Photo-magnetic transitions: Spin crossover molecules Amandine Bellec - - PowerPoint PPT Presentation

▶
photo magnetic transitions spin crossover molecules
SMART_READER_LITE
LIVE PREVIEW

Photo-magnetic transitions: Spin crossover molecules Amandine Bellec - - PowerPoint PPT Presentation

Jan 19, 2024 49 likes •514 views

Photo-magnetic transitions: Spin crossover molecules Amandine Bellec amandine.bellec@univ-paris-diderot.fr Laboratoire Matriaux et Phnomnes Quantiques (Universit Paris Diderot/CNRS) Sept 2018 Amandine Bellec ESM 1 Molecular switch

slide-1
SLIDE 1

Photo-magnetic transitions: Spin crossover molecules

Amandine Bellec

amandine.bellec@univ-paris-diderot.fr

Laboratoire Matériaux et Phénomènes Quantiques (Université Paris Diderot/CNRS)

Sept 2018 1 Amandine Bellec – ESM

slide-2
SLIDE 2

Molecular switch

External stimuli: Light, temperature, pressure, electric field Change in the molecular material properties:

  • Electronic
  • Magnetic
  • Optical
  • Mechanical

Bistability: Ability to be observed in two different macroscopic states in hysteretic region depending on the history Property External stimuli

Sept 2018 Amandine Bellec – ESM 2

slide-3
SLIDE 3

Ingredients for magnetic properties

Open shell:

  • transition metal (d-orbitals)
  • lanthanide (f-orbitals)
  • molecular radical

Sept 2018 Amandine Bellec – ESM 3

SCO compounds Prussian blue analogues Fe4 Dy(cp)2 Molecular radicals

slide-4
SLIDE 4

Outline

Sept 2018 Amandine Bellec – ESM 4

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogues
  • Molecular radicals
slide-5
SLIDE 5

Ligand field

Sept 2018 Amandine Bellec – ESM 5

  • Transition metal ion (d4 to d7 – Cr, Mn, Fe, Co) surrounded by organic ligands

dx2-y2 dz2 dxy dyz dzx d-orbitals (n=3, l=2)

  • Octahedral symmetry

ΔO 3ΔO/5 2ΔO/5 d-orbitals eg t2g

Central ion Ligands

slide-6
SLIDE 6

Jahn-Teller distorsion

Sept 2018 Amandine Bellec – ESM 6

dz2, dx2-y2 dxy, dxz,dyz dz2 dx2-y2 dxy dxz,dyz dx2-y2 dz2 dxy dxz,dyz Oh Elongation along z Compression along z

slide-7
SLIDE 7

Spin crossover molecules

Sept 2018 Amandine Bellec – ESM 7

Central ion Ligands

FeII: [Ar] 3d6 4s0 LS HS S=0 S=2 T, P, h ΔO LS > Π ΔO HS < Π Volume change: 2-6%

ΔO: ligand field Π : pairing energy

slide-8
SLIDE 8

SCO: effect of ligand functionalization

FeII[HB(PPz)3]2 FeII[HB(Pz)3]2 FeII[HB(3,5-Me2Pz)3]2 HS blocked SCO around 190 K LS < 350K

Sept 2018 Amandine Bellec – ESM 8

slide-9
SLIDE 9

UV-Vis absorption spectroscopy

Sept 2018 Amandine Bellec – ESM 9

[Fe(ptz)6](BF4)2

Hauser et al., Top. Curr. Chem., 234, 155 (2004)

1000 500 333 nm 250

Marino et al., Angew. Chem. Int. Ed., 53, 3863 (2014)

t2g

6eg 0L0

t2g

5eg 0L1

MLCT process d-d transitions HS LS

slide-10
SLIDE 10

SQUID measurements

Sept 2018 Amandine Bellec – ESM 10

Iasco et al., Inorga. Chem., 54, 1791 (2015)

SQUID on polycrystalline powder FeII (pap-5NO2)2

slide-11
SLIDE 11

Outline

Sept 2018 Amandine Bellec – ESM 11

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogs
  • Molecular radicals
slide-12
SLIDE 12

