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 Ln(III)(depma)(NO3)(3)(hmpa)(2) (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365nm 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 degrees C or partially on light irradiating at 254nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto-optic property.