Synthesis of hydrogen-and methyl-capped long-chain polyynes by intense ultrashort laser pulse irradiation of toluene

Hydrogen- and methyl-capped polyynes have been synthesized by irradiating pure liquid toluene with 35 fs, 300 μJ laser pulses having a central wavelength of 800 nm, generated by a regeneratively amplified Ti:sapphire tabletop laser at a repetition rate of 1 kHz. Raman spectroscopy was used to confirm the presence of polyynes in the irradiated samples while high-performance liquid chromatography was used to separate hydrogen-capped polyynes up to C₁₈H₂ and methyl-capped polyynes up to HC₁₄CH₃. These represent the first such methyl-capped polyynes and the longest hydrogen capped chains synthesized to date by the ultrafast laser based method. Furthermore our results show that choice of the starting solvent molecule directly influences the end caps of the polyynes which can be produced.