Thermal transition

Sept 2018 Amandine Bellec – ESM 12

To have the stable spin state, minimization of the Gibbs free energy: Enthalpy:

  • Volume variation: 2-6%

: LS favored

  • LS more symmetric

ΔH around 10 kJ.mol-1

slide-13
SLIDE 13

Thermal transition

SCO transition when: SCO driven by the entropy term High temperature: high spin - Low temperature: low spin Transition temperature:

Sept 2018 Amandine Bellec – ESM 13

Entropy:

  • Electronic contribution, due to the spin:
  • Vibrational contribution:

: HS favored

Intramolecular dominates the intermolecular contribution

As longer M-L bonds for the HS

slide-14
SLIDE 14

Molecules without interaction

Sept 2018 Amandine Bellec – ESM 14

  • Assembly of molecules in HS and LS exhibiting SCO transition
  • No interaction between the molecules
  • Additional term of mixing entropy

x fraction of HS (1-x) fraction of LS ΔH = 10.2 kJ.mol-1 ΔS = 53.8 J.mol-1. K-1

slide-15
SLIDE 15

Cooperativity in SCO crystals, films

Sept 2018 Amandine Bellec – ESM 15

Ridier et al., Solid State Sciences, 74, A1 (2017)

Cooperativity

slide-16
SLIDE 16

Slichter and Drickamer model

Sept 2018 Amandine Bellec – ESM 16

  • C. Slichter and H. Drickamer, J.Chem. Phys., 56, 2142, (1972)

Weak cooperativity Smooth transition Abrupt transition Strong cooperativity 1st order transition, hysteresis ΔH = 10.2 kJ.mol-1 ΔS = 53.8 J.mol-1. K-1

slide-17
SLIDE 17

Thermal transition in crystal

Sept 2018 Amandine Bellec – ESM 17

Optical microscopy on single micro-crystals of [{Fe(NCSe)(py)2}2(m-bpypz)]

Traiche et al., J. Phys. Chem. C,121, 11700 (2017)

Cooling down Heating up

http://dx.doi.org/10.1021/acs.jpcc.7b02816

slide-18
SLIDE 18

Outline

Sept 2018 Amandine Bellec – ESM 18

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogs
  • Molecular radicals
slide-19
SLIDE 19

Light induced transition

Sept 2018 Amandine Bellec – ESM 19

Light induced excited spin state trapping (LIESST): Discovered in 1984, for [Fe(ptz)6](BF4)2 T<50K, LS to HS transition under light

Decurtins et al., Chem. Phys. Lett., 105, 1 (1984)

N N N N C H3

ptz: propyltetrazol

slide-20
SLIDE 20

Light induced transition

Sept 2018 Amandine Bellec – ESM 20

Light induced excited spin state trapping (LIESST):

Hauser et al., Top. Curr. Chem., 234, 155 (2004) Real et al., Dalton Trans., 12, 2062 (2005)

For [Fe(ptz)6](BF4)2 Here d-d transition

slide-21
SLIDE 21

Intermediate states

Sept 2018 Amandine Bellec – ESM 21

Marino et al., Angew. Chem. Int. Ed., 53, 3863 (2014)

For [Zn1-xFex(ptz)6](BF4)2 (x=0.1) at 120K

40 ps 2 ps

Reverse LIESST: evidence of the intermediate state, sequential double intersystem crossing

Excitation pulse: 100 fs, 830 nm Probe: 300 nm

slide-22
SLIDE 22

Excited phonon modes

Sept 2018 Amandine Bellec – ESM 22

Breathing mode Period 300 fs, damping 160 fs Bending mode Bend ligand and N-Fe-N angles, period 390 fs t2g

6eg 0L0

t2g

5eg 0L1

MLCT process

Cammarata et al., Phys. Rev. Lett., 113, 227402 (2014)

By ultra-fast dynamics: pump-probe experiments X-ray pulse ~ 30 fs (XANES), laser pulse ~ 50 fs (optical reflectivity and transmission)

50 fs 160 fs 900 fs

http://link.aps.org/doi/10.1103/PhysRevLett.113.227402

slide-23
SLIDE 23

Cooperativity

Sept 2018 Amandine Bellec – ESM 23

950 x 270 x 35 nm2 7.5 x 0.64 x 0.21 µm2 300 x 200 x 15 µm2

Different time scales:

