Acceptor and donor substituted alkoxy(phenyleneethynylenes) (Alkoxy-PEs): Synthesis, thermal, linear and nonlinear optical properties

- Thermal stabilities of alkoxy(phenyleneethynylenes) depend on the acceptor and donor substitutents.
- In the emission spectrum, large stokes shift is observed for the A-D-A materials.
- Continuous wave (CW) closed aperture Z-scan technique gives the signature of third-order optical nonlinearity.

A series of acceptor and donor substituted bis(alkoxy)phenyl ethynyl oligomers 4,4′-((2,5-alkyoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(nitrobenzene) (alkyl = C4H93a; C8H173b and C12H253c) and 4,4′-((2,5-alkyoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(methylbenzene) (alkyl = C4H94a; C8H174b and C12H254c) has been synthesized by the palladium catalyzed cross coupling reaction of 1,4-dialkoxy-2,5-diiodobenzene with appropriate alkynes. The newly synthesized products were characterized by UV-Vis, IR and multinuclear NMR spectroscopic techniques as well as elemental analyses. All the synthesized bis-(alkoxy)phenyl ethynyl derivatives exhibit good thermal stability (T5 = 329-347 °C) as evident by thermo gravimetric analysis. In nitrophenyl substituted 3a-c, emission is observed in the green region, while in tolyl substituted 4a-c, emission is observed in the blue region of the electromagnetic radiation. Continuous wave (CW) closed aperture Z-scan technique reveals the signature of third-order nonlinearity in the materials that are thermal in nature.