Mesophase and magnetic behavior in cobalt(II) and iron(II) compounds

The metal complexes with long alkyl chains [Co(C16-terpy)3](BF4)2 (1) and [Fe(C16-terpy)2](BF4)2 (2) were synthesized and the physical properties of the complex were characterized by magnetic susceptibility, Mössbauer spectroscopy, polarizing optical microscopy, differential scanning calorimetry, and X-ray scattering, where C16-terpy is 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine. Variable-temperature magnetic susceptibility measurements and/or Mössbauer studies revealed that the complex 1 exhibited unique spin transition (T1/2↓ = 217 K and T1/2↑ = 260 K) induced by structural phase transition, and the complex 2 was in the low-spin state in the temperature region of 5–400 K before the first mesophase transition. The cobalt(II) and iron(II) complexes exhibited liquid-crystal properties in the temperature range of 371–528 K and 466–556 K, respectively. After mesophase transition, the complex 1 exhibited only slight spin transition (T1/2↓ = 266 K and T1/2↑ = 279 K), and the complex 2 was in the low-spin state. The compounds with multifunction, i.e., magnetic property and liquid-crystal properties, are important in the development of molecular materials.

The metal complexes with long alkyl chains [Co(C16-terpy)3](BF4)2 (1) and [Fe(C16-terpy)2](BF4)2 (2) were synthesized and the physical properties of the complex were characterized. The complex 1 exhibited unique spin transition (T1/2↓ = 217 K and T1/2↑ = 260 K) induced by structural phase transition, and the complex 2 was in the low-spin state in the temperature region of 5–400 K before the first mesophase transition. The compound 1 exhibited mesophase transitions, K to SmE at 371 K, SmE to SmC at 430 K, SmC to SmA at 511 K, and the compound 2 also exhibited mesophase transitions, K3 to DL2 at 466 K. After mesophase transition, the complex 1 exhibited only slight spin transition (T1/2↓ = 266 K and T1/2↑ = 279 K), and the complex 2 was in the low-spin state. The compounds with multifunction, i.e., magnetic property and liquid-crystal properties, are important in the development of molecular materials.Figure optionsDownload as PowerPoint slide