Spin-transition in nearly cubic site in [FeII(L)3][PF6]2

Abstract

The spin-transition (1A1 ↔ 5T2) behaviour of a new mononuclear iron(II) compound [FeII(L)3][PF6]2[L = 2-[3-(2´-pyridyl)pyrazole-1-ylmethyl]pyridine] has been investigated by 57Fe Mössbauer spectroscopy. Analysis of the Mössbauer spectra revealed low value of the quadrupole splitting of the high-spin state which reflects iron(II) to be in nearly cubic lattice site. Mössbauer spectra under light show the light-induced excited spin state trapping effect and the observed quadrupole splitting of the metastable high-spin state is found little sensitive to the high-spin fraction value. DFT calculations are in progress to document the almost cubic nature of the ligand-field acting on the iron atom

Spin State Crossover, Vibrational, Computational, and Structural Studies of FeII 1‐Isopropyl‐1H‐tetrazole Derivatives

“…We recall that Δ T 80 represents the temperature range over which 80 % of the active Fe spins are switched , . Around 60 K, χ M T increases slightly before decreasing, a behavior characteristic of spin freezing, as found for [FeL 3 ](PF 6 ) 2 with L = 2‐[3‐(2′‐pyridyl)pyrazole‐1‐ylmethyl]pyridine in the same temperature range . On cooling further, a gradual decrease in χ M T is observed before dropping down below 25 K due to the zero‐field splitting effect of the remaining HS Fe II ions.…”

“…[46,47] Around 60 K, M T increases slightly before decreasing, a behavior characteristic of spin freezing, as found for [FeL 3 ](PF 6 ) 2 with L = 2-[3-(2′-pyridyl)pyrazole-1-ylmethyl]pyridine in the same temperature range. [48] On cooling further, a gradual decrease in M T is observed before dropping down below 25 K due to the zero-field splitting effect of the remaining HS Fe II ions. The transition temperatures T 1/2 were evaluated at 105 K and 85 K for 1 and 2, respectively.…”

Spin Crossover Behavior in a Homologous Series of Iron(II) Complexes Based on Functionalized Bipyridyl Ligands

“…On warming, no hysteresis loop is detected but a small decrease of the χ M T product on warming is noticed, just before the transition temperature of 77K. This behaviour presumably calls for a freezing-in effect27 , that hinders further the spin conversion. 57 Fe Mössbauer spectroscopy (vide infra), carried out on the same sample batch, confirms the incomplete character of the SCO behaviour with ca.…”

Spin-transition in [FeII(L5)2][ClO4]2 [L5 = 2-[3-(2′-pyridyl)pyrazol-1-ylmethyl](1-methylimidazole)]: a further example of coexistence of features typical for disorder and cooperativity

“…6. Afterwards, relaxation occurred rapidly with a stretched exponential character typical of a distribution of relaxation rates which are better shown in the following figures (8,9). We analyzed the data with the non-cooperative model previously used for compound 1•H 2 O.…”

“…4,5 This study stems from our continued interest in the design of new SC systems by tuning the ligand-field strength of the tridentate heterocyclic chelating ligands (Scheme 1), based on their electronic as well as steric properties. [7][8][9] Understandably, the ligand modification is the most predictable approach to tuning SC properties. 10 The present work was undertaken mainly to study the influence of modification of the pyridine-pyrazole family of ligand systems with a new ligand L 5 , containing three different heterocyclic rings (pyridyl, pyrazole and imidazole), on the spin-transition of its Fe II bis(ligand) complex.…”