Determination of reaction quantum yields of photochromic fulgides using mid-IR spectroscopy: quantitative evaluation and normal mode analysis

To demonstrate the feasibility of non-destructive readout of optically recorded data using IR absorption spectroscopy [1], the ring-closure/ring-opening reactions of photochromic fulgides are monitored without perturbation, and the respective reaction quantum yields are determined quantitatively. The values are identical to those determined from UV/VIS spectroscopy. Variation of substituents and a normal mode analysis based on semi-empirical QCFF/PI calculations reveal the nature of the vibrational modes relevant for the method, thus helping to understand the underlying mechanisms.