Linking electronic and geometrical structure to local magnetism in lanthanide hexacyanoferrates by paramagnetic solid-state NMR
Year: 2026
Type: preprint
Abstract: Lanthanide hexacyanoferrates, LnFe(CN)6·xH2O, combine the structural versatility of cyanidebridged frameworks with the strong spin–orbit coupling and crystal-field effects of lanthanide ions. Yet, the local (ion-specific) origins of the magnetic response of these materials remain difficult to resolve by conventional solid-state chemistry techniques. Here, we report the 1H and 13C solid-state nuclear magnetic resonance (NMR) spectra of LnFe(CN)6·xH2O (Ln = La to Yb), with assignments supported by first-principles calculations and optical spectroscopy. We interpret the 1H NMR spectra in terms of free (interstitial) and bound (Ln-coordinated) water environments within the porous framework. The 1H shifts and shift anisotropies scale approximately linearly with the lanthanide Bleaney coefficients, establishing a direct and quantifiable link between 1H spectra and single-ion anisotropy. Using 13C NMR spectra, we are able to isolate the impact of Ln composition, despite the Ln contribution comprising only a small fraction (up to 3%) of the total paramagnetic NMR shift. The 13C shift anisotropy also tracks linearly with the Bleaney coefficients, whilst the trend against the isotropic shift is weaker, underlining the site-specific effect of Fermi contact and dipolar contributions to the total shift. Together, out results establish solid-state NMR spectroscopy as a sensitive and quantitative probe of single-ion anisotropy in cyanide-based frameworks.
Source: ChemRxiv
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213282635