Qualitative analysis of intermolecular interactions: Hirshfeld surface and 2D fingerprint plots
Hirshfeld surface (HS) has widely been used as a qualitative tool to analyze the intermolecular contacts present in the title complex. The 2D-fingerprint plots (2D-FP) were obtained for the individual component of the complex from the HS analysis (Fig. 5). For the lysinium cation, the intermolecular H···H interactions (with the contribution of 45.9%) are appeared as a single spike (d i+d e = 2.0 Å;d i and d e are the distances from the surface to the nearest nucleus internal and external to the surface, respectively) which confirms the existence of C6–H6B···H14–C14 contact (motif D3). The next contribution comes from the intermolecular H···O interactions and shown as double spikes with the shortest d i+d edistance of 1.8 Å. It should be noted that the intermolecular H···C contacts (sum of d i and d edistance is being 2.8 Å) are contributing 11% to the total HS area of the cation. The entire contribution emanated from the donor molecules (d e > d i) for these interactions. The C=Olp···Cπcontacts contribute about 0.8% to the total HS area.
For mandelate anion, the H···H contacts are also shown as a single spike on the FP with the shortest contact at 2.0 Å. In the case of H···O contacts, there is a remarkable difference noticed on the FP as compared to the lysinium ion. The contribution from donor molecules (d e > d i) is reduced by ca . 2.5% that of the acceptor molecules (d e < d i) of the anion. Similarly, the acceptor molecules contributing more to the H···C contacts from the anion as compared to the cation in which the contribution of donor molecules is more towards crystal packing. Furthermore, the contributions of H···H and H···O also varied between water molecules.