Long Wavelength Azo Dye Monomers for Photomechanical Applications

Azo dyes have long been incorporated into photomechanical systems with promise as wireless actuators (White, T.J.; Broer, D.J. Nat. Mater. 2015, 14, 1087-1098). Most azo dyes photoisomerize in the ultraviolet to blue/green region of the electromagnetic spectrum. However, these high energy wavelengths correspond with maximum photodegradation of the material and competitive absorption by other device components. Furthermore, these wavelengths are incompatible with mammalian tissue thus limiting any potential biomedical applications. Recently, Aprahamian and coworkers published a series of BF₂-coordinated azo dyes which photoisomerize in the red (Yang, Y.; Hughes, P.; Aprahamian, I. J. Am. Chem. Soc.2012,134, 15221-15224) to near-infrared (Yang, Y.; Hughes, P.; Aprahamian, I.J. Am. Chem. Soc. 2014, 136, 13190-13193) region of the spectrum. These lower energy wavelengths minimize absorption by mammalian tissue, photodegradation of the material, and competitive absorption by other device components. Analogs of Aprahamian’s dyes with polymerizable “handles” are therefore being prepared that may then be incorporated into photomechanical polymers in a project that spans research groups in organic chemistry and materials science / mechanical engineering. Synthetic efforts to date and future plans for this nascent research collaboration are described in this poster.