Implications of bond disorder in a S=1 kagome lattice

Strong hydrogen bonds such as F···H···F offer new strategies to fabricate molecular architectures exhibiting novel structures and properties. Along these lines and, to potentially realize hydrogen-bond mediated superexchange interactions in a frustrated material, we synthesized [H₂F]₂[Ni₃F₆(Fpy)₁₂][SbF₆]₂ (Fpy = 3-fluoropyridine). It was found that positionally-disordered H₂F⁺ ions link neutral NiF₂(Fpy)₄ moieties into a kagome lattice with perfect 3-fold rotational symmetry. Detailed magnetic investigations combined with density-functional theory (DFT) revealed weak antiferromagnetic interactions (J ~ 0.4 K) and a large positive-D of 8.3 K with m_s = 0 lying below m_s = ±1. The observed weak magnetic coupling is attributed to bond-disorder of the H₂F⁺ ions which leads to disrupted Ni-F···H-F-H···F-Ni exchange pathways. Despite this result, we argue that networks such as this may be a way forward in designing tunable materials with varying degrees of frustration.