doi:10.1039/d4tc03152kengBartolomé, ElenaArauzo, AnaLuzón, JavierGasque, LauraLight-induced magnetic switching in a coumarin-based Tb single molecule magnetART-2025-141581We present the intriguing magneto-optical properties of the lanthanide complex [Tb(coum)3(batho)]·[0.7EtOH], named Tb–batho, based on coum = 3-acetyl-4-hydroxylato-coumarin and batho = bathophenanthroline ligands. Tb–batho displays visible-range luminescence with a notable quantum yield (58%) upon sensitization of the “antenna” ligands. Employing a SQUID magnetometer equipped with a magneto-optic option, we conducted comprehensive in situ measurements of light-induced magnetization changes across varied magnetic fields, temperatures, and frequencies, utilizing light wavelengths ranging from 275 to 800 nm. A reversible magnetic modulation of magnetization is observed upon toggling the light “on” and “off,” particularly pronounced at 380 nm excitation, resulting in a magnetization change ΔM(off/on) = 0.376μB fu−1 (ca. 42.6% of the magnetization) at 1.8 K and 1 kOe. Although Tb–batho exhibits field-induced single ion magnet (SIM) behavior, characterized by a thermally-activated process with an activation energy of Ueff/kB = 16.6 K @ 3 kOe and a slow direct process influenced by bottleneck effects, light irradiation does not noticeably alter its dynamic properties. All in all, Tb–batho emerges as a versatile multifunctional molecular material integrating SIM behavior, luminescence and light-induced magnetic switching, holding interest for diverse electronic applications, sensors, or quantum computing.2025http://zaguan.unizar.es/record/14803410.1039/d4tc03152khttp://zaguan.unizar.es/record/148034oai:zaguan.unizar.es:148034info:eu-repo/grantAgreement/ES/AEI/CEX2023-001263-Sinfo:eu-repo/grantAgreement/ES/AEI/CEX2023-001286-Sinfo:eu-repo/grantAgreement/ES/DGA-FSE/E12-23R-RASMIAinfo:eu-repo/grantAgreement/ES/MICINN/PID2022-138492NB-I00JOURNAL OF MATERIALS CHEMISTRY C 13, 2 (2025), 831-841by-nchttps://creativecommons.org/licenses/by-nc/4.0/deed.esinfo:eu-repo/semantics/openAccess