40 research outputs found

    A Synthetic Approach of New Trans-Substituted Hydroxylporphyrins

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    The synthesis of new trans A2B2-substituted porphyrins bearing oxygenic substituent (methoxy, acetoxy, hydroxy) at the periphery of the ring are described. All of the synthesized products were characterized by 1H-N.M.R., 13C-N.M.R., and H.R.M.S. Electrochemical studies revealed two one-electron oxidations and two reductions. In addition, the X-ray structure of one methoxy-derivative was determined

    Efficient Bimolecular Mechanism of Photochemical Hydrogen Production Using Halogenated Boron-Dipyrromethene (Bodipy) Dyes and a Bis(dimethylglyoxime) Cobalt(III) Complex

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    A series of Boron-­dipyrromethene (Bodipy) dyes were used as photosensitizers for photochemical hydrogen production in conjunction with [CoIII(dmgH)2pyCl] (where dmgH = dimethylglyoximate, py = pyridine) as the catalyst and triethanolamine (TEOA) as the sacrificial electron donor. The Bodipy dyes are fully characterized by electrochemistry, x-­‐ray crystallography, quantum chemistry calculations, femtosecond transient absorption and time-­‐resolved fluorescence, as well as in long-­‐term hydrogen production assays. Consistent with other recent reports, only systems containing halogenated chromophores were active for hydrogen production, as the long-­‐lived triplet state is necessary for efficient bimolecular electron transfer. Here, it is shown that the photostability of the system improves with Bodipy dyes containing a mesityl group versus a phenyl group, which is attributed to increased electron donating character of the mesityl substituent. Unlike previous reports, the optimal ratio of chromophore to catalyst is established and shown to be 20:1, at which point this bimolecular dye/catalyst system performs 3-­‐4 times better than similar chemically linked systems. We also show that the hydrogen production drops dramatically with excess catalyst concentration. The maximum turnover number of ~700 (with respect to chromophore) is obtained under the following conditions: 1.0 × 10­‐4 M [Co(dmgH)2pyCl], 5.0 × 10-6 M Bodipy dye with iodine and mesityl substituents, 1:1 v:v (10% aqueous TEOA):MeCN (adjusted to pH 7), and irradiation by light with λ \u3e 410 nm for 30 h. This system, containing discrete chromophore and catalyst, is more active than similar linked Bodipy – Co(dmg)2 dyads recently published, which, in conjunction with our other measurements, suggests that the nominal dyads actually function bimolecularly

    Unravelling the mechanism of water sensing by the Mg2+ dihydroxy-terephthalate MOF (AEMOF-1 ‘)

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    In this contribution we build upon our previous work on the MOF [Mg(H(2)dhtp)(H2O)(2)]center dot DMAc (AEMOF-1 center dot DMAc) and its activated dry version AEMOF-1 ‘ which has been shown to exhibit excellent luminescence sensing properties towards water in organic solvents. We demonstrate through combined structural and photophysical studies that the observed changes in the fluorescence properties of AEMOF-1 ‘ upon hydration arise from a structural transformation to the mononuclear complex [Mg(H(2)dhtp)(H2O)(5)]center dot H2O (H(4)dhtp = 2,5-dihydroxyterepthalic acid) (1). In the latter complex, excited state intramolecular proton transfer (ESIPT) is strongly favoured thereby leading to enhanced and red shifted emission in comparison to AEMOF-1 center dot DMAc. Powder X-ray diffraction measurements confirmed that complex 1 is identical to the hydrated form of AEMOF-1 center dot DMAc. As in the case of AEMOF-1 ‘, the dry form of complex 1 (1 ‘) is also an effective sensor for the determination of traces of water in tetrahydrofuran (THF). This work demonstrates that the same chromophore may exhibit very different emission properties when it exists in different chemical environments and that these transformations may be controlled and utilized in water sensing applications

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

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    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

    Luminescent d-block metal polypyridyl complexes bearing secondary macrocyclic or non-macrocyclic binding sites

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    Towards white-light emission by Tb3+/Eu3+ substitution in a Ca2+ framework

