Light- and radical-induced modification of magnetic and magnetocaloric effects in viologen-based lanthanide materials

Abstract

Achieving dual regulation of both photomagnetic properties and magnetocaloric effects (MCE) in lanthanide-based materials is a significant challenge. In this study, two lanthanide coordination polymers (CPs), [(Bpydp)Ln(H₂O)(PTA)]·NO₃·2H₂O (Ln = Dy, namely 1-Dy; Gd, namely 1-Gd) and [(Bpydp)_0.5Dy₂(IPA)₃]_n namely 2-Dy, based on the 4,4′-bipyridine ligand, are synthesized and their photomagnetic behaviors are systematically investigated. In 1-Dy, the combined action of light irradiation and photogenerated radicals produces a more pronounced photomagnetic relaxation, thereby increasing the effective energy barrier. By contrast, the isostructural 1-Gd system illustrates how both light exposure and radical formation can modulate the magnetocaloric effect in Ln-based coordination polymers. Magnetic measurements and theoretical analyses confirm that these photoinduced processes collectively regulate the magnetic response. This dual strategy of utilizing light stimulus alongside radical generation represents a novel route for engineering advanced materials with tunable photomagnetic and thermomagnetic functionalities.