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The main target of this thesis is to gain a deeper understanding of the reduction chemistry of group 16 elements (sulfur, selenium and tellurium) and their derivatives by using divalent lanthanide reagents as reduction agents. Different from cyclopentadienyl counterparts reported by Evans, the employed formidinate lanthanides in this work are supported by a sterically more demanding ligand and the reactivity of these complexes has been discussed by Junk and Deacon and proved by previous work of Roesky et al. The initial target of this project is the reduction of elemental chalcogens by [(DippForm)2Ln(THF)2]. Nano-sized selenium and tellurium were prepared considering the poor solubility of them. As part of the major focus, it is also interesting to study the reduction of diphenyldichalcogenides Ph2E2 (E = S, Se, Te) and perfluorinated diphenyldiselenides (4-RC6H4Se)2 (R = F, OMe) in order to determine whether this reaction can be used for the synthesis of a broad class of such compounds. Moreover, based on the previous study on lanthanides, it is also of interest to extend such reduction chemistry to transition metal complexes. However, as a minor target of this project and also a very initial study, such extension limits only to [(DippNafnaf)Fe(C7H8)] (DippNafnaf = CH[CHN(2, 6-diisopropylphenyl)]2). Due to the high reactivity of FeI complex and interesting application potentials of ?-diketiminato ligand supported iron chalcogenides, the reaction between [(DippNafnaf)Fe(toluene)] and elemental chalcogens has the potential to give some interesting results and thus was studied.

Using the second-order Møller–Plesset perturbation theory (MP2), together with Dunning’s all-electron correlation consistent basis set aug-cc-pVTZ, we show that the covalently bound oxygen atom present in a series of 21 prototypical monomer molecules examined does conceive a positive (or a negative) σ-hole. A σ-hole, in general, is an electron density-deficient region on a bound atom M along the outer extension of the R–M covalent bond, where R is the reminder part of the molecule, and M is the main group atom covalently bonded to R. We have also examined some exemplar 1:1 binary complexes that are formed between five randomly chosen monomers of the above series and the nitrogen- and oxygen-containing Lewis bases in N2, PN, NH3, and OH2. We show that the O-centered positive σ-hole in the selected monomers has the ability to form the chalcogen bonding interaction, and this is when the σ-hole on O is placed in the close proximity of the negative site in the partner molecule. Although the interaction energy and the various other 12 characteristics revealed from this study indicate the presence of any weakly bound interaction between the monomers in the six complexes, our result is strongly inconsistent with the general view that oxygen does not form a chalcogen-bonded interaction.

Chalcogen–containing therapeutic agents (TAs), which include sulfur (S), selenium (Se), and tellurium (Te) atoms, have recently emerged as a promising class of photosensitizers (PSs) and photothermal agents (PTAs) for cancer phototherapy. The incorporation of heavier chalcogens into organic chromophores leads to visible–to–near–infrared (VIS–NIR) light absorption, efficient triplet harvesting, and adequate heat and energy transfer efficiency, all of which are paramount for photodynamic therapy (PDT) and photothermal therapy (PTT). However, chalcogen–based PSs/PTAs suffer from photostability, bioavailability, and targeted delivery issues, which minimize their PDT/PTT performances. Nevertheless, significant progress in the rational design of nanoencapsulation strategies has been achieved to overcome the challenges of chalcogen–based TAs for effective phototherapeutic cancer treatment. This review highlights the recent advances (within the last five years) in nano-drug delivery approaches adapted for chalcogen–substituted PSs/PTAs for PDT, PTT, or synergistic PDT/PTT, integrating imaging and treatment. The PSs/PTAs described in this review are classified into three classes: (i) sulfur, (ii) selenium, and (iii) tellurium–containing TAs used in phototherapy applications. This review offers a comprehensive perspective on the design of chalcogen–substituted photosensitizers (PSs) and photothermal agents (PTAs), covering spectroscopic and computational characterization, nanoformulation strategies, and their roles in enhancing reactive oxygen species (ROS) generation and photothermal conversion efficiency for improved in vitro and in vivo performance. We hope this work will encourage further research into nanotechnological strategies designed to enhance the phototherapeutic efficacy of chalcogen–containing therapeutic agents.

Although 1,2σ λ -oxaphosphetanes have been known for a long time, the \"low-coordinate\" 1,2σ λ -oxaphosphetanes have only been known since their first synthesis in 2018 via decomplexation. Apart from ligation of this P-heterocycle to gold(I)chloride and the oxidation using -chloranil, nothing on their chemistry has been reported so far. Herein, we describe the synthesis of new 1,2σ λ -oxaphosphetane complexes ( - ) and free derivatives ( - ), as well as reactions of with chalcogens and/or chalcogen transfer reagents, which yielded the -chalcogenides ( - ; Ch = O, S, Se). We also report on the theoretical results of the reaction pathways of -phenyl-substituted 1,2 σ λ -oxaphosphetanes and ring strain energies of 1,2σ λ -oxaphosphetane -chalcogenides.

In this review, several examples of the application of pnictogen (Pn) (group 15) and chalcogen (Ch) bonding (group 16) interactions in organocatalytic processes are gathered, backed up with Molecular Electrostatic Potential surfaces of model systems. Despite the fact that the use of catalysts based on pnictogen and chalcogen bonding interactions is taking its first steps, it should be considered and used by the scientific community as a novel, promising tool in the field of organocatalysis.

High sensitivity and specificity are two desirable features in biomedical imaging. Raman imaging has surfaced as a promising optical modality that offers both. Here we report the design and synthesis of a group of near-infrared absorbing 2-thienyl-substituted chalcogenopyrylium dyes tailored to have high affinity for gold. When adsorbed onto gold nanoparticles, these dyes produce biocompatible SERRS nanoprobes with attomolar limits of detection amenable to ultrasensitive in vivo multiplexed tumour and disease marker detection. Raman imaging offers great potential in biomedical imaging due to the combination of specificity and sensitivity. Here, the authors show nanoparticles functionalized with a chalcogenopyrylium reporter molecule, giving bright probes with low limits of detection for in vivo imaging.

