Photogenerated cumulenic structure of adamantyl endcapped linear carbon chains: an experimental and computational investigation based on infrared spectroscopy.

摘要: The infrared (IR) spectrum of an adamantyl endcapped α, ω-polyyne (the hexayne, Ad–C12–Ad) is investigated both experimentally and computationally. A new IR band observed upon UV photoexcitation the compound (embedded in a poly methyl methacrylate matrix at 78 K), thus, revealing existence photogenerated molecular structure trapped low temperature. Complete reversibility found, demonstrating that responsible for generation metastable excited states molecule. Density functional theory time dependent density calculations indicate these result from forbidden singlet (S1) or triplet (T1) states, geometry optimizations polyyne either S1 and/or T1 demonstrate carbon chain takes on cumulenic structure. Comparison experimental computed spectra molecule confirms features are clear ...