Temperature-Induced Single-Crystal-to-Single-Crystal Transformations with Consequential Changes in the Magnetic Properties of Fe(III) Complexes

The present article
deals with an one-to-one structure–property
correspondence of a dinuclear iron complex, [Dipic­(H2O)­FeOH]2·H2O (1) (Dipic = pyridine-2,6-dicarboxylic
acid). Variable-temperature X-ray single-crystal structural analysis
confirms a phase transition of complex 1 to complex 2 ([Dipic­(H2O)­FeOH]2) at 120 °C.
Further, single-crystal-to-single-crystal (SCSC) transformation was
monitored by temperature-dependent single crystal X-ray diffraction,
powder X-ray diffraction, time-dependent Fourier-transform infrared
spectroscopy, and differential scanning calorimetry. SCSC transformation
brings the change in space group of single crystal. Complex 1 crystallizes in the C2/c space group, whereas complex 2 crystallizes in the Pi̅ space group. SCSC transformation brings the change
in packing diagram as well. Complex 1 shows two-dimensional
network through H-bonding, whereas the packing diagram of complex 2 shows a zigzag-like arrangement. Phase transformation not
only fetches structural changes but also in the magnetic properties.
Difference in Fe–O–Fe bond angles of two complexes creates
notable variation in their antiferromagnetic interactions with adjacent
metal centers.