0000000000146801
AUTHOR
Miroslav Boča
Spin crossover in iron(II) tris(2-(2′-pyridyl)benzimidazole) complex monitored by variable temperature methods: synchrotron powder diffraction, DSC, IR spectra, Mössbauer spectra, and magnetic susceptibility
Abstract The thermal expansion of the spin crossover system [Fe(pybzim) 3 ](ClO 4 ) 2 · H 2 O (pybzim=2-(2 ′ -pyridyl)benzimidazole) has been determined from powder X-ray data between 50 and 250 K; the wavelength of the synchrotron source was 1.21888(1) A. The unit cell parameters of the triclinic crystal system were a =12.091 A, b =12.225 A, c =14.083 A, α =77.70°, β =80.35°, γ =74.35°, and V =1944.9 A 3 at 250 K. In addition to the linear thermal expansion of the unit cell volume, an extra expansion due to the low-spin (LS) to high-spin (HS) transition is observed. The V ( T ) function shows a sudden increase comparable with the step in the effective magnetic moment at the transition reg…
Tuning the spin crossover above room temperature: iron(II) complexes of substituted and deprotonated 2,6-bis(benzimidazol-2-yl)pyridine
Abstract The complex [Fe(tzimpy)2](ClO4)2 · 2H2O (tzimpy = 2,4,6-tris-(benzimidazol-2-yl)pyridine) shows an abrupt spin crossover (S = 0–2 transition) above room temperature centered at Tc = 323 K with a hysteresis width of ΔT = 35 K. The neutral iron(II) complex with deprotonated bzimpy ligands (bzimpy = 2,6-bis(benzimidazol-2-yl)pyridine) exhibits a gradual spin transition on the first heating with Tc = 424 K. There are irreversible changes between T = 503 and 523 K: the liberation of the crystal water, the color change (blue–green) followed by a structure change. Next thermal cycles are reproducible though, heating/cooling paths are different from the first heating.
Structure of the copper (II) perchlorate complex with Schiff base ligand containing pyridine N-oxide fragments and propylene bridges: Solvatochromic effect
Abstract The copper (II) perchlorate complexes with Schiff base ligands were investigated by X-ray single crystal analysis, electron spectroscopy, infrared and electron paramagnetic spectroscopy. The Schiff bases were obtained as condensation products of 2-pyridinecarboxaldehyde N-oxide with dipropylenetriamine (L1) and triethylenetetramine (L3), respectively. The structure of the complex [CuL2](ClO4)2 was solved. In the structure, the ligand exists in the form of aliphatic polyamine containing two Schiff bases in contrary to the free form of this ligand with one pyrimidine ring and one Schiff base. Electronic spectra of the copper (II) perchlorate complexes of both ligands in different sol…