Takashi Hirose

Helically twisted graphenes can be considered as a promising candidate for the nanometer-sized molecular inductors in molecular electronics and molecular spring materials in nanomechanics. Here, we report the synthesis of hexa- peri-hexabenzo[7]helicene, which represents a primary substructure of the helical graphenes. The helically twisted polycyclic aromatic hydrocarbon was synthesized by a tetrasubstituted alkene formation using McMurry coupling followed by stepwise photocyclodehydrogenation

Helicenes are promising candidates for chiral optoelectronic materials because of their helically twisted π-conjugated system. However, the emission intensity of unsubstituted helicenes is very weak (Φ_f < 0.05) due to a small oscillator strength for the S₁ → S₀ transition. In this work, we investigated the substitution position of the [7]helicene framework so that the S₁ → S₀ transition has a large transition magnetic dipole moment (TMDM) an

Although many chiral molecules exhibiting circularly polarized luminescence (CPL) have been reported recently, few molecular design guidelines are known for increasing the dissymmetry factor for CPL (<i>g</i>_lum). We demonstrate that a figure-eight-shaped molecule with <i>D</i>₂ symmetry has excellent chiroptical properties (Φ_f = 0.08, |<i>g</i>_lum| = 1.5 × 10^-2), which are attributed to the parallel arrangement of <b>μ</b> and <i><b>m</b></

A π-expanded helicene that is the helically twisted analogue of kekulene was synthesized using a 6-fold ring-closing olefin metathesis (RCM) reaction as a key step. The π-expanded geometry with large helical diameter ( d_h = 10.2 Å), consisting only of carbon and hydrogen atoms (C₅₄H₃₀), was unambiguously determined by single-crystal X-ray analysis. We found that the π-expanded helicene with large helical diameter will act as a soft molecular spring with a small s

Diarylethene derivatives with hexaethylene glycol side chains were synthesized and their self-assembling and photochromic reactivity were investigated. The diarylethenes showed photochromism in organic solvents and even in water. The aqueous solution of the compounds turned turbid quickly upon heating. The clouding behavior was investigated using 1H NMR spectroscopy, dynamic light scattering, and absorption spectroscopy. It was revealed that, in the aqueous solution, the compounds self-assembled

We designed an automatic system to measure body length, diameters and volume of a C. elegans worm. By using this system, mutants with an increased body volume exceeding 50% were isolated. Four of them are grossly normal in morphology and development, grow longer to be almost twice as big, and have weak egg-laying defects and extended lifespan. All the four mutants have a mutation in the egl-4 gene. We show that the egl-4 gene encodes cGMP-dependent protein kinases. egl-4 promoter::gfp fusion gen

A photochromic diarylethene derivative having hexa(ethylene glycol) side chains connected by an amide group was synthesized and the thermo- and the photoresponsive behavior was investigated. The cloud-point temperature was varied in a controlled manner over a range of 23 to 45 °C by irradiation with the appropriate wavelength of light (see figure).

Helically twisted conductive nanocarbon materials are applicable to optoelectronic and electromagnetic molecular devices working on the nanometer scale. Herein, we report the synthesis of per-peri-perbenzo[5]- and [9]helicenes in addition to previously reported π-extended [7]helicene. The homogeneously π-extended helicenes can be regarded as helically fused oligo-phenanthrenes. The HOMO-LUMO gap decreased significantly from 2.14 to 1.15 eV with increasing helical length, suggesting the large eff

The cooperative self-assembly of chiral zinc porphyrins is regulated by a photoresponsive phenylazopyridine ligand. Porphyrin stacks depolymerize into dimers upon axial ligation and the strength of the coordination is regulated by its photoinduced isomerization, which shows more than 95 % conversion ratio for both photostationary states.

The decision of a cell to undergo programmed cell death is tightly regulated during animal development and tissue homeostasis. Here, we show that the Caenorhabditis elegans Six family homeodomain protein C. elegans homeobox (CEH-34) and the Eyes absent ortholog EYA-1 promote the programmed cell death of a specific pharyngeal neuron, the sister of the M4 motor neuron. Loss of either ceh-34 or eya-1 function causes survival of the M4 sister cell, which normally undergoes programmed cell death. CEH

PCTAIRE are members of a subfamily of Cdc2-related kinases that have been shown to be preferentially expressed in post-mitotic cells. To examine the neural functions of PCTAIRE, rat cDNA clones encoding PCTAIRE 1, 2, and 3 were isolated, and their expression patterns in the brain were analyzed. Among the three rat PCTAIREs, only PCTAIRE 2 was found to be specifically expressed in the brain. Furthermore, its expression was transiently increased during brain development, peaking 7-15 days after bi

PCTAIRE 2 is a Cdc2-related kinase that is predominantly expressed in the terminally differentiated neuron. To elucidate the function of PCTAIRE 2, proteins that associate with PCTAIRE 2 were screened by the yeast two-hybrid system. A positive clone was found to encode a novel protein that could bind to PCTAIRE 2 in vitro as well as in vivo, and was designated as Trap (tudor repeat associator with PCTAIRE 2). The overall structure of Trap shows no significant homology to any proteins, but contai

Helically twisted π-conjugated compounds are promising candidates for chiroptical dyes with strong circular dichroism and circularly polarized luminescence. Herein we report the synthesis of tetrabenzo[<i>f</i>,<i>jk</i>,<i>mn</i>,<i>r</i>][7]helicene as a near-infrared (NIR) emitter with thermally stable helical chirality. Tetrabenzo[7]helicene (C₄₄H₂₄), which consists of only 44 carbon atoms, showed broad fluorescence in the NIR region up to 850 nm. On the basis of densit

The fluorescence enhancement effect of covalently fixed fluorescent chromophores has been investigated by means of kinetic analysis of decay rate constants and theoretical calculations. Derivatives of 1-cyano-1,2-diphenylethene dimer have a distorted cyclic structure when both ends are clipped with two naphthalene-1,8-diyl linker units. In contrast to the reference monomer derivative, which exhibits only slight fluorescence in solution (Φf < 0.01, τf < 0.1 ns), the dimer derivative shows high fl