1. Do the chemists know how to align the spins of electrons in molecules, parallel or antiparallel ?

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

3. Interaction Models between Localised Electrons Scalar Coupling : describes, does not explain

4. Energy levels

5. J = 2 k + 4ßS if S = 0 Orthogonality if S≠0;|ßS|>>k Overlap >0 <0 H2H2 Aufbau O2O2 Hund

6. J. Miró « Overlap » ? Catalogue raisonné, N°1317

7. J. Miró, Pomme de terre, detail

8. An old game … AF F Palace Museum, TaiPei, Neolithic period, Yang-Shao Culture

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

10. ≈ 5 Å Negligible Interaction ! How to create the interaction … ? Problem : Cu(II)

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

12. A B Examples with the ligand Cyanide Ligand

13. Monet Claude, Charing Cross Bridge Non linear and linear bridges Monet Claude, Waterloo Bridge

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

15. Dinuclear µ -cyano homometallic complexes

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

17. Cr(III) Ni(II) Dinuclear µ -cyano heterometallic complexes NB : A dissymetric ligand helps to get stable heterometallic complexes … « Birds of the same feathers flock together » …

18. Polynuclear complex, synthetic strategy Hexacyanometalate “Heart” Lewis Base Mononuclear Complex Lewis Acid Polynuclear Complex 3- + 6 2+ 9+

19. Hexacyanochromate complex Cr(III) [Cr III (CN) 6 ] 3- Electrons in

20. M-C  N-M'   Polynuclear complex, ferromagnetic strategy Cr(III)Ni(II) 6 S = 6x1+3/2 = S = 15/2 Orthogonality : Ferromagnetism !

21. M-C  N-M’ Cr(III)Mn(II) 6 S = 6x5/2 + 3/2 = S = 27/2 Overlap = antiferromagnetism Polynuclear complex, ferrimagnetic strategy  

22. Ferromagnetic … Eros Paul KLEE Nocturnal separation, 1922 Ferrimagnetic …

23. CrCu6 S = 9/2 CrNi6 S = 15/2 CrMn6 S = 27/2 Hexagonal R -3 a = b = 15,27 Å; c = 78,56 Å a = b= 90°; g = 120°; V = 4831 Å 3 Hexagonal R -3 a = b = 15,27 Å; c = 41,54 Å a = b= 90°; g = 120°; V = 8392 Å 3 Hexagonal R -3 a = b = 23,32 Å; c = 40,51 Å a = b= 90°; g = 120°; V = 19020 Å 3 … High Spin Heptanuclear Complexes Marvaud et al., Chemistry, 2003, 9, 1677 and 1692

24. Chemists have transformed good old Prussian blue, a blue pigment that Michael Faraday precipitated in his time at Royal Institution, into a room temperature magnet also useful in display devices.

25. Alfred Bader, « End of Mistery », Chemistry in Britain, 37, 7, July 2001, 99 Greeting Card of RSC, Benevolent Fund, Thomas Graham House, Science Park, Milton Road, Registered Charity N° 207890. This painting does not depict neither W.T. Brande nor Michael Faraday making Prussian blue, Thomas Philips RA, ca 1816 (from Alfred Bader, Hon FRSC)

26. 1704 … Diesbach, draper in Berlin … … prepares a blue pigment « Prussian blue » … said to be the first coordination compound 2004 : 300th anniversary !

27. Anna Atkins, Cyanotype in Hart-Davis Adam Chain Reactions, pioneers of british science and technology National Portrait Gallery London, 2000

28. Classical coordination chemistry … Fe 2+ aq + 6CN - aq [Fe(CN) 6 ] 4- aq Complexes as Ligands, or « bricks » + Lewis Acid-Base Interaction + [4-] [3+] 3[Fe(CN) 6 ] 4- aq + 4Fe 3+ aq {Fe 4 [Fe(CN) 6 ] 3 } 0 15H 2 O

29. since : 1936, modified 1972 … an evergreen in inorganic chemistry … a simple face-centered cubic structure … Stoichiometry [A II ] 4 [B II (CN) 6 ] 3 or A 4 B 3 [A II ] 4 [B II ] 3  1  = vacancy J.F. Keggin, F.D. Miles, Nature 1936, 137, 577 A. Ludi, H.U. Güdel, Struct. Bonding (Berlin) 1973, 14, 1

30. Coming back to Prussian Blue T C  z |J| z : number of magnetic neighbours |J| : coupling constant between nearest neighbours Néel, Annales de Physique, 1948

31. Coming back to Prussian Blue T C  z |J| z : number of magnetic neighbours |J| : coupling constant between nearest neighbours Néel, Annales de Physique, 1948 T C = 5.6 K

32. Towards Prussian blue analogues … T C  z |J| T C >> 5.6 K J Ferro > 0 Orthogonality

33. Towards Prussian blue analogues … T C  z |J| T C >> 5.6 K J Antiferro < 0 Overlap …

34. V 4 [Cr(CN) 6 ] 8/3.nH 2 O Room Temperature T C On a rational basis ! Gadet et al., J.Am. Chem. Soc. 1992Mallah et al. Science 1993Ferlay et al. Nature, 1995

35. V 4 [Cr(CN) 6 ] 8/3.nH 2 O Room Temperature T C On a rational basis !

36. A blue, transparent, low density magnet at room temperature

37. Oscillating Magnet : Experiment

38. A thermodynamical machine transforming Light in Mechanical Energy

40. Permanent Magnet Hot Couple Sample (MM) Magnetic Switch… Or thermal probe … Other device

41. Up to 2004 …magnetic analogues used as … … devices and demonstrators

42. Chemists have managed to transform isolated single molecules into magnets

43. molecule-based magnets ? Why ? Low density Transparent Nanosized, identical molecules Often biocompatible and biodegradable Very flexible chemistry Mild chemistry : Room T, Room P, Solution Chemistry Fragile Aging Diluted Specific properties To overcome To improve

