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1. Metalloimmunotherapy with Rhodium and Ruthenium Complexes: Targeting Tumor‐Associated Macrophages

   https://doi.org/10.1002/chem.202104430  

   Toupin, Nicholas; Herroon, Mackenzie K.; Thummel, Randolph P.; Turro, Claudia; Podgorski, Izabela; Gibson, Heather; Kodanko, Jeremy J. (March 2022, Chemistry – A European Journal)

   Abstract Tumor associated macrophages (TAMs) suppress the cancer immune response and are a key target for immunotherapy. The effects of ruthenium and rhodium complexes on TAMs have not been well characterized. To address this gap in the field, a panel of 22 dirhodium and ruthenium complexes were screened against three subtypes of macrophages, triple‐negative breast cancer and normal breast tissue cells. Experiments were carried out in 2D and biomimetic 3D co‐culture experiments with and without irradiation with blue light. Leads were identified with cell‐type‐specific toxicity toward macrophage subtypes, cancer cells, or both. Experiments with 3D spheroids revealed complexes that sensitized the tumor models to the chemotherapeutic doxorubicin. Cell surface exposure of calreticulin, a known facilitator of immunogenic cell death (ICD), was increased upon treatment, along with a concomitant reduction in the M2‐subtype classifier arginase. Our findings lay a strong foundation for the future development of ruthenium‐ and rhodium‐based chemotherapies targeting TAMs. 

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2. Exploring the Formation of Copper–Ruthenium Bimetallic Complexes in Olefin Metathesis

   https://doi.org/10.1021/acs.organomet.3c00338  

   Almuzaini, Hanan N; Slebodnick, Carla; Schulz, Michael D (December 2023, Organometallics)

   Copper(I) halides are often added to olefin metathesis reactions to inhibit catalyst degradation, control product isomerization, enhance catalyst activation, or facilitate catalyst dimerization. In each of these examples, the copper salt is presumed to operate as an independent species, separate from the ruthenium center. We have discovered, however, that certain copper salts can form complexes with the ruthenium catalyst itself, forming hetero-bimetallic copper-ruthenium olefin metathesis catalysts. We confirmed the formation of two complexes through single-crystal X-ray crystallography and NMR spectroscopy. The crystal structure revealed the presence of a four-member ring containing ruthenium, carbon, copper, and chlorine or bromine. The hetero-bimetallic catalyst displayed higher latency and lower activity in the ring-opening metathesis polymerization (ROMP) of norbornene compared to analogous monometallic catalysts. For example, norbornene polymerization catalyzed by the monometallic complex reached 80 % conversion after 4 h, but only 12% conversion when catalyzed by the hetero-bimetallic copper-ruthenium complex under the same conditions. Conversion increased to 63 % when the temperature increased to 50 °C for 1 h, indicating that the bimetallic complex retains activity but requires a higher temperature to activate. The formation of these copper-ruthenium bimetallic complexes suggests the possibility of multi-metallic olefin metathesis catalysts, potentially with different activity and properties than their traditional monometallic counterparts. 

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3. Dinuclear nitrido-bridged osmium complexes inhibit the mitochondrial calcium uniporter and protect cortical neurons against lethal oxygen–glucose deprivation

   https://doi.org/10.1039/d2cb00189f  

   Woods, Joshua J.; Novorolsky, Robyn J.; Bigham, Nicholas P.; Robertson, George S.; Wilson, Justin J. (January 2023, RSC Chemical Biology)

   We have investigated the biological properties of the osmium analogue of a potent ruthenium-based mitochondrial calcium uniporter inhibitor and have found it to possess distinct properties. 

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4. Hydrogen evolution reaction catalyzed by ruthenium ion-complexed graphitic carbon nitride nanosheets

   https://doi.org/10.1039/c7ta03826g  

   Peng, Yi; Lu, Bingzhang; Chen, Limei; Wang, Nan; Lu, Jia En; Ping, Yuan; Chen, Shaowei (January 2017, Journal of Materials Chemistry A)

   The development of cost-effective, high-performance electrocatalysts for hydrogen evolution reaction (HER) is urgently needed. In the present study, a new type of HER catalyst was developed where ruthenium ions were embedded into the molecular skeletons of graphitic carbon nitride (C 3 N 4 ) nanosheets of 2.0 ± 0.4 nm in thickness by refluxing C 3 N 4 and RuCl 3 in water. This took advantage of the strong affinity of ruthenium ions to pyridinic nitrogen of the tri- s -triazine units of C 3 N 4 . The formation of C 3 N 4 –Ru nanocomposites was confirmed by optical and X-ray photoelectron spectroscopic measurements, which suggested charge transfer from the C 3 N 4 scaffold to the ruthenium centers. Significantly, the hybrid materials were readily dispersible in water and exhibited apparent electrocatalytic activity towards HER in acid and their activity increased with the loading of ruthenium metal centers in the C 3 N 4 matrix. Within the present experimental context, the sample saturated with ruthenium ion complexation at a ruthenium to pyridinic nitrogen atomic ratio of ca. 1 : 2 displayed the best performance, with an overpotential of only 140 mV to achieve the current density of 10 mA cm −2 , a low Tafel slope of 57 mV dec −1 , and a large exchange current density of 0.072 mA cm −2 . The activity was markedly lower when C 3 N 4 was embedded with other metal ions such as Fe 3+ , Co 3+ , Ni 3+ and Cu 2+ . This suggests minimal contributions from the C 3 N 4 nanosheets to the HER activity, and the activity was most likely due to the formation of Ru–N moieties where the synergistic interactions between the carbon nitride and ruthenium metal centers facilitated the adsorption of hydrogen. This was strongly supported by results from density functional theory calculations. 

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5. Disentangling types of lattice disorder impacting superconductivity in Sr ₂ RuO ₄ by quantitative local probes

   https://doi.org/10.1063/5.0085279  

   Goodge, Berit H.; Nair, Hari P.; Baek, David J.; Schreiber, Nathaniel J.; Miao, Ludi; Ruf, Jacob P.; Waite, Emily N.; Carubia, Philip M.; Shen, Kyle M.; Schlom, Darrell G.; et al (April 2022, APL Materials)

   The unconventional superconductivity in Sr 2 RuO 4 is infamously susceptible to suppression by small levels of disorder such that it has been most commonly studied in extremely high-purity bulk crystals. Here, we harness local structural and spectroscopic scanning transmission electron microscopy measurements in epitaxial thin films of Sr 2 RuO 4 to disentangle the impact of different types of crystalline disorder on superconductivity. We find that cation off-stoichiometry during growth gives rise to two distinct types of disorder: mixed-phase structural inclusions that accommodate excess ruthenium and ruthenium vacancies when the growth is ruthenium-deficient. Several superconducting films host mixed-phase intergrowths, suggesting this microstructural disorder has relatively little impact on superconductivity. In a non-superconducting film, on the other hand, we measure a high density of ruthenium-vacancies [Formula: see text] with no significant reduction in the crystallinity of the film. The results suggest that ruthenium vacancy disorder, which is hidden to many structural probes, plays an important role in suppressing superconductivity. We discuss the broader implications of our findings to guide the future synthesis of this and other layered systems. 

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