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

TL;DR

This study demonstrates a novel laser-based method to synthesize long-chain hydrogen- and methyl-capped polyynes from toluene, revealing solvent influence on end-cap formation and producing the longest chains to date.

Contribution

First synthesis of methyl-capped polyynes and longest hydrogen-capped chains using ultrafast laser irradiation of toluene, highlighting solvent effects on end-cap formation.

Findings

Methyl-capped polyynes up to HC14CH3 were synthesized.

Hydrogen-capped polyynes up to C18H2 were produced.

Solvent choice influences the end caps of the resulting polyynes.

Abstract

Hydrogen- and methyl-capped polyynes were synthesized by irradiating pure liquid toluene with 35 femtosecond, 300 {\mu}J 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.