  Investigating metal organic systems with time-resolved photocrystallography
poses a unique challenge while interpreting the time dependent photodifference
maps. In these difference Fourier maps, the signals correspond to the movement
of heavy metal atoms always overpower the signals from much lighter atoms
attached to them. For a systematic assessment of the quality of the
photodifference maps obtained from metal organic systems, in this work,
LaueUtil and PRECOGNITION software were used to treat time-resolved Laue
crystallography data of a [2x2] matrix-like Fe(II) complex. The rigid spot
identification method in LaueUtil allows to identify and index > 250,000
reflections per 10 datasets. Though this leads to low completeness (< 30%), the
software only treats the information from highly reliable diffraction spots. As
a result, clean photodifference maps and small values in the thermal scale
factor have been obtained. In the PRECOGNITION case, the package indexed more
than 160,000 reflections per dataset. The resulting completeness is higher
(>86%) and useful photodifference maps can be obtained by careful data
treatment. However, the dependence on the refinement of the lambda curve as
well as the degradation of the sample may be reflected on the large thermal
scale factors which also contribute as noise in the photodifference maps.
