spin crossover in transition metal complexesschnack/... · the origins of spin crossover (sco) 2....
TRANSCRIPT
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Spin Crossover inSpin Crossover in
Transition Metal ComplexesTransition Metal Complexes
Michael Shatruk
Department of Chemistry and BiochemistryFlorida State University, Tallahassee, FL
ICMM-2012
October 7-11, 2012
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OutlineOutline1. The origins of spin crossover (SCO)2. Characterization methods3. Examples of SCO in transition metal complexes4. The role of cooperativity in SCO5. Pressure- and light-driven SCO6. Charge-transfer induced spin transitionsg p
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MagnetsMagnets
Disorder Order
T, p, H
Magnetic bistability is the fundamental cause for the development of technologies utilizing magnetic materials
The simplest example:two states of the electron spin
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Splitting of dSplitting of d--OrbitalsOrbitals by the by the LigandLigand FieldField
eg
10Dq
Octahedral symmetry
Mn+, d
t2g
q
Spectrochemical series of ligand-field strength:
I– < Br– < Cl– < SCN– < NO3– < F– < OH– < H2O <
NCS– < py < NH3 < en < NO2– < PPh3 < CN– < CO
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O ti l b ti
Absorption SpectroscopyAbsorption Spectroscopy
W l th Å
eg
10Dq
Optical absorption spectrum of [Ti(H2O)6]3+
Wavelength, Åt2g
Ti3+, 3d1
q
tivity
, 3d
lar a
bsor
pt
10Dq = Δo ≈ 20,000 cm–1
Mol
Frequency, cm–1 ×10–3
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TanabeTanabe--Sugano DiagramsSugano Diagramsd2 I d3 Id2 Ion d3 Ion
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TanabeTanabe--Sugano DiagramsSugano Diagramsd5 I d6 Id5 Ion d6 Ion
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The History of SCO PhenomenonThe History of SCO PhenomenonObserved for d4 d5 d6 d7 metal ionsObserved for d4, d5, d6, d7 metal ionsThese ions exhibit two possible electron configurations in the octahedral ligand field
eg eg
Example – d5 ion
octahedral ligand fieldSwitching between the states is achieved by changing temperature, pressure or by photoexcitation
t2g t2g
HS, S = 5/2LS, S = 1/2pressure, or by photoexcitation
1931 – Cambi and Szego observed SCO in Fe(III) dithiocarbomates Interesting sequence in 1950s:
Pauling initially explained their results by the change in the bond type from covalent to ionic
- Ligand field theory established- Mössbauer effect discovered- Spin crossover explained
Orgel was the first to suggest the correct explanation based on the change in the spin state of the ion
p p
Cambi, L.; Szegö, L. Ber. Deutsch. Chem. Gesell. 1931, 64, 167.Pauling, L. J. Am. Chem. Soc. 1937, 59, 633.Orgel, L. E. 10th Chemical Conference, Brussels, 1956, 289.
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Ab t 90% f p t d s s f SCO
Spin Crossover (SCO)Spin Crossover (SCO) in Fe(II) complexesin Fe(II) complexes
HS, S = 2LS, S = 0
About 90% of reported cases of SCO have been observed in Fe(II) complexes
eg
t
eg
t2gt2g
10Dq > Π 10Dq < Π
10Dq – ligand-field splittingΠ – electron pairing energy
Complexes: HS SCO LS
Hauser, A. Top. Curr. Chem. 2004, 233, 49-58.
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The antibonding orbitals (e *) are
MetalMetal--LigandLigand DistancesDistances
HS S = 2LS S = 0The antibonding orbitals (eg ) are populated only in the HS state
eg eg
t2
HS, S = 2LS, S = 0
t2gt2g
r(Fe–L): 1.95-2.00 Å 2.15-2.20 ÅUseful relationship:
10Dq ~ 1/rn (n = 5 – 9)
Using the average r(Fe–L) for SCO complexes, one can estimate that 10Dq /10Dq ~ 1 75that 10DqLS/10DqHS ~ 1.75
Important: the Fe-N bond lengths and orbital overlap lengths and orbital overlap change upon SCO, and therefore 10Dq is different for the LS and HS states of the same complex
Hauser, A. Top. Curr. Chem. 2004, 233, 49-58.
