Silver(I) Citrate Carboxylate Coordination Polymers: Synthesis, Crystal Structures, and Thermale Behavior

Coordination polymers $n{{(\text{Pipy})}^{{2}+}}[\text{A}{{\text{g}}_{4}}{{(\text{citr})}_{2}}]_{n}^{2-}\cdot {2}n{{\text{H}}_{2}}\text{O}$ (1) and {[Ag(bpy)]+[Ag2(citr)(bpy)2]–}n·10nH2O (2) are formed by the interaction of silver acetate with citric acid (H3citr) and piperazine (Pipy) / 4,4′-bipyridine (bpy) during slow diffusion. Their structures are determined by the single crystal X-ray diffraction (XRD) analysis. According to the single crystal XRD data, both compounds are ionic polymers. In the complexes, the Ag+ cations and bridging COO-groups of citric acid form eight-member cycles (–Ag–O–C–O–Ag–O–C–O–) with argentophilic interactions. Unlike complex 1 in which protonated piperazine fragments Pipy2+ occupy the outer-sphere positions, bpy coordinates to the complexing agent in 2, forming [Ag(bpy)]+ cationic chains. In the coordination polymers, the system of hydrogen bonds and π–π interactions participate in the additional stabilization of the structures. Simultaneous thermal analysis (STA) data show that complex 2 is the highly stable compound.