Multipolar model and Hirshfeld atom refinement of tetraaquabis(hydrogenmaleato)iron(II).

A high-resolution charge density study using the Hansen-Coppens multipolar model was performed on tetraaquabis(hydrogenmaleato)iron(II). The experimental electron density was subjected to Bader's topological analysis. Hirshfeld atom refinement and topological analysis of the molecular wavefunction were also conducted. A comparison of the properties obtained under different resolution and acquisition conditions are presented. The performance of these models is evaluated in terms of their ability to achieve bond lengths close to those from neutron diffraction, provide accurate anisotropic displacement parameters and model electron densities precisely, and to determine atomic charges under different experimental and modeling conditions. The structure presents a short intramolecular hydrogen bond, which is found to have a distinct character compared to other interactions, as the hydrogen interacts covalently with two oxygen atoms. Different models were evaluated, each outperforming the others in specific aspects. Overall, the analysis of these models provide deeper insights into electron density distribution and the nature of the interactions present in the structure.