This is an updated critical review of the advances towards the full exploitation of diverse Electro-Fenton technologies for the decontamination of real effluents at industrial scale. The main ...relevant innovations spanning almost three decades are analyzed from a historical perspective. Electro-Fenton, Photoelectro-Fenton, Peroxi-coagulation, Sonoelectro-Fenton and related methods are assessed. Economic aspects and engineering challenges that should be overcome to reach the title goal, such as efficient cathodes for H2O2 electrogeneration, heterogeneous catalysis, the pH issue, and the iron sludge problem are particularly highlighted. A special section is devoted to examining the R&D works on actual wastewaters. Overviews of both pilot scale studies currently available in the literature and companies that already provide some of these technologies are presented. Finally, suggestions for further development at a large scale, depending on wastewater characteristics, are summarized.
Abstract
The physical nature of a series of 20 new open clusters is confirmed employing existing data on putative star members, mainly from the second
Gaia
Data Release (DR2). The clusters were ...discovered as overdensities of stars by visual inspection of either photographic DSS plates or proper motion plots of random source fields. The reported objects are not present in the most comprehensive or recent catalogs of stellar clusters and associations. For all of them, clumps of comoving stars are revealed in the proper motion space. The parallaxes of the clumped stars are compatible with the real existence of open clusters over narrow ranges of distances. Surface density calculations, free of most noise from non-member sources, allow differentiating a cluster core and an extended cluster corona in some instances. Color-magnitude diagrams generally show a definite main sequence that allows confirmation of the physical existence of the clusters and some of their characteristics. Two of the new clusters seem to form a double system with a common origin. Several of the new clusters challenge the claim of near completeness of the known OC population in the distance range from 1.0 to 1.8 kpc from the Sun (Kharchenko et al.).
In this article, some quinoidal
p
-quinodimethanes compounds that convert partially or completely to diradicals or biradicaloids are analyzed. The aromatic/quinoidal balance is revisited with the ...objective of providing a common interpretation for most of them. For that purpose, important structural and energetic parameters such as the bond length alternation pattern and the singlet–triplet gaps are analyzed and interpreted in the framework of double spin polarization and π-conjugation.
p
-Quinodimethanes based in oligothiophenes, polycyclic aromatic hydrocarbons, oligophenylenes, thienothiophenes, charged dications and cyclic conjugated molecules are discussed. There are excellent reviews in the field of singlet diradicals; however, a revision similar to that proposed here can help the reader to have another perspective on these promising new functional materials. The focus has been put on molecules which are well known by the author and another of relevance in the field. In this regard, the article finishes with a discussion of some important applications of these diradicals in organic electronics. New chemical systems based on the
p
-quinodimethane building blocks are waiting us around the corner, bringing us new and challenging structures and fascinating novel properties, which describe a very rich field of research in chemistry and in physics with an excellent present and a bright future.
The Primordial Group hypothesis states that only sufficiently young open clusters (OCs) can be multiple, and old OCs are essentially isolated. We tested this postulate through four different studies ...using a manual search of Gaia EDR3 and extensive literature. First, we revisited the work of de La Fuente Marcos and de La Fuente Marcos (2009), which states that only ca. 40% of OC pairs are of primordial origin. However, no plausible binary system among their proposed OC pairs having at least one member older than 0.1 Gyr was found. Second, we researched the OCs < 0.01 Gyr old in Tarricq et al. (2021) and found that ca. 71% of them remain in their primordial groups. Third, a similar study of the oldest OCs (age > 4 Gyr) showed that they are essentially alone. Forth, the well-known case of the double cluster in Perseus and some other binary systems described in the literature were also shown to accommodate the title hypothesis. A simplified bimodal model allows for retrieval of the overall fraction of related OCs (approximately 12–16%) from our results, assuming that young clusters remain associated at ~0.04 Gyr. The obtained results further support that OCs are born in groups (Casado 2021).
In the present study, we continue testing the Primordial Group hypothesis (Casado 2022), which postulates that only sufficiently young open clusters can be binary or multiple, and old clusters are ...essentially single. To this end, we revisit all the remaining binary cluster candidates in the Galaxy having at least one cluster older than 100 Myr through Gaia data and careful revision of the literature. We found no convincing case for an old binary system among the 120 pairs/groups revised. Most of the pairs are optical pairs or flyby encounters. However, we found three dubious pairs that could falsify the title hypothesis upon further research. We also found two possible primordial pairs older than expected. Our results confirm that the vast majority of binary/multiple OCs in the Galaxy, if not all, are of primordial origin and are not stable for a long time. This finding is in line with similar studies of the Magellanic Clouds and theoretical N-body simulations in the Galaxy. The pairs of OCs in these groups are generally not binary systems since they are not gravitationally bound. We also point out some inconsistencies in previous works and databases, such as false open clusters and duplicities.
