Fluoride ion batteries are potential “next-generation” electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion–conducting electrolytes are known only in the solid state. We report a liquid fluoride ion–conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents. Pairing this liquid electrolyte with a copper–lanthanum trifluoride (Cu@LaF3) core-shell cathode, we demonstrate reversible fluorination and defluorination reactions in a fluoride ion electrochemical cell cycled at room temperature. Fluoride ion–mediated electrochemistry offers a pathway toward developing capacities beyond that of lithium ion technology.
Polyphenolic antioxidants from dietary sources are frequently a topic of interest due to widespread scientific agreement that they may help lower the incidence of certain cancers, cardiovascular and neurodegenerative diseases, and DNA damage and even may have antiaging properties. On the other hand, questions still remain as to whether some antioxidants could be potentially harmful to health, because an increase in glycation-mediated protein damage (carbonyl stress) has been reported in some cases. Nevertheless, the quest for healthy aging has led to the extensive use of phytochemically derived antioxidants to disrupt age-associated deterioration in physiological function and to prevent many age-related diseases. Although a diet rich in the polyphenolic forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders, it is still too early to define their exact clinical benefit for treating age-related disease. This review critically examines polyphenolic antioxidants, such as flavonoids, curcumene, and resveratrol in health, disease, and aging with the hope that a better understanding of the many mechanisms involved with these diverse compounds may lead to better health and novel treatment approaches for age-related diseases.
Amyloid-beta (Abeta), the major component of senile plaques in Alzheimer's disease, is known to complex transition metal ions mainly through histidine residues. In this study, using 1H NMR titration experiments, we show that histidine binds strongly to Zn(II), Cu(II), and Fe(III) ions at a biologically relevant pH (pH 7.4), with a stoichiometry of Zn(II): histidine binding of 1:2. The observed deshielding of the chemical shifts and relative line broadening indicate that Fenton-active Cu(II) and Fe(III) bind to histidine relatively more efficiently as compared to Zn(II). Parallel studies showed that glutamic acid and aspartic acid are relatively inefficient in metal ion binding. From these studies, we suggest that Abeta-chelated Zn(II) is readily displaced by Cu(II) and Fe(III) ions and leads to a propagation of oxidative stress.
Null
aggregates are an elusive, emergent class of molecular assembly
categorized as spectroscopically uncoupled molecules. Orthogonally
stacked chromophoric arrays are considered as a highlighted architecture
for null aggregates. Herein, we unveil the null exciton character in a series of crystalline Greek
cross (+)-assembly of 6,13-bisaryl-substituted pentacene derivatives.
Quantum chemical computations suggest that the synergistic perpendicular
orientation and significant interchromophoric separations realize
negligible long-range Coulombic and short-range charge-transfer-mediated
couplings in the null aggregate. The Greek cross (+)-orientation of
pentacene dimers exhibits a selectively higher electron-transfer coupling
with near-zero hole-transfer coupling and thereby contributes to the
lowering of charge-transfer-mediated coupling even at shorter interchromophoric
distances. Additional investigations on the nature of excitonic states
of pentacene dimers proved that any deviation from a 90° cross-stacked
orientation results in the emergence of delocalized Frenkel/mixed-Frenkel–CT
character and the consequent loss of null exciton/monomer-like properties.
The retention of exciton isolation even at a short-range coupling
regime reassures the universality of null excitonic character in perpendicularly
cross-stacked pentacene systems. The null-excitonic character was
experimentally verified by the observation of similar spectral characteristics
in the crystalline and monomeric solution state for 6,13-bisaryl-substituted
pentacene derivatives. The partitioned influence of aryl and pentacene
fragments on interchromophoric noncovalent interactions and photophysical
properties, respectively, resulted in the emergence of pentacene centric
Kasha’s ideal null exciton, providing novel insights toward
design strategies for cross-stacked chromophoric assemblies. Identifying
the Greek cross (+)-stacked architecture-mediated null excitons with
a charge-filtering phenomenon for the first time in the ever-versatile
pentacene chromophoric systems can offer an extensive ground for the
engineering of functional materials with advanced optoelectronic properties.
Novel fluorinated boroxines, tris(2,6-difluorophenyl)boroxin (DF), tris(2,4,6-trifluorophenyl)boroxin (TF), and tris(pentafluorophenyl)boroxin (PF), have been investigated for potential applications in lithium ion batteries through fluoride anion binding, ab initio calculations, and ionic conductivity measurements. Structures of the fluorinated boroxines and boroxin-fluoride complexes have been confirmed by comparing their (19)F and (11)B NMR chemical shifts with those obtained by the DFT-GIAO method. The stoichiometry of the fluoride anion binding to these boroxines has been shown to be 1:1 using (19)F NMR and UV-vis spectroscopy. UV-vis spectroscopic studies show the coexistence of more than one complex, in addition to the 1:1 complex, for perfluorinated boroxin, PF. DFT calculations (B3LYP/6-311G**) show that the fluoride ion complex of DF prefers unsymmetrical, covalently bound structure (7) over the symmetrically bridged species (10) by 12.5 kcal/mol. Rapid equilibration of the fluoride anion among the three borons in these boroxines results in a single (19)F NMR absorption for all of the aromatic ortho- or para-fluorines at ambient temperature. The effect of these anion receptors on lithium ion conductivities was also explored for potential applications in dual ion intercalating lithium batteries.
The introduction of the trialkylsilylethynyl group to the acene core is known to predominantly transform the herringbone structure of pentacene to a slip-stacked packing. However, herein, the occurrence of an unforeseen polymorph of 6,13-bis(trimethylsilylethynyl)pentacene (TMS-pentacene), with an atypical γ-herringbone packing arrangement, is reported. Intermolecular noncovalent interactions in the γ-herringbone polymorph are determined from Hirshfeld surface and quantum theory of atoms-in-molecules (QTAIM) analyses. Furthermore, a comparative truncated symmetry-adapted perturbation theory (SAPT(0)) energy decomposition analysis discloses the role of exchange repulsions that govern molecular packing in the γ-herringbone polymorph. Moreover, the computationally predicted electronic coupling and anisotropic mobility reveal the possibility of enhanced hole transport (μ =3.7 cm V s ) in the γ-herringbone polymorph, in contrast to the reported polymorph with a hole mobility of μ =0.1 cm V s .
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