Relaxation and ligand hyperfine effects in an isostructural early lanthanide series [Ln(Cptt)3] (Ln = Ce, Nd, Sm; Cptt = C5H3tBu2-1,3) by pulsed EPR spectroscopy

25 August 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


We examine lanthanide (Ln)-ligand bonding in a family of early Ln3+ complexes [Ln(Cptt)3] (1-Ln, Ln = La, Ce, Nd, Sm; Cptt = C5H3tBu2-1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin T1 and Tm relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.7 μs (1-Sm), respectively, at 5 K: the T1 relaxation of 1-Nd is more than 102 times faster than its valence isolelectronic uranium analogue. 13C and 1H hyperfine sublevel correlation (HYSCORE) spectroscopy reveals that the extent of covalency is negligible in these Ln compounds, with much smaller hyperfine interactions than observed for equivalent actinide (Th and U) complexes. This is corroborated by ab initio calculations, confirming the predominant electrostatic nature of the metal-ligand bonding in these complexes.


Pulsed EPR spectroscopy
Ab initio calculations

Supplementary materials

Supplementary Information
Supporting data and figures


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