Controlled depolymerisation, as assessed by analytical ultracentrifugation, of low molecular weight chitosan for potential use in archaeological conservation

The heterogeneity and molecular weight of a chitosan of low molecular weight (molar mass) and low degree of acetylation (0.1), for potential use as a consolidant for decayed archaeological wood, has been examined by sedimentation velocity and sedimentation equilibriumin the analytical ultracentrifuge before and after depolymerisation. Sedimentation velocity before polymerisation revealed a uniform distribution of sedimentation coefficient with little concentration dependence. SEDFIT-MSTAR analysis revealed a weight average molecular weight Mw of (14.2 + 1.2) kDa, and polydispersity index of ~ 1.2. Further analysis using MULTISIG revealed a distribution of material between 2-20 kDa and consistent with the weight average Mw. Controlled depolymerisation using hydrogen peroxide and UV in an acetic acid medium reduced this to (4.9 + 0.7) kDa, with a similar polydispersity. The depolymerised material appears to be within the range that has been predicted to fully penetrate into archaeological wood. The consequences for this and the use of the analytical ultracentrifuge in wood conservation strategies is considered

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification

Identification of inorganic compounds in composite alum-treated wooden artefacts from the Oseberg collection

Abstract Alum-treated wooden artefacts from the Oseberg collection display a great deal of morphological, structural and compositional inhomogeneity. Thus, an in-depth understanding of chemical processes underlying their degradation requires consideration of a variety of local environments. In addition to alum, sources of inorganic compounds include metal parts, corrosion products of which can migrate into the surrounding wood. In order to characterise the inorganic compounds a range of local environments, samples from several locations in a selection of composite objects have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS). We have found that corrosion of iron rods used in reconstruction has formed iron(II) sulfates, which have migrated into the alum-treated wood to form sulfates containing combinations of potassium, aluminium, iron(II) and iron(III) cations. Reactions of alum were also evident from the presence of alunite in some samples. Areas with significant abundances of zinc sulfates, zinc sulfide and elemental sulfur were also detected. These results provide a first-time window into the complex array of inorganic species that can be present in such composite alum-treated objects

Dihydroperimidine-Derived N‑Heterocyclic Pincer Carbene Complexes via Double C–H Activation

The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR₂, R = Ph, Cy) directly afford <i>N</i>,<i>N′</i>-bis­(phoshinomethyl)­dihydroperimidines H₂C­(NCH₂PR₂)₂C₁₀H₆ (R = Ph (<b>1a</b>), Cy (<b>1b</b>)), the methylene group of which undergoes chelate-assisted double C–H activation with [RhCl­(PPh₃)₃] to afford dihydroperimidine-derived N-heterocyclic pincer carbene (<i>per</i>-NHC) complexes [RhCl­{C­(NCH₂PR₂)₂C₁₀H₆}] (R = Ph (<b>2a</b>), Cy (<b>2b</b>)). Insight into the mechanism of these C–H activation processes is provided by the reaction of <b>1b</b> with [IrCl­(CO)­(PPh₃)₂] to provide the dihydroperimidinyl-hydrido complex [IrHCl­(CO)­{CH­(NCH₂PR₂)₂C₁₀H₆}] (<b>3b</b>), which in turn reacts with silver salts Ag­[Y] to afford, via hydride abstraction and subsequent C–H activation, the <i>per</i>-NHC ligated salts [IrHCl­(CO)­{C­(NCH₂PR₂)₂C₁₀H₆}] ([<b>4b</b>]­Y, Y = PF₆, SbF₆, PO₂F₂)

Dihydroperimidine-Derived N‑Heterocyclic Pincer Carbene Complexes via Double C–H Activation

The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR₂, R = Ph, Cy) directly afford <i>N</i>,<i>N′</i>-bis­(phoshinomethyl)­dihydroperimidines H₂C­(NCH₂PR₂)₂C₁₀H₆ (R = Ph (<b>1a</b>), Cy (<b>1b</b>)), the methylene group of which undergoes chelate-assisted double C–H activation with [RhCl­(PPh₃)₃] to afford dihydroperimidine-derived N-heterocyclic pincer carbene (<i>per</i>-NHC) complexes [RhCl­{C­(NCH₂PR₂)₂C₁₀H₆}] (R = Ph (<b>2a</b>), Cy (<b>2b</b>)). Insight into the mechanism of these C–H activation processes is provided by the reaction of <b>1b</b> with [IrCl­(CO)­(PPh₃)₂] to provide the dihydroperimidinyl-hydrido complex [IrHCl­(CO)­{CH­(NCH₂PR₂)₂C₁₀H₆}] (<b>3b</b>), which in turn reacts with silver salts Ag­[Y] to afford, via hydride abstraction and subsequent C–H activation, the <i>per</i>-NHC ligated salts [IrHCl­(CO)­{C­(NCH₂PR₂)₂C₁₀H₆}] ([<b>4b</b>]­Y, Y = PF₆, SbF₆, PO₂F₂)

Arrested B–H Activation en Route to Installation of a PBP Pincer Ligand on Ruthenium and Osmium

