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Abstract The study of actinide electronic structure and bonding within rigorously controlled environments is fundamental to advancing nuclear applications. Here, we report a new set of isostructural actinide organometallics; An(COT^big)₂, (An = Th, U, Np, and Pu), where COT^bigis the bulky 1,4-bis(triphenylsilyl)-substituted cyclooctatetraenyl dianion (1,4-(Ph₃Si)₂C₈H₆)^2-. The actinide(IV) metallocene sandwiches have a clam-shell structure, offering a new molecular symmetry to exploref-orbital contributions in bonding. Combined experimental and computational studies reveal that An(COT^big)₂complexes strongly differ from the previously published coplanar An(COT)₂sandwiches due to the bent geometry and electron-withdrawing nature of the substituents. While COT^bigdisplays comparatively weaker electron donation, the low-energyf-ftransitions in An(COT^big)₂have increased molar absorptivity consistent with the removal of the parity selection rule and better energetic matching between ligand and actinide 5forbitals as the series is traversed. For Pu(COT^big)₂, covalent mixing of donor 5fmetal orbitals and the ligand-π orbitals is especially strong. 

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. 

We report our investigation into the MCU-inhibitory activity of Co 3+ complexes in comparison to Ru265. These compounds reversibly inhibit the MCU with nanomolar potency. Mutagenesis studies and molecular docking simulations suggest that the complexes operate through interactions with the DIME motif of the MCU pore. 

Luminescent lanthanides possess ideal properties for biological imaging, including long luminescent lifetimes and emission within the optical window. Here, we report a novel approach to responsive luminescent Tb( iii ) probes that involves direct modulation of the antenna excited triplet state energy. If the triplet energy lies too close to the 5 D 4 Tb( iii ) excited state (20 500 cm −1 ), energy transfer to 5 D 4 competes with back energy transfer processes and limits lanthanide-based emission. To validate this approach, a series of pyridyl-functionalized, macrocyclic lanthanide complexes were designed, and the corresponding lowest energy triplet states were calculated using density functional theory (DFT). Subsequently, three novel constructs L3 (nitro-pyridyl), L4 (amino-pyridyl) and L5 (fluoro-pyridyl) were synthesized. Photophysical characterization of the corresponding Gd( iii ) complexes revealed antenna triplet energies between 25 800 and 30 400 cm −1 and a 500-fold increase in quantum yield upon conversion of Tb( L3 ) to Tb( L4 ) using the biologically relevant analyte H 2 S. The corresponding turn-on reaction can be monitored using conventional, small-animal optical imaging equipment in presence of a Cherenkov radiation emitting isotope as an in situ excitation source, demonstrating that antenna triplet state energy modulation represents a viable approach to biocompatible, Tb-based optical turn-on probes. 

Hydrogen sulfide (H 2 S) is an endogenous gasotransmitter with potential therapeutic value for treating a range of disorders, such as ischemia-reperfusion injury resulting from a myocardial infarction or stroke. However, the medicinal delivery of H 2 S is hindered by its corrosive and toxic nature. In addition, small molecule H 2 S donors often generate other reactive and sulfur-containing species upon H 2 S release, leading to unwanted side effects. Here, we demonstrate that H 2 S release from biocompatible porous solids, namely metal–organic frameworks (MOFs), is a promising alternative strategy for H 2 S delivery under physiologically relevant conditions. In particular, through gas adsorption measurements and density functional theory calculations we establish that H 2 S binds strongly and reversibly within the tetrahedral pockets of the fumaric acid-derived framework MOF-801 and the mesaconic acid-derived framework Zr-mes, as well as the new itaconic acid-derived framework CORN-MOF-2. These features make all three frameworks among the best materials identified to date for the capture, storage, and delivery of H 2 S. In addition, these frameworks are non-toxic to HeLa cells and capable of releasing H 2 S under aqueous conditions, as confirmed by fluorescence assays. Last, a cellular ischemia-reperfusion injury model using H9c2 rat cardiomyoblast cells corroborates that H 2 S-loaded MOF-801 is capable of mitigating hypoxia-reoxygenation injury, likely due to the release of H 2 S. Overall, our findings suggest that H 2 S-loaded MOFs represent a new family of easily-handled solid sources of H 2 S that merit further investigation as therapeutic agents. In addition, our findings add Zr-mes and CORN-MOF-2 to the growing lexicon of biocompatible MOFs suitable for drug delivery. 

Abstract Hydrogen sulfide (H₂S) is a gaseous molecule that has received attention for its role in biological processes and therapeutic potential in diseases, such as ischemic reperfusion injury. Despite its clinical relevance, delivery of H₂S to biological systems is hampered by its toxicity at high concentrations. Herein, we report the first metal‐based H₂S donor that delivers this gas selectively to hypoxic cells. We further show that H₂S release from this compound protects H9c2 rat cardiomyoblasts from an in vitro model of ischemic reperfusion injury. These results validate the utility of redox‐activated metal complexes as hypoxia‐selective H₂S‐releasing agents for use as tools to study the role of this gaseous molecule in complex biological systems.