The endohedral fullerene Sc(3)NC@C(80)-I(h) has been synthesized and characterized; it has an unprecedented planar quinary cluster in a fullerene cage. It is also the first chemical compound in which the presence of an unprecedented (NC)(3-) trianion has been disclosed. The fascinating intramolecular dynamics in Sc(3)NC@C(80)-I(h) enables the whole molecule to display high polarity and promising ferroelectricity. This finding inspires the possibility that such a planar quinary cluster may be useful in constructing many other endohedral fullerenes.

The dissolution mechanism of cellulose in ionic liquids has been investigated by using cellobiose and 1-ethyl-3-methylimidazolium acetate (EmimAc) as a model system under various conditions with conventional and variable-temperature NMR spectroscopy. In DMSO-d(6) solution, NMR data of the model system clearly suggest that hydrogen bonding is formed between hydroxyls of cellobiose and both anion and cation of EmimAc. The CH(3)COO(-) anion favors the formation of hydrogen bonds with hydrogen atoms of hydroxyls, and the aromatic protons in bulky cation [Emim](+), especially the most acidic H2, prefer to associate with the oxygen atoms of hydroxyls with less steric hindrance, while after acetylation of all hydroxyls in cellobiose the interactions between cellobiose octaacetate and EmimAc become very weak, implying that hydrogen bonding is the major reason of cellobiose solvation in EmimAc. Meanwhile the stoichiometric ratio of EmimAc/hydroxyl is estimated to be between 3:4 and 1:1 in the primary solvation shell, suggesting that there should be one anion or cation to form hydrogen bonds with two hydroxyl groups simultaneously. In situ and variable-temperature NMR spectra suggest the above mechanism also works in the real system.

Two new tetraphenylethylene (TPE) compounds 1 and 2 bearing adenine and thymine moieties, respectively, were found to be fluorescence "turn on" chemosensors for Ag(+) and Hg(2+) by making use of the AIE feature of TPE motif and the specific binding of adenine/thymine with Ag(+)/Hg(2+).

Asymmetric hydrogenation of quinolines catalyzed by chiral cationic η(6)-arene-N-tosylethylenediamine-Ru(II) complexes have been investigated. A wide range of quinoline derivatives, including 2-alkylquinolines, 2-arylquinolines, and 2-functionalized and 2,3-disubstituted quinoline derivatives, were efficiently hydrogenated to give 1,2,3,4-tetrahydroquinolines with up to >99% ee and full conversions. This catalytic protocol is applicable to the gram-scale synthesis of some biologically active tetrahydroquinolines, such as (-)-angustureine, and 6-fluoro-2-methyl-1,2,3,4-tetrahydroquinoline, a key intermediate for the preparation of the antibacterial agent (S)-flumequine. The catalytic pathway of this reaction has been investigated in detail using a combination of stoichiometric reaction, intermediate characterization, and isotope labeling patterns. The evidence obtained from these experiments revealed that quinoline is reduced via an ionic and cascade reaction pathway, including 1,4-hydride addition, isomerization, and 1,2-hydride addition, and hydrogen addition undergoes a stepwise H(+)/H(-) transfer process outside the coordination sphere rather than a concerted mechanism. In addition, DFT calculations indicate that the enantioselectivity originates from the CH/π attraction between the η(6)-arene ligand in the Ru-complex and the fused phenyl ring of dihydroquinoline via a 10-membered ring transition state with the participation of TfO(-) anion.

Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/N,N-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), (13)C, (35)Cl, and (7)Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl(-), during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li(+)-Cl(-) ion pairs. Simultaneously, the Li(+) cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl(-) to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work clarifies the interactions in the cellulose/DMAc/LiCl solution at molecular level and the dissolution mechanism of cellulose in DMAc/LiCl, which is important for understanding the principle for selecting and designing new cellulose solvent systems.

For the first time, we have produced the stable compound Sc(4)C(2)@C(80)-I(h) and characterized it as a metal carbide endofullerene by FTIR and Raman spectroscopies in combination with DFT calculations. Furthermore, DFT calculations have demonstrated that this molecule has a Russian-doll-type structure, C(2)@Sc(4)@C(80).

RNA G-quadruplexes (G4s) play important roles in translational regulation, mRNA processing events and gene expression. Therefore, a fluorescent probe that is capable of efficiently recognizing RNA G-quadruplex structures among other RNA forms is highly desirable. In this study, a water-soluble fluorogenic dye (i.e., Thioflavin T (ThT)) was employed to recognize RNA G-quadruplex structures using UV-Vis absorption spectra, fluorescence spectra and emission lifetime experiments. By stacking on the G-tetrad, the ThT probe exhibited highly specific recognition of RNA G-quadruplex structures with striking fluorescence enhancement compared with other RNA forms. The specific binding demonstrates that ThT is an efficient fluorescence sensor that can distinguish G4 and non-G4 RNA structures.One of the most important types of nucleic acid structure is the G-quadruplex (G4), which is formed from four guanine bases by stacking of Hoogsteen bonded G-quartets 1 . The G-quadruplexes play a vital role in the human genome and transcriptome 2,3 . The DNA or RNA G-quadruplexes that are formed in cells are associated with many important cellular processes 4-8 . G-quadruplexes have been viewed as emerging therapeutic targets due to their correlation with human diseases [8][9][10][11][12] . Most of the early studies of G-quadruplexes focused on DNA strands, and few studies focused on RNA G-quadruplexes. Recently, RNA G-quadruplexes have been associated with many biological processes, such as telomere maintenance, pre-mRNA splicing and polyadenylation, RNA turnover, mRNA targeting and translation 13 . Therefore, the development of techniques that could efficiently recognize RNA G-quadruplexes structures and investigate their biological functions and impacts is highly desirable. Many techniques including X-ray crystallography and NMR experiments have been utilized to identify high-resolution structures of RNA G-quadruplexes 14,15 . However, these techniques are more suitable for comprehensively studying targeted RNA G-quadruplex structures. Additionally, circular dichroism (CD) has been extensively used to monitor G-quadruplex formation because the positive band at 264 nm and the negative band at 240 nm indicate the formation of parallel-type G-quadruplex structures 16 . However, it is difficult to interpret the G-quadruplex type in the presence of different forms of nucleic acids. Because the probe recognition sites in RNA G-quadruplexes are different from those in other RNA motifs, small molecules that selectively bind to RNA G-quadruplexes and emit fluorescence may be used as RNA G-quadruplex detectors. Our previous study revealed a cyanine dye (CyT) that was able to selectively recognize RNA G-quadruplex structures with ~2000-fold fluorescence enhancement 17 . Due to the important biological functions of RNA G-quadruplex, the development of a multiband probe that can selectively recognize RNA G-quadruplex structures is needed to further expand the application of RNA G-quadruplexes, which have been recognized as significant molecular...

Winding and rewinding: How many times can helical aromatic oligomers wind around one another? At least four, as judged by the aggregation behavior of oligoamides based on 8‐fluoroquinoline (see scheme depicting the formation of a quadruple helix; red spheres: sites in the hollow space partially occupied by water molecules).