Thermal- and Light-Induced Spin Crossover in Novel 2D Fe(II) Metalorganic Frameworks {Fe(4-PhPy)2[MII(CN)x]y}·sH2O: Spectroscopic, Structural, and Magnetic Studies

2009 ◽  
Vol 48 (13) ◽  
pp. 6130-6141 ◽  
Author(s):  
M. Seredyuk ◽  
A. B. Gaspar ◽  
V. Ksenofontov ◽  
M. Verdaguer ◽  
F. Villain ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Magnetic Studies ◽  
Metalorganic Frameworks

scholarly journals Solvent-Induced Hysteresis Loop in Anionic Spin Crossover (SCO) Isomorph Complexes

2021 ◽  
Vol 7 (6) ◽  
pp. 75
Author(s):  
Emmelyne Cuza ◽  
Samia Benmansour ◽  
Nathalie Cosquer ◽  
Françoise Conan ◽  
Carlos J. Gómez-García ◽  
...  
Keyword(s):  
Metal Ion ◽  
Spin Crossover ◽  
Magnetic Behaviour ◽  
Magnetic Studies ◽  
Tridentate Ligands ◽  
Tripodal Ligand ◽  
Single Crystal Structures ◽  
One Step ◽  
Lower Temperature ◽  
Step Transition

Reaction of Fe(II) with the tris-(pyridin-2-yl)ethoxymethane (py3C-OEt) tripodal ligand in the presence of the pseudohalide ancillary NCSe- (E = S, Se, BH3) ligand leads to the mononuclear complex [Fe(py3C-OEt)2][Fe(py3C-OEt)(NCSe)3]2·2CH3CN (3), which has been characterised as an isomorph of the two previously reported complexes, Fe(py3C-OEt)2][Fe(py3C-OEt)(NCE)3]2·2CH3CN, with E = S (1), BH3 (2). X-ray powder diffraction of the three complexes (1–3), associated with the previously reported single crystal structures of 1–2, revealed a monomeric isomorph structure for 3, formed by the spin crossover (SCO) anionic [Fe(py3C-OEt)(NCSe)3]− complex, associated with the low spin (LS) [Fe(py3C-OEt)2]2+ cationic complex and two solvent acetonitrile molecules. In the [Fe(py3C-OEt)2]2+ complex, the metal ion environment involves two py3C-OEt tridentate ligands, while the [Fe(py3C-OEt)(NCSe)3]− anion displays a hexacoordinated environment involving three N-donor atoms of one py3C-OEt ligand and three nitrogen atoms arising from the three (NCSe)− coligands. The magnetic studies for 3 performed in the temperature range 300-5-400 K, indicated the presence of a two-step SCO transition centred around 170 and 298 K, while when the sample was heated at 400 K until its complete desolvation, the magnetic behaviour of the high temperature transition (T1/2 = 298 K) shifted to a lower temperature until the two-step behaviour merged with a gradual one-step transition at ca. 216 K.

scholarly journals Spin Cross-Over (SCO) Complex Based on Unsymmetrical Functionalized Triazacyclononane Ligand: Structural Characterization and Magnetic Properties

2019 ◽  
Vol 5 (1) ◽  
pp. 19 ◽  
Author(s):  
Merzouk Halit ◽  
Mélissa Roger ◽  
Véronique Patinec ◽  
Said Yefsah ◽  
Carlos Gómez-García ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Magnetic Properties ◽  
Nmr Spectroscopy ◽  
Functional Groups ◽  
Structural Characterization ◽  
Spin Crossover ◽  
Magnetic Studies ◽  
Dsc Measurements ◽  
Hexadentate Ligand

The unsymmetrical ligand 1-(2-aminophenyl)-4,7-bis(pyridin-2-ylmethyl)-1,4,7-triazacyclononane (L6) has been prepared and characterized by NMR spectroscopy. The L6 ligand is based on the triazamacrocycle (tacn) ring that is functionalized by two flexible 2-pyridylmethyl and one rigid 2-aminophenyl groups. Reaction of this ligand with Fe(ClO4)2·xH2O led to the complex [Fe(L6)](ClO4)2 (1), which was characterized as the first Fe(II) complex based on the unsymmetrical N-functionalized tacn ligand. The crystal structure revealed a discrete monomeric [FeL6]2+ entity in which the unsymmetrical N-functionalized triazacyclononane molecule (L6) acts as hexadentate ligand. As observed in the few parent examples that are based on the symmetrical N-functionalized tacn ligands, the triazacyclononane ring is facially coordinated and the N-donor atoms of the three functional groups (two pyridine and one aniline groups) are disposed in the same side of the tacn ring, leading to a distorted FeN6 environment. The magnetic studies of 1 revealed the presence of an incomplete spin crossover (SCO) transition above 425 K, whose progress would be prevented by a very exothermic thermal decomposition at ca. 472 K, as shown by thermogravimetric and DSC measurements.

