Absorbate-Induced Piezochromism in a Porous Molecular Crystal

Atmospherically stable porous frameworks and materials are interesting for heterogeneous solid–gas applications. One motivation is the direct and selective uptake of pollutant/hazardous gases, where the material produces a measurable response in the presence of the analyte. In this report, we present a combined experimental and theoretical rationalization for the piezochromic response of a robust and porous molecular crystal built from an extensively fluorinated trispyrazole. The electronic response of the material is directly determined by analyte uptake, which provokes a subtle lattice contraction and an observable bathochromic shift in the optical absorption onset. Selectivity for fluorinated absorbates is demonstrated, and toluene is also found to crystallize within the pore. Furthermore, we demonstrate the application of electronic structure calculations to predict a physicochemical response, providing the foundations for the design of electronically tunable porous solids with the chemical properties required for development of novel gas-uptake media

Learning to look : evaluating the student experience of an interactive image appraisal activity

Introduction: Student radiographers have expressed difficulty in performing image appraisal tasks. The purpose of this study was to investigate the value of a workshop delivered to level 4 undergraduate students. All students completed an image appraisal activity, inputting their appraisal into software that displayed their response alongside an expert opinion. They were asked to identify and discuss any discrepancy. Methods: All Level 4 students participated in an image appraisal workshop and were subsequently invited to take part in a focus group immediately after the activity. Twenty-three students took part in three focus groups (n = 7; n = 8; n = 8). A thematic analysis of transcripts was performed alongside validation from observations during the image appraisal activity. Results: Findings demonstrate that despite teaching and resources being available, students had focused on learning a generic checklist for image appraisal, had not appreciated the application of projection specific criteria and felt underprepared. The use of specific criteria and repetition within the task was considered useful. They identified learning needs and misconceptions through peer discussion and via the expert opinion, highlighting the value of feedback. Students enjoyed the workshop and made suggestions for implementation into the curriculum. Conclusion: Educators must not assume that the provision of resources will result in students developing deep knowledge. Teaching and learning strategies that are task specific are recommended to avoid a surface approach to learning. Time, repetition and appropriate feedback are essential to enable learners to develop competence and confidence for complex visual tasks, such as image appraisal

Comparison of rhenium–porphyrin dyads for CO₂ photoreduction: photocatalytic studies and charge separation dynamics studied by time-resolved IR spectroscopy

We report a study of the photocatalytic reduction of CO₂ to CO by zinc porphyrins covalently linked to [ReI(2,2′-bipyridine)(CO)₃L]⁺/⁰ moieties with visible light of wavelength >520 nm. Dyad 1 contains an amide C₆H₄NHC(O) link from porphyrin to bipyridine (Bpy), Dyad 2 contains an additional methoxybenzamide within the bridge C₆H₄NHC(O)C₆H₃(OMe)NHC(O), while Dyad 3 has a saturated bridge C₆H₄NHC(O)CH₂; each dyad is studied with either L = Br or 3-picoline. The syntheses, spectroscopic characterisation and cyclic voltammetry of Dyad 3 Br and [Dyad 3 pic]OTf are described. The photocatalytic performance of [Dyad 3 pic]OTf in DMF/triethanolamine (5 : 1) is approximately an order of magnitude better than [Dyad 1 pic]PF₆ or [Dyad 2 pic]OTf in turnover frequency and turnover number, reaching a turnover number of 360. The performance of the dyads with Re–Br units is very similar to that of the dyads with [Re–pic]⁺ units in spite of the adverse free energy of electron transfer. The dyads undergo reactions during photocatalysis: hydrogenation of the porphyrin to form chlorin and isobacteriochlorin units is detected by visible absorption spectroscopy, while IR spectroscopy reveals replacement of the axial ligand by a triethanolaminato group and insertion of CO₂into the latter to form a carbonate. Time-resolved IR spectra of [Dyad 2 pic]OTf and [Dyad 3 pic]OTf (560 nm excitation in CH₂Cl₂) demonstrated electron transfer from porphyrin to Re(Bpy) units resulting in a shift of ν(CO) bands to low wavenumbers. The rise time of the charge-separated species for [Dyad 3 pic]OTf is longest at 8 (±1) ps and its lifetime is also the longest at 320 (±15) ps. The TRIR spectra of Dyad 1 Br and Dyad 2 Br are quite different showing a mixture of 3MLCT, IL and charge-separated excited states. In the case of Dyad 3 Br, the charge-separated state is absent altogether. The TRIR spectra emphasize the very different excited states of the bromide complexes and the picoline complexes. Thus, the similarity of the photocatalytic data for bromide and picoline dyads suggests that they share common intermediates. Most likely, these involve hydrogenation of the porphyrin and substitution of the axial ligand at rhenium

What do the public know about anatomy?:Anatomy education to the public and the implications

Public knowledge of the anatomical “self” is lacking and evidence points towards a growing need for anatomy education to the wider public. The public were offered the opportunity to learn human anatomy and complete an anatomical knowledge survey afterwards. Sixty-three participants volunteered to attempt to place 20 anatomical structures on a blank human body template. Responses were scored independently and then collated. A mixed effects logistic model was used to examine any associations with participants’ as a random effect and all other factors as fixed effects. Results showed a statistically significant quadratic trend with age. Participants in health-related employment scored significantly higher than those not in health-related employment. There was a significant interaction between gender and organ type with males scoring higher than females in identifying muscles, but not in identifying internal organs. The current study demonstrates the general public’s eagerness to learn anatomy despite their limited knowledge of the human body, and the need for widening participation. Furthermore, it raises an awareness of the anatomical literacy needs of the general public, especially in school children and young adults. Furthermore, it emphasizes the value of health literacy as a focus in undergraduate medical education. Anatomy literacy appears to be neglected, and this experience provides an example of a possible mode of public engagement in anatomy

