Unveiling ultrafast dynamics in bridged bimetallic complexes using optical and X-ray transient absorption spectroscopies

In photosynthetic systems employing multiple transition metal centers, the properties of charge-transfer states are tuned by the coupling between metal centers. Here, we use ultrafast optical and X-ray spectroscopies to elucidate the effects of metal–metal interactions in a bimetallic tetrapyridophenazine-bridged Os(ii)/Cu(i) complex. Despite having an appropriate driving force for Os-to-Cu hole transfer in the Os(ii) moiety excited state, no such charge transfer was observed. However, excited-state coupling between the metal centers is present, evidenced by variations in the Os MLCT lifetime depending on the identity of the opposite metal center. This coupling results in concerted coherent vibrations appearing in the relaxation kinetics of the MLCT states for both Cu and Os centers. These vibrations are dominated by metal–ligand contraction at the Cu/Os centers, which are in-phase and linked through the conjugated bridging ligand. This study shows how vibronic coupling between transition metal centers affects the ultrafast dynamics in bridged, multi-metallic systems from the earliest times after photoexcitation to excited-state decay, presenting avenues for tuning charge-transfer states through judicious choice of metal/ligand groups.

In photosynthetic systems employing multiple transition metal centers, the properties of charge-transfer states are tuned by the coupling between metal centers.     

Advances in Medical Wearable Biosensors: Design,Fabrication and Materials Strategies in Healthcare Monitoring

In the past decade, wearable biosensors have radically changed our outlook on contemporary medical healthcare monitoring systems. These smart, multiplexed devices allow us to quantify dynamic biological signals in real time through highly sensitive, miniaturized sensing platforms, thereby decentralizing the concept of regular clinical check-ups and diagnosis towards more versatile, remote, and personalized healthcare monitoring. This paradigm shift in healthcare delivery can be attributed to the development of nanomaterials and improvements made to non-invasive biosignal detection systems alongside integrated approaches for multifaceted data acquisition and interpretation. The discovery of new biomarkers and the use of bioaffinity recognition elements like aptamers and peptide arrays combined with the use of newly developed, flexible, and conductive materials that interact with skin surfaces has led to the widespread application of biosensors in the biomedical field. This review focuses on the recent advances made in wearable technology for remote healthcare monitoring. It classifies their development and application in terms of electrochemical, mechanical, and optical modes of transduction and type of material used and discusses the shortcomings accompanying their large-scale fabrication and commercialization. A brief note on the most widely used materials and their improvements in wearable sensor development is outlined along with instructions for the future of medical wearables.     

Kinetics of the reactions of hydroxyl radicals (OH) and of chlorine atoms (Cl) with methylethylether over the temperature range 274–345 K

The rate constants for the gas-phase reactions between methylethylether and hydroxyl radicals (OH) and methylethylether and chlorine atoms (Cl) have been determined over the temperature range 274–345 K using a relative rate technique. In this range the rate constants vary little with temperature and average values of k_MEE+OH = (6.60_−2.62^+3.88) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ and k_MEE+Cl= (34.9 ± 6.7) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ were obtained. The atmospheric lifetimes of methylethylether have been estimated with respect to removal by OH radicals and Cl atoms to be ca. 2 days and ca. 30–40 days, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 231–236, 1997.     

Enantioselective Total Synthesis of (+)-Incargranine A Enabled by Bifunctional Iminophosphorane and Iridium Catalysis

Herein we report the first enantioselective total synthesis of (+)-incargranine A, in nine steps. The total synthesis was enabled by an enantioselective intramolecular organocatalysed desymmetrising Michael addition of a malonamate ester to a linked dienone substrate that established pivotal stereocentres with excellent enantio- and complete diastereoselectivity. Furthermore, a key hemiaminal intermediate was accessed by developing an iridium-catalysed reductive cyclisation, and the scope of this transformation was explored to produce a range of bicyclic hemiaminal motifs. Once installed, the hemiaminal motif was used to initiate a biomimetic cascade to access the natural product directly in a single step.     

Revealing Excited-State Trajectories on Potential Energy Surfaces with Atomic Resolution in Real Time

Photoexcited molecular trajectories on potential energy surfaces (PESs) prior to thermalization are intimately connected to the photochemical reaction outcome. The excited-state trajectories of a diplatinum complex featuring photo-activated metal–metal σ-bond formation and associated Pt−Pt stretching motions were detected in real time using femtosecond wide-angle X-ray solution scattering. The observed motions correspond well with coherent vibrational wavepacket motions detected by femtosecond optical transient absorption. Two key coordinates for intersystem crossing have been identified, the Pt−Pt bond length and the orientation of the ligands coordinated with the platinum centers, along which the excited-state trajectories can be projected onto the calculated PESs of the excited states. This investigation has gleaned novel insight into electronic transitions occurring on the time scales of vibrational motions measured in real time, revealing ultrafast nonadiabatic or non-equilibrium processes along excited-state trajectories involving multiple excited-state PESs.     

The role of monomer in the chain transfer reaction in cobaloxime‐mediated free‐radical polymerization

The role of monomer in catalytic chain transfer polymerization was studied by determination of the chain transfer constants of the tetraphenyl derivative of cobaloxime boron fluoride (COPhBF) in methyl methacrylate at 60°C varying the monomer concentration instead of the COPhBF concentration as is common practice. Toluene and tert‐butyl acetate were used as diluents in these studies and it was found that the chain transfer constants obtained in the present studies were not significantly different from those observed in conventional experiments. These results suggest the absence of a direct participation of monomer molecules in the hydrogen abstraction step in catalytic chain transfer.     

eHydrogenation: Hydrogen-free Electrochemical Hydrogenation

Hydrogenation reactions are staple transformations commonly used across scientific fields to synthesise pharmaceuticals, natural products, and various functional materials. However, the vast majority of these reactions require the use of a toxic and costly catalyst leading to unpractical, hazardous and often functionally limited conditions. Herein, we report a new, general, practical, efficient, mild and high-yielding hydrogen-free electrochemical method for the reduction of alkene, alkyne, nitro and azido groups. Finally, this method has been applied to deuterium labelling.