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    Very recently, we discovered that the two-dimensional framework, namely [Ca(H4L)(DMA)(2)]center dot 2DMA (Ca-MOF) was capable of exchanging the Ca2+ ions by Cue(+2) almost quantitatively in a matter of seconds in aqueous solution and that enabled us to utilized the Ca-MOF as an ion-exchange material with potential applications in water treatment and/or recovery of valuable metals. To this end, we turned our attention toward exchanging the Ca2+ ion by lanthanides [i.e. Tb3+ and Eu3+] in order to afford materials that emit white-light. We discovered that the Ca-MOF slowly exchanges approximately 95% of the Ca2+ ions by Tb3+/Eu3+ yielding materials that combine the initial blue emission of the Ca-MOF with the green and red emission of the Tb3+ and Eu3+, respectively, leading to materials with almost white-light emission. (C) 2018 Elsevier Ltd. All rights reserved

    Synthesis, structural characterization, and fluorescence of a series of 1D rare earth coordination polymers with a substituted iminodiacetate ligand

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    The combination of the polycarboxylic ligand N-(4-carboxy-benzyl)iminodiacetic acid (LH3) with rare earth (RE) chlorides under hydrothermal conditions leads to the formation of 1D cationic coordination polymers formulated as {[RE(LH2)2(H2O)4]Cl}n [where RE = Y (1), Eu (2), Tb (3) and Yb (4)]. All compounds are isostructural and characterized with IR spectroscopy, and thermal (TG) studies. Compounds 1, 2 and 4 were characterized with single crystal X-ray diffraction while 2 and 3 with fluorescence spectroscopy. The ligand utilizes only two of the available for coordination carboxylates and the crystal structures are stabilized by an extended array of H-bonds that gives rise to a 3D supramolecular architecture.</p

    Functionalised Al(III) metal organic frameworks for fluorescence sensing of nitroaromatic vapours

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    The employment of fluorescence sensors provides a platform for rapid and efficient in-field detection of nitroaromatic compounds and is gaining increasing reserach ground. Herein, we report the synthesis and characterisation of three new fluorescent Al(ΙΙΙ) MOFs, structurally analogous to MIL–53, with the assigned formula {Al(OH)(bdc)1-n(L–1)n}·xsolv (bdc2- = terephthalate; L–1 = 2–((benzyl)amino)-terephthalate). L–1 is a strongly fluorescent dicarboxylic ligand with a pendant π–electron rich aromatic group suitable for electron transfer processes towards electron–deficient nitroaromatic guests. Our MOFs show strong fluorescence quenching upon exposure to vapours of nitrobenzene, 1,3-dinitrobenzene, 4-nitrotoluene, 2,4-dinitrotoluene. Additionally, we prepare and study MOF-polymer composites in the form of thin films that are strongly quenched in the presence of nitrobenzene vapours

    Luminescent metal–organic frameworks as chemical sensors: common pitfalls and proposed best practices

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    The ever-increasing need to determine and monitor the chemical constituents of the constantly evolving environment has led the global scientific community to invest considerable research effort in the development of efficient and user-friendly chemical sensors. The development of improved chemical sensors largely depends on the synthesis of novel materials with the ability to transform a molecular recognition event into a readable signal. Among the various types of sensory materials, those where analyte detection is based on the change of a luminescence signal are gaining increasing attention due to the extremely high sensitivities which can be achieved in combination with new technological advances enabling the integration of optical detection systems in small, portable and easy to use devices. In this critical review we approach the emerging field of sensory materials based on luminescent metal-organic frameworks (LMOFs) by beginning with a survey of the general principles of luminescence-based sensing. In particular, after a brief overview, we first focus on the working principles and successes of well established sensory materials based on small molecules and conjugated polymers. Subsequently, we concentrate on the special features of LMOFs which make them promising sensory materials and we discuss best practices which researchers in the field should follow in order to prove the sensing ability of LMOFs and avoid common misconceptions and errors. We continue with presenting selected examples of LMOF-based sensors for nitroaromatics, humidity and heavy metal ions from the recent literature and we conclude with a summary of the state-of-the-art of LMOF sensors. Finally, we propose some directions for future research on LMOF sensors
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