The main chemical, spectroscopic and material research done in tetracyano quinoidal oligothiophenes in the last 30 years has been reviewed. Their use as semiconducting substrates in organic ...electronic and their versatility to act as multifunctional materials have been highlighted. This tutorial review has been paralleled by the description of the main findings provided by Raman spectroscopy, in particular, associated with the discovery of the intrinsic diradical properties inherent to the pro-aromatic character of the quinoidal arrangement. It turns out that the fascinating properties of these materials are the manifestation of the diradical fingerprint behind a rather unconventional electronic structure.
Aromatic & Quinoidal:
together but not mixed.
Pro-aromaticity of tetracyano quinoidal thiophenes promotes the appearance of radical and diradical structures during exposition to different external stimuli. This might be exploited in multifunctional materials (semiconductors, molecular magnets, multiphoton materials,
etc.
).
The conceptual connections between 4n Hückel antiaromaticity, disjoint orbitals, correlation energy, pro‐aromaticity and diradical character for a variety of extended π‐conjugated systems, including ...some salient recent examples of nanographenes and polycyclic aromatic radicals, are provided based on their 4nannulene peripheries. The realization of such structure–property relationships has led to a beneficial pedagogic exercise establishing design guidelines for diradicaloids. The antiaromatic fingerprint of the 4nannulene peripheries upon orbital interactions due to internal covalent connectors gives insights into the diradicaloid property of a diversity of π‐conjugated molecules that have fascinated chemists recently.
A conceptual electronic structure trip from 4n Hückel antiaromatics to diradicaloids and to more hierarchical complex molecular shapes made by internal covalent hybridization of the peripheral 4n π‐electron circuit is described. Focus is on the underlying physical organic chemistry implications.
The charged forms of π-conjugated chromophores are relevant in the field of organic electronics as charge carriers in optoelectronic devices, but also as energy storage substrates in organic ...batteries. In this context, intramolecular reorganization energy plays an important role in controlling material efficiency. In this work, we investigate how the diradical character influences the reorganization energies of holes and electrons by considering a library of diradicaloid chromophores. We determine the reorganization energies with the four-point adiabatic potential method using quantum-chemical calculations at density functional theory (DFT) level. To assess the role of diradical character, we compare the results obtained, assuming both closed-shell and open-shell representations of the neutral species. The study shows how the diradical character impacts the geometrical and electronic structure of neutral species, which in turn control the magnitude of reorganization energies for both charge carriers. Based on computed geometries of neutral and charged species, we propose a simple scheme to rationalize the small, computed reorganization energies for both n-type and p-type charge transport. The study is supplemented with the calculation of intermolecular electronic couplings governing charge transport for selected diradicals, further supporting the ambipolar character of the investigated diradicals.
A through‐space conjugated multi‐phenalenyl triradical 1 a has been prepared and characterized. Partial occupancy of doubly degenerate molecular orbitals in 1 a leads to Jahn–Teller distortion, ...creating a molecular skeleton in which C2v doublet states are lower in energy than undistorted D3h doublet and quartet states. Triradical 1 a exists in an acute form in the solution state, whereas it adopts a preferred obtuse form in the solid state. The results of the investigation show that these two distorted forms are reversibly interconverted by thermal energy.
The formally equilateral triradical with D3h symmetry is subject to Jahn–Teller distortion to create two distorted C2v structures (i.e., acute and obtuse forms) and these two distorted forms are reversibly interconverted in the solution and solid states.
This article explores the use of populism by comparatively privileged groups, a specific type of populism we call the ‘populism of the privileged’. Our argument is not merely that ‘populisms of the ...privileged’ are also forms of populism, but that they warrant a specific label. We first identify intersections between populism and privilege on the levels of populist actors, support for populism and beneficiaries of populism, which we call populism by, with and for the privileged. We then present a discursive conceptualization of ‘populism of the privileged’. Building on this we develop analytical strategies for the study the ‘populism of the privileged’, zooming in on how ‘the people’ and ‘the elite’ are constructed in such populisms, their sociological directionality, the layeredness of privilege and un(der)privilege, the discursive construction of ‘crisis’ and ‘unmet demands’ and the role of discourses about populism in reproducing the claims of populisms of the privileged.
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