Europium(II) Coordination Polymers with Bipyrimidine Linkers: Structural, Spectroscopic, and Magnetic Studies

The accessible divalent oxidation state of europium confers unique electronic, magnetic, and redox properties among lanthanoid ions. However, coordination polymers (CPs) with divalent lanthanoid ions remain rare due to their high reactivity and limited stability. Here, we report two new one-dimensional europium(II) coordination polymers incorporating redox-active bridging ligands: [EuII(Bp)2(μ-bpym)]n (CP1) and [EuII(Tp)I(μ-bpym)]n (CP2) (where Bp– = hydrobis(1-pyrazolyl)borate, bpym = 2,2′-bipyrimidine, and Tp– = hydrotris(1-pyrazolyl)borate). Structural characterization confirms the formation of extended chain architectures stabilized by the scorpionate ligands, and spectroscopic studies highlight their electronic properties. Notably, CP2, under inert conditions, exhibits exceptional stability in solution, a rare feature among CPs, potentially broadening their options for solution-processable materials. Magnetic studies reveal exchange interactions between Eu(II) centers, providing insights into the fundamental magnetic behavior of divalent lanthanoid systems.