Near-infrared-II photothermal conversion and magnetic dynamic regulation in [Ln3Rad2] aggregation by rigidity modification of nitronyl nitroxide

Radical-metal compounds used as functional materials can be applied to multiple fields such as solar-thermal conversion and ultra-high density data storage. However, the reactivity and instability of organic radicals usually hamper the development and application of radical-metal compounds. Herein, we utilized persistent nitronyl nitroxide to construct two categories of nitronyl nitroxide-Ln compounds, [Gd3(hfac)9(NIT4bpym)2]2<middle dot>4CH2Cl2<middle dot>C6H14 (1-Gd), [Dy3(hfac)9(NIT4bpym)2] (1-Dy) and [Dy3(hfac)9(NITPzCH2IM)2]<middle dot>2CH2Cl2 (2-Dy) (NIT4bpym = 2,2 '-dipyridyl-4-(1 '-oxyl-3 '-oxido-4 ',4 ',5 ',5 '-tetramethyl-4,5-hydro-1H-imidazol-2-yl); NITPzCH2IM = [2-(1-methylimidazole)methyl-1-pyrazol]-4-(1 '-oxyl-3 '-oxido-4 ',4 ',5 ',5 '-tetramethyl-4,5-hydro-1H-imidazol-2-yl) (hfac = hexafluoroacetylacetonate), involving a rare [4f-2p-4f-2p-4f] multi-spin motif with an electron donor-acceptor pattern. Notably, thanks to the rigidity modification of nitronyl nitroxide, prominent enhancement of photothermal conversion efficiency from 56.9% to 74.0% and the magnetic switching phenomenon have been observed with molecular structure transformation from flexibility (2-Dy) to stiffness (1-Dy), offering an avenue for the regulation of the photothermal effect and magnetic dynamics.