Graphite oxides synthesized by one and two step Brodie oxidation (BGO) andHummers (HGO) methods were analysed by a variety of characterization methods in order to evaluate the reasons behind the difference in their properties. It is found that the Brodie method results in a higher relative amount of hydroxyl groups and a more homogeneous overall distribution of functional groups over the planar surface of the graphene oxide flakes. The higher number of carbonyl and carboxyl groups in HGO, detected by several methods, including XPS, NMR and FTIR, unavoidably results in defects of the graphene "skeleton", holes and overall disruption of the carbon-carbon bond network, stronger deviation from planar flake shape and poor ordering of the graphene oxide layers. It is also suggested that functional groups in HGO are less homogeneously distributed over the flake surface, forming some nanometer-sized graphene areas. The presence of differently oxidized areas on the GO surface results in inhomogeneous solvation and hydration of HGO and effects of inter-and intrastratification. The proposed interpretation of the data explains the higher mechanical strength of multi-layered BGO membranes/papers, which are also less affected by humidity changes, thus providing an example of a membrane property superior to that of HGO.

Polymeric forms of C60 are now well known, but numerous attempts to obtain C70 in a polymeric state have yielded only dimers. Polymeric C70 has now been synthesized by treatment of hexagonally packed C70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300 degrees C), which confirms predictions from our modeling of polymeric structures of C70. Single-crystal x-ray diffraction shows that the molecules are bridged into polymeric zigzag chains that extend along the c axis of the parent structure. Solid-state nuclear magnetic resonance and Raman data provide evidence for covalent chemical bonding between the C70 cages.

Solvothermal reaction of graphite oxide (GO) with benzene-1,4-diboronic acid (DBA) was reported previously to result in formation of graphene oxide framework (GOF) materials. The theoretical structure of GOFs consists of graphene layers separated by benzene-diboronic “pillars” with ∼1 nm slit pores thus providing the opportunity to use it as a model material to verify the effect of a small pore size on hydrogen adsorption. A set of samples with specific surface area (SSA) in the range of ∼50–1000 m2/g were prepared using variations of synthesis conditions and GO/DBA proportions. Hydrogen storage properties of GOF samples evaluated at 293 and 77 K were found to be similar to other nanocarbon trends in relation to SSA values. Structural characterization of GO/DBA samples showed all typical features reported as evidence for formation of a framework structure such as expanded interlayer distance, increased temperature of thermal exfoliation, typical features in FTIR spectra, etc. However, the samples also exhibited reversible swelling in polar solvents which is not compatible with the idealized GOF structure linked by benzene-diboronic molecular pillars. Therefore, possible alternative nonframework models of structures with pillars parallel and perpendicular to GO planes are considered.

Sixty R3SiX/solvent (S) and R2HSiX/S systems with R = methyl, ethyl, butyl and S = methylene chloride, DMPU, DMSO, sulfolane, HMPA, acetonitrile, pyridine, N-methylimidazole, and triethylamine were investigated with the help of NMR spectroscopy for different concentration ratios of R3SiX/S and R2HSiX/S as well as different temperatures. With the help of measured δ29Si and δ13C chemical shifts as well as 1 J Si - C and 2 J Si - P coupling constants, typical NMR parameters for R3SiX and R2HSiX, R3Si(S)+, R2HSi(S)+, and R2HSi(S)2 + were established and discussed to distinguish between possible silylium cation−solvent complexes and equilibria between them. In addition, the NMR/ab initio/IGLO method (based on the continuum solvent model PISA and IGLO-PISA chemical shift calculations) was used to determine geometry, stability, and other properties of Me3Si(S) n + and Me2HSi(S) n + complexes in different solutions. NMR measurements and ab initio calculations clearly show that R3Si(S)+ and R2HSi(S)+ complexes with tetracoordinated Si are formed with solvents (S) more nucleophilic than methylene chloride while complexes with two S molecules and a pentacoordinated Si atom can only be found for R3 - n H n Si+ cations with n ≥ 1. This is a result of internal (hyperconjugative) stabilization of R3Si+ by alkyl groups and external stabilization by S coordination, as well as of steric factors involving R and S. Complex binding energies are in the range of 40−60 kcal/mol, which is significantly different from complex binding energies in the gas phase. In all cases investigated, (weakly) covalent bonds between Si and S are formed that exclude any silylium cation character for the solvated R3Si+ and R2HSi+ ions.

A series of new viologen analogues bearing two ammonioalkyl groups (2-4) were synthesized in order to study their complexation with bis(18-crown-6)stilbene (1b). Electronic spectroscopy and 1 H NMR measurements show that in acetonitrile, bis(crown) stilbene 1b forms highly stable 1 : 1 and 2 : 1 chargetransfer (CT) complexes with p-acceptors 2-4 owing to host-guest bonding. The influence of geometric and electronic factors on the complex formation constants are discussed. The structures of the supramolecular CT complexes are analyzed on the basis of 1 H and 13 C NMR data obtained in solution and in the solid state. X-Ray diffraction data for 1b and for model tetramethoxystilbene are also reported.