40 research outputs found
A Synthetic Approach of New Trans-Substituted Hydroxylporphyrins
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
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 ‘)
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
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
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Towards white-light emission by Tb3+/Eu3+ substitution in a Ca2+ framework
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
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
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
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