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Absorptions Spectra of HS and LS ComplexesAbsorptions Spectra of HS and LS Complexes
10Dq cm–110Dq, cm
10,000[Fe(H2O)6]2+
[F (CN) ]3
33,000
[Fe(CN)6]3–
Hauser, A. Top. Curr. Chem. 2004, 233, 49-58.
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Absorption Spectra of SCO ComplexesAbsorption Spectra of SCO Complexes
[F ( t ) ](BF ) 1A1→1T2[Fe(ptz)6](BF4)2
HSLS
1A1→1T1
1A1→3T2
LS1A1→3T1 (×10)
5T2→5E
Hauser, A. J. Chem. Phys. 1991, 94, 2741.
10DqHS = 11 800 cm–1 10DqLS = 19 410 cm–1
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Pairing Energy and Pairing Energy and LigandLigand--Field StrengthField Strength
Th i i i b t The pairing energy is about the same in the LS and HS states: Π ≈ 15,000 cm–1 for Fe(II) complexesFe(II) complexes10Dq is changing during the spin transition:
10DqHS < 10DqLS
ΔE0ВН
0 qHS 0 qLS
If 10DqHS < 10,000 cm–1 orIf 10DqHS 10,000 cm or10DqLS > 23,000 cm–1, the SCO is impossibleConditions for observation of SCO in Fe(II) complexes:
10DqHS ≈ 11,000 – 12,500 cm–1
10DqLS ≈ 19,000 – 22,000 cm–110DqВС 10DqНС
ΔE0HL = E0
HS – E0LS
Hauser, A. Top. Curr. Chem. 2004, 233, 49-58.
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Characterization MethodsCharacterization MethodsMangetometryg y
HSCrystallography χT = 3.3-3.8
emu·K/molLS HS
Å
LSχT ≈ 0
d(FeII‐N) (Å) 1.95‐2.00 2.15‐2.20
57Fe Mössbauer Spectroscopy
F (II) LS 4 2 KOther spectroscopic
Fe(II) LS
rptio
n
4.2 K
123 K
p ptechniques
Abs
or 160 K
298KFe(II) HS ΔEQ HS
LS
Velocity (mm/s)-4 -2 0 2 4
Q HS
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MagnetometryMagnetometry
Th fi t t d The first reported SCO complex of Fe(II)
2.5
3.0
3.5
/mol
1 0
1.5
2.0
χT, e
mu·
K/
SCNSCN
NFe
0.0
0.5
1.0
0 50 100 150 200 250 300 350χ
N
NFe
N
0 50 100 150 200 250 300 350
Temperature, K
At T = 180 KAt T1/2 = 180 K,
LSHS
HS
total
HSHS Fe][Fe][
Fe][Fe][Fe][
+==γ
König, Madeja Chem. Commun. 1966, 61-62.
LSHStotal Fe][Fe][Fe][ +
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CrystallographyCrystallography
FeN6 NiN6
d(Fe–N), Å d(Ni–N), Å
Guionneau, P.; Marchivie, M.; Bravic, G.; Létard, J.-F.; Chasseau, D. Top. Curr. Chem. 2004, 234, 97-128.
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CrystallographyCrystallographyFormula FeCl O N C H (1) FeCl O N C H (2·1 5CH OH)Formula FeCl2O8N8C32H30 (1) FeCl2O9.2N8C41.2H38.8 (2·1.5CH3OH)
Temperature 123 K 210 K 123 K 210 K
Space group (No.) P21/c (14) P21/c (14) P21/n (11) P21/n (11)
V Å3V, Å3 3231.06 3372.03 4716.8 4768.89d(Fe–N)av, Å 2.002(4) 2.184(4) 2.188(4) 2.188(3)
Σ(N-Fe-N), deg 71.9(2) 118.1(2) 166.9(2) 165.5(1)
2+ 2+
∑=
−=Σ12
190
iiφ
NHNNN
NNNN
1 2
φi
N NHFe
NN
N NFe
NN
Phan, H.; Chakraborty, P.; Chen, M.; Calm, Y. M.; Kovnir, K.; Keniley, L. K.; Hoyt, J. M.; Knowles, E. S.; Besnard, C.; Meisel, M. W.; Hauser, A.; Achim, C.; Shatruk, M. Chem. Eur. J. 2012, 18, 15805-15815.
