo antitumor studies reveal that BP-ester-C60 exhibits dramatically enhanced PTT efficacy with considerable biosafety relative to the pristine BPNSs. This is interpreted by the boost of NIR light absorption on account of the modulation of the band energy level resulting from intramolecular electron transfer from BPNSs to C60.

Boosting Antitumor Sonodynamic Therapy Efficacy of Black Phosphorus via Covalent Functionalization.

Sonodynamic therapy (SDT) triggered by ultrasound represents an emerging tumor therapy approach with minimally invasive treatment featuring nontoxicity and deep tissue-penetration, and its efficacy sensitively depends on the sonosensitizer which determines the generation of reactive oxygen species (ROS). Herein, for the first time covalently functionalized few-layer black phosphorus nanosheets (BPNSs) are applied as novel sonosensitizers in SDT, achieving not only boosted SDT efficacy but also inhibited cytotoxicity relative to the pristine BPNSs. Three different covalently functionalized-BPNSs are synthesized, including the first fullerene-functionalized BPNSs with C60 covalently bonded onto the surface of BPNSs (abbreviated as C60 -s-BP), surface-functionalized BPNSs by benzoic acid (abbreviated as BA-s-BP), and edge-functionalized BPNSs by C60 (abbreviated as C60 -e-BP), and the role of covalent functionalization pattern of BPNSs on its SDT efficacy is systematically investigated. Except C60 -e-BP, both surface-functionalized BPNSs (C60 -s-BP, BA-s-BP) exhibit higher SDT efficacies than the pristine BPNSs, while the highest SDT efficacy is achieved for BA-s-BP due to its strongest capability of generating the hydroxyl (·OH) radicals, which act as the dominant ROS to kill the tumor cells.