Supramolecular Luminescent Sensors

There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed

A Paper-Based Device for Ultrasensitive, Colorimetric Phosphate Detection in Seawater

High concentrations of certain nutrients, including phosphate, are known to lead to undesired algal growth and low dissolved oxygen levels, creating deadly conditions for organisms in marine ecosystems. The rapid and robust detection of these nutrients using a colorimetric, paper-based system that can be applied on-site is of high interest to individuals monitoring marine environments and others affected by marine ecosystem health. Several techniques for detecting phosphate have been reported previously, yet these techniques often suffer from high detection limits, reagent instability, and the need of the user to handle toxic reagents. In order to develop improved phosphate detection methods, the commonly used molybdenum blue reagents were incorporated into a paper-based, colorimetric detection system. This system benefited from improved stabilization of the molybdenum blue reagent as well as minimal user contact with toxic reagents. The colorimetric readout from the paper-based devices was analyzed and quantified using RGB analyses (via ImageJ), and resulted in the detection of phosphate at detection limits between 1.3 and 2.8 ppm in various aqueous media, including real seawater

Environmental Application of Cyclodextrin Metal-Organic Frameworks in an Undergraduate Teaching Laboratory

Reported herein is a multidisciplinary laboratory experiment for advanced undergraduate students that includes elements of material synthesis, in the synthesis of cyclodextrin-containing metal–organic frameworks (CD-MOFs), and environmental chemistry, in the use of these MOFs for pollutant removal. This multiday laboratory experiment starts with the synthesis of cyclodextrin-containing metal–organic frameworks (CD-MOFs) using vapor diffusion crystal growth procedures, followed by the use of the CD-MOFs for a pollutant removal application. Specifically, the CD-MOFs were used for the removal of a methylene blue dye (a common mimic of aromatic pollutants) from an organic solution, with the monitoring of the success of the removal procedures using UV–vis spectroscopy. This experiment was implemented as part of a larger multiday unit, and undergraduate students were particularly engaged with and excited by the CD-MOF synthesis and methylene blue removal experimental modules. As a result, the decision was made to make these two components a stand-alone multidisciplinary laboratory experiment, the results of which are reported herein

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Electron-donating capabilities and evidence for redox activity in low oxidation state iron complexes bearing bis(amidine)pyrimidylidene ligands

<p>Low-valent iron complexes bearing bis(amidine)pyrimidylidene (or carbenodiamidine, CDA) ligands have been synthesized and characterized by X-ray crystallography, Mössbauer spectroscopy, infrared spectroscopy, EPR spectroscopy, and DFT calculations. One electron reduction of (CDA)FeCl₂ (<b>1</b>) resulted in the formation of (CDA)FeCl (<b>2</b>), which demonstrated an unusual metal−N-heterocyclic carbene (NHC) interaction where a redox non-innocent NHC participates in a one electron <i>π</i>-interaction with the metal center. This interaction renders the complex best described as a low-spin iron(II) complex that is antiferromagnetically coupled to a singly reduced CDA ligand. Two electron reduction of <b>1</b> under an atmosphere of carbon monoxide resulted in the formation of the diamagnetic complex (CDA)Fe(CO)₂ (<b>3</b>). Complex <b>3</b> demonstrated significantly lower CO stretching frequencies compared to previously reported bis(imino)pyridine and even bis(N-heterocyclic carbene)pyridine iron complexes, which reflects the significant <i>σ</i>-donating capabilities of the CDA ligands.</p

A polycationic pillar[5]arene for the binding and removal of organic toxicants from aqueous media

The ability to bind and detect analytes with high levels of selectivity, sensitivity and broad applicability for a variety of analytes is an essential goal, with applications in public health and environmental remediation. Methods to achieve effective binding and detection include electrochemical, and spectroscopic methods. The use of supramolecular chemistry to accomplish such detection, by binding a target in a host and transducing that binding into a measurable signal, has advantages, including tunability of the sensor and the ability to rationally design hosts through an understanding of non-covalent interactions. Reported herein is the design and use of pillar[5]arenes to accomplish precisely such detection. Water-soluble pillar[5]arenes containing 10 cationic linker arms on their periphery bound toxicants in their hydrophobic cores with association constants of 105–106M−1. With the use of cationic exchange resins, the pillar[5]arene hosts were removed from solution with their encapsulated guests, allowing for effective toxicant removal

Magnetic Circular Dichroism and Density Functional Theory Studies of Iron(II)-Pincer Complexes: Insight into Electronic Structure and Bonding Effects of Pincer N‑Heterocyclic Carbene Moieties