Structure and Magnetic Studies on a Series of Two-Dimensional Iron(II) Framework Materials with Varying Ligand Characteristics

2017 ◽  
Vol 70 (5) ◽  
pp. 623 ◽  
Author(s):  
Matthew A. D. Roxburgh ◽  
Samantha Zaiter ◽  
Xina I. B. Hudson ◽  
Benjamin R. Mullaney ◽  
John E. Clements ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Large Family ◽  
Structural Motif ◽  
Magnetic Studies ◽  
Bridging Ligands ◽  
Coordination Environment ◽  
Pyridyl Ligands ◽  
Framework Materials ◽  
Grid Topology ◽  
Varying Length

Targeting the general (4,4)-grid structural motif, we have prepared seven new coordination polymers in the general family [Fe(NCX)2(L)2]·(guest) (L = bis-pyridyl-type bridging ligands; X = S, Se) as an extension of the well-established spin crossover framework (SCOF) family. In all cases, the (4,4)-grid topology is formed by the bridging of octahedral iron(ii) sites in the equatorial plane by bis-pyridyl ligands of varying length, flexibility, and intermolecular interaction capacity. In particular, the six ligands n-(4-pyridyl)-isonicotinamide (pin), trans-1,2-bis(4′-pyridyl)ethane (tvp), 1,2-dibromo-1,2-bis(4′-pyridyl)ethane (dbbpe), bis(4-pyridyl)-1,2,4,5-tetrazine (bptz), 4,4′-bis(pyridyl)acetylene (bpac), and 1,4-bis(4-pyridylethynyl)benzene (bpeben) have been utilised. The seven new materials [Fe(NCS)2(pin)2]·2(MeCN) (pin-S), [Fe(tvp)2(NCS)2]·1/2(tvp)·(CH3CH2OH) (tvp-S), [Fe(dbbpe)2(NCS)2]·6(CH3CN) (dbbpe-S), [Fe(NCS)2(bptz)2]·2(CHCl3)·6(EtOH) (bptz-S), [Fe(NCSe)2(bptz)2]·4(CHCl3)·(EtOH)·(H2O) (bptz-Se), [Fe(NCS)2(bpac)2]·2(PrOH) (bpac-S), and [Fe(NCS)2(bpeben)2]·2(CHCl3) (bpeben-S) all form (4,4)-grids of varying size that are arranged in a parallel stacked topology. Despite being in the [FeN6] coordination environment known to be conducive to spin crossover, these materials all remain high-spin with thermal variation. These results are discussed in context with the large family of SCOFs that show varied spin crossover behaviours.

scholarly journals Solvent-Induced Hysteresis Loop in Anionic Spin Crossover (SCO) Isomorph Complexes

2021 ◽  
Author(s):  
Emmelyne Cuza ◽  
Samia Benmansour ◽  
Nathalie Cosquer ◽  
Francoise Conan ◽  
Carlos J. Gómez-García ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Magnetic Studies ◽  
Tridentate Ligands ◽  
Tripodal Ligand ◽  
X Ray ◽  
Mononuclear Complexes ◽  
One Step ◽  
Step Transition ◽  
Heating Up ◽  
Crystal Characterizations

Reactions of Fe(II) with the tris-(pyridin-2-yl)ethoxymethane (py3C-OEt) tripodal ligand in presence of the pseudohalide ancillary NCE- (E = S, Se, BH3) ligands led to a series of three mononuclear complexes formulated as [Fe(py3C-OEt)2][Fe(py3C-OEt)(NCE)3]2·2CH3CN, with E = S (1), BH3 (2) and Se (3). Single crystal characterizations (complexes 1-2) and X-ray powder diffraction (complexes 1-3) reveal monomeric isomorph structures formed by the spin crossover (SCO) anionic [Fe(py3C-OEt)(NCE)3] complex, associated with the low spin (LS) cationic [Fe(py3C-OEt)2]2+ complex and two solvent acetonitrile molecules. In the [Fe(py3C-OEt)2]2+ cation, the Fe(II) is coordinated by two py3C-OEt tridentate ligands, while the [Fe(py3C-OEt)(NCE)3] anion displays a hexacoordinated environment involving three N-donor atoms of one py3C-OEt ligand and three nitrogen atoms arising from of the three (NCE) coligands. The magnetic studies show the presence of gradual SCO behavior for the three complexes: a one-step transition around 205 K for 1 and two step-transitions for compounds 2 and 3, centred at 245 K and 380 K for 2, and at 170 K and 298 K for 3. The magnetic behaviors of complexes 1 and 2 remain unchanged when heating up to 500 K, while complex 3 shows significant changes which are caused by the crystallisation solvent loss above room temperature.

