3.2. Molecular Hirshfeld Surface Analysis

Molecular Hirshfeld surfaces and fingerprint plots based on the CIF files obtained from the CSD search were generated with Crystal Explorer 3.0 program [75] in order to analyze the scheme of intermolecular interactions around the platinum center. Hydrogen atom positions were normalized to standard bond lengths from neutron diffraction (C–H = 1.083 Å, O–H = 0.983 Å, N–H = 1.009 Å) [76] using the automatic procedures implemented in the program. The normalized contact distance (d_norm) was mapped onto the Hirshfeld surfaces. The normalized contact distance used in the study is defined using the following formula: d_norm = [(d_i–r_i)/r_i] + [(d_e–r_e)/r_e], [77] where d_i and d_e are the distances between a chosen point of the Hirshfeld surface and, respectively, the nearest atom of the analyzed molecule (internal d_i) and the neighboring molecule (external d_e); r_i and r_e are van der Waals radii of the corresponding atoms. The results of mapping onto the molecular Hirshfeld surfaces are presented in this paper according to the standard red-white-blue coloring scheme: white color corresponds to intermolecular contacts of length close to the van der Waals separations, red-denotes shorter contacts of negative values of d_norm, and blue corresponds to long contacts characterized by positive values of d_norm. This relatively new method was effectively used to describe intermolecular interactions in various types of crystals [78,79,80,81].