Spin-State Ordering on One Sub-lattice of a Mononuclear Iron(III) Spin Crossover Complex Exhibiting LIESST and TIESST

The thermally induced Spin-CrossOver (SCO) undergone by the mononuclear iron(ii) complex [Fe(PM-AzA)2(NCS)2] (PM = N-2′-pyridylmethylene, AzA = 4-(phenylazo)aniline) is fully pictured by a quasi-continuous structural determination all along the spin-state modification within the sample.

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Structural Evidence of Spin State Selection and Spin Crossover Behavior of Tripodal Schiff Base Complexes of tris(2-aminoethyl)amine and Related Tripodal Amines

Magnetochemistry ◽

10.3390/magnetochemistry6020028 ◽

2020 ◽

Vol 6 (2) ◽

pp. 28

Author(s):

Greg Brewer

Keyword(s):

Schiff Base ◽

Spin State ◽

Density Functional ◽

Spin Crossover ◽

Bimodal Distribution ◽

Structural Features ◽

Schiff Base Complexes ◽

Mononuclear Iron ◽

Experimental Values ◽

State Selection

A review of the tripodal Schiff base (SB) complexes of tris(2-aminoethyl)amine, Nap(CH2CH 2NH2)3 (tren), and a few closely related tripodal amines with Cr(II), Mn(III) (d4), Mn(II), Fe(III) (d5), Fe(II) (d6), and Co(II) (d7) is provided. Attention is focused on examination of key structural features, the M-Nimine, M-Namine, or M-O and M-Nap bond distances and Nimine-M-N(O) bite and C-Nap-C angles and how these values correlate with spin state selection and spin crossover (SCO) behavior. A comparison of these experimental values with density functional theory calculated values is also given. The greatest number, 132, of complexes is observed with cationic mononuclear iron(II) in a N6 donor set, Fe(II)N6. The dominance of two spin states, high spin (HS) and low spin (LS), in these systems is indicated by the bimodal distribution of histogram plots of Fe(II)-Nimine and Fe(II)-Nazole/pyridine bond distances and of Nimine–Fe(II)-Nazole/pyridine and C-Nap-C bond angles. The values of the two maxima, corresponding to LS and HS states, in each of these histograms agree closely with the theoretical values. The iron(II)-Nimine and iron(II)-Nazole/pyridine bond distances correlate well for these complexes. Examples of SCO complexes of this type are tabulated and a few of the 20 examples are discussed that exhibit interesting features. There are only a few mononuclear iron(III) cationic complexes and one is SCO. In addition, a significant number of supramolecular complexes of these ligands that exhibit SCO, intervalence, and chiral recognition are discussed. A summary is made regarding the current state of this area of research and possible new avenues to explore based on analysis of the present data.

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Spin crossover and high spin electroneutral mononuclear iron(iii) Schiff base complexes involving terminal pseudohalido ligands

New Journal of Chemistry ◽

10.1039/c4nj01363h ◽

2015 ◽

Vol 39 (1) ◽

pp. 508-519 ◽

Cited By ~ 18

Author(s):

Petra Masárová ◽

Pavel Zoufalý ◽

Ján Moncol ◽

Ivan Nemec ◽

Ján Pavlik ◽

...

Keyword(s):

Schiff Base ◽

High Spin ◽

Spin State ◽

Spin Crossover ◽

High Spin State ◽

Schiff Base Complexes ◽

Mononuclear Iron ◽

State Behaviour

Six new Schiff-base complexes (1–6) with pseudohalido terminal ligands exhibits spin crossover or high spin state behaviour.

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Influence of ligand substituent conformation on the spin state of an iron(ii)/di(pyrazol-1-yl)pyridine complex

Dalton Transactions ◽

10.1039/d1dt00590a ◽

2021 ◽

Vol 50 (10) ◽

pp. 3464-3467

Author(s):

Rafal Kulmaczewski ◽

Mark J. Howard ◽

Malcolm A. Halcrow

Keyword(s):

Spin State ◽

Spin Crossover ◽

Solution Phase ◽

Pyridine Complex

The temperature of the solution-phase spin-crossover equilibrium in iron(ii) complexes of 4-alkylsulfanyl-2,6-di{pyrazol-1-yl}pyridine (bppSR) complexes depends strongly on the alkylsulfanyl substituent.

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Spin-state-dependent electrical conductivity in single-walled carbon nanotubes encapsulating spin-crossover molecules

Nature Communications ◽

10.1038/s41467-021-21791-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Julia Villalva ◽

Aysegul Develioglu ◽

Nicolas Montenegro-Pohlhammer ◽

Rocío Sánchez-de-Armas ◽

Arturo Gamonal ◽

...

Keyword(s):

Carbon Nanotubes ◽

Spin State ◽

Spin Crossover ◽

Single Walled Carbon Nanotubes ◽

Guest Molecules ◽

Spintronic Devices ◽

Single Walled Carbon ◽

State Dependent ◽

Lack Of Control ◽

Walled Carbon Nanotubes

AbstractSpin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

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Spin Crossover in Nickel(II) Tetraphenylporphyrinate via Forced Axial Coordination at the Air/Water Interface

Molecules ◽

10.3390/molecules26144155 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4155

Author(s):

Alexander V. Shokurov ◽

Daria S. Kutsybala ◽

Andrey P. Kroitor ◽

Alexander A. Dmitrienko ◽

Alexander G. Martynov ◽

...

Keyword(s):

Spin State ◽

Spin Crossover ◽

High Spin State ◽

Water Interface ◽

Metal Centers ◽

Axial Coordination ◽

Vis Spectroscopy ◽

Air Water Interface ◽

Nickel Cation

Coordination-induced spin crossover (CISCO) in nickel(II) porphyrinates is an intriguing phenomenon that is interesting from both fundamental and practical standpoints. However, in most cases, realization of this effect requires extensive synthetic protocols or extreme concentrations of extra-ligands. Herein we show that CISCO effect can be prompted for the commonly available nickel(II) tetraphenylporphyrinate, NiTPP, upon deposition of this complex at the air/water interface together with a ruthenium(II) phthalocyaninate, CRPcRu(pyz)2, bearing two axial pyrazine ligands. The latter was used as a molecular guiderail to align Ni···Ru···Ni metal centers for pyrazine coordination upon lateral compression of the system, which helps bring the two macrocycles closer together and forces the formation of Ni–pyz bonds. The fact of Ni(II) porphyrinate switching from low- to high-spin state upon acquiring additional ligands can be conveniently observed in situ via reflection-absorption UV-vis spectroscopy. The reversible nature of this interaction allows for dissociation of Ni–pyz bonds, and thus, change of nickel cation spin state, upon expansion of the monolayer.

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