  • Local photo excitation + swelling (few 100 fs)
  • Elastic step: volume change + strain propagation (0.1 to 50 ns)
  • Thermal conversion (50 µs)

Bertoni et al., Nat. Mater., 16, 606 (2016)

slide-24
SLIDE 24

Cooperativity: mechanoelastic model

Sept 2018 Amandine Bellec – ESM 24

Above xHS

h threshold:

Self-amplification of the photoconversion Lattice expansion due to volume change

Bertoni et al., Nat. Mater., 16, 606 (2016)

slide-25
SLIDE 25

Self-amplification mechanism

Sept 2018 Amandine Bellec – ESM 25

Bertoni et al., Nat. Mater., 16, 606 (2016)

slide-26
SLIDE 26

Non-adiabatic multiphonon relaxation

Sept 2018 Amandine Bellec – ESM 26

Below 50 K: Tunneling process between HS and LS Temperature increase:

  • > population of the vibronic states
  • > increase of the tunneling rate

Above 100K: thermally activated

Hauser et al., Top. Curr. Chem., 234, 155 (2004)

Rate for a series of FeII molecules

slide-27
SLIDE 27

T LIESST

Sept 2018 Amandine Bellec – ESM 27

Measuring the temperature at which the system relaxes Procedure: At 10K, light on until the saturation is reached Light off, ramping up of the temperature at 0.3 K min-1

Chastanet et al., Chem2, doi: 10.28954/2018.csq.07.001 (2018)

slide-28
SLIDE 28

T LIESST

Sept 2018 Amandine Bellec – ESM 28

Measuring the temperature at which the system relaxes Procedure: At 10K, light on until the saturation is reached Light off, ramping up of the temperature at 0.3 K min-1

Chastanet et al., Chem2, doi: 10.28954/2018.csq.07.001 (2018) Hayami et al., Inorg. Chem., 40, 3240 (2001)

T LIESST = 130 K Fe(L)(CN)2 Prussian blue analogues

slide-29
SLIDE 29

Photo-excitation in the thermal hysteresis

Sept 2018 Amandine Bellec – ESM 29

[Fe(pyrazine){Pt(CN)4}] Laser pulse: 532 nm, 4ns, 11 mJ.cm-2 Above Pth = 5 mJ.cm-1, LS to HS transition at 301 K ΔH = 25 kJ.mol-1 ΔS = 84 J.mol-1. K-1 Γ = 7.11 kJ.mol-1

Bonhommeau et al., Angew. Chem., 44, 4069 (2005) Bonhommeau et al., Polyhedron, 28, 1610 (2009)

slide-30
SLIDE 30

Ligand Driven - Light induced spin change (LD-LISC)

Sept 2018 Amandine Bellec – ESM 30

Modulation of the ligand field strength by photochemical reaction on the ligand trans-stpy cis-stpy Styrylpyridine Show different behavior depending on the stpy conformation In solution at RT: Photoisomerisation inducing a spin state change

Boillot et al., New J. of Chem., 23, 176 (1999) Boillot et al., Inorg. Chem., 35, 3975 (1996)

slide-31
SLIDE 31

Ligand-driven coordination-induced spin-state switching (LD-CISSS)

Sept 2018 Amandine Bellec – ESM 31

Venkataramani et al., Science, 331, 445 (2011)

Not SCO But change of the coordination sphere

slide-32
SLIDE 32

Outline

Sept 2018 Amandine Bellec – ESM 32

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogues
  • Molecular radicals
slide-33
SLIDE 33

Displays

Sept 2018 Amandine Bellec – ESM 33

Initial state: LS (pink) When temperature increase: transition from LS to HS (white)

Kahn et al., Science, 279, 5347 (1998) Létard et al., Top Curr. Chem, 235, 221 (2004)

slide-34
SLIDE 34

Applications for molecular electronics/spintronics

Sept 2018 Amandine Bellec – ESM 34

Depending on the spin state modification of the mobility in the graphene SCO for monolayer or single molecules in direct contact with metal?