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MMöössbauerssbauer SpectroscopySpectroscopy
Excited state E
Nucleus 1
E
Nucleus 2
state EES EES
Ground state EGS EGS
γ-source γ-receiver
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Mössbauer Periodic TableMössbauer Periodic Table
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Experimental ImplementationExperimental Implementation
Variation of the source speed causes the change in energy
Mössbauer spectrum:
due to the Doppler effect
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Isomer ShiftIsomer Shift
standardsample
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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QuadrupoleQuadrupole Splitting (Splitting (II=3/2,=3/2,5757Fe)Fe)
m
I
Im
23
± The quadrupole splitting arises from asymmetric distribution (gradient) of
23I
21
±δ distribution (gradient) of
electron density around the absorbing nucleus
0EAE
0
21
21
±
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Example: HighExample: High--Spin FeSpin Fe2+2+ and Feand Fe3+3+ IonsIons
HS Fe2+
S = 2
mis
sion
Δ
eg
t2g
ve T
rans
m
HS Fe3+
S = 5/2
Rel
ativ eg
t2g
δFe3+ Fe2+
-4 -2 0 2 4Velocity (mm/s)
δ-4 -2 0 2 4
Velocity (mm/s)
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Magnetic Hyperfine Splitting (Magnetic Hyperfine Splitting (II=3/2,=3/2,5757Fe)Fe)
Im
Selection rule: ΔmI = 0, ±1ΔI = ±1
Im
123
−
The magnetic hyperfine splitting in a Mössbauer spectrum is an indication
23I
21
+
2−
of magnetic ordering or an applied magnetic field.
2
23
+
21
+
21
2
21
−Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Example: Example: Magnetite, FeMagnetite, Fe33OO44
Sit A Site B: Fe2+/Fe3+
Site A: Fe3+
Site B: Class III mixed-valent system
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Depending on the local environments of Fe atoms
Splitting of Nuclear Energy Levels (Splitting of Nuclear Energy Levels (II=3/2,=3/2,5757Fe)Fe)Depending on the local environments of Fe atoms and magnetic properties, Mössbauer spectra can consist of a singlet, a doublet, or a sextet.
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Depending on the local environments of Fe atoms
Appearance of Appearance of MössbauerMössbauer SpectraSpectraDepending on the local environments of Fe atoms and magnetic properties, Mössbauer spectra can consist of a singlet, a doublet, or a sextet.
eld
t e sp
littin
g
yper
fine
fi
som
er s
hift
Qua
drup
ole
Mag
netic
h
Symmetric chargeN ti fi ld
Asymmetric chargeN ti fi ld
Symmetric or asymmetric charge f l ( l l)
Δ Bhfδ Is Q M
No magnetic field No magnetic field Magnetic field (internal or external)
Gütlich, P.; Trautwein, A. X.; Link, R. F. Mössbauer Spectroscopy and Transition Metal Chemistry, 1978.
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Example: Various Fe(II) ComplexesExample: Various Fe(II) Complexes
FeSO4·7H2Ohigh-spin
K4[Fe(CN)6]·3H2Olow-spin
N [F (CN) (NO)] 2H ONa2[Fe(CN)5(NO)]·2H2Olow-spin
Gütlich, P. Lectures Notes on Mössbauer Spectroscopy. University of Mainz.
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Example: Example: [Fe(phen)[Fe(phen)33]Cl]Cl22 vs. vs. Fe(phen)Fe(phen)22(NCS)(NCS)22
HSLS
3 03.5
1.52.02.53.0
mu·
K/m
ol X = NCS–
LS LS
0.00.51.0
0 100 200 300
χT, e
m
0 100 200 300
Temperature, K
Gütlich, P. Lectures Notes on Mössbauer Spectroscopy. University of Mainz.
