Thread, enhancement

Additional reports on olefination reactions have appeared [64] including the preparation of several phosphonium salts using a domestic MW oven wherein the reaction of neat triphenylphosphine and organic halide shows remarkable rate enhancement in a pressure tube with a threaded Teflon cap [65]. 

Gibson and coworkers utilized the expected complexation between crown ethers and acrylonitrile for the preparation of poly(acrylonitrile-crown ether rotax-ane)s 94 [137]. Relative to that with the polystyrene backbone, the enhanced threading supported the intermediacy of the expected complex. The reaction intermediates, the cations 95 and 96 in the preparation of poly(phenylene vinylene) (PPV) also provided a source for interaction with crown ethers [70], The solution polymerization of precursor 95 in the presence of crown ethers followed by transformation of 96 produced polyrotaxanes 97. 

Gong et al. reported that the solubility of a polymeric cyclic can be altered significantly by threading with paraquat, the formation of 84 [126, 128]. Whereas polymer 83 was only partially soluble in acetone, polyrotaxanes 84 were soluble and had an orange color. Whereas polymer 83 was totally soluble in THF and paraquat was not soluble, 84 even up to min=0.971 were initially soluble except for a small amount of uncomplexed paraquat the solubility of paraquat was indeed enhanced by complexation with polymer 83. CH3CN was a good solvent for paraquat but poor for 83. However, all polyrotaxanes 84 with m n>0.428 were soluble, whereas 84 with m/n =0.232 was not this means that a certain amount of paraquat incorporation is necessary for 83 to be soluble. 

Because elaborate equipment is required to test metal ductility, we tested the ductility of the copper, silver, and iron wires in Activity 6.1 indirectly. Ductility is a physical property of metals that allows them to be drawn or stretched into thin threads without the metal breaking. Two of the most ductile metals are gold and silver. One gram of gold can be drawn into a thread two miles long 3 Threads can be used as lines in art. We know that lines in art are used to communicate what we see and feel. A thread, used as a line, can enhance a sculpture or even serve as the sole material for the sculpture. Because many pieces of jewelry are sculptures in miniature, threads of gold and silver are excellent materials for creating attractive pieces of jewelry. 

Pedersen, Cram and Lehn respectively gives us the other thread to the present story. The first example of fluorescence enhancement caused by a supramolecu-lar interaction between a metal ion and a neutral receptor (8) was reported by the Bordeaux-Strasbourg collaboration of Bouas-Laurent, Desvergne and Lehn [15]. An older example of luminescence arising from a strong coordinate interaction between a neutral ligand and a metal ion is (9) [16]. Anionic ligands,... 

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