A difunctional Dy(III) complex exhibiting single-molecule magnet behaviour and fluorescent cellular imaging

A mononuclear Dy(III) complex, with formula [Dy(Dicnq)(TFNB)₃] (1), is synthesized through self-assembly with 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (TFNB) and 6,7-dicyanodipyrido [2,2-d:2',3'-f] quinoxaline (Dicnq) ligands. Single-crystal structure determination reveals that the Dy(III) ion in complex 1 features an N₂O₆ octacoordinated environment with distorted square-antiprism (D_4d) geometry. Magnetic data analysis shows that 1 behaves as a single-molecule magnet, with an energy barrier of 192 K under a zero dc field. With an external field of 1200 Oe, the quantum tunneling of magnetization is suppressed in 1, resulting in an enhanced energy barrier of 261 K. Additionally, 1 displays room-temperature photoluminescence. Leveraging its optical properties and minimal cytotoxic effects, we assess its suitability for cellular-imaging applications. Subsequent laser confocal microscopy analysis revealed that 1 is capable of efficiently traversing the plasma membrane and nuclear membrane of HeLa cells, an observation that is not commonly reported in dysprosium-based complexes.