Interplay of anthracene luminescence and dysprosium magnetism by steric control of photodimerization

Systematic control of the intermolecular pair-wise [4 + 4] photocycloaddition of a series of dysprosium phosphonates through fine-tuning of two different phosphonate ligands, one with a bidentate blocker and one with an anthracene antenna, both with alkyl substituents, reveals a size dependent rate. With bulky isopropyl on the diphosphonate blocker little response to UV light is observed. In contrast, compounds with ethyl which has less steric hindrance exhibit almost complete photocycloaddition. Interestingly, the alkyl substituents attached to anthracene monophosphonate have no evident effect on the reaction rate. Although no direct relationship can be found between the substitutions and the observed differences in field-induced single molecule magnetism, remarkable changes in magnetic dynamics are observed for complexes before and after the complete photocycloaddition reactions.