44. Top down Nanosystems Nice Chemistry Single molecule magnets Applications (far …) Recording Quantum computing Fragments Threads Dots New Physics Quantum / Classical Quantum tunneling Bottom up Giant Molecular Clusters 0D, Molecules 3D Metals Oxydes

45. Synthesis Properties Theory Idea New Materials New Functions New Concepts … Single molecule magnets Giant Molecular Clusters Mn4 and many others High Spin + Anisotropy ∆E = DS z 2 Mn12 Fe8 See Gatteschi Hendrickson Christou Winpenny …

46. = What is named Single Molecule Magnet ? High Spin Anisotropic

47. High Spin Paramagnetic Molecule H

48. Single Molecule Magnet Towards information storage at the molecular level ? Below T < T Blocking H

49. Single Molecule Magnet Towards information storage at the molecular level ? Below T < T Blocking

50. Single molecule magnets DS z 2 = 400K ? |D| = 1K S = 20 (D < 0)

51. K. Vostrikova, P. Rey et al., JACS 2000, 122, 718 2nd generation 1rst generation Complex

52. Decurtins, Angewandte, 2000 Hashimoto, JACS, 2000 Marvaud, Chemistry, 2003, 9, 1677 y 1692 Rey, JACS 2000, 122, 718 Some examples … S = 27/2 S = 39/2 (AF) S = 14/2

53. CoNi5 CoNi3 CoCo3 CoCu3 CrNi 5/2 CrNi2 CoCo2CoNi2 CoCu2 7/2 Marvaud et al., Chemistry, 2003, 9, 1677 and 1692 Ariane Scuiller, Caroline Decroix, Martine Cantuel, Fabien Tuyèras …

54. CrNi2 CoCo2 CoCu6 CrNi CoNi5 CrNi3 CoNi2 CoNi3 CrNi3 CoCo6 CoCu2 CoCo3 CrCo3 CoCu3 5/2 7/2 9/2 27/2 Anisotropy High spin V. Marvaud CrMn 6 CoMn 6 CrNi6 15/2 CrCu6

55. [Mn 12 O 12 (CH 3 COO) 16 (H 2 O) 4 ].2CH 3 COOH.4H 2 0 Mn(IV) Mn(III) Ion Oxyde Carbone S=10 or Mn 12 From D.Gatteschi and R. Sessoli S=2 S=3/2 S =8x2 -4x3/2 =

56. Mn12 is a hard magnet Bistability : in zero field the magnetisation can be positive or negative depending of the story of the sample Coercive Field Remnant Magnetisation From D.Gatteschi and R. Sessoli

57. Ground State Energy Levels H = 0 M=±10 M=±9 M=±8 From D.Gatteschi and R. Sessoli

58. At low temperature, a magnetic field populates only the M = -S state M=-S M=S Energy Levels in a Magnetic Field H0H0 S -S

59. Going back to equilibrium : Thermal activation :trivial H=0  E=DS 2 M=-SM=S  =  0 exp(  E/k B T) Axial symmetry E(M) = DM 2 From D.Gatteschi and R. Sessoli

60. H=0 M=SM=-S Tunneling effect : new ! Towards equilibrium : From D.Gatteschi and R. Sessoli

61. M H Mn12 is a Hard Magnet + Steps in the magnetisation curve M saturation H coercive M remnant From D.Gatteschi and R. Sessoli

62. Resonnant Tunneling Effect for H = nD/g  B H = nD/g  B M=-S M=S From D.Gatteschi and R. Sessoli

63. Conditions to observe tunnelling effect Degenerated wave functions must superpose A transversal field must couple the two wave functions Coupling splits the two levels : “tunnel splitting” Tunnelling Effect Probability increases with tunnel splitting” From D.Gatteschi and R. Sessoli

64. M H Tunneling Effect From D.Gatteschi and R. Sessoli

65. No resonnant Tunneling Effect with a magnetic field parallel to z H  nD/g  B M = -S M = S From D.Gatteschi and R. Sessoli

66. M H No tunneling effect From D.Gatteschi and R. Sessoli

67. Anisotropic precursor [Fe(III)(bipy)(CN) 4 ] - R. Lescouëzec, M. Julve, Valencia, Spain D. Gatteschi, W. Wernsdorfer Angewandte Chem. 2003, 142, 1483-6 Feasibility of « Molecular nanowires » (or SCM) ?

68. [{Fe III (bpy)(CN) 4 } 2 M II (H 2 O)]. CH 3 CN. 1/2H 2 O [M = Mn, Co, Cu] [{Fe III (L)(CN) 4 } 2 Co II (H 2 O) 4 ]. 4H 2 O [{Fe III (L)(CN) 4 } 2 M II (H 2 O) 4 ]. 4H 2 O [L = 2,2’-bipy and 1, 10-phen), M = Mn, Co, Cu, Zn] Trinuclear species Double zig-zag chains Bis double zig-zag chains

69. M vs. t plots along the b axis. Magnetization as a function of time Thermally activated relaxation of the magnetization ac: E a = 142 K,  0 = 6.10 -11 s Slow relaxation of the magnetisation … W. Wernsdorfer, Grenoble

70. The dream … Surface Magnetic Tip H ≈ 10 nm High Spin "down" High Spin "down"

71. Surface Magnetic Tip H ≈ 10 nm High Spin "down" High Spin "down"

72. … information storage at the molecular level ! Surface Magnetic Tip H ≈ 10 nm HSM «up» High Spin "down" The dream …

73. Nanosciences … … a challenge for chemists and friends … Surface H ≈ 10 nm HSM «up» High Spin "down"