Coexistence of spin crossover and magnetic ordering in a dendrimeric Fe(III) complex

Vorobeva, V.E.; Domracheva, N. E.; Pyataev, A. V.; Груздев, М. С.; Chervonova, U. V.

doi:10.1063/1.4906311

Cited by 11 publications

(5 citation statements)

References 15 publications

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“…At 300 K, complexes 2·MeOH , 4 , and 5 exhibit a spectral feature which indicates a Fe(III) high-spin system with a strong ( D > h ν = 0.3 cm –1 ) low-symmetric ( E / D ∼1/3) crystal field environment . At 350 K, the EPR spectra of complexes 1 and 3·H 2 O show broadened doublet spectra around g ∼ 2 and a low field signal arises, which indicates the presence of high-spin Fe(III) species, which is in line with their solid-state magnetic data, and which shows that after 300 K both the complexes undergo SCO. At 400 K, EPR spectra of both complexes 1 and 3·H 2 O completely change and match closely with the spectra of complexes 2·MeOH , 4 , and 5 which indicates that at 400 K complexes 1 and 3·H 2 O are fully converted to high-spin states .…”

Section: Resultssupporting

confidence: 71%

Steric Effects on Spin States in a Series of Fe(III) Complexes

Dey

Cirera

Mehta

et al. 2023

Crystal Growth & Design

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Spin crossover (SCO) is very sensitive toward electronic and steric effects. The latter can lead to a distorted structure, which in turn can change the electronic properties of the complex possibly leading to a change in the spin state. Herein, we investigated the steric effects of the ligand substituents on the structure and magnetic properties of Fe(III) complexes by applying two different ligand systems. We chose the less bulky Nmethylethylenediamine and the bulkier N-phenylethylenediamine and coupled them with 3-methoxysalicylaldehyde affording HL1− HL2, while coupling with 3-ethoxysalicylaldehyde afforded HL3−HL4. Complexes [Fe(L1) 2 ]NCSe (1) and [Fe(L3) 2 ]•NCSe•H 2 O (3•H 2 O) formed with the less bulky ligand exhibit SCO behavior, while complexes [Fe(L2) 2 NCSe]•MeOH (2•MeOH), [Fe(L4) 2 NCSe] (4), and [Fe(L4) 2 NCS] ( 5) formed with the bulkier amine stay in the high-spin state. The effect of the bound anion was also investigated for complexes 4 and 5. Both experimental and theoretical methods were employed to understand the observed behavior.

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Section: Resultssupporting

confidence: 71%

Steric Effects on Spin States in a Series of Fe(III) Complexes

Dey

Cirera

Mehta

et al. 2023

Crystal Growth & Design

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“…At the highest temperature (380 K) two new peaks are observed at g 1 =9.29 and g 2 =3.78 along with an isotropic peak at g iso =2, these signals correspond to Fe(III) high spin center with high rhombicity (E/D∼0.33) . It is important to note that separate observation of high spin and low spin signals in the same spectrum is an indication that the rate of spin state conversion is much slower than the frequency of EPR spectroscopy measurement (∼10 10 S −1 in X‐band) …”

Section: Resultsmentioning

confidence: 93%

Effect of Ligand Field Strength on the Spin Crossover Behaviour in 5‐X‐SalEen (X=Me, Br and OMe) Based Fe(III) Complexes

Dey

Mondal

Konar

2020

Chemistry An Asian Journal

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The reaction of Fe(NCS) 3 prepared in situ in MeOH with 5-X-SalEen ligands (5-X-SalEen = condensation product of 5-substituted salicylaldehyde and N-ethylethylenediamine) provided three Fe(III) complexes, [Fe(5-X-SalEen) 2 ]NCS; X=Me (1), X=Br (2), X=OMe (3). All the complexes reveal similar structural features but a very different magnetic profile. Complex 1 shows a gradual spin crossover while complexes 2 and 3 show a sharp spin transition. The T 1/2 for complex 2 is 237 K while for complex 3 it is much higher with a value of 361 K. The spin transition temperature is shifted towards higher temperature with increasing electron-donation ability of the ligand substituents. This experimental observation has been rationalized with DFT calculations. UV-Vis and cyclic voltammetry studies support the fact that the electron density on the ligand increases from Me to Br to OMe substituents. To understand the change in spin states, temperature-dependent EPR spectra have been recorded. The spin state equilibrium in the liquid state has been probed with Evans NMR spectroscopic method, and thermodynamic parameters have been evaluated for all complexes.

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“…Antiferromagnetic exchange interactions between LS-LS, LS-HS and HS-HS centers are observed in the temperature range between 4.2 -50 K, magnetoelectric behavior is likely to occur in the range of 50 -200 K and finally, spin-transition from the LS to the HS state was detected in the third temperature range between 200 and 330 K. Another series of dendronized SCO [(FeL 2 )PF 6 ] complexes was developed in the same group, with the same core structure whereas the terminal groups were now long alkyl chains (-OC14H29), giving a more complete dendritic structure, with various counter-anions. [100][101][102] The authors enriched the studies of the magnetic properties of the dendrimeric materials using also magnetometry together with EPR and Mössbauer spectroscopies. The EPR spectra of the PF6and Clcomplexes show the presence of three different magnetic iron species (two HS and one LS); while for the ClO4only one HS and LS iron center is observed.…”

Section: Sco Dendrimersmentioning

confidence: 99%

Spin crossover polymer composites, polymers and related soft materials

Enríquez-Cabrera

Rapakousiou

Piedrahita‐Bello

et al. 2020

Coordination Chemistry Reviews

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We review the synthesis, properties and applications of spin crossover polymer composites, polymers and some related 'soft' materials. These materials have received recently much attention because they provide an efficient way for the processing of spin crossover complexes in various shapes at various size scales and can give rise also to unique physical properties. First, we discuss in detail the state of the art of the elaboration of spin crossover polymer composites, using either inorganic complex precursors in solution or pre-formed spin crossover powder. A particular attention is paid on the influence of the polymer matrix on the spin crossover properties and on the use of 'active' polymers for development of synergies between the properties of the matrix and the load. Polymer composite devices for applications in the fields of artificial muscles, energy harvesting and thermochromic sensors are also highlighted. Then, more recent works, in which organic polymeric chains are used as ligands for the transition metal ions are presented. Finally, we overview various related 'soft' spin crossover compounds including spin crossover dendrimers, gels, liquid crystals and Langmuir Blodgett films with particular emphasis on compounds with supramolecular interactions of alkyl chains.

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Coexistence of spin crossover and magnetic ordering in a dendrimeric Fe(III) complex

Cited by 11 publications

References 15 publications

Steric Effects on Spin States in a Series of Fe(III) Complexes

Steric Effects on Spin States in a Series of Fe(III) Complexes

Effect of Ligand Field Strength on the Spin Crossover Behaviour in 5‐X‐SalEen (X=Me, Br and OMe) Based Fe(III) Complexes

Spin crossover polymer composites, polymers and related soft materials

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