Non-isothermal kinetics of spin crossover

2017 ◽  
Vol 19 (26) ◽  
pp. 16955-16959 ◽  
Author(s):  
Mark B. Bushuev ◽  
Elena B. Nikolaenkova ◽  
Viktor P. Krivopalov
Keyword(s):  
Activation Energy ◽  
Spin Crossover ◽  
Spin Transition ◽  
Isothermal Kinetics ◽  
Magnetic Studies ◽  
Kinetics Of

Non-isothermal magnetic studies can be used to estimate the activation energy of cooperative spin transition.

scholarly journals Iron(III) Azadiphenolate Compounds in a New Family of Spin Crossover Iron(II)–Iron(III) Mixed-Valent Complexes

2019 ◽  
Vol 5 (2) ◽  
pp. 37 ◽  
Author(s):  
Wasinee Phonsri ◽  
David S. Macedo ◽  
Barnaby A. I. Lewis ◽  
Declan F. Wain ◽  
Keith S. Murray
Keyword(s):  
Crystal Structures ◽  
Spin Crossover ◽  
Crystal Packing ◽  
Spin Transition ◽  
Double Salt ◽  
Magnetic Studies ◽  
Cationic Precursor ◽  
New Family ◽  
Double Spin ◽  
Crystal Design

A new family of mixed valent, double salt spin crossover compounds containing anionic FeIII and cationic FeII compounds i.e., [FeII{(pz)3CH}2][FeIII(azp)2]2·2H2O (4), [FeII(TPPZ)2][FeIII(azp)2]2]·H2O (5) and [FeII(TPPZ)2][FeIII(azp)2]2]·H2O·3MeCN (6) (where (pz)3CH = tris-pyrazolylmethane, TPPZ = 2,3,5,6, tetrapyridylpyrazine and azp2− = azadiphenolato) has been synthesized and characterised. This is the first time that the rare anionic spin crossover species, [FeIII(azp)2]−, has been used as an anionic component in double salts complexes. Single crystal structures and magnetic studies showed that compound 6 exhibits a spin transition relating to one of the FeIII centres of the constituent FeII and FeIII sites. Crystal structures of the anionic and cationic precursor complexes were also analysed and compared to the double salt products thus providing a clearer picture for future crystal design in double spin crossover materials. We discuss the effects that the solvent and counterion had on the crystal packing and spin crossover properties.

Steric Trapping of the High Spin State in FeIII Quinolylsalicylaldimine Complexes

2014 ◽  
Vol 67 (11) ◽  
pp. 1574 ◽  
Author(s):  
Darunee Sertphon ◽  
David J. Harding ◽  
Phimphaka Harding ◽  
Keith S. Murray ◽  
Boujemaa Moubaraki ◽  
...  
Keyword(s):  
Schiff Base ◽  
Electronic Properties ◽  
High Spin ◽  
Spin State ◽  
Schiff Base Ligand ◽  
Room Temperature ◽  
Spin Crossover ◽  
High Spin State ◽  
Electrochemical Studies ◽  
Magnetic Studies

A new sterically bulky Schiff base ligand, N-(8-quinolyl)-5-tert-butylsalicylaldimine (Hqsal-5-tBu) has been prepared and a series of FeIII complexes, [Fe(qsal-5-tBu)2]Y (Y = Cl 1, ClO4 2, NO3 3, BF4 4) utilising this ligand are reported and fully characterised. UV-vis spectroscopic and electrochemical studies indicate that 1–4 are high spin (HS) in solution at room temperature and further suggest that the tBu group only slightly alters the electronic properties of 1–4 compared with related [Fe(qsal-5-X)2]+ systems. The structures of [Fe(qsal-5-tBu)2]Cl·4MeOH·H2O 1, [Fe(qsal-5-tBu)2]ClO4·MeOH 2, and [Fe(qsal-5-tBu)2]NO3 3 determined at 100 K reveal HS FeIII centres in all cases. Four-fold parallel aryl embraces and π–π interactions serve to link the cations forming 2D sheets mirroring the motifs found in other [Fe(qsal-5-X)2]+ complexes. Despite this the tBu group causes strong distortions at the Fe centre which as magnetic studies reveal prevent spin crossover trapping 1–4 in the HS state.

Spin crossover behaviour in the iron(II)-2,2-dipyridilamine system: Synthesis, X-ray structure and magnetic studies

2005 ◽  
Vol 358 (13) ◽  
pp. 4089-4094 ◽  
Author(s):  
A.B. Gaspar ◽  
G. Agustí ◽  
V. Martínez ◽  
M.C. Muñoz ◽  
G. Levchenko ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Magnetic Studies ◽  
System Synthesis ◽  
X Ray

Thermal and Light-Induced Spin Crossover Phenomena in New 3D Hofmann-Like Microporous Metalorganic Frameworks Produced As Bulk Materials and Nanopatterned Thin Films

2008 ◽  
Vol 20 (21) ◽  
pp. 6721-6732 ◽  
Author(s):  
Gloria Agustí ◽  
Saioa Cobo ◽  
Ana B. Gaspar ◽  
Gábor Molnár ◽  
Nawel Ould Moussa ◽  
...  
Keyword(s):  
Thin Films ◽  
Spin Crossover ◽  
Bulk Materials ◽  
Metalorganic Frameworks

Kinetics of spin crossover with thermal hysteresis

2018 ◽  
Vol 20 (8) ◽  
pp. 5586-5590 ◽  
Author(s):  
Mark B. Bushuev
Keyword(s):  
Spin Crossover ◽  
Thermal Hysteresis ◽  
Spin Transition ◽  
Reaction Model ◽  
Magnetic Studies ◽  
Kinetics Of

Non-isothermal magnetic studies allow establishing a reaction model of hysteretic spin transition.

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