Extended polyynes

Matsuzawa, N. and Dixon, D.A. (1992) Semiempirical calculations of hyperpolarizabilifies for extended n-systems Polyenes, polyynes, and polyphenyls. International Journal of Quantum Chemistry, 44, 497-515. 

The approach to form carbon ring molecules from organic precursors has been extended to produce three-dimensional macrocyclic polyynes of larger sizes (Section 6.4). Despite the fragility and explosive reactivity, the precursory molecules containing polyyne structures are successfully isolated and well characterized. The liberated pure carbon molecules have been... 

However, Tobe has shown that the polyyne route can be extended to the size-selective formation of a large fullerene C78 [54]. Regarding large fullerenes, it has been well known that the number of possible geometrical isomers... 

The synthesis, optical, and structural properties of another Pt(II) polyyne-containing biphenyl moiety, P12, were reported recently.44 The system has also been extended to the Au(I) and Hg(II) congeners (see Sections IV and V). The influence of the metal center on the spatial extent of S and T excited states was characterized in detail. The ligand-based phosphorescence emissions can be harvested by the heavy-atom effect of these transition metals, which facilitates efficient intersystem crossing from the S] state to the T] state. 

A new Pt(II) polyyne polymer, P15, prepared from the reaction of cfs-[Pt(PPh3)2Cl2] with l,4-diethynyl-2,5-dihexadecyloxybenzene using the extended one pot polymerization route, was tested for its sensing properties and showed fast and reproducible response to relative humidity variations and methanol vapor in surface acoustic-wave (SAW) sensors.46 A SAW sensor was fabricated from polymer P15 as a sensitive membrane, and the polymer was deposited as thin film on the surface of SAW delay lines implemented on three different piezoelectric substrates. High sensitivity and reproducibility were recorded for such devices. The acoustic characterization of the polymer film was also studied with the aid of theoretical results obtained by the perturbation theory. 

The generally rigid, extended nature of metal polyynes is also evident in their tendency to form lyotropic liquid crystalline phases " " (see also Chapter 12.05 on the topic of organometallic mesogens). Homometallic polymers, as well as mixed metal systems, that contain Pt, Ni, and Pd, have all been shown to exhibit liquid... 

Attempts were also made to extend the woik to some robust and stable silylacetylene derivatives functionalized with aromatic entity such as Lj [89], which can then afford new Pt polyynes 4 and oligoynes 5 and 6 [90]. Scheme 3.2 depicts the synthetic routes to these materials. Polymer 4 was prepared as a structural analog to /nms-[-Pt(PBu3)jC = C (p-CgH )C = CPt(PEt3)jC s C(p-C H )C=C-] (VI) in order to evaluate the effect of... 

Use of similar synthetic methodologies as above leads to the generation of rigid-rod polyynes containing extended spacer units (Fig 8.37) [67]. 

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