Computational polyynes

For a polyyne chain142 the static al and dynamic a(— co)L polarizabilities have been computed using non-linear sequence transformations for the extrapolation and besides RPA the SOPPA (correlated second order polarization propagator approximation) method. In this way the authors have obtained for a C2 iH2 (polyyne) chain quite stable extrapolated values for both quantities. 

Kirtman et al.149 show how low frequency collective modes contribute to the dynamic vibrational hyperpolarizabilities of different linear chains (polyacetylene, polyyne, polyethylene and polysilane). In another work Champagne et al.150 have calculated the static vibrational yvL/N of polyacetylene and they have found it to be 30% larger than the electronic contribution, while in the case of polyyne yj[/yL is 0.92151 at the extrapolated infinite chain length. For polydiacetylene and polybutatriene both the static electronic and the vibrational contributions to a /N and ctvL/N, and yl/N and yj JN, respectively, were computed. Also in these cases for both chains the vibrational contributions are of the same order as the electronic ones. One should mention, however, that in these cases the yL/N values extrapolated to infinity are about 10% larger than the values obtained for seven or ten units, respectively, in the two chains. Finally for d -trans polysilane154 the static y /N and yvL/N and values were also calculated. Their values have been found also to be of comparable magnitude. 

Evidence for conjugation is easily depicted in the pictures of the frontier orbitals (HOMO and HOMO-1 extracted from DFT computations Figure 4.4), where atomic contributions from the Pd d orbitals placed parallel with are depicted, hi many ways (i.e., structures, presence of thermal stabihties, and luminescence), the arylisocyanide-containing polymers have much in common with the corresponding aryl polyynes. The major difference is that the former exhibit a lesser degree of emission intensity, particularly at room temperature. 

Metal containing polyynes are multifunctional materials which combine the properties of organic polymers with those of metal centers coordinated to the organic moiety and are able to form nanotemplates, colloidal photonic crystals, multilayer capsules and hollow vesicles [127, 128], An example of a rod-like polymetallayne self-assembly in hollow nanorods has been recently reported [129] the computer simulations of the nanostructure show that the polymer chains are ordered in parallel lines that give rise to a tubular morphology rather unusual for these materials, but promising for sensor devices applications. 

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