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NMR SpectroscopyNMR SpectroscopyFe(μ2-btr)2(NCSe)2F (μ2 )2( )2
[Coordination polymer]
The linewidth is much narrower The linewidth is much narrower in the LS state due to the absence of spin-spin relaxation:the S = 0 spin state does not the S 0 spin state does not interact with the nuclear spin; as a result, the excited-state lifetime is higher in the LS state.
Ozarowski, A.; Shunzhong, Y.; McGarvey, B. R.; Mislankar, A.; Drake, J. E. Inorg. Chem. 1991, 30, 3167-3174.
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IR SpectroscopyIR Spectroscopy
SCNSCN
SCN
NN
Fe
N
NN
N=C=SM N N=C=SM-N
Sankar, G.; Thomas, J. M.; Varma, V.; Kulkarni, G. U.; Rao, C. N. R. Chem. Phys. Lett. 1996, 251, 79-83.
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The Physics of Spin CrossoverThe Physics of Spin Crossover
Two contributions to the total Fe(II), d6
eg
t2g
eg
t2g
Two contributions to the total electron energy are important:- d-orbital splitting, 10Dq
d electron pairing energy
Fe(II), d
LS, S = 2 HS, S = 0- d-electron pairing energy,Π ≈ 15,000 cm–1 for Fe2+
SCO is possible when10DqHS < Π < 10DqLS
SCO is not possible when10DqHS < 10,000 cm–1 orqHS ,10DqLS > 23,000 cm–1
Conclusion:The SCO depends on the ligand field The SCO depends on the ligand field and the charge on the metal ion
Spectrochemical series:I– < Br– < Cl– < SCN– < NO – < F–I < Br < Cl < SCN < NO3 < F< OH– < H2O < NCS– < py < NH3< en < NO2
– < PPh3 < CN– < CO
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Ground States of dGround States of d44--dd77 Metal IonsMetal Ions
Configuration Ion HS LS
d4Cr(II)
Mn(III) 5Eg, S = 2 3T1g, S = 1
d5 Mn(II)Fe(III)
6A1g, S = 5/2 2T2g, S = 1/2
d6 Fe(II) 5T S 2 1A S 0d6Co(III)
5T2g, S = 2 1A1g, S = 0
d7 Co(II)Ni(III)
4T1g, S = 3/2 2Eg, S = 1/2( )
Garcia, Y.; Gütlich, P. Top. Curr. Chem. 2004, 234, 49-62.
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Spin Crossover in Complexes of dSpin Crossover in Complexes of d44 Metal IonsMetal Ionse eeg
t2g
eg
t2g
HS S 2LS S 1Cr(depe)2I2
the first example of SCO in Cr(II) complexes
Cr(II), Mn(III)
HS, S = 2LS, S = 1
SCO in Cr(II) complexes
The ligand-field effect:
C (d ) I SCO t T 170 KγHS
- Cr(depe)2I2 – SCO at T1/2 = 170 K
- Cr(depe)2Br2 – LS, but contains a small admixture of the HS state at R.T.
- Cr(depe)2Cl2 – LS at all temperatures
Temperature, К
Halepoto, D. M.; Holt, D. G. L.; Larkworthy, L. F.; Leigh, G. L.; Povey, D. C.; Smith, G. W. Chem. Commun. 1989, 1322.Girolami, G. S.; Wilkinson, G.; Galas, A. M.; Thornton-Pett, M.; Hursthouse, M. B. Dalton 1985, 1339.
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Spin Crossover in Complexes of dSpin Crossover in Complexes of d44 Metal IonsMetal Ions
Mn(trp)the first example of SCO in d4 complexes
Sim, P. G.; Sinn, E. J. Am. Chem. Soc. 1981, 103, 241.
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e e
Spin Crossover in Complexes of dSpin Crossover in Complexes of d55 Metal IonsMetal Ions
MnCp2manganocene
eg
t2g
eg
t2g
HS S 5/2LS S 1/2
Mn(II), Fe(III)
HS, S = 5/2LS, S = 1/2
4 h li4-morpholine
1-pyrrolidone1 pyrrolidone
1-pyrrole
Ammeter, J. H.; Bucher, R.; Oswald, N. J. Am. Chem. Soc. 1974, 96, 7883.Garcia, Y.; Gütlich, P. Top. Curr. Chem. 2004, 234, 49-62.
