1. Physical Methods in Inorganic Chemistry or How do we know what we made
and does it have
interesting
properties?

2. What is electronic spectroscopy?
Absorption of radiation leading to electronic transitions within a molecule or complex
Absorption
Absorption
[Ru(bpy)3]2+
[Ni(H2O)6]2+
104 10
~14 000
25 000
50 000
200
400
700
visible UV UV
visible
n / cm-1 (frequency) -
l / nm (wavelength)
UV = higher energy transitions - between ligand orbitals
visible = lower energy transitions - between d-orbitals of transition metals
- between metal and ligand orbitals

3. Absorption maxima in a visible spectrum have three important characteristics
number (how many there are)
This depends on the electron configuration of the metal centre
2. position (what wavelength/energy)
This depends on the ligand field splitting parameter, Doct or Dtet and on the degree of inter-electron repulsion
intensity
This depends on the "allowedness" of the transitions which is described by two selection rules

4. [Ti(OH2)6]3+ = d1 ion, octahedral complex
Absorption of light
[Ti(OH2)6]3+ = d1 ion, octahedral complex
white light nm 3+ Ti
blue: nm
yellow-green: nm
red: nm A
This complex is has a light purple colour in solution because it absorbs green light
l / nm
lmax = 510 nm

5. [Ti(OH2)6]3+ lmax = 510 nm Do is  243 kJ mol-1 20 300 cm-1
The energy of the absorption by [Ti(OH2)6]3+ is the ligand-field splitting, Do ES ES eg eg hn Do GS GS
t2g
t2g
d-d transition
complex in electronic
Ground State (GS)
complex in electronic
excited state (ES)
[Ti(OH2)6]3+ lmax = 510 nm Do is  243 kJ mol-1
cm-1
An electron changes orbital; the ion changes energy state

6. d2 ion
Electron-electron repulsion eg eg z2
x2-y2 z2
x2-y2
t2g
t2g xy xz yz xy xz yz
xy + z2
xz + z2 z z y y x x
lobes overlap, large electron repulsion
lobes far apart, small electron repulsion
These two electron configurations do not have the same energy

7. Transition e complexes
Selection Rules
Transition e complexes
Spin forbidden 10-3 – 1 Many d5 Oh complexes
Laporte forbidden [Mn(OH2)6]2+
Spin allowed
Laporte forbidden 1 – 10 Many Oh complexes
[Ni(OH2)6]2+
10 – 100 Some square planar complexes
[PdCl4]2-
100 – coordinate complexes of low symmetry, many square planar complexes particularly with organic ligands
Spin allowed 102 – 103 Some MLCT bands in cxs with unsaturated ligands
Laporte allowed
102 – 104 Acentric complexes with ligands such as acac, or with P donor atoms
103 – 106 Many CT bands, transitions in organic species

8. e Tanabe-Sugano diagram for d2 ions
10 000 e
30 000
n / cm-1 - 10
20 000 5
[V(H2O)6]3+: Three spin allowed transitions
E/B
= 32
n1 = cm-1 visible
n2 = cm-1 visible
n3 = obscured by CT transition in UV
D/B = 32
n3 = 2.1n1 = 2.1 x
 n3 = cm-1
= 1.44
17 800
D/B

9. Magnetism

10. macroscopic world
« traditional, classical » magnets N S

11. macroscopic world N S A pioneering experiment by M. Faraday
« Farady lines of forces »
about magnetic flux N S

12. macroscopic world
« traditional » magnets N S N S
attraction N S

13. macroscopic world
« traditional » magnets N S N S
repulsion N S

14. macroscopic world looking closer to the magnetic domains S N    
many
sets of
domains
many
sets of    
atomic
magnetic
moments

15. The magnetic moments order at Curie temperature
A set of molecules / atoms :
Solid, Magnetically Ordered
thermal agitation (kT) weaker
than the interaction (J)
between molecules
… Paramagnetic solid : thermal agitation (kT) larger than the interaction (J) between molecules T C
kT ≈ J
Magnetic Order
Temperature
or Curie
kT << J
kT >> J

