Hybrids of Polyynes and Azo Dyes: Synthesis, Characterization, and Two-Photon Absorption

Polyynes are one-dimensional carbon atomic wires possessing sp hybridization and alternating triple and single bonds. Their electronic structure is particularly attractive and has a significant impact on their optical properties. Here, we report the first synthesis and characterization of blends of polyynes and azo dyes. The dominant contribution of the azo tautomer in the resulting dye end-capped linear carbon rods was unambiguously confirmed using X-ray single-crystal diffraction. Linear and non-linear optical properties of the hybrids of polyynes and azo dyes were investigated in detail and influence of the length of sp-hybridized carbon chain on two-photon absorption (2PA) was analyzed. Reported RC8R hybrids of azo dye and polyyne moieties exhibit significantly stronger two-photon absorption compared to the previously reported aryl-substituted polyynes or parent alkyne-substituted azo dye RC2TMS.