Non-covalent halogen bonding interactions are quintessential in crystal engineering for the construction of distinctive supramolecular synthons. Here, we report the first crystalline evidences of unique boat and chair shaped cyclic hexahalogen synthons in the crystal structures of α,α,α',α',4-pentabromo-o-xylene (PBX) and α,α,α',α',4,5-hexabromo-o-xylene (HBX) respectively. Nature and stability of constituent interactions in the supramolecular synthons are scrutinized with the help of quantum-chemical calculations.
View Article and Find Full Text PDFNull 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.
View Article and Find Full Text PDFFluoride 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.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFPolyphenolic 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.
View Article and Find Full Text PDFAmyloid-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.
View Article and Find Full Text PDFNovel 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.
View Article and Find Full Text PDFColloids Surf B Biointerfaces
October 2008
Carnosine and histidine are biologically interesting antioxidants. In order to probe whether they exert their antioxidant effect through metal ion chelation, the Cu(II) ion chelating abilities of these compounds were measured by UV-vis spectroscopy. Both of these compounds showed 1:1 complexations with Cu(II) ions as shown by their Job's plot.
View Article and Find Full Text PDF