16. ferro-, antiferro- and ferri-magnetism
Magnetic Order :
ferro-, antiferro- and ferri-magnetism + =
Ferromagnetism :
Magnetic moments
are identical
and parallel + =
Ferrimagnetism (Néel) :
Magnetic moments
are different
and anti parallel +
= 0
Antiferromagnetism :
Magnetic moments
are identical
and anti parallel

17. Origin of Magnetism … the electron everything, tiny, elementary
I am an electron
• rest mass me,
• charge e-,
• magnetic moment µB
everything, tiny, elementary

18. µtotal = µorbital + µspin
Origin of Magnetism
« Orbital » magnetic moment
« Intrinsic » magnetic moment
µorbital
due to the spin
s = ± 1/2
µspin e-
µorbital = gl x µB x
µspin = gs x µB x s ≈ µB
µtotal = µorbital + µspin

19. Dirac Equation 1905 1928 The Principles of Quantum Mechanics, 1930
Nobel Prize 1933
1905
1928
Equation (10) can be regarded as the Schrödinger equation for an electron interactiong with fields describable by the potentials A and j .

20. Electron : particle and wave
Wave function or « orbital » n, l, ml …
l = s p d
angular representation

21. Electron : also an energy level
Orbitals
Energy
Empty
Singly occupied
Doubly occupied

22. Electron : also a spin ! Up Singly occupied Doubly occupied Down
« Paramagnetic »
S = ± 1/2
« Diamagnetic »
S = 0

23. Molecules
are most often regarded
as isolated, non magnetic
Dihydrogen
diamagnetic
Spin S = 0

24. the dioxygen that we continuously breath is a magnetic molecule
orthogonal π
molecular
orbitals
paramagnetic, spin S =1
Two of its electrons have parallel magnetic moments that shapes
aerobic life and allows our existence as human beings

25. Transition Elements

26. Mononuclear complex ML6
Splitting of the
energy levels E

27. How large is the splitting ?
Weak Field
Intermediate Field
Temperature
Dependent
Spin Cross-Over
Strong Field
High spin
Low spin
L = H2O
[C2O4]2-
L = CN-

28. Spin Cross-Over Red 3 The system « remembers » its thermal past !
Room Temperature 3
Red
The system « remembers » its thermal past !
O. Kahn, C. Jay and ICMC Bordeaux

29. Understanding … to get magnetic compounds …
why the spins of two neighbouring electrons (S = 1/2) become :
antiparallel ?
S=O
or parallel ?
S=1

30. Interaction Models between Localized Electrons

31. Energy levels

32. J = 2 k + 4ßS <0 >0 O2 H2 if S = 0 Orthogonality
if S≠0;|ßS|>>k
Overlap O2
Hund H2
Aufbau

33. Exchange interactions can be very weak …
Energy ≈
Exchange interactions
order of magnitude :
cm-1 or Kelvins …
« Chemical » bonds
Robust !
order of magnitude :
>> 150 kJ mol-1 …

34. How to create the interaction … ?
Cu(II)
Cu(II)
≈ 5 Å
Negligible Interaction !
How to create the interaction … ?
Problem :

35. ≈ 5 Å
Cu(II)
The ligand !
Solution :
Ligand
Orbital Interaction …

36. Examples with the ligandB
Ligand
Examples with the ligand
• Cyanide

37. CN-
Cyanide Ligand
Friendly ligand : small, dissymetric, forms stable complexes
Warning : dangerous, in acid medium gives HCN, lethal

38. homometallic complexes
Dinuclear µ-cyano
homometallic complexes

39. “Models” Compounds Cu(II)-CN-Cu(II)
J/cm-1
Compounds exp
[Cu2(tren)2CN]3+
[Cu2(tmpa)2CN]3+
-160
-100
Overlap : antiferromatic coupling …
Rodríguez-Fortea et al. Inorg. Chem. 2001, 40, 5868