Introducing a closed system approach for the investigation of chemical steps involving proton and electron transfer; as illustrated by a copper-based water oxidation catalyst

Solid state NMR/Biophysical Organic Chemistr

Water oxidation with ruthenium catalysts

CeIV-activated water oxidation: A family of 29 mononuclear RuII complexes have been prepared and characterized by 1H NMR, electronic absorption, and cyclic voltammetry. These complexes are studied as catalysts for water oxidation. The complexes may be divided into three basic types. The type-1 complexes involve a [RuII(NNN)(NN)(X)]n (NNN = tridentate ligand, NN = a bidentate ligand, and X = halogen and n = 1+; X = H2O and n = 2+). The type-2 complexes contain a NNN, two molecules of 4-methylpyridine (pic), and halogen or H2O to form a [RuII(NNN)(pic)2(X)]n complex. The type-3 complexes contain no water molecule and thus are constructed from a tetradentate ligand (NNNN) and two molecules of pic to provide a [RuII(NNNN)(pic)2]2+ complex. In general the type-2 catalysts are more reactive than the type-1. The type-2 iodo-catalyst shows first-order behavior and, unlike the bromo- and chloro-catalysts, does not require water-halogen exchange to show good activity. The importance of steric strain and hindrance around the metal center is examined. The introduction of three t-butyl groups at the 4, 4′, and 4″ positions of tpy (ttbt) sometimes improves catalyst activity, but the effect does not appear to be additive. Photo-activated water oxidation: Two mononuclear RuII complexes, [Ru(ttbt)(pynap)(I)]I and [Ru(tpy)(pic)2(I)]I (tpy = 2,2';6,2''-terpyridine; pynap = 2-(pyrid-2'-yl)-1,8-naphthyridine), are effective catalysts for the oxidation of water. This oxidation can be driven by a blue LED light source using [Ru(bpy)3]Cl2 (bpy = 2,2'-bipyridine) as the photosensitizer. Sodium persulfate acts as a sacrificial electron acceptor to oxidize the photosensitizer that in turn drives the catalysis. The presence of all four components: light, photosensitizer, sodium persulfate, and catalyst are required for water oxidation. A dyad assembly has been prepared using a pyrazine-based linker to join a photosensitizer and catalyst moiety. Irradiation of this intra-molecular system with blue light produces oxygen with a higher turnover number than the analogous intermolecular component system under the same conditions.Chemistry, Department o

Redox Intercalation and Electrochemical Reactions of Metal-Organic Frameworks and a Mixed Transition Metal Oxide with Applications in Lithium and Magnesium Batteries

This dissertation focuses on the redox properties of metal-organic frameworks and a microporous mixed transition metal oxide. The study is divided into two main areas: an intercalation of a redox active molecular guest into host single crystals, and an intercalation of reactive alkali and alkaline earth metals, Li and Mg, by solid state electrochemical reactions into the microporous compounds with applications in lithium and magnesium rechargeable batteries. A metal-organic framework [VIV(O)(bdc)](H2bdc)0.71 (1) was synthesized. This solid was activated to remove the guest molecules, and an empty framework of [VIV(O)(bdc)] (2) was obtained. 2 was used as a host to undergo a vapor-phase redox intercalation of an electroactive organic guest, hydroquinone. In ambient atmosphere, [VIII(OH)(bdc)]•{(O-C6H4-O)(HO-C6H4-OH)}0.76•(H2O)0.48 (3) was formed, whereas under anhydrous conditions, the product was [VIII(O-C6H4-O)(bdc)] (4). Structural deformations as a function of temperature of 2 and 4 were also studied. [VIV(O)(bdc)] (2) was used in solid state electrochemical reaction with lithium. The Li cells with 2 as the cathode material were reversibly cycled with good rate capability and specific capacity. The cell performance and electrochemical profiles at various current conditions were discussed. Structural evolution associated with the electrochemical lithiation was characterized. A metal-organic framework, [NH2(CH3)2][FeIIIFeII(HCOO)6] (FeFOR), was used as cathode in secondary lithium batteries. The electrochemical profiles suggested that FeFOR reacted reversibly with Li. The mechanism involved in the electrochemical reaction was proposed to be intercalation-based and conversion-based with LiHCOO being the matrix involved. A microporous molybdenum-vanadium oxide with large open 1D channels, Mo2.5+yVO9+δ, was used as an intercalation positive electrode material in lithium batteries. The electrochemical profiles showed good specific capacity at high current densities. The cells were found to be reversible even without conducting additives. The structural changes taking place during Li-ion insertion were described, and the chemical deintercalation of lithium was also performed to demonstrate the reversibility. Mo2.5+yVO9+δ was found to reversibly undergo not only lithium insertion in Li-based batteries, but also magnesium intercalation. The compound was used as cathode material, and reversibly cycled with magnesium as the counter electrode with good specific capacity. The effect of varying current densities on the discharge profiles was included.Chemistry, Department o