Search results for "LIESST"

Metastable electronic states induced by nuclear decay and light

1994

Radioactive atoms incorporated in insulating solid-state compounds create various kinds of chemical and physical “after-effects” upon nuclear disintegration. Mossbauer emission spectroscopy of57Co-labelled coordination compounds has undoubtedly become the most informative technique to detect such after-effects like aliovalent charge and spin states of the nucleogenic iron atom resulting from the57Co(EC)57Fe decay, low energy excitations of crystal field and Zeeman states, linkage isomerism, radical formation with subsequent redox reactions, and others. We have extensively studied57Co-labelled complexes with [CoIIN6] cores employing time-integral and time-resolved Mossbauer emission spectros…

Stimuli responsive hybrid magnets : tuning the photoinduced spin-crossover in Fe(III) complexes inserted into layered magnets

2013

The insertion of a [Fe(sal_2 trien)]^+ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin crossover (LIESST effect) in compounds [Fe^{III}(sal_2 trien)][Mn^{II}Cr^{III}(ox)_3]·CHCl_3 (1·CHCl_{3}) [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CHBr_{3} (1·CHBr_{3}) and [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CH_{2}Br_{2} (1·CH_{2}Br_{2}). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^{II} and Cr^{III} ions linked through oxalate ligands and a layer of [Fe(sal_{2} trien)]^{+} complexes and solvent molecules (CHCl_{3} CHBr_{…

Thermo- and photo-modulation of exciplex fluorescence in a 3D spin crossover Hofmann-type coordination polymer

2018

[EN] The search for bifunctional materials showing synergies between spin crossover (SCO) and luminescence has attracted substantial interest since they could be promising platforms for new switching electronic and optical technologies. In this context, we present the first three-dimensional Fe-II Hofmann-type coordination polymer exhibiting SCO properties and luminescence. The complex {Fe-II(bpben)[Au(CN)(2)]}@pyr (bpben = 1,4-bis(4-pyridyl)benzene) functionalized with pyrene (pyr) guests undergoes a cooperative multi-step SCO, which has been investigated by single crystal X-ray diffraction, single crystal UV-Vis absorption spectroscopy, and magnetic and calorimetric measurements. The resu…

Spin crossover in iron(II)-complexes

2007

Photo-switching spin pairs—synergy between LIESST effect and magnetic interaction in an iron(ii) binuclear spin-crossover compound

2001

The decrease of the magnetic response under irradiation at very low temperature was interpreted as a new evidence of synergy between magnetic interaction and spin transition in an iron(II) binuclear SC compound. Real Cabezos, Jose Antonio, Jose.A.Real@uv.es

X-ray powder diffraction and LIESST-effect of the spin transition material [Fe(bpp)2](NCS)2·2H2O

2006

Abstract We have studied the X-ray powder diffraction of the spin transition material [Fe(bpp)2](NCS)2 · 2H2O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) at room temperature. Two crystallographic phases have been observed depending on the sample history of this material. The results obtained corroborate the earlier observations from magnetic and calorimetric studies. Relatively prolonged exposure of the sample to X-rays caused a structural change. LIESST and Reverse-LIESST effects, characterised by 57Fe Mossbauer spectroscopy, have been observed in this material.

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2(bpym)}

2007

Using Fourier transform infrared spectroscopy, x-ray diffraction, and magnetic susceptibility measurements under light irradiation, the selective light-induced excited spin state trapping (LIESST) and the reversible-LIESST effect have been evidenced and studied in depth in the binuclear spin crossover compound {[Fe(bt)(NCS)2]2bpym}. In this system, each magnetic site can switch from low spin (LS) to high spin (HS), so that three states exist, namely, the LS-LS, HS-LS, and HS-HS. All these techniques shine a new light on the high phototunability of this system. In addition to the direct photoswitching from the LS-LS to the HS-LS or to the HS-HS state, here we show that photoinduced switching…

LIESST Effect in Fe(II) 1,2,4-Triazole Chains

2016

One-dimensional Fe(II) chains with 1,2,4-triazole as bridging ligands present the LIESST effect; i.e. their spin state switched from low-spin to high-spin after light irradiation at low temperature. This account summarizes the findings in this area of photomagnetism where 57Fe Mossbauer spectroscopy was used as a primary detection tool of the LIESST effect.

Bimetallic MnIII–FeII hybrid complexes formed by a functionalized MnIII Anderson polyoxometalate coordinated to FeII: observation of a field-induced …

2015

The synthesis and crystal structure of an Anderson POM functionalized with two 2,6-di(pyrazol-1-yl)-pyridine (1-bpp) ligands are reported (compound 1). High-frequency electron paramagnetic resonance (HF-EPR) and magnetic measurements show that it presents a significant negative axial zero-field splitting and field-induced slow relaxation of magnetization due to the presence of isolated MnIII anisotropic magnetic ions. Complexation of 1 with FeII gives rise to a 2D cationic network formed by Anderson POMs coordinated to two FeII ions through the two tridentate 1-bpp ligands and to other two FeII ions through two oxo ligands in compound 2, and to an anionic polymeric network formed by Anderso…

Fascinating electronic games in iron complexes

1996

Coordination compounds of transition metal ions with open-shell electron configurations may exhibit dynamic electronic-structure phenomena, depending on the nature of the coordinating ligand sphere. The change of spin state with temperature («thermal spin-crossover»), light-induced electron transfer processes leading to long-lived metastable charge and spin states (e.g., «LIESST» effect), are some of the fascinating electronic games encountered in transition metal compounds, which are presently under extensive study by chemists and physicists. Mossbauer spectroscopy plays a dominant role in the investigation of such phenomena in iron compounds, as will be demonstrated in this paper. This wo…