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Kazukuni Tahara

Publications and source records attributed to Kazukuni Tahara.

8 recordsLinked to original sources
PubMed2006

Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation.

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagomé network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the pi-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl chains (DBAs 3c-e) a transition from honeycomb networks to linear networks was observed in TCB, an observation attributed to stronger molecule-substrate interactions. Third, the effect of solvent on the structure of the nonpolar DBA networks was investigated in four different solvents: TCB as a polar aromatic solvent, 1-phenyloctane as a solvent having both aromatic and aliphatic moieties, n-tetradecane as an aliphatic solvent, and octanoic acid as a polar alkylated solvent. The solvent dramatically changes the structure of the DBA networks. The solvent effects are discussed in terms of factors that influence the mobility of molecules at the liquid-solid interface such as solvation.

Alkylation↗
PubMed2006

Synthesis and electrochemistry of double-decker buckyferrocenes.

D5d- and C5v-symmetric double-decker buckyferrocene Fe2(C60R10)Cp2 (R10 = Me5Ph5 and Me10) represents a new type of diiron complexes featuring conjugative connection of two ferrocene groups by a hoop-shaped [10]cyclophenacene. The compounds exhibit two-electron oxidation and two-electron reduction behavior, generating dicationic and dianionic species. The two iron atoms interact with each other through the pi-conjugation of the cyclophenacene, as revealed by differential pulse voltammetric analysis of the D5d Fe2(C60Me10)Cp2.

Journal Article↗
PubMed2006

Molecular geometry directed Kagomé and honeycomb networks: toward two-dimensional crystal engineering.

We present here the formation of a molecular Kagomé network within a two-dimensional (2D) crystal on a surface. This system provides a clear example of how, by design, molecular geometry can be expressed at the level of the 2D crystal lattice, leading to the formation of open networks. Key elements to control molecular network formation are core symmetry, location and orientation of interacting and connecting substituents, as well as symmetry matching between the networks and the surface.

Journal Article↗
PubMed2004

Creation of hoop- and bowl-shaped benzenoid systems by selective detraction of [60]fullerene conjugation. [10]cyclophenacene and fused corannulene derivatives.

Selective penta-addition of a methylcopper reagent followed by addition of a phenylcopper reagent to a suitably modified synthetic intermediate results in creation of 40pi-electron systems-hoop- and bowl-shaped cyclic benzenoid compounds, [10]cyclophenacene, and dibenzo-fused corannulene derivatives. The 40pi-electron cyclophenacene derivatives have been found to be chemically stable, yellow-colored, luminescent (560 nm), and EPR-silent. X-ray crystallographic analysis provided precision structural data sets. The dibenzo-fused corannulene derivatives exhibit blue-green (460 nm) to red (649 nm) fluorescence.

Journal Article↗
PubMed2003

Theoretical studies on structures and aromaticity of finite-length armchair carbon nanotubes.

[structure: see text] Depending on the exact length of the tube, the chemical structure of finite-length armchair [n,n] single-wall carbon nanotube (n = 5 and 6) falls into three different classes that may be referred to as Kekulé, incomplete Clar, and complete Clar networks. The C-C bond lengths, nucleus-independent chemical shift analysis, and orbital energies suggest that the chemical reactivities of the finite-length tube change periodically as the tube length is elongated by one-by-one layering of cyclic carbon array.

Journal Article↗
PubMed2003

Synthesis, structure, and aromaticity of a hoop-shaped cyclic benzenoid [10]cyclophenacene.

The first hoop-shaped cyclic benzenoid compounds, [10]cyclophenacene derivatives that contain 40 pi electrons, have been synthesized in three or four steps from [60]fullerene by rationally designed chemical modification. The compounds thus synthesized are chemically stable, yellow-colored, luminescent, and EPR-silent. X-ray crystallographic analysis provided high precision structural data sets. On the basis of these results and theoretical investigations, the new cyclic benzenoid molecules were proven to be aromatic.

Journal Article↗