Shorter Alkyl Chains Enhance Molecular Diffusion and Electron Transfer Kinetics between Photosensitisers and Catalysts in CO2-Reducing Photocatalytic Liposomes

Covalent functionalisation with alkyl tails is a common method for supporting molecular catalysts and photosensitisers onto lipid bilayers, but the influence of the alkyl chain length on the photocatalytic performances of the resulting liposomes is not well understood. In this work, we first prepared a series of rhenium-based CO₂-reduction catalysts [Re(4,4’-(C_nH_2n+1)₂-bpy)(CO)₃Cl] ( ReC_n ; 4,4’-(C_nH_2n+1)₂-bpy=4,4’-dialkyl-2,2’-bipyridine) and ruthenium-based photosensitisers [Ru(bpy)₂(4,4’-(C_nH_2n+1)₂-bpy)](PF₆)₂ ( RuC_n ) with different alkyl chain lengths (n=0, 9, 12, 15, 17, and 19). We then prepared a series of PEGylated DPPC liposomes containing RuC_n and ReC_n , hereafter noted C_n , to perform photocatalytic CO₂ reduction in the presence of sodium ascorbate. The photocatalytic performance of the C_n liposomes was found to depend on the alkyl tail length, as the turnover number for CO (TON) was inversely correlated to the alkyl chain length, with a more than fivefold higher CO production (TON=14.5) for the C₉ liposomes, compared to C₁₉ (TON=2.8). Based on immobilisation efficiency quantification, diffusion kinetics, and time-resolved spectroscopy, we identified the main reason for this trend: two types of membrane-bound RuC_n species can be found in the membrane, either deeply buried in the bilayer and diffusing slowly, or less buried with much faster diffusion kinetics. Our data suggest that the higher photocatalytic performance of the C₉ system is due to the higher fraction of the more mobile and less buried molecular species, which leads to enhanced electron transfer kinetics between RuC₉ and ReC₉ .     

Maximum Spin Polarization in Chromium Dimer Cations as Demonstrated by X‐ray Magnetic Circular Dichroism Spectroscopy

X‐ray magnetic circular dichroism spectroscopy has been used to characterize the electronic structure and magnetic moment of Cr₂⁺. Our results indicate that the removal of a single electron from the 4sσ_g bonding orbital of Cr₂ drastically changes the preferred coupling of the 3d electronic spins. While the neutral molecule has a zero‐spin ground state with a very short bond length, the molecular cation exhibits a ferromagnetically coupled ground state with the highest possible spin of S=11/2, and almost twice the bond length of the neutral molecule. This spin configuration can be interpreted as a result of indirect exchange coupling between the 3d electrons of the two atoms that is mediated by the single 4s electron through a strong intraatomic 3d‐4s exchange interaction. Our finding allows an estimate of the relative energies of two states that are often discussed as ground‐state candidates, the ferromagnetically coupled ¹²Σ and the low‐spin ²Σ state.     

Pyridyl-Functionalized 1-Phosphabarrelene: Synthesis,Coordination Chemistry and Photochemical di-π-Methane Rearrangement

The [4+2] cycloaddition of 2-(2′-pyridyl)-4,6-diphenyl-λ³-phosphinine with the highly reactive dienophile hexafluoro-2-butyne has been studied and the first pyridyl-functionalized 1-phosphabarrelene was obtained and structurally characterized. Although monodentate CF₃-1-phosphabarrelenes show only a poor coordination ability, the chelating nature of the novel P,N-hybrid ligand gives access to various transition-metal complexes. Upon irradiation with UV light, the pyridyl-functionalized 1-phosphabarrelene undergoes a rather selective di-π-methane rearrangement in the coordination sphere of the metal center, leading to the formation of a complex based on a hitherto unknown pyridyl-functionalized 5-phosphasemibullvalene derivative. DFT calculations provide first insights into the mechanism of this reaction.     

From 3D to 2D Transition Metal Nitroprussides by Selective Rupture of Axial Bonds

1-methyl-2-pyrrolidone (1m2p) is a solvent with proven abilities for 2D-solid exfoliation due to its extremely high surface tension. In principle, such a feature could be used also to induce the selective breaking of certain bonds in solids to obtain new materials. Such a hypothesis is demonstrated in this study for transition metal nitroprussides, where 2D solids are obtained from 3D frameworks by selective rupture of axial bonds. This contribution discusses the mechanism involved in such molecular manufacture. The crystal structure for the formed 2D solids was solved and refined from XRD powder patterns recorded using synchrotron radiation. Mössbauer, IR and Raman spectra provided fine details on the electronic structure of the resulting new series of layered materials. The experimental information was complemented with calculations for the molecule configuration in its non-activated and activated forms. In the obtained 2D solids, neighboring layers of about 1 nm of thickness remain separated by activated 1m2p molecules. The interaction between neighboring layers is of a physical nature, without the presence of a chemical bond between them, as corresponds to a 2D material.     