The reaction of HB­(NCH₂PPh₂)₂C₆H₄-1,2 with [MCl₂(PPh₃)₃] (M = Ru, Os) affords the six-coordinate σ-borane complexes [MCl₂(PPh₃)­{σ-<i>BH</i>-κ²-<i>P,P</i>′-HB­(NCH₂PPh₂)₂-C₆H₄}], in which the B–H bond remains intact while coordinated to the metal center. Replacement of the unique phosphine by π-acceptor ligands, e.g., CO and CNC₆H₂Me₃, induces B–H activation followed by spontaneous dehydrochlorination with the formation of the boryl pincer complexes [RuCl­(CA)₂{B­(NCH₂PPh₂)₂C₆H₄}] (A = O, NC₆H₂Me₃-2,4,6)

Dihydroperimidine-Derived PNP Pincer Complexes as Intermediates en Route to N‑Heterocyclic Carbene Pincer Complexes

The reaction of <i><i>N</i>,<i>N</i></i>′-bis­(dicyclohexylphosphinomethyl)­dihydroperimidine (H₂C­(NCH₂PCy₂)₂C₁₀H₆-1,8, <b>1a</b>) with [RuCl₂(PPh₃)₃] in THF affords the perimidinylidene-based N-heterocyclic carbene (<i>per</i>-NHC) pincer complex [RuCl₂(OC₄H₈)­{C­(NCH₂PCy₂)₂C₁₀H₆}] (<b>2</b>) via chelate-assisted double C–H activation. In contrast, the reactions of the tetraphenyl analogue H₂C­(NCH₂PPh₂)₂C₁₀H₆ (<b>1b</b>) with [RuCl₂(PPh₃)₃] and of <b>1a</b> with [RuCl­(R)­(CO)­(PPh₃)₂] (R = Ph, CHCHPh) do not result in C–H activation but rather give the asymmetric, PNP-coordinated complexes [RuCl₂(PPh₃)­{κ³<i>P</i>,<i>N</i>,<i>P</i>′-CH₂(NCH₂PPh₂)₂C₁₀H₆}] (<b>3</b>) and [RuCl­(R)­(CO)­{κ³<i>P</i>,<i>N</i>,<i>P</i>′-CH₂(NCH₂PCy₂)₂C₁₀H₆}] (R = Ph (<b>4</b>), CHCHPh (<b>5</b>)), respectively, in which the ruthenium migrates rapidly between nitrogen donors. This provides insight into the mechanistic pathway by which the proligands <b>1</b> undergo <i>per</i>-NHC formation, as demonstrated by the thermal conversion of <b>4</b> to [RuHCl­(CO)­{C­(NCH₂PCy₂)₂C₁₀H₆}] (<b>6</b>) and benzene

Dihydroperimidine-Derived N‑Heterocyclic Pincer Carbene Complexes via Double C–H Activation

The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR₂, R = Ph, Cy) directly afford <i>N</i>,<i>N′</i>-bis­(phoshinomethyl)­dihydroperimidines H₂C­(NCH₂PR₂)₂C₁₀H₆ (R = Ph (<b>1a</b>), Cy (<b>1b</b>)), the methylene group of which undergoes chelate-assisted double C–H activation with [RhCl­(PPh₃)₃] to afford dihydroperimidine-derived N-heterocyclic pincer carbene (<i>per</i>-NHC) complexes [RhCl­{C­(NCH₂PR₂)₂C₁₀H₆}] (R = Ph (<b>2a</b>), Cy (<b>2b</b>)). Insight into the mechanism of these C–H activation processes is provided by the reaction of <b>1b</b> with [IrCl­(CO)­(PPh₃)₂] to provide the dihydroperimidinyl-hydrido complex [IrHCl­(CO)­{CH­(NCH₂PR₂)₂C₁₀H₆}] (<b>3b</b>), which in turn reacts with silver salts Ag­[Y] to afford, via hydride abstraction and subsequent C–H activation, the <i>per</i>-NHC ligated salts [IrHCl­(CO)­{C­(NCH₂PR₂)₂C₁₀H₆}] ([<b>4b</b>]­Y, Y = PF₆, SbF₆, PO₂F₂)

Novel Carbon Monochalcogenide Coordination Mode: [Rh₂{μ-SeCMo(CO)₂(Tp*)}₂(η⁴-cod)₂] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate; cod = <i>cyclo</i>-octa-1,5-diene)

The reaction of [Et₄N]­[Mo­(CSe)­(CO)₂(Tp*)] (Tp* = hydrotris­(3,5-dimethylpyrazol-1-yl)­borate) with [Rh₂(μ-Cl)₂(η⁴-cod)₂] (cod = cyclo-octa-1,5-diene) results in the formation of the tetrametallic complex [Rh₂{SeCMo­(CO)₂(Tp*)}₂(η⁴-cod)₂] in which the CSe ligand adopts a crystallographically confirmed and unprecedented μ₃:σ,σ′(Se),σ″(C) coordination mode

Novel Carbon Monochalcogenide Coordination Mode: [Rh₂{μ-SeCMo(CO)₂(Tp*)}₂(η⁴-cod)₂] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate; cod = <i>cyclo</i>-octa-1,5-diene)

The reaction of [Et₄N]­[Mo­(CSe)­(CO)₂(Tp*)] (Tp* = hydrotris­(3,5-dimethylpyrazol-1-yl)­borate) with [Rh₂(μ-Cl)₂(η⁴-cod)₂] (cod = cyclo-octa-1,5-diene) results in the formation of the tetrametallic complex [Rh₂{SeCMo­(CO)₂(Tp*)}₂(η⁴-cod)₂] in which the CSe ligand adopts a crystallographically confirmed and unprecedented μ₃:σ,σ′(Se),σ″(C) coordination mode