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e e Fe(phen) (NCS)
Spin Crossover in Complexes of dSpin Crossover in Complexes of d66 Metal IonsMetal Ionseg
t2g
eg
t2g
HS S 2LS S 0
Fe(phen)2(NCS)2
SCNSCN
N
Fe(II), Co(III)
HS, S = 2LS, S = 0 SCN
N
NN
FeN
2 5
3.0
3.5
ol
N
1 0
1.5
2.0
2.5
emu·
K/m
o
0.0
0.5
1.0
0 50 100 150 200 250 300
χT,
0 50 100 150 200 250 300
Temperature, KKönig, Madeja Chem. Commun. 1966, 61-62.
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31P NMR
Spin Crossover in Complexes of dSpin Crossover in Complexes of d66 Metal IonsMetal IonsP NMR
Gütlich, P.; McGarvey, B. R.; Kläui, W. Inorg. Chem. 1980, 19, 3704-3706.
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e e [Co(terpy) ]X
Spin Crossover in Complexes of dSpin Crossover in Complexes of d77 Metal IonsMetal Ionseg
t2g
eg
t2g
HS S 3/2LS S 1/2
[Co(terpy)2]X2
X = Cl–, Br–, etc.
Co(II), Ni(III)
HS, S = 3/2LS, S = 1/2
[NiF6]3-
Goodwin, H. A. Top. Curr. Chem. 2004, 234, 23-47.Reinen, D.; Friebel, C.; Propach, V. Z. Anorg. Allg. Chem. 1974, 408, 187.
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Classification of SCO Compounds by NuclearityClassification of SCO Compounds by Nuclearity
Extended 1D, 2D, and 3D structuresMono- and Binuclear Complexes
(Usually) higher cooperativity of the spin transition
Gütlich, P.; Goodwin, H. A. Top. Curr. Chem. 2004, 234, 1-47.
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CooperativityCooperativity of the Spin Transitionof the Spin TransitionHS Latice LS in the HS LaticeHS Latice LS in the HS Latice
HS i h LS L i LS L iHS in the LS Latice LS Latice
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CooperativityCooperativity of the Spin Transitionof the Spin Transition
[Fe(ptz)6](BF4)2T 125 К
[Zn1-xFex(ptz)6](BF4)2T1/2 = 95 К
T1/2 = 125 К
Hauser, A.; Gütlich, P.; Spiering, H. Inorg. Chem. 1986, 25, 4245.
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Prussian Blue Prussian Blue –– The First The First Synthetic Coordination CompoundSynthetic Coordination Compound
Diesbach and Dippel (Berlin, 1703)
PotashGreen vitriol Prussian Blue [+ox blood](K2CO3)(FeSO4)
Prussian Blue
Blue industrial pigmentBl i (Pi ’ bl i d)
FeFe44[Fe(CN)[Fe(CN)66]]33··nn HH22OO
Blue paint (Picasso’s blue period)
Woodward, M. D. Philos. Trans. 1724, 33, 15-17.Brown, J. Philos. Trans. 1724, 33, 17-24.http://www.artchive.com/artchive/P/picasso_blue.html
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SCO in Prussian Blue AnaloguesSCO in Prussian Blue Analogues
C {F II[C III(CN) ]} H O F II N C C III (i )Cs{FeII[CrIII(CN)6]}·x H2O – FeII–N≡C–CrIII (isomer):- abrupt SCO due to increased cooperativity- thermal hysteresis (ΔT = 27 K)th rma hyst r s s ( 7 K)
Cr Fe
Kosaka, W.; Nomura, K.; Hashimoto, K.; Shin-ichi, O. J. Am. Chem. Soc. 2005, 127, 8590
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CooperativityCooperativity of the Spin Transitionof the Spin TransitionFi d li d fi ld P ti f SCO Fixed ligand field,variable cooperativity
Propagation of SCO (Monte Carlo simulation)
Enachescu, C.; Nishino, M.; Miyashita, S.; Stoleriu, L.; Stancu, A. Phys. Rev. B 2012, 86, 054114
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CooperativityCooperativity of the Spin Transitionof the Spin TransitionT t SCOTwo-step SCO
253 K → → 243 K
243 K → → 253 K
Reedijk, J. et al. Chem. Mater. 2009, 21, 1123.
