NMR Spectroscopic Study of the Complexation Behaviors of Deuterated Cyclodextrins and [60]Fullerene

Cyclodextrins (CDxs) have been selectively deuterated using a Ru/C-catalyzed H–D exchange reaction in D₂O. The structures of the deuterated CDxs barely changed and their ¹H NMR spectra became very simple, which made it possible for the deuterated CDxs to be applied to the analysis of CDx complexes. Furthermore, the deuterated CDxs allowed for the existence of the equilibrium between free and complexed CDx to be confirmed, even at rt

Electrochemistry, Charge Transfer Properties, and Theoretical Investigation of a Macrocyclic Boronate Dimer of 1′,1‴-Biferrocenediboronic Acid and Related Ferrocenyl Boronate Complexes

The target compound of this study is the macrocyclic tetraferrocenyl boronate complex <b>CP</b>_<b>2</b><b>C</b>, which has two types of metal connections (i.e., Fe^II–CpCp–Fe^II and Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II (Cp = cyclopentadienyl)) in the finite structure (<b>C</b> = 1′,1‴-biferrocenediboronic acid, <b>P</b> = pentaerythritol). The electrochemical behavior of <b>CP</b>_<b>2</b><b>C</b> in dichloromethane was compared with that of the related boronate complexes <b>APA</b> and <b>BP</b>_<b>2</b><b>B</b>, having Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II, and <b>Cester</b>, having Fe^II–CpCp–Fe^II. The effects of the counteranion of the supporting electrolyte on potential splitting revealed that <b>CP</b>_<b>2</b><b>C</b> exhibits an intrabiferrocenyl through-bond interaction through the CpCp ligand, as well as an interbiferrocenyl through-space interaction across the CpBO₂C₅H₈O₂BCp ligand. Chemical oxidation of <b>CP</b>_<b>2</b><b>C</b> with AgSbF₆ produced the one- and two-electron-oxidized species <b>CP</b>_<b>2</b><b>C</b>^<b>+</b> and <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>, which exhibit intervalence charge transfer transition bands through the CpCp ligand in the near-infrared region, giving one and two valence isomers, respectively. DFT calculations revealed the charge distribution of <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>; the positive charges are localized on each biferrocenium unit, especially on the longer diagonal, to minimize the electrostatic repulsion over the CpBO₂C₅H₈O₂BCp ligand

Electrochemistry, Charge Transfer Properties, and Theoretical Investigation of a Macrocyclic Boronate Dimer of 1′,1‴-Biferrocenediboronic Acid and Related Ferrocenyl Boronate Complexes

The target compound of this study is the macrocyclic tetraferrocenyl boronate complex <b>CP</b>_<b>2</b><b>C</b>, which has two types of metal connections (i.e., Fe^II–CpCp–Fe^II and Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II (Cp = cyclopentadienyl)) in the finite structure (<b>C</b> = 1′,1‴-biferrocenediboronic acid, <b>P</b> = pentaerythritol). The electrochemical behavior of <b>CP</b>_<b>2</b><b>C</b> in dichloromethane was compared with that of the related boronate complexes <b>APA</b> and <b>BP</b>_<b>2</b><b>B</b>, having Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II, and <b>Cester</b>, having Fe^II–CpCp–Fe^II. The effects of the counteranion of the supporting electrolyte on potential splitting revealed that <b>CP</b>_<b>2</b><b>C</b> exhibits an intrabiferrocenyl through-bond interaction through the CpCp ligand, as well as an interbiferrocenyl through-space interaction across the CpBO₂C₅H₈O₂BCp ligand. Chemical oxidation of <b>CP</b>_<b>2</b><b>C</b> with AgSbF₆ produced the one- and two-electron-oxidized species <b>CP</b>_<b>2</b><b>C</b>^<b>+</b> and <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>, which exhibit intervalence charge transfer transition bands through the CpCp ligand in the near-infrared region, giving one and two valence isomers, respectively. DFT calculations revealed the charge distribution of <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>; the positive charges are localized on each biferrocenium unit, especially on the longer diagonal, to minimize the electrostatic repulsion over the CpBO₂C₅H₈O₂BCp ligand

Electrochemistry, Charge Transfer Properties, and Theoretical Investigation of a Macrocyclic Boronate Dimer of 1′,1‴-Biferrocenediboronic Acid and Related Ferrocenyl Boronate Complexes