A multiple criteria information system for pedagogical evaluation and professional development of teachers

Information systems for the evaluation of pedagogical practices aim to improve teaching activity and encourage the pedagogical development of teachers. The implementation of these systems has been interpreted in different ways, depending on each school’s administration board and/or the person responsible for the evaluation process. This ambiguity (and inherent subjectivity) is a barrier to the principles of transparency, equity and fairness in the pedagogical performance evaluation of teachers. From this premise, the main objective of this paper consists in proposing a multiple criteria information system to support the evaluation of pedagogical practices. By combining cognitive mapping and the measuring attractiveness by a categorical based evaluation technique (MACBETH), our framework allows for the conception of a more transparent evaluation system, bringing new insights to the pedagogical appraisal and professional development of teachers. The strengths and weaknesses of our framework are also discussed.     

HPLC-fluorescence detection and MEKC-LIF detection for the study of amino acids and catecholamines labelled with naphthalene-2,3-dicarboxyaldehyde

Naphthalene-2,3-dicarboxyaldehyde (NDA) is commonly used for detection of primary amines in conjunction with their separation with HPLC and CE. The fluorescence of the derivatives can be measured by a conventional fluorometer or via LIF. NDA is a reactive dye, which can replace o-phthaldehyde (OPA) and provides for derivatives which are considerably more stable than OPA derivatives. In addition, NDA can be used to derivatize primary amines at concentrations as low as 100 pM. In this work, HPLC/fluorescence and MEKC/LIF experiments were performed to separate/detect six neuroactive compounds, the amino acids, Gly, Glu, Asp, gamma-aminobutyric acid (GABA) and the catecholamines, dopamine and noradrenaline. The two methods were compared in terms of performance of separation. The amino acids can be separated in HPLC in less than 30 min and an identical separation is obtained in CE using MEKC and lithium salts with greater resolution (the number of theoretical plates was approximately 5000 for HPLC and 200 000 for MEKC). The lowest detected concentration was in the range of 0.1 nM for CE/LIF. The presence of a high salt concentration does not affect the separation of the samples. Examples of the analysis of microdialysate samples as well as amino acids in Ringer's solution are presented.     

An Organometallic Gold(I) Bis-N-Heterocyclic Carbene Complex with Multimodal Activity in Ovarian Cancer Cells

The organometallic Au^I bis-N-heterocyclic carbene complex [Au(9-methylcaffeine-8-ylidene)₂]⁺ ( AuTMX₂ ) was previously shown to selectively and potently stabilise telomeric DNA G-quadruplex (G4) structures. This study sheds light on the molecular reactivity and mode of action of AuTMX₂ in the cellular context using mass spectrometry-based methods, including shotgun proteomics in A2780 ovarian cancer cells. In contrast to other metal-based anticancer agents, this organogold compound is less prone to form coordinative bonds with biological nucleophiles and is expected to exert its drug effects mainly by non-covalent interactions. Global protein expression changes of treated cancer cells revealed a multimodal mode of action of AuTMX₂ by alterations in the nucleolus, telomeres, actin stress-fibres and stress-responses, which were further supported by pharmacological assays, fluorescence microscopy and cellular accumulation experiments. Proteomic data are available via ProteomeXchange with identifier PXD020560.     

LC�CMS Analysis of Sertraline and Its Active Metabolite in Human Serum Using a Silica Column with a Non-Aqueous Polar Mobile Phase

A sensitive liquid chromatography?Cmass spectrometry method for the simultaneous determination of sertraline (SER) and its major metabolite norsertraline (NOR) from serum was developed and validated in the context of a pharmacokinetic study in pregnant women. The separations were achieved on a silica column with a non-aqueous polar mobile phase consisting of acetonitrile, methanol and ammonium acetate at a flow rate of 0.5 mL min^?1. The concentrations were measured using a single quadruple mass spectroscopic detector supplied with atmospheric pressure ionization electrospray. Sample preparation consisted of a simple liquid?Cliquid procedure. The detector was set in selective ion mode for each compound of interest, 306 m/z for SER and 275 m/z for NOR. Calibration curves were generated by least square linear regression for concentration of 5?C160 ng mL^?1 for SER and from 10 to 320 ng mL^?1 for NOR. The curves for both compounds of interest were linear, with correlation coefficients r ² ?? 0.999.