Conjugation length dependence of Raman scattering in a series of linear polyenes: Implications for polyacetylene

Abstract

Donor-acceptor substituted linear polyenes: Chain length dependent electronic structure of anthrylpolyenes J. Chem. Phys. 98, 7969 (1993); 10.1063/1.464551 Resonant Raman scattering of controlled molecular weight polyacetyleneWe have measured the solid state Raman scattering spectra of a homologous series of linear polyenes, with the number of alternated double bonds varying from 3 to 12. While we find a linear dependence of the Raman shifts of resonantly coupled modes with inverse conjugation length, we have also followed the suggestion of previous work in examining the inverse square product of the several Raman frequencies as a function of the logarithm of the measured energy gap of the molecule. This provides a linear relationship, as found for transpoly acetylene, a result which is qualitatively consistent with the amplitude mode model of Horovitz and co-workers. We also find, consistent with previous work on polyacetylene, a monotonic decrease in the ratios of oscillator strengths of the two strongest bands with conjugation length, as recently predicted by a series of molecular dynamics calculations. Suggested interpretations of a number of qualitative observations, including splitting of modes for shorter conjugation length, are offered, and the implications for the structure of transpolyacetylene are discussed. The present work confirms that the previously measured dispersion in the Raman spectra of trans-polyacetylene is due to a distribution of conjugation lengths and brings into question some of the quantitative aspects of the amplitude mode model.

Modeling high pressure reactivity in unsaturated systems: Application to dimethylacetylene

“…For identification purposes, the most relevant signature on the Raman spectrum of the transformed sample is that appearing at 1643 cm 21 , unambiguously assigned to a C¼ ¼C stretch. However, this value is higher than that observed in the Raman spectrum of polyenic chains on both cis 41,42 and trans 43,44 configurations. In fact, from existing correlations in polyenes 43 the Figure 5.…”

“…However, this value is higher than that observed in the Raman spectrum of polyenic chains on both cis 41,42 and trans 43,44 configurations. In fact, from existing correlations in polyenes 43 the Figure 5. Evolution of the electronic density for the transformation as predicted with monodeterminantal methodologies.…”

The effects of environment on <i>Arctica islandica</i> shell formation and architecture

“…3). The number of single (N 1 ) and double carbon bonds (N 4 ) was calculated by applying the equations by Schaffer et al (1991):…”

Raman, Ft Raman and Ftir Spectra of Molluscan Shells.

“…The exact chemical nature of the marine carotenoids of Molluscan origin is not known, but they are believed to be carotenoid derivatives 42,43 . Raman spectral features have been used extensively for probing the structural nature of carotenoids [44][45][46] and of the carotenoids' industrial counterparts, the polyacetylene derivatives [47][48][49][50][51][52] . Also the 514.5 nm laser wavelength falls within or close to the energy required for the electronic transition of most carotenoids or polyacetylene systems, resulting in the resonance Raman Effect that occurs for carotenoids.…”