Crystal structure, electronic properties, and intermolecular interactions of the [Ag(imidazole)2]ClO4 complex: A combined DFT, Hirshfeld surface, QTAIM, and RDG study

In this study, the [Ag(imidazole)2]ClO4 complex was successfully synthesized and its structural and electronic properties were comprehensively investigated using combined experimental and theoretical approaches. The crystal structure was determined by single-crystal X-ray diffraction analysis, while quantum chemical calculations were performed at the DFT/B3LYP/DGDZVP level of theory. A good agreement between the optimized geometry and the experimental structure confirmed the reliability of the theoretical model in describing the structural characteristics of the complex. Hirshfeld surface analysis together with two-dimensional fingerprint plots revealed that the crystal packing is predominantly stabilized by a cooperative network of H···O/O···H, H···H, C···H/H···C, and N···H/H···N intermolecular interactions. Molecular electrostatic potential (MEP) analysis demonstrated that the oxygen atoms of the perchlorate anion constitute the most electron-rich regions, in excellent agreement with the Hirshfeld surface results. Frontier molecular orbital analysis yielded a HOMO–LUMO energy gap of 6.41 eV, indicating high electronic stability and low chemical reactivity of the complex. The HOMO is mainly localized on the perchlorate counterion, whereas the LUMO is distributed over the Ag(I) coordination center and the coordinated imidazole ligands. Furthermore, the Quantum Theory of Atoms in Molecules (QTAIM) and reduced density gradient (RDG) analyses provided detailed insight into the nature of the coordination bonds and weak intermolecular interactions, confirming that van der Waals interactions together with weak hydrogen bonds play a key role in stabilizing the crystal lattice. The combined experimental and theoretical results demonstrate that the structural and electronic stability of the [Ag(imidazole)2]ClO4 complex originates from the synergistic contribution of its coordination geometry, favorable electron-density distribution, and cooperative supramolecular interactions.