The target compound of this study is the macrocyclic tetraferrocenyl boronate complex <b>CP</b>_<b>2</b><b>C</b>, which has two types of metal connections (i.e., Fe^II–CpCp–Fe^II and Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II (Cp = cyclopentadienyl)) in the finite structure (<b>C</b> = 1′,1‴-biferrocenediboronic acid, <b>P</b> = pentaerythritol). The electrochemical behavior of <b>CP</b>_<b>2</b><b>C</b> in dichloromethane was compared with that of the related boronate complexes <b>APA</b> and <b>BP</b>_<b>2</b><b>B</b>, having Fe^II–CpBO₂C₅H₈O₂BCp–Fe^II, and <b>Cester</b>, having Fe^II–CpCp–Fe^II. The effects of the counteranion of the supporting electrolyte on potential splitting revealed that <b>CP</b>_<b>2</b><b>C</b> exhibits an intrabiferrocenyl through-bond interaction through the CpCp ligand, as well as an interbiferrocenyl through-space interaction across the CpBO₂C₅H₈O₂BCp ligand. Chemical oxidation of <b>CP</b>_<b>2</b><b>C</b> with AgSbF₆ produced the one- and two-electron-oxidized species <b>CP</b>_<b>2</b><b>C</b>^<b>+</b> and <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>, which exhibit intervalence charge transfer transition bands through the CpCp ligand in the near-infrared region, giving one and two valence isomers, respectively. DFT calculations revealed the charge distribution of <b>CP</b>_<b>2</b><b>C</b>^<b>2+</b>; the positive charges are localized on each biferrocenium unit, especially on the longer diagonal, to minimize the electrostatic repulsion over the CpBO₂C₅H₈O₂BCp ligand

Regioselective Recognition of a [60]Fullerene-Bisadduct by Cyclodextrin

The three different regioisomers of bis-<i>N</i>-methylfulleropyrrolidines have been separated by controlling the relative amounts of γ-cyclodextrin and dimethyl sulfoxide (DMSO) contained in solutions of these compounds. When a small amount of γ-CDx was used in a mechanochemical high-speed vibration milling apparatus, the <i>trans-1</i> and <i>trans-2</i>•γ-CDx complexes were separated from the <i>trans-3</i>•γ-CDx complex. In contrast, <i>trans-3</i> was extracted in a relatively high ratio with an excess of γ-CDx. The addition of DMSO to aqueous solutions of the fullerene derivative•γ-CDx complexes allowed for the three regioisomers to be obtained in high purity (>95%). The basis for the observed regioselective separation was a competition between the relative stabilities and solubilities of the complexes in the water and water-DMSO solvents. The stabilities of the complexes in water were assessed by the number of hydrogen bonding interactions between the two γ-CDx units using molecular dynamics simulations. To the best of our knowledge, this is the first reported example of the isolation of the different regioisomers of fullerene derivatives using host–guest complexes

Spontaneous Lipid Nanodisc Fomation by Amphiphilic Polymethacrylate Copolymers

There is a growing interest in the use of lipid bilayer nanodiscs for various biochemical and biomedical applications. Among the different types of nanodiscs, the unique features of synthetic polymer-based nanodiscs have attracted additional interest. A styrene–maleic acid (SMA) copolymer demonstrated to form lipid nanodiscs has been used for structural biology related studies on membrane proteins. However, the application of SMA polymer based lipid nanodiscs is limited because of the strong absorption of the aromatic group interfering with various experimental measurements. Thus, there is considerable interest in the development of other molecular frameworks for the formation of polymer-based lipid nanodiscs. In this study, we report the first synthesis and characterization of a library of polymethacrylate random copolymers as alternatives to SMA polymer. In addition, we experimentally demonstrate the ability of these polymers to form lipid bilayer nanodiscs through the fragmentation of lipid vesicles by means of light scattering, electron microscopy, differential scanning calorimetry, and solution and solid-state NMR experiments. We further demonstrate a unique application of the newly developed polymer for kinetics and structural characterization of the aggregation of human islet amyloid polypeptide (also known as amylin) within the lipid bilayer of the polymer nanodiscs using thioflavin-T-based fluorescence and circular dichroism experiments. Our results demonstrate that the reported new styrene-free polymers can be used in high-throughput biophysical experiments. Therefore, we expect that the new polymer nanodiscs will be valuable in the structural studies of amyloid proteins and membrane proteins by various biophysical techniques