Reversible SC-SC Transformation involving [4+4] Cycloaddition of Anthracene: A Single-Ion to Single-Molecule Magnet and Yellow-Green to Blue-White Emission.

In search of magneto-optic materials, the mononuclear compounds LnIII (depma)(NO3 )3 (hmpa)2 (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365 nm without loss of crystallinity. The Dy compound switches from a single-ion to a single-molecule magnet with doubling of the spin reversal barrier energy and from yellow-green to blue-white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto-optic property.