Charge density investigations on [2,2]-paracyclophane – in data we trust.

Four datasets on [2,2]-paracyclophane were collected in-house and at the Advanced Photon Source at two different temperatures for charge density investigation. Global data quality indicators such as high resolution, high I/σ(I) values, low merging R values and high multiplicity were matched for all four datasets. The structural parameters did not show significant differences, but the synchrotron data depicted deficiencies in the topological analysis. In retrospect these deficiencies could be assigned to the low quality of the innermost data, which could have been identified by e.g. merging R values for only these reflections. In the multipole refinement these deficiencies could be monitored using DRK-plot and residual density analysis. In this particular example the differences in the topological parameters were relatively small but significant.