Graphite oxide (GO) and its derivatives have been studied using 13C and 1H NMR. NMR spectra of GO derivatives confirm the assignment of the 70 ppm line to C−OH groups and allow us to propose a new structural model for GO. Thus we assign the 60 ppm line to epoxide groups (1,2-ethers) and not to 1,3-ethers, as suggested earlier, and the 130 ppm line to aromatic entities and conjugated double bonds. GO contains two kinds of regions:  aromatic regions with unoxidized benzene rings and regions with aliphatic six-membered rings. The relative size of the two regions depends on the degree of oxidation. The carbon grid is nearly flat; only the carbons attached to OH groups have a slightly distorted tetrahedral configuration, resulting in some wrinkling of the layers. The formation of phenol (or aromatic diol) groups during deoxygenation indicates that the epoxide and the C−OH groups are very close to one another. The distribution of functional groups in every oxidized aromatic ring need not be identical, and both ...

Structure of Graphite Oxide Revisited

Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

2.5. Stabilization of IL Emulsions by Nanoparticles 2623 3. Hydrogenations in ILs 2623 3.1. Hydrogenation on IL-Stabilized Nanoparticles 2623 3.1.1. Hydrogenation of 1,3-Butadiene 2623 3.1.2. Hydrogenation of Alkenes and Arenes 2624 3.1.3. Hydrogenation of Ketones 2624 3.2. Homogeneous Catalytic Hydrogenation in ILs 2624 3.3. Hydrogenation of Functionalized ILs 2625 3.3.1. Selective Hydrogenation of Polymers 2625 3.4. Asymmetric Hydrogenations 2626 3.4.1. Enantioselective Hydrogenation 2626 3.5. Role of the ILs Purity in Hydrogenation Reactions 2628

Catalysis in ionic liquids

The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.1,2 Among all asymmetric catalytic methods, asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines, have become one of the most efficient methods for constructing chiral compounds.3 The development of homogeneous asymmetric hydrogenation was initiated by Knowles4a and Horner4b in the late 1960s, after the discovery of Wilkinson’s homogeneous hydrogenation catalyst [RhCl(PPh3)3]. By replacing triphenylphosphine of the Wilkinson’s catalystwithresolvedchiralmonophosphines,6Knowles and Horner reported the earliest examples of enantioselective hydrogenation, albeit with poor enantioselectivity. Further exploration by Knowles with an improved monophosphine CAMP provided 88% ee in hydrogenation of dehydroamino acids.7 Later, two breakthroughs were made in asymmetric hydrogenation by Kagan and Knowles, respectively. Kagan reported the first bisphosphine ligand, DIOP, for Rhcatalyzed asymmetric hydrogenation.8 The successful application of DIOP resulted in several significant directions for ligand design in asymmetric hydrogenation. Chelating bisphosphorus ligands could lead to superior enantioselectivity compared to monodentate phosphines. Additionally, P-chiral phosphorus ligands were not necessary for achieving high enantioselectivity, and ligands with backbone chirality could also provide excellent ee’s in asymmetric hydrogenation. Furthermore, C2 symmetry was an important structural feature for developing new efficient chiral ligands. Kagan’s seminal work immediately led to the rapid development of chiral bisphosphorus ligands. Knowles made his significant discovery of a C2-symmetric chelating bisphosphine ligand, DIPAMP.9 Due to its high catalytic efficiency in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids, DIPAMP was quickly employed in the industrial production of L-DOPA.10 The success of practical synthesis of L-DOPA via asymmetric hydrogenation constituted a milestone work and for this work Knowles was awarded the Nobel Prize in 2001.3k This work has enlightened chemists to realize * Corresponding author. 3029 Chem. Rev. 2003, 103, 3029−3069

New Chiral Phosphorus Ligands for Enantioselective Hydrogenation

Asymmetric 1,3-Dipolar Cycloaddition Reactions

The intermolecular contacts between chalcogen atoms and cyano lone pairs were found to stabilize the crystalline state by electrostatic interaction. This interaction is one of the sources of the directionality in crystal paccking of organic molecules and causes the formation of various types of inclusion lattices in the charge-transfer (CT) crystals of I-3. By using highly selective formation of CT crystals with substituted aromatic hydrocarbons, particular isomers such as p-xylene or 2,6-dimethylnaphthalene (2,6-DMN) could be separated from the corresponding isomer mixtures

Clathrate formation and molecular recognition by novel chalcogen-cyano interactions in tetracyanoquinodimethanes fused with thiadiazole and selenadiazole rings

The first stable cyclic disilene: Hexakis(trialkylsilyl)tetrasilacyclobutene

The First Stable Cyclotrisilene

Stable Tetrakis(trialkylsilyl)disilenes; Synthesis, X-Ray Structures, and UV/VIS Spectra

New analogues of calix[4]arenetetrasulfonate (1) were prepared, in which the methylene bridges are replaced by S (2) and SO2 (3). The complexation ability of these calixarene ligands 1–3 toward Tb3+ ion and luminescence properties of the resulting complexes were examined. All the ligands formed complexes with lanthanide ions (Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+), among which the Tb3+ complex exhibited strong energy transfer luminescence. The pH dependence of the luminescence intensity suggested that the analogues 2 and 3 possess higher complexation ability towards
Tb3+ than the parent 1, which should be ascribed to the higher acidity of the phenolic OH groups as well as the coordinating ability of the bridging groups S and SO2. The composition of the complexes of 2 and 3 was determined to be Tb3+·2 and Tb3+·3 by a molar ratio method. The photophysical properties such as emission lifetimes (τ) and quantum yields (Φ) of the complexes were estimated. Both Tb3+·2 and Tb3+·3 gave comparable τ values (0.7 ms), which are larger than that of Tb3+·(1)2 (0.6 ms). Comparison of their lifetimes in D2O solution suggested that Tb3+·2 and Tb3+·3 have four to five coordinated water molecules responsible for quenching. On the other hand, complex Tb3+·2 gave the largest Φ value (0.15), whereas Tb3+·(1)2 and Tb3+·3 gave very close Φ values (0.12 and 0.13, respectively). The results of this study showed that thiacalix[4]arenetetrasulfonate 2 and the sulfonyl analogue 3 are promising candidates for the scaffold
to construct luminescence devices from the viewpoint of the higher complexation ability and luminescent performance.

Chizuko Kabuto

Papers

Clathrate formation and molecular recognition by novel chalcogen-cyano interactions in tetracyanoquinodimethanes fused with thiadiazole and selenadiazole rings

The first stable cyclic disilene: Hexakis(trialkylsilyl)tetrasilacyclobutene

The First Stable Cyclotrisilene

Stable Tetrakis(trialkylsilyl)disilenes; Synthesis, X-Ray Structures, and UV/VIS Spectra

Energy transfer luminescence of Tb3+ ion complexed with calix[4]arenetetrasulfonate and the thia and sulfonyl analogue. The effect of bridging groups