Prepare a 5.0 × 10 M solution of 6-NO -BIPS in toluene. Using a hot bath, record the absorption
of the sample with 5 different temperatures between 30 and 60 °C. Figure 14 shows an example of
measurements done at five varying temperatures.
Figure 14:
Transient absorption of Spiropyran in Toluene at 600 nm detection wavelength.
An example of the generated absorbance vs. time profile is shown in Figure 15 for a temperature of
55°C. Also shown in this plot is the fitted exponential decay function (red line) calculated using
OriginLab Origin, a commercial graphing software. This fit provides the lifetime of the back
reaction, which in this example is 1.29 seconds. Once lifetimes at five different temperatures are
obtained, a plot like the one in Figure 16 can be obtained. Using Origin, a line is fit through the five
data points and the slope of this line is used to calculate the activation energy, E , of the back
reaction.
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