Synthesis and structure of di­aqua­bis­(nicotinamide-κO)bis­(nitrato-κ2O,O′)calcium(II)

The title complex features an eight-coordinate Ca²⁺ center with a distorted trigonal–dodeca­hedral geometry.

The title complex, [Ca(NO₃)₂(C₆H₆N₂O)₂(H₂O)₂], crystallizes with an eight-coordinate Ca²⁺ ion in a distorted trigonal–dodeca­hedral coordination environment. The metal ion is coordinated to two nicotinamide ligands via their carbonyl O atoms, two bidentate nitrate anions and two water mol­ecules. The nicotinamide ligands adopt a nearly trans geometry, while the nitrate anions and aqua ligands are arranged in a pseudo-trans fashion. In the crystal, a three-dimensional supra­molecular framework is constructed through N—H⋯O and O—H⋯O hydrogen bonds involving water, nitrate, and nicotinamide functional groups, reinforced by offset π–π stacking inter­actions between nearly parallel pyridine rings [centroid-to-centroid distance = 3.783 (2) Å]. A Hirshfeld surface analysis revealed that the inter­molecular inter­actions are dominated by O⋯H/H⋯O (42.3%) and H⋯H (26.2%) contacts, corresponding to classical hydrogen bonding and van der Waals forces, respectively.