Synthesis, Crystal Structure and DFT Studies of a New Dinuclear Ag(I)-Malonamide Complex

The synthesis and structural aspects of a new dinuclear silver (I) complex with malonamide type ligand (L) is reported. Each Ag ion in the [Ag₂L₂(NO₃)₂]·H₂O complex is coordinated to two ligands, L, each acting as a bridged ligand via its two pyridine arms; Ag(I) acts as a connector between them. Two types of Ag-ligands close contacts were detected: Ag-N1, Ag-N4 from the two L units, and Ag-O5, Ag-O6 from the two nitrate anions, wherein both the nitrate ions are inside the cage formed by the [Ag₂L₂] unit. The coordination geometry around each Ag(I) is a distorted tetrahedron. The [Ag₂L₂(NO₃)₂] complex units are connected by weak intermolecular C-H…O interactions. The different intermolecular interactions were quantified using Hirshfeld surface analysis. Using two DFT methods (B3LYP and WB97XD), the nature and strength of the Ag-N and Ag-O interactions were described using atoms in molecules (AIM) and natural bond orbital (NBO) analyses. Topological parameters indicated that the strength of the two Ag-N bonds was similar, while that of the two Ag-O interactions were significantly different. Moreover, the Ag-N interactions have a predominant covalent character, while the Ag-O interactions are mainly ionic. The NBO analysis indicated that the most important anti-bonding Ag-orbital in these interactions has an s-orbital character.