Noncovalent wrapping of chemically modified graphene with π-conjugated disk-like molecules

A facile and scalable preparation of dispersion of isolated graphene in various organic solvents has been developed by combining between covalent and noncovalent functionalizations of the graphene surface. Covalently functionalized graphene (FRG) was prepared by the reaction of partially reduced graphene oxide with aryl diazonium salts, followed by the graphene oxide being completely reduced with hydrazine. The resulting FRG disperse readily in organic solvents such as N,N′-dimethylformamide (DMF) and N-methyl-2-pyrrolidinone and the functionalization of graphene was characterized by Fourier transform infrared spectroscopy, thermogravimetric thermogram, X-ray photoelectron spectroscopy, and Raman spectroscopy. The hydrophobic surface of FRG was noncovalently wrapped with aromatic hexakis-dodecylhexa-peri-benzocorone (HBC) by simply mixing of dispersion of FRG in DMF with toluene solution of HBC. The complexation of FRG and HBC was monitored by viewing the absorption and fluorescence spectral changes. Atomic force microscopic images confirmed that graphene was covalently and noncovalently functionalized, while keeping a two-dimensional sheet shape.     

Construction of a thermal conductivity measurement system for small single crystals of organic conductors

Journal of Thermal Analysis and Calorimetry - We newly constructed a thermal conductivity measurement system for single crystals of molecular compounds. This system enables us to measure the...     

Mössbauer spectroscopy of the new iron oxide Fe3B7O13(OH)

In order to investigate the electronic state, the local structure, and the magnetic structure of a new ion oxide Fe₃B₇O₁₃(OH), we have applied ⁵⁷Fe Mössbauer spectroscopy. The room-temperature values of isomer shift and quadrupole splitting are 1.16 mm/s and 3.21 mm/s, respectively, which indicate that the Fe ions are in high spin Fe^2?+? state. The spectrum at 4.2 K is composed of a well-resolved hyperfine sextet with the hyperfine field of 3.6 T. In a trimer, each Fe^2?+? magnetic moment is supposed to be directed from Fe^2?+? to OH^???.     

A clue to elusive macrocycles: unusually facile, spontaneous polymerization of a hexagonal diethynylbenzene macrocycle

[structures: see text] A hexagonal diethynylbenzene macrocycle having exterior octyloxymethyl groups undergoes spontaneous polymerization at room temperature to form hardly soluble materials, in contrast to the corresponding dehydrotetramer and dehydrooctamer, which are stable enough to show their melting points at higher than 140 degrees C.     

5-Chloro-8-quinolyl group as high efficient phosphate protecting group for the synthesis of oligoribonucleotides

5-Chloro-8-quinolyl group is found to be very suitable for the protecting group on phosphates in the internucleotidic bonds. The oligoribonucleotides were obtained in good yields by a simple procedure using this phosphate protecting group.     

Electrophilic behavior of the pi delocalized azepinium ion: Friedel-Crafts reactions with benzenes and five-membered aromatic heterocycles

[reaction: see text] Although the reactivity of tropylium ion with aromatic substrates is low, the reaction of azepinium ion with aromatic substrates such as benzene, phenol, furan, and thiophene resulted in the formation of 2-aryl-2H-azepine as a major product. An exceptional result in the formation of ring-contracted product was observed in the reaction with pyrrole.     

Synthesis and reactivity of a (mu-1,1-hydroperoxo)(mu-hydroxo)dicopper(II) complex: ligand hydroxylation by a bridging hydroperoxo ligand

A new tetradentate tripodal ligand (L3) containing sterically bulky imidazolyl groups was synthesized, where L3 is tris(1-methyl-2-phenyl-4-imidazolylmethyl)amine. Reaction of a bis(mu-hydroxo)dicopper(II) complex, [Cu2(L3)2(OH)2]2+ (1), with H2O2 in acetonitrile at -40 degrees C generated a (mu-1,1-hydroperoxo)dicopper(II) complex [Cu2(L3)2(OOH)(OH)]2+ (2), which was characterized by various physicochemical measurements including X-ray crystallography. The crystal structure of 2 revealed that the complex cation has a Cu2(mu-1,1-OOH)(mu-OH) core and each copper has a square pyramidal structure having an N3O2 donor set with a weak ligation of a tertiary amine nitrogen in the apex. Consequently, one pendant arm of L3 in 2 is free from coordination, which produces a hydrophobic cavity around the Cu2(mu-1,1-OOH)(mu-OH) core. The hydrophobic cavity is preserved by hydrogen bondings between the hydroperoxide and the imidazole nitrogen of an uncoordinated pendant arm in one side and the hydroxide and the imidazole nitrogen of an uncoordinated pendant arm in the other side. The hydrophobic cavity significantly suppresses the H/D and 16O/18O exchange reactions in 2 compared to that in 1 and stabilizes the Cu2(mu-1,1-OOH)(mu-OH) core against decomposition. Decomposition of 2 in acetonitrile at 0 degrees C proceeded mainly via disproportionation of the hydroperoxo ligand and reduction of 2 to [Cu(L3)]+ by hydroperoxo ligand. In contrast, decomposition of a solid sample of 2 at 60 degrees C gave a complex having a hydroxylated ligand [Cu2(L3)(L3-OH)(OH)2]2+ (2-(L3-OH)) as a main product, where L3-OH is an oxidized ligand in which one of the methylene groups of the pendant arms is hydroxylated. ESI-TOF/MS measurement showed that complex 2-(L3-OH) is stable in acetonitrile at -40 degrees C, whereas warming 2-(L3-OH) at room temperature resulted in the N-dealkylation from L3-OH to give an N-dealkylated ligand, bis(1-methyl-2-phenyl-4-imidazolylmethyl)amine (L2) in approximately 80% yield based on 2, and 1-methyl-2-phenyl-4-formylimidazole (Phim-CHO). Isotope labeling experiments confirmed that the oxygen atom in both L3-OH and Phim-CHO come from OOH. This aliphatic hydroxylation performed by 2 is in marked contrast to the arene hydroxylation reported for some (mu-1,1-hydroperoxo)dicopper(II) complexes with a xylyl linker.