The two enantiomers of chiral phosphonate 4-phenyldinaphtho2,1-d:1',2'-f1,3,2dioxaphosphepine 4-oxide, O=PPh(BINOL), were synthesized from the proper 1,1'-bi-2-naphtol (BINOL) enantiomer and ...characterized. The structure of the (
)-enantiomer was elucidated by means of single-crystal X-ray diffraction. The reaction with anhydrous ZnBr
afforded complexes having the general formula ZnBr
{O=PPh(BINOL)}
that showed intense fluorescence centered in the near-UV region rationalized on the basis of TD-DFT calculations. The corresponding Mn(II) complexes with the general formula MnX
{O=PPh(BINOL)}
(X = Cl, Br) exhibited dual emission upon excitation with UV light, with the relative intensity of the bands dependent upon the choice of the halide. The highest energy transition is comparable with that of the Zn(II) complex, while the lowest energy emission falls in the red region of the spectrum and is characterized by lifetimes in the hundreds of microseconds range. Although the emission at lower energy can also be achieved by direct excitation of the metal center, the luminescence decay curves suggest that the band in the red range is possibly derived from BINOL-centered excited states populated by intersystem crossing.
•A computational model for adsorption packed bed reactors of any potential geometry.•Parametric study of five reactor geometries for adsorption cooling applications.•Quantification of the effect of ...solid volume fraction, fin thickness and fin length.•Study of the influence of adsorbed mass spatial distribution on desorption.•Comparison of copper and aluminium as heat exchanger materials.
Environmental concerns regarding global warming and ozone depletion urge towards sustainable solutions for satisfying the increasing cooling demand. Adsorption cooling technology could form part of the solution since it can be driven by solar energy and industrial or vehicular waste heat, as well as it employs non ozone-destructive refrigerants. However, its low performance hinders its extensive development and commercialization. The design of the adsorption reactor is crucial for its performance improvement, since its inherent cyclic operation imposes a compromise between the Specific Cooling Power and the Coefficient of Performance. A generalized three-dimensional computational model based on unstructured meshes is presented, capable to simulate all potential geometries. Dynamic conjugate simulations of the packed bed and the heat exchanger allow to study the latter’s influence on the reactor performance. A parametric study of five reactor geometries was conducted, demonstrating quantitatively the strong impact of the solid volume fraction, fin length and fin thickness on the performance. Within the studied range, the Specific Cooling Power is maximized for the highest solid volume fraction and for the lowest fin thickness and fin length. The effect of the adsorbed mass spatial distribution on the desorption phase is discussed. A sensitivity analysis exhibits the importance of the heat transfer coefficient between the two domains. Copper and aluminium are compared as heat exchanger materials, revealing that the former performs more effectively, although the difference is appreciable only for longer fin lengths. The presented numerical model can be employed for improving the design of adsorption packed bed reactors.
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a frequent and severe chronic disease drastically impairing life quality. The underlying pathomechanism is incompletely understood yet ...but there is convincing evidence that in at least a subset of patients ME/CFS has an autoimmune etiology. In this review, we will discuss current autoimmune aspects for ME/CFS. Immune dysregulation in ME/CFS has been frequently described including changes in cytokine profiles and immunoglobulin levels, T- and B-cell phenotype and a decrease of natural killer cell cytotoxicity. Moreover, autoantibodies against various antigens including neurotransmitter receptors have been recently identified in ME/CFS individuals by several groups. Consistently, clinical trials from Norway have shown that B-cell depletion with rituximab results in clinical benefits in about half of ME/CFS patients. Furthermore, recent studies have provided evidence for severe metabolic disturbances presumably mediated by serum autoantibodies in ME/CFS. Therefore, further efforts are required to delineate the role of autoantibodies in the onset and pathomechanisms of ME/CFS in order to better understand and properly treat this disease.
•The pathogenesis of ME/CFS is multifactorial, and immunological and environmental factors play a role.•Autoimmune mechanisms can be linked with ME/CFS at least in a subset of patients.•Autoantibodies mostly against nuclear and neurotransmitter receptors are found in a subset of ME/CFS patients.•Immunomodulatory therapeutic strategies targeting autoantibodies may be beneficial and should be pursued.
