Fig. 2: TRIR spectral evolution of the triazine-based systems upon S₁ ← S₀ excitation.

a O in the non-polar cyclohexane. b O in medium-polar chloroform and c Q in medium-polar chloroform. The inset in a shows the time dependence of the integrated 2400–2800 cm⁻¹ intensity for a–c. d D in the medium-polar chloroform showcasing the alkyne–allene transformation. The cartoon depicts the molecular motion associated with this photoisomerization (electron-accepting moiety is in green, electron donor is in yellow). The inset in d zooms into the spectral region with non-zero signal for D. The gray-shaded spectra are the negative stationary IR spectra (offset for clarity). The region near 2350 cm⁻¹ is shaded to cover interferences caused by atmospheric CO₂.