Solid polymorphism and dynamic magnetic properties of a dodecylated vanadyl-porphyrinato complex: spin-lattice relaxations modulated by phase stabilisation

The dynamic magnetic behavior of metal complexes correlates with their phonon modes, which depend on solid polymorphs. However, no systematic study has revealed the correlation between solid phases and spin-lattice relaxation. Herein, we report the magnetism of a VO2+-porphyrinato complex that contains dodecyl chains (1). Owing to the flexibility of the molecular structure, we successfully isolated the metastable crystalline phase 1m, the glass phase 1g and the stable crystalline phase 1s. Although the chemical compositions of the three phases are the same, 1s with the lowest entropy exhibited the longest magnetic relaxation time. Our results suggest that (1) phase stabilization is an effective method for elongating the spin-lattice relaxation time and (2) spin-lattice relaxation correlates with the entropy of the solid.