Anomalous pressure dependence of the Lamb-Mössbauer factor in a spin crossover system

The dependence of the f-factor on temperature and on pressure up to 1500 bar has been measured in the spin crossover compound [Fe(2-pic-ND2)3]cl2·EtOD. In the transition region around Tc=146.7 K the pressure dependence of f shows an anomalous increase, which can be explained on the basis of a theoretical model for spin transitions developed by us.

Quadrupole splitting of Fe(II) spin crossover compounds study of temperature and pressure dependence and the implication for the interaction mechanism

The temperature and pressure dependence of the quadrupole splitting ΔE Q of the 3/2→1/2 nuclear Mossbauer transition of57Fe in the spin crossover compounds [Fe x Zn1−x (2-pic)3]Cl2⋆EtOH and the deuterated analog [Fe x Zn1−x (2-pic-ND2)3] Cl2⋆EtOD (2-pic=2-picolylamine) have been studied. The change of ΔE Q can be linearly related to the defomation of the lattice as observed by X-ray measurements. The dependence of ΔE Q on temperatureT, pressurep, and the fraction γ of molecules in the electronic high spin state in the pure iron (x=1) compounds is therefore interpreted as a result of the change of the lattice contribution to the electric field gradient (EFG) at the nucleus only. The intrinsi…

Mössbauer effect study of the electronic ground state of iron(II) in [57FexM1−x(bipy)3](ClO4)2 (M = Mn, Ni, Zn) and [57FexM1−x(phen)3](ClO4)2 (M = Ni, Zn) at very lowiron concentrations

Earlier work in our laboratory on the effect of metal dilution on the 5T2(Oh ⇌ 1A1(Oh) equilibrium in polycrystalline spin crossover systems of iron(II) has shown that the relative stability of the high spin state, 5T2(Oh), at a given temperature, increases markedly with decreasing iron concentration. These results have initiated the present work. Using 57Fe Mossbauer spectroscopy, we have investigated the electronic ground state of iron(II) in the highly diluted solid solutions [FexM1−xL3] with L = bipy, M = Mn, Ni, Zn, x ≲ 0.005 and L = phen, M = Ni, Zn, x ≲ 0.005. Although the critical field potential (Vc) of the pure iron complexes, which are known to be low spin, is reported to be not …

57Fe- MÖSSBAUER EMISSION SPECTROSCOPY OF AN IRON (II) COMPLEX WITH TEMPERATURE DEPENDENT SPIN STATE

The effect of low pressure on a high-spin—low-spin transition

Abstract The effect of low pressure ( p = 150 bar) on the high-spin (HS)—low-spin (LS) transition in [Fe x Zn 1− x (2-pic) 3 ]Cl 2 · EtOH ( x = 0.5, 1.0) was measured by Mossbauer spectroscopy and the results compared with theory. The linear dependence of the volume of the lattice on the HS fraction, which is the basic assumption of the theory, was proven by temperature dependent X-ray measurements.

Anomalous pressure dependence of the Lamb-Mössbauerf-factor in the spin crossover system [Fe(2-pic-ND2)3]Cl2·EtOD

The pressure dependence of the Lamb-Mossbauer factor of the spin crossover compound [Fe(2-pic-ND2)3]Cl2·EtOD(2-pic-ND2=2-picolylamine, deuterated at the−NH2 group) has been measured at pressures up to 1500 bar and at three temperatures (115.7, 146.7, 185.6 K) around the transition temperatureT t=135 K. The temperature dependence of the unit cell volume has been determined by X-ray diffraction. In the transition region (T=146.7 K), the pressure dependence of thef-factor shows an anomalous increase as compared to the dependence below and above the transition. The behaviour off(p, T), its anomaly and absolute value, can be consistently explained within a theoretical model which treats the comp…