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The organic (optoelectronic) revolution  What is optoelectronics? The study and application of electronic devices that sou...
Advantages of organic versus inorganic LEDs  <ul><li>tuning of chemical structure    different optical and electronic pro...
Classes of organic emitters for OLEDs <ul><li>purely organic dyes </li></ul><ul><ul><li>- fluorescent (limited to 25% effi...
Properties of lanthanide ions <ul><li>Shielding of 4f orbitals   </li></ul><ul><ul><li>similar chemical properties </li><...
Advantages of lanthanide complexes in optoelectronics <ul><li>one ligand, different emission colors (even NIR)  </li></ul>...
Sensitization of lanthanide ions Indirect excitation by energy transfer from a suitable  antenna  to the lanthanide ion <u...
Antennas for lanthanides organic chromophores  (pyridines, phenantroline) d-metal complexes  (Ru II , Pt II , Ir III ) mat...
The design of lanthanide complexes <ul><li>Connecting the antenna to negatively charged groups (carboxylate)   </li></ul><...
Luminescent lanthanide architectures for optoelectronics  <ul><li>synthesize new stable lanthanide architectures </li></ul...
The tetrazole motif in coordination chemistry <ul><li>carboxylate often used for lanthanide coordination </li></ul><ul><li...
Lanthanide complexes based on pyridine-tetrazolates
Design of tetrazole-based ligands terpyridine  ligands – pentadentate bipyridine  ligands – tetradentate pyridine  ligands...
Organic synthesis of terpyridine-based ligands Andreiadis et al,  submitted ; patent pending
Organic synthesis of bipyridine-based ligands
Organic synthesis of pyridine-based ligands Easy access to tetrazole-based ligands
Lanthanide complexes with terpyridine-based ligands Giraud,  Inorg. Chem.  2008 ,  47 , 3952-3954 the tetrazole-based liga...
Lanthanide complexes with bipyridine-based ligands Andreiadis et al,  submitted [Ln( L ) 2 ] - , Ln = Eu, Tb
Lanthanide complexes with pyridine-based ligands Andreiadis et al,  submitted [Ln( L ) 3 ] 3- , Ln = Nd, Eu, Tb
Increasing the solubility in chlorinated solvents isolated as an oil <ul><li>ligand functionalization </li></ul><ul><li>ch...
Stability of tetrazolate-based complexes logβ 2  = 10.5(5)  logβ 2  = 11.8(4) [Eu L ] + [Eu L 2 ] - L 2- [Eu L ] + [Eu L 2...
Absorption properties of pyridine-based complexes 250 275 300 325 350 0 1 2 3 4 Wavelength / nm ε  / 10 4  cm -1 M -1 arom...
Absorption properties of bipyridine-based complexes 250 275 300 325 350 375 400 0 1 2 3 4 Wavelength / nm ε  / 10 4  cm -1...
Absorption properties of terpyridine-based complexes 250 300 350 400 450 500 0 2 4 6 8 10 Wavelength / nm ε  / 10 4  cm -1...
Photophysical properties of terpyridine-based complexes Modulation of ligand triplet state Ligand triplet states
Photophysical properties of terpyridine-based complexes Emission quantum yields Eu: 35% Tb: 6% Nd: 0.22% Eu: 36% Tb: 35% N...
Photophysical properties of terpyridine-based complexes Emission quantum yields Eu: 35% Tb: 6% Nd: 0.22% Eu: 36% Tb: 35% N...
Photophysical properties of bipyridine-based complexes Eu: 45% Tb: 27% Eu: 54% Tb: 13% Eu: 63% Tb: 6% Measured after dryin...
Photophysical properties of pyridine-based complexes Eu: 61% Tb: 65% Nd: 0.21% Eu: 39% Eu: 24% * Tb: 22% * * Chauvin, Spec...
Neutral lanthanide diketonate complexes
New approach towards neutral lanthanide complexes <ul><li>Lanthanide complexes employed in optoelectronics  </li></ul><ul>...
Terpyridine carboxylic acid leads to stable homoleptic mono- or poly-metallic complexes [Ln  (LnL 2 ) 6 ](OTf) 9 ∩ [Ln(L) ...
Synthesis and properties of the complexes QY = 41% QY = 13% Investigate potential applications in OLED devices <ul><li>com...
Preliminