Hysteresis Photomodulation via Single-Crystal-to-Single-Crystal Isomerization of a Photochromic Chain of Dysprosium Single-Molecule Magnets

A one-dimensional
coordination solid 1c is synthesized by reaction
of a bispyridyl dithienylethene (DTE)
photochromic unit with the highly anisotropic dysprosium-based single-molecule
magnet [Dy­(Tppy)­F­(pyridine)2]­PF6.
Slow magnetic relaxation characteristics are retained in the chain
compound 1c, and photoisomerization of
the bridging DTE ligand induces a single-crystal-to-single-crystal
transformation that can be monitored using photocrystallography. Notably,
the resulting chain compound 1o exhibits faster
low-temperature relaxation than that of 1c, which is apparent in magnetic hysteresis data collected for both
compounds as high as 4 K. Ab initio calculations suggest that this
photomodulation of the magnetic relaxation behavior is due to crystal
packing changes rather than changes to the crystal field splitting
upon ligand isomerization.