Abstract
Intermolecular interactions play a vital role in crystal structures. Therefore, we conducted a topological study, using Hirshfeld surfaces and atom in molecules (AIM) analysis, to decompose and analyze, respectively, the different intermolecular interactions in six hydrazone-diacetyl platinum(II) complexes. Using AIM and natural bond orbital (NBO) analyses, we determined the type, nature, and strength of the interactions. All the studied complexes contain C-H⋯O interactions, and the presence of bond critical points along the intermolecular paths underlines their significance. The electron densities (ρ(r)) at the bond critical points (0.0031–0.0156 e/a03) fall within the typical range for H-bonding interactions. Also, the positive values of the Laplacian of the electron density (∇2ρ(r)) revealed the depletion of electronic charge on the interatomic path, another characteristic feature of closed-shell interactions. The ratios of the absolute potential energy density to the kinetic energy density (|V(r)|/G(r)) and ρ(r) are highest for the O2⋯H15-N3 interaction in [Pt(COMe)2(2-pyCMe=NNH2)] (1); hence, this interaction has the highest covalent character of all the O⋯H intermolecular interactions. Interestingly, in [Pt(COMe)2(H2NN=CMe-CMe=NNH2)] (3), there are significant N-H⋯Pt interactions. Using the NBO method, the second-order interaction energies, E(2), of these interactions range from 3.894 to 4.061 kJ/mol. Furthermore, the hybrid Pt orbitals involved in these interactions are comprised of dxy, dxz, and s atomic orbitals.
Highlights
In a crystal, the molecules are packed in a unique pattern held together by weak and strong intermolecular interactions
Molecular Hirshfeld surfaces of molecules in a crystal structure are constructed based on the electron distribution, which is calculated as the sum of spherical atom electron densities [14,15,16,17,18,19,20,21,22]
Graphical plots of the molecular Hirshfeld surfaces are mapped with the normalized contact distance, and these indicate regions of important intermolecular interactions [14,15,16,17,18,19,20,21,22,27,28]
Summary
The molecules are packed in a unique pattern held together by weak and strong intermolecular interactions. The concepts of chemical bonding and bond strength can be explained using the electron density distribution functions [2,3], obtained from the AIM theory In this topological analysis, the electron density description of chemical bonding is made using bond paths and bond critical points (BCP). Topological descriptors such as the electron density (ρ(r)) and the Laplacian of the electron density (∇2 ρ(r)) at the BCP can be obtained from the AIM theory These descriptors and others have been used to characterize the strength of hydrogen bonds in various molecular systems. The significant intermolecular contacts obtained from Hirshfeld analyses of the solid-state crystal structures of six structurally related hydrazone-diacetyl platinum(II) complexes were investigated, and AIM and NBO analyses were used to understand the type, nature, and strength of these interactions. We placed particular focus on the characterization of hydrogen-bonding interactions
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