High-temperature cooperative spin crossover transitions and single-crystal reflection spectra of [Fe III (qsal) 2 ](CH 3 OSO 3 ) and related compounds

Kazuyuki Takahashi, Kaoru Yamamoto, Takashi Yamamoto, Yasuaki Einaga, Yoshihito Shiota, Kazunari Yoshizawa, Hatsumi Mori

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10 Citations (Scopus)


New Fe(III) compounds from qsal ligand, [Fe(qsal) 2 ](CH 3 OSO 3 ) (1) and [Fe(qsal) 2 ](CH 3 SO 3 )·CH 3 OH (3), along with known compound, [Fe(qsal) 2 ](CF 3 SO 3 ) (2), were obtained as large well-shaped crystals (Hqsal = N-(8-quinolyl)salicylaldimine). The compounds 1 and 2 were in the low-spin (LS) state at 300 K and exhibited a cooperative spin crossover (SCO) transition with a thermal hysteresis loop at higher temperatures, whereas 3 was in the high-spin (HS) state below 300 K. The optical conductivity spectra for 1 and 3 were calculated from the single-crystal reflection spectra, which were, to the best of our knowledge, the first optical conductivity spectra of SCO compounds. The absorption bands for the LS and HS [Fe(qsal) 2 ] cations were assigned by time-dependent density functional theory calculations. The crystal structures of 1 and 2 consisted of a common one-dimensional (1D) array of the [Fe(qsal) 2 ] cation, whereas that of 3 had an unusual 1D arrangement by π-stacking interactions which has never been reported. The crystal structures in the high-temperature phases for 1 and 2 indicate that large structural changes were triggered by the motion of counter anions. The comparison of the crystal structures of the known [Fe(qsal) 2 ] compounds suggests the significant role of a large non-spherical counter-anion or solvate molecule for the total lattice energy gain in the crystal of a charged complex.

Original languageEnglish
Article number81
Issue number2
Publication statusPublished - 2019


  • Counter-anion
  • Fe(III) complex
  • Lattice energy
  • Optical conductivity spectrum
  • Qsal ligand
  • Solvate
  • Spin crossover
  • Structure phase transition
  • Thermal hysteresis

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Inorganic Chemistry


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