Energy transfer dynamics in wire-type dendrimers having oligophenylene peripheries

Energy transfer and shielding effect are studied in wire-type dendrimers (GnPPV: nth generation dendrimer with poly-(p-phenylenevinylene) backbone; n=1, 2) having oligophenylene light-harvesting (LH) antenna. Following the excitation of the LH-antennae, backbone-polymers in GnPPV give rise to intense photoluminescence (PL) bands. This is due to the presence of highly efficient energy transfer from the LH-antennae to the backbone-polymers. The intensity of backbone-PL increases faster than the decay of the antenna-PL. This result indicates that rapid energy transfer from antenna to backbone takes place utilizing the overlap of wavefunctions in the excited states. In G2PPV having larger LH-antenna, shielding effect against inter-backbone interactions is recognized more effectively than G1PPV. In solid films of GnPPV, red shifts of the backbone-PL bands are observed. This is caused by inter-backbone interactions of the wire-type dendrimers due to aggregation. The extent of the red shift in G2PPV is smaller than that of G1PPV. This result suggests that the larger LH-antenna in G2PPV substantially wraps its backbone-polymer and shields the inter-backbone interactions.     

Non-linear dynamic behaviour of multi-folding microstructure systems based on origami skill

This paper presents the theoretical basis for both static and dynamic numerical approaches to the elastic stability and elasto-plastic stability of a folding multi-layered truss. Both analyses are based on bifurcation theory and include geometrical non-linearity. The dynamic analysis includes an allowance for contact between nodes. Comparisons are made between elastic behaviour and elasto-plastic behaviour obtained from both numerical dynamic methods in which bifurcations are demonstrated as a theoretically elastic analysis. Our analysis reveals that several folding behaviours in the pantographic truss are identified during the elastic and elasto-plastic instabilities, where the folding behaviour of the truss is shown to be a function of the initial geometry and velocity of the dynamic loading. The authors suggest that understanding this behaviour will be very useful for developing light-weight structures subject to dynamic loading based on static bifurcation analysis and dynamic analysis.     

One-step synthesis of triethynylvinylmethanes and tetraethynylmethanes by GaCl(3)-promoted diethynylation of 1,4-enynes and 1,4-diynes

The treatment of 1,4-enynes with chlorotriethylsilylacetylene at 130 degrees C in the presence of GaCl3 gave triethynylvinylmethanes by the diethynylation at the allylic methylene moiety. The addition of 2,6-di(tert-butyl)-4-methylpyridine and tert-butyldiphenylsilanol considerably improved the yields of the products by reducing the decompositions of the substrates and products. The reaction should involve the initial formation of allylgallium from the enynes and GaCl3, where GaCl3 activated hydrocarbon C-H to generate a nucleophilic organogallium intermediate. Carbometalation with chloroacetylene followed by beta-elimination then led to the ethynylated product. Triethynylvinylmethanes were obtained by the repeated regioselective ethynylation at the 3-position of the enynes. The reaction of allylsilanes with the chloroacetylene also gave diethynylvinylmethanes, in which 1,4-enynes were formed in situ by the addition-elimination of allylgallium formed from allylsilane and GaCl3. Tetraethynylmethanes were obtained by reacting 1,4-diynes with the chloroacetylene at 150 degrees C. The structure and amount of silanol can be used to control the reactivity of GaCl3.     

Formation and observation of dimers of a metal complex with long alkyl side chains aligned on a graphite surface

Scanning tunnelling microscope was successfully applied to observe self-assembled molecular images of (bis(5-dodecylsalicylidene)ethylenediaminato)nickel(II) in the form of dimers on highly oriented pyrolytic graphite.     

Generation and characterization of highly strained dibenzotetrakisdehydro[12]annulene

We report here the generation of tetrakisdehydro[12]annulene possessing a highly deformed triyne component from the [4.3.2]propellatriene-annelated precursor by its photolysis extruding indan and the characterization of the highly reactive annulene by chemical and spectroscopic methods. In addition to the chemical evidence for the formation of the title compound in solution such as interception as a Diels-Alder adduct, we succeeded in its characterization by UV-vis and FTIR spectra in an argon matrix at 20 K. The experimental IR spectrum agreed well with the theoretical one calculated by the DFT method.