“…Optical spectroscopy can contribute to the understanding of the SMM properties by the analysis of the fine structure of f–f transitions, in particular in low-temperature photoluminescence (PL) spectra, and by the correlation of the determined level splitting with magnetic behaviour. 1–5 Since the first report on the Dy(DOTA) complex by Sessoli et al in 2012, 6 the vast majority of such studies were devoted to Dy 6–17 and Yb 8,18–25 complexes, with rare instances of Tb, 8,26–28 Ho, 29 Nd, 30–33 and Er SMMs. 34,35 Recent trends also include a development of luminescence thermometry based on the temperature-dependent PL of Ln-SMMs, 2,21,29,36,37 and the use of lanthanide complexes with a narrow optical linewidth for photonic quantum technologies.…”