Artificial neuromorphic systems based on populations of spiking neurons are an indispensable tool in understanding the human brain and in constructing neuromimetic computational systems. To reach areal and power efficiencies comparable to those seen in biological systems, electroionics-based and phase-change-based memristive devices have been explored as nanoscale counterparts of synapses. However, progress on scalable realizations of neurons has so far been limited. Here, we show that chalcogenide-based phase-change materials can be used to create an artificial neuron in which the membrane potential is represented by the phase configuration of the nanoscale phase-change device. By exploiting the physics of reversible amorphous-to-crystal phase transitions, we show that the temporal integration of postsynaptic potentials can be achieved on a nanosecond timescale. Moreover, we show that this is inherently stochastic because of the melt-quench-induced reconfiguration of the atomic structure occurring when the neuron is reset. We demonstrate the use of these phase-change neurons, and their populations, in the detection of temporal correlations in parallel data streams and in sub-Nyquist representation of high-bandwidth signals. A nanoscale phase-change device can be used to create an artificial neuron that exhibits integrate-and-fire functionality with stochastic dynamics.

The 5-lipoxygenase (5-LOX) pathway gives rise to bioactive inflammatory lipid mediators, such as leukotrienes (LTs). 5-LOX carries out the oxygenation of arachidonic acid to the 5-hydroperoxy derivative and then to the leukotriene A epoxide which is converted to a chemotactic leukotriene B (LTB ) by leukotriene A hydrolase (LTA H). In addition, LTA H possesses aminopeptidase activity to cleave the N-terminal proline of a pro-inflammatory tripeptide, prolyl-glycyl-proline (PGP). Based on the structural characteristics of LTA H, it is possible to selectively inhibit the epoxide hydrolase activity while sparing the inactivating, peptidolytic, cleavage of PGP. In the current study, chalcogen-containing compounds, 4-(4-benzylphenyl) thiazol-2-amine (ARM1) and its selenazole (TTSe) and oxazole (TTO) derivatives were characterized regarding their inhibitory and binding properties. All three compounds selectively inhibit the epoxide hydrolase activity of LTA H at low micromolar concentrations, while sparing the aminopeptidase activity. These inhibitors also block the 5-LOX activity in leukocytes and have distinct inhibition constants with recombinant 5-LOX. Furthermore, high-resolution structures of LTA H with inhibitors were determined and potential binding sites to 5-LOX were proposed. In conclusion, we present chalcogen-containing inhibitors which differentially target essential steps in the biosynthetic route for LTB and can potentially be used as modulators of inflammatory response by the 5-LOX pathway.

Ab initio calculations are employed to assess the relative strengths of various noncovalent bonds. Tetrel, pnicogen, chalcogen, and halogen atoms are represented by third-row atoms Ge, As, Se, and Br, respectively. Each atom was placed in a series of molecular bonding situations, beginning with all H atoms, then progressing to methyl substitutions, and F substituents placed in various locations around the central atom. Each Lewis acid was allowed to engage in a complex with NH3 as a common nucleophile, and the strength and other aspects of the dimer were assessed. In the context of fully hydrogenated acids, the strengths of the various bonds varied in the pattern of chalcogen > halogen > pnicogen ≈ tetrel. Methyl substitution weakened all bonds, but not in a uniform manner, resulting in a greatly weakened halogen bond. Fluorosubstitution strengthened the interactions, increasing its effect as the number of F atoms rises. The effect was strongest when the F atom lay directly opposite the base, resulting in a halogen > chalcogen > pnicogen > tetrel order of bond strength. Replacing third-row atoms by their second-row counterparts weakened the bonds, but not uniformly. Tetrel bonds were weakest for the fully hydrogenated acids and surpassed pnicogen bonds when F had been added to the acid.

Transition metal dichalcogenide (TMD) nanomaterials, especially the mono- or few-layer ones, have received extensive research interest owing to their versatile properties, ranging from true metals (e.g., NbS2 and VSe2) and semimetals (e.g., WTe2 and TiSe2) to semiconductors (e.g., MoS2 and We2) and insulators (e.g., HfS2). Therefore, the reliable production of these nanomaterials with atomically thin thickness and laterally uniform dimension is essential for their promising applications in transistors, photodetectors, electroluminescent devices, catalysis, energy conversion, environment remediation, biosensing, bioimaging, and so on. Recently, the electrochemical lithium ion intercalation-based exfoliation method has emerged as a mature, efficient and promising strategy for the high-yield production of mono- or few-layer TMD nanosheets; monolayer MoS2 (yield of 92%), monolayer TaS2 (yield of 93%) and bilayer TiS2 (yield of 93%) with lateral dimensions of ~1 µm (refs. 1–3). This Protocol describes the details of experimental procedures for the high-yield synthesis of mono- or few-layer TMDs and other inorganic nanosheets such as MoS2, WS2, TiS2, TaS2, ZrS2, graphene, h-BN, NbSe2, WSe2, Sb2Se3 and Bi2Te3 by using the electrochemical lithium ion intercalation-based exfoliation method, which involves the electrochemical intercalation of lithium ions into layered inorganic crystals and a mild sonication process. The whole protocol takes 26–38 h for the successful production of ultrathin inorganic nanosheets.The electrochemical lithium ion intercalation-based exfoliation of mono- or few-layer transition metal dichalcogenides nanosheets described here results in materials that can be used in diverse applications, e.g., biosensing and catalysis.