Iron complexes containing pincer ligands that incorporate N-heterocyclic carbene (NHC) moieties are of significant interest in organometallic catalysis in order to generate more oxidatively robust complexes that may exhibit novel catalytic properties. In order to define the effect that introducing NHC moieties into pincer ligands has on electronic structure and bonding in iron­(II)-pincer complexes, MCD and DFT studies of (^iPrCDA)­FeBr₂, (^iPrPDI)­FeBr₂, and (^iPrCNC)­FeBr₂ were performed. These studies quantify the electronic structures and bonding interactions as a function of pincer ligand variation. They also demonstrate that the observed ligand fields (and, hence, spin states) directly correlate to the increased Fe–C bonding and pincer-donating abilities that result from introducing NHC moieties into the pincer ligand. However, the net donor abilities of the pincers and the strength of the Fe-pincer interaction do not directly correlate to the number of NHC moieties present, but instead are determined to be due to differences in Fe–C and overall Fe-pincer bonding as a result of the position of the NHC moieties in the pincer ligand and the overall geometric constraints of the pincer architecture

Magnetic Circular Dichroism and Density Functional Theory Studies of Iron(II)-Pincer Complexes: Insight into Electronic Structure and Bonding Effects of Pincer N‑Heterocyclic Carbene Moieties

Iron complexes containing pincer ligands that incorporate N-heterocyclic carbene (NHC) moieties are of significant interest in organometallic catalysis in order to generate more oxidatively robust complexes that may exhibit novel catalytic properties. In order to define the effect that introducing NHC moieties into pincer ligands has on electronic structure and bonding in iron­(II)-pincer complexes, MCD and DFT studies of (^iPrCDA)­FeBr₂, (^iPrPDI)­FeBr₂, and (^iPrCNC)­FeBr₂ were performed. These studies quantify the electronic structures and bonding interactions as a function of pincer ligand variation. They also demonstrate that the observed ligand fields (and, hence, spin states) directly correlate to the increased Fe–C bonding and pincer-donating abilities that result from introducing NHC moieties into the pincer ligand. However, the net donor abilities of the pincers and the strength of the Fe-pincer interaction do not directly correlate to the number of NHC moieties present, but instead are determined to be due to differences in Fe–C and overall Fe-pincer bonding as a result of the position of the NHC moieties in the pincer ligand and the overall geometric constraints of the pincer architecture

Magnetic Circular Dichroism and Density Functional Theory Studies of Iron(II)-Pincer Complexes: Insight into Electronic Structure and Bonding Effects of Pincer N‑Heterocyclic Carbene Moieties

Iron complexes containing pincer ligands that incorporate N-heterocyclic carbene (NHC) moieties are of significant interest in organometallic catalysis in order to generate more oxidatively robust complexes that may exhibit novel catalytic properties. In order to define the effect that introducing NHC moieties into pincer ligands has on electronic structure and bonding in iron­(II)-pincer complexes, MCD and DFT studies of (^iPrCDA)­FeBr₂, (^iPrPDI)­FeBr₂, and (^iPrCNC)­FeBr₂ were performed. These studies quantify the electronic structures and bonding interactions as a function of pincer ligand variation. They also demonstrate that the observed ligand fields (and, hence, spin states) directly correlate to the increased Fe–C bonding and pincer-donating abilities that result from introducing NHC moieties into the pincer ligand. However, the net donor abilities of the pincers and the strength of the Fe-pincer interaction do not directly correlate to the number of NHC moieties present, but instead are determined to be due to differences in Fe–C and overall Fe-pincer bonding as a result of the position of the NHC moieties in the pincer ligand and the overall geometric constraints of the pincer architecture

Altered TMPRSS2 usage by SARS-CoV-2 Omicron impacts tropism and fusogenicity

SARS-CoV-2オミクロン株による中和抗体回避と感染指向性の変化. 京都大学プレスリリース. 2022-02-03.The SARS-CoV-2 Omicron BA.1 variant emerged in 20211 and bears multiple spike mutations2. Here we show that Omicron spike has higher affinity for ACE2 compared to Delta as well as a marked change of antigenicity conferring significant evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralising antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralisation. Importantly, antiviral drugs remdesivir and molnupiravir retain efficacy against Omicron BA.1. Replication was similar for Omicron and Delta virus isolates in human nasal epithelial cultures. However, in lower airway organoids, lung cells and gut cells, Omicron demonstrated lower replication. Omicron spike protein was less efficiently cleaved compared to Delta. Replication differences mapped to entry efficiency using spike pseudotyped virus (PV) assays. The defect for Omicron PV to enter specific cell types effectively correlated with higher cellular RNA expression of TMPRSS2, and knock down of TMPRSS2 impacted Delta entry to a greater extent than Omicron. Furthermore, drug inhibitors targeting specific entry pathways3 demonstrated that the Omicron spike inefficiently utilises the cellular protease TMPRSS2 that promotes cell entry via plasma membrane fusion, with greater dependency on cell entry via the endocytic pathway. Consistent with suboptimal S1/S2 cleavage and inability to utilise TMPRSS2, syncytium formation by the Omicron spike was markedly impaired compared to the Delta spike. Omicron’s less efficient spike cleavage at S1/S2 is associated with shift in cellular tropism away from TMPRSS2 expressing cells, with implications for altered pathogenesis