Fig. 1: Structural design and electronic spectra of asymmetric DAE polyynes.
a General structure of asymmetric DAE polyyne and reversible photo-conversion between the open and closed forms under light irradiations. Heterocycle (blue shaded area), polyyne (red shaded area), and end-capping substitution (green circle) were employed to tune the electronic spectra in the near-IR region. b Absorption wavelength optimization of asymmetric DAE polyynes in the closed forms. The absorption maxima indicated by arrows can be tuned from 560 nm to 720 nm. c Heterocycles variation from benzothiophene to 5-dimethylamino-1-methylindole caused large absorption redshifts of 160 nm. d Polyyne elongation from monoyne to triyne tuned the absorption maxima in the range of 50 nm. e End-capping substitutions from electron-donating -NH2 to electron-withdrawing -CN group fine-tuned the absorption wavelengths within 10 nm.