Dugay et al., Nano Lett., 17, 186 (2017)

Stretching induced conversion to HS and an increase of conduction

Fresenda et al., Nano Lett., 16, 4733 (2016)

Thin films (10 to 100nm): Conduction depending

  • n the spin state

Lefter et al., Adv. Mater., 28, 7508 (2016)

slide-35
SLIDE 35

X-Ray absorption spectroscopy (XAS)

Sept 2018 Amandine Bellec – ESM 35

LS HS Ei Ef ħ ω At the Fe L2,3 edge Element specific Sensitive to the spin state of the molecules 3d 2p 2p1/2 2p3/2 t2g eg

Bernien et al., ACS Nano, 9, 8960 (2015)

slide-36
SLIDE 36

Thermal and light excitation on a surface

Sept 2018 Amandine Bellec – ESM 36

ΔH = 7.2(5) kJ.mol-1 ΔS = 45(3) J.mol-1. K-1

Bernien et al., ACS Nano, 9, 8960 (2015)

τ=20.4(7)s

φ=4.2(8).1014 photons.s-1.mm-2

Complete SCO in direct contact with HOPG Sub monolayer (~ 0.2ML) deposition on HOPG Green light, 6K

slide-37
SLIDE 37

Cooperativity in thermal transition

Sept 2018 Amandine Bellec – ESM 37

Kipgen et al., Nature Comm., 9, 2984 (2018)

From 0.35 ML to 10 ML on HOPG Increase of cooperativity with increasing the coverage

slide-38
SLIDE 38

LIESST

Sept 2018 Amandine Bellec – ESM 38

LS to HS: Individual molecule-photon interactions (no cooperativity!) Similar to bulk HS to LS: Relaxation rates are 3 order of magnitude lower than in bulk

Kipgen et al., Nature Comm., 9, 2984 (2018)

slide-39
SLIDE 39

Sept 2018 Amandine Bellec – ESM 39

Scanning Tunneling Microscopy (STM)

Tunneling Current Local density of state (LDOS) : Local density of states of the sample

t

s

: Density of states of the tip

Repp et al., Phys. Rev. Lett., 94, 026803 (2005)

Pentacene / NaCl / Cu(111)

slide-40
SLIDE 40

Self-assembly on Au(111)

Sept 2018 Amandine Bellec – ESM 40

Distance (nm) Apparent height (Å) 10 nm 10 nm

Self-assembly in a dense plane

Step height: 0.65 ± 0.01 nm

V = -1.5V

slide-41
SLIDE 41

Spin-dependent superstructure

Sept 2018 Amandine Bellec – ESM 41

V = -1.5 V, I = 20 pA V = 0.3 V, I = 50 pA V = -0.7 V, I = 50 pA Long-range superstructure Origin: spin state of the molecule

slide-42
SLIDE 42

Light induced SCO

Sept 2018 Amandine Bellec – ESM 42

Excitation wavelength : 405 nm; around 6 min / image

Bairagi et. al., Nature Communications, 7, 12212 (2016)

http://www.nature.com/doifinder/10.1038/ncomms12212

slide-43
SLIDE 43

Outline

Sept 2018 Amandine Bellec – ESM 43

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogues
  • Molecular radicals
slide-44
SLIDE 44

Sept 2018 Amandine Bellec – ESM 44

Prussian Blue analogues

S=0 (LS) S=0 (LS) S=1/2 (LS) S=3/2 (HS) Paramagnetic (high temperature) Diamagnetic (low temperature)

Li et al., JACS, 130, 252 (2008) Mathonière et al., Euro. J. Inorga. Chem., 3, 248 (2018)

Photostability: 10 years at 120 K

slide-45
SLIDE 45

Sept 2018 Amandine Bellec – ESM 45

  • Spin crossover compounds
  • Introduction
  • Thermal transition
  • Light induced transition
  • SCO on surface
  • Prussian blue analogues
  • Molecular radicals
slide-46
SLIDE 46

Sept 2018 Amandine Bellec – ESM 46

Molecular radicals

σ - dimer S=0 π - radicals S=1/2

Phan et al., JACS, 135, 15674 (2013)

By light: photo-dissociation of the dimer Stabilization of the radicals up to 240 K AFM coupling between the radicals