Nanometer scale lateral heterostructures with atomically sharp band discontinuities can be conceived as the 2D analogues of vertical Van der Waals heterostructures, where pristine properties of each ...component coexist with interfacial phenomena that result in a variety of exotic quantum phenomena. However, despite considerable advances in the fabrication of lateral heterostructures, controlling their covalent interfaces and band discontinuities with atomic precision, scaling down components and producing periodic, lattice‐coherent superlattices still represent major challenges. Here, a synthetic strategy to fabricate nanometer scale, coherent lateral superlattice heterojunctions with atomically sharp band discontinuity is reported. By merging interdigitated arrays of different types of graphene nanoribbons by means of a novel on‐surface reaction, superlattices of 1D, and chemically heterogeneous nanoporous junctions are obtained. The latter host subnanometer quantum dipoles and tunneling in‐gap states, altogether expected to promote interfacial phenomena such as interribbon excitons or selective photocatalysis.
A 2D lateral superlattice heterostructure with unprecedented single‐bond band discontinuities and heterocomponent dimensions down to one nanometer is realized by the coupling of interdigitated nanoribbons into a nitrogen‐doped nanoporous graphene structure. The atomic scale band discontinuities at the nanoporous heterojunctions endow this nanomaterial with a multifunctionality that can be relevant for photodetection, excitonic solar cells, water splitting, or selective nanosieving.
Tetrahedral Zn(II) complexes having general formula ZnX2{O=P(NMe2)2Ind}2 (X=Cl, Br, I, NCS) were isolated from the reaction between the indol‐1‐yl substituted phosphoramide ...N,N,N′,N′‐tetramethyl‐P‐indol‐1‐ylphosphonic diamide O=P(NMe2)2Ind and anhydrous Zn(II) precursors under mild conditions. The structures of the three halide derivatives were ascertained by single‐crystal X‐ray diffraction. The bromo‐ and iodo‐derivatives revealed to be appreciably luminescent in the green region upon excitation with light below 300 nm, with emission bands centred between 520 and 530 nm. The large Stokes shifts and the excited state lifetimes in the milliseconds range indicated that triplet excited states are involved in the emission. TD‐DFT calculations indicated that the luminescence is related to a ligand‐centred transition with the involvement of triplet states.
Tetrahedral Zn(II) complexes with indolyl‐substituted phosphoramides and heavy halides in the coordination sphere showed appreciable photoluminescence in the visible range upon excitation with UV light. Experimental and computational data indicate that the emissions are associated to ligand‐centred triplet states.
An on‐surface Diels–Alder reaction Castro‐Esteban, Jesús; Albrecht, Florian; Fatayer, Shadi ...
Angewandte Chemie International Edition,
December 6, 2021, Letnik:
60, Številka:
50
Journal Article
Recenzirano
Odprti dostop
The Diels–Alder reaction is one of the most popular reactions in organic chemistry. However, its use in the field of on‐surface synthesis is hampered by the spatial restrictions of this cycloaddition ...reaction. Herein we selected a cyclic strained triyne to demonstrate an on‐surface hexadehydro‐Diels–Alder reaction in a single molecule. The reaction was studied in detail by means of atomic force microscopy (AFM) with CO‐functionalized tips. Our results pave the way to use this iconic pericyclic reaction for on‐surface synthesis, introducing the concept of atom economy in the field.
A hexadehydro‐Diels–Alder reaction was demonstrated on‐surface in single molecules of a cyclic strained triyne. The starting material, several intermediates and the product were visualized by means of atomic force microscopy (AFM) with CO‐functionalized tips. Our results pave the way to use this iconic pericyclic reaction for on‐surface synthesis, introducing the concept of atom economy in the field.
Intense red-emitting heteroleptic Cu(I) complexes were isolated using 2,1,3-benzothiadiazole (BTD) as N-donor ligand and triphenylphosphine, bis(2-diphenylphosphino)phenyl ether (DPEphos) or ...bis(diphenylphosphino)methane (dppm) as P-donors. The structures of two mononuclear and one dinuclear derivatives with one nitrogen and two phosphorus atoms in the Cu(I) coordination sphere were ascertained by means of X-ray diffraction, revealing an overall tetrahedral geometry at the solid state due to the direct interaction of the counterion with Cu(I). Upon excitation with UV and violet-blue light, the Cu(I) complexes exhibited emissions centred between 623 and 683 nm with photoluminescence quantum yields up to 46%. Lifetimes in the tens-thousands millisecond range were observed. The values resulted affected by the choice of the counterion, and an increase of up to 15% was observed passing from tetrafluoroborate to perchlorate in the mononuclear BTD complex with two PPh3 ligands. DFT calculations indicated that the lowest energy absorptions have charge transfer nature, from the {CuP2} fragments with the contributions of the P-bonded aryl substituents to an unoccupied π* orbital of BTD. The triplet→singlet emissions involve the metal centre, the phosphine ligands, and the occupied and empty orbitals of BTD.