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Spin Crossover Under PressureSpin Crossover Under Pressure
Under applied external pressure, the LS state is stabilized with respect to the HS state
ÅΔd(Fe-L)LS→HS ~ 0.1 Å for Fe(III)0.2 Å for Fe(II) p2 > p1
Experimental conditions:Hydrostatic presure is preferred, in order to avoid defect formation and shear dislocationsPressure-transmitting fluid:He, Ar, or mineral oilBelow 1 GPa: clamp cells Above 1 GPa: diamond anvil cells1 GPa = 10 kbar ~ 10,000 atm,
Gütlich, P.; Ksenofontov V.; Gaspar, A. B. Coord. Chem. Rev. 2005, 249, 1811.
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SCO Under Pressure: Fe(phen)SCO Under Pressure: Fe(phen)22(NCS)(NCS)22
SCNSCN
NF 105 Pa before
N
NFe
N10 Pa before and after compression
Under increasing pressure, the spin transition is shifted th sp n trans t on s sh ft to higher temperaturesThe transition broadens because of increasing defect gconcentration under pressure
Gütlich, P.; Gaspar, A. B.; Ksenofontov V.; Garcia, Y. J. Phys. Cond. Matter 2004, 16, 1.
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SCO Under Pressure: Cr(SCO Under Pressure: Cr(depedepe))22II22
A l h ff At low pressures, the effect is small, but the changes become much more pronounced at p > 0 3 GPapronounced at p > 0.3 GPaThe initial “delay” is caused by high compressibility of I–
At 0.80 GPa and above, the complex exists only in the LS state
Gütlich, P.; Gaspar, A. B.; Ksenofontov V.; Garcia, Y. J. Phys. Cond. Matter 2004, 16, 1.
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SCO Under Pressure: [Fe(SCO Under Pressure: [Fe(mtzmtz))66](BF](BF44))22
Under ambient pressure:The extent of the HS→LS transition is only 50%, because y ,there are two inequivalent Fe(II) sites in the crystal structureAbove 0.57 GPa, the complete pSCO is observed
Hinek, R.; Gütlich, P.; Hauser, A. Inorg. Chem. 1994, 33, 567-572.
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SCO Under Pressure: Fe(SCO Under Pressure: Fe(abptabpt))22(NCS)(NCS)22
NSCN
N
N
NH
N
NCSN
N
FeN
N
H2N
NH2
N
Under ambient pressure, this The incomplete SCO at low p ,complex exists only in the HS stateApplied pressure causes SCO
ppressures is explained by the slow kinetics that result in the “frozen” HS→LS equilibrium.
Gaspar, A. B.; Muñoz, M. C.; Moliner, N.; Ksenofontov, V.; Levchenko, G.; Gütlich, P.; Real, J. A. Monats. Chem. 2003, 134, 285.
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1MLCT
PhotoinducedPhotoinduced SCOSCO (LIESST)(LIESST)
1T1
1T2
1MLCTIrradiation into characteristic absorption bands of the LS state results in photoinduced population
3T1
3T2 5Eresults in photoinduced population of the metastable HS state.
This phenomenon is known as
5T2HS
hνLight-Induced Excited Spin State Trapping, or LIESST
1AA1LS
Hauser, A. Top. Curr. Chem. 2004, 234, 155-198.
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LIESSTLIESST: : The First ObservationThe First Observation
[Fe(ptz)6](BF4)2
Ground States:- LS = 1А1- HS = 5Т22
Hauser, A. Chem. Phys. Lett. 1986, 124, 543.
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LIESSTLIESST: : The First ObservationThe First Observation
[Fe(ptz) ](BF )
Three spectra at 10 К:
[Fe(ptz)6](BF4)2
⎯ after slow cooling from 300 К to 10 К, the complex is in the LS state
···· irradiation with λ = 515 nm at 10 К causes spin transition (LIESST) into the metastable HS statethe metastable HS state
--- irradiation with λ =830 nmat 10 К causes a reverse spin transition (RLIESST)spin transition (RLIESST)into the ground LS state
Hauser, A. Chem. Phys. Lett. 1986, 124, 543.
