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.