Display omitted
•Cu(I) phosphine complexes with 2,1,3-benzothiadiazole as N-donor were isolated.•Two mononuclear and one dinuclear derivatives were structurally characterized.•The direct interaction of tetrafluoroborate and perchlorate with Cu(I) was revealed.•Intense photoluminescence in the red region was observed.•Quantum yields and lifetimes resulted dependent upon the nature of the counterion.
Manganese(
ii
) halide complexes with
N
,
N
,
N
′,
N
′-tetramethyl-
P
-naphtalen-2-ylphosphonic diamide were synthesized from anhydrous MnX
2
salts (X = Cl, Br, I) and characterized. Single-crystal ...X-ray diffraction revealed in all the cases slightly distorted tetrahedral geometry of the coordination sphere. The photoluminescence spectra showed the superimposition of a green emission, related to the
4
T
1
(
4
G) →
6
A
1
(
6
S) transition of Mn(
ii
), with a band in the red range. Different possible attributions to the lowest-energy emission were taken into account. The emission spectra of the isolated products are dependent upon the nature of the halide and, in the case of X = Br, also upon the excitation wavelength.
X-ray diffraction revealed tetrahedral geometry for manganese(
ii
) halide complexes with napthylphosphonic diamide ligands. The photoluminescence spectra showed the superimposition of green Mn(
ii
) emission with a band in the red range.
As a response to the COVID-19 pandemic, many governments have introduced steps such as spatial distancing and “staying at home” to curb its spread and impact. The fear resulting from the disease, the ...‘lockdown’ situation, high levels of uncertainty regarding the future, and financial insecurity raise the level of stress, anxiety, and depression experienced by people all around the world. Psychoactive substances and other reinforcing behaviors (e.g., gambling, video gaming, watching pornography) are often used to reduce stress and anxiety and/or to alleviate depressed mood. The tendency to use such substances and engage in such behaviors in an excessive manner as putative coping strategies in crises like the COVID-19 pandemic is considerable. Moreover, the importance of information and communications technology (ICT) is even higher in the present crisis than usual. ICT has been crucial in keeping parts of the economy going, allowing large groups of people to work and study from home, enhancing social connectedness, providing greatly needed entertainment, etc. Although for the vast majority ICT use is adaptive and should not be pathologized, a subgroup of vulnerable individuals are at risk of developing problematic usage patterns. The present consensus guidance discusses these risks and makes some practical recommendations that may help diminish them.
•The COVID-19 pandemic is impacting on individuals' mental health.•Technology is being used to help alleviate stress and anxiety caused by the pandemic.•The risk of problematic internet use (PIU) is increased during the pandemic.•Guidance is needed related to decreasing the risk of PIU.•Practical recommendations to diminish the risk of PIU are presented.
Luminescent mono- and dinuclear cationic heteroleptic Cu( i ) complexes Cu(N ∧ N′)(P) 2 + , Cu(N ∧ N′)(P ∧ P) + or Cu 2 (N ∧ N′) 2 (μ-P ∧ P) 2 2+ containing bidentate N-donor ligands (N ∧ N′) with ...benzotriazole, pyridine, pyrimidine or substituted triazine moieties in combination with mono- (P) and bidentate (P ∧ P) phosphines were synthesized and characterized. Eight single-crystal X-ray diffraction structures were obtained and showed marked distortions from the ideal tetrahedral geometry around Cu( i ). Cyclic voltammetry on selected complexes showed reduction processes around −2 V vs. ferrocene/ferrocenium and irreversible oxidation close to 1 V. The long-wavelength absorptions were observed in the range of 350 to 450 nm and attributed to MLCT transitions. Upon excitation with near-UV and violet light, the complexes exhibited emissions from bright yellow (max 538 nm) to red (max 637 nm). Emission maxima, luminescence lifetimes and photoluminescence quantum yields that reach up to 0.92 on powder samples resulted in strong dependence on the choice of the coordinated ligands, the acceptor character of the N ∧ N′ ligands in particular. DFT calculations confirmed the electrochemical and photophysical outcomes and strongly suggested that the emission has a metal-to-ligand charge transfer (MLCT) nature, with intersystem crossing affording triplet emitting states.
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