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LIESSTLIESST: : Stability of CrystalsStability of Crystals[Fe(pic)3]Cl2[Fe(pic)3]Cl2
Crystals of this compound are converted into fine powder under irradiation at 23 Kunder irradiation at 23 K
(λ = 515 nm)
Before and after irradiation at 23 КTemperature-dependent spectra Before and after irradiation at 23 К
after i di ti
Temperature dependent spectra
irradiation
before irradiation
Romstedt, H.; Hauser, A.; Spiering, H. J. Phys. Chem. Solids 1998, 59, 265.Vef, A.; Manthe, U.; Gütlich, P.; Hauser, A. J. Chem. Phys. 1994, 101, 9326.
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LigandLigand--Induced SCOInduced SCO
Th LS HS t iti t k l d The LS → HS transition takes place due to the change in the d-orbital splitting when the ligand is photoisomerized
Th d t f thi h i th The advantage of this approach is the possibility to realize the photoinducedtransition even at room temperature
Boillot et al. New J. Chem. 1999, 179-183.
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LigandLigand--Induced SCOInduced SCO
R = H R = NO2
Nishihara, H. et al. Inorg. Chem. 2012, 51, 5188.
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ChargeCharge--Transfer Induced Transfer Induced Spin Transition Spin Transition ((CTIST)CTIST)
Co Fe
AxCo3-x[Fe(CN)6]2·H2O; A = K, Rb
This is the first famous example of photomagnetic switching in a of photomagnetic switching in a molecule-based material
A reversible electron transfer between the Co and Fe centers between the Co and Fe centers results in photoswitchablemagnetic behavior
CoII−N≡C −FeIII CoIII−N≡C −FeIIhν1
hν2
eg
t2g
eg
t2g
eg
t2g
eg
t2g
LS, S = 0LS, S = 0LS, S = 1/2HS, S = 3/2
Sato, O.; Iyoda, T.; Fujishima, A.; Hashimoto, K. Science 1996, 272, 704-705.
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PhotomagnetismPhotomagnetism inin AAxxCoCo33--xx[Fe(CN)[Fe(CN)66]]22·nH·nH22OO
CoII−N≡C −FeIII
CoIII−N≡C −FeII
Sato, O.; Iyoda, T.; Fujishima, A.; Hashimoto, K. Science 1996, 272, 704-705.
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PhotomagnetismPhotomagnetism inin AAxxCoCo33--xx[Fe(CN)[Fe(CN)66]]22·nH·nH22OO
CoII−N≡C −FeIIIF
CoIII−N≡C −FeII
Shimamoto, N.; Ohkoshi, S.; Sato, O.; Hashimoto, K. Inorg. Chem. 2002, 41, 678-684.
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SCO in SCO in NanoparticlesNanoparticles
Ni3[Cr(CN)6]2 - shell
RbCo[Fe(CN)6] - core
Dumont, M. F.; Knowles, E. S.; Guiet, A.; Pajerowski, D. M.; Gomez, A.; Kycia, S. W.; Meisel, M. W.; Talham, D. R. Inorg. Chem. 2011, 50, 4295-4300.
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eg e
HS, S = 2LS, S = 0
I ld lik t th k th i s f th
AcknowledgmentsAcknowledgmentseg
t2g
eg
t2g
I would like to thank the organizers of the ICMM converence, Prof. Stephen Hill and Prof. Enrique Del Barco, for giving me an opportunity to present this tutorial.pp y p
I especially would like to acknowledge the seminal contributions to this field by Prof. Philipp Gütlich, Prof. Andreas Hauser, Prof. Philipp Gütlich, Prof. Andreas Hauser, Prof. Harold Goodwin, Prof. Prof. Harold Goodwin, Prof. KazuhitoKazuhitoHashimoto,Hashimoto, and their research groups.
The publications and reviews by these authors have been an invaluable resource during the preparation of these slides.
Gütlich, P.; Goodwin, H. A. Top. Curr. Chem. 2004, 233, 1-47.Hauser, A. Top. Curr. Chem. 2004, 233, 49-58.Hashimoto, K., et al. Science 1996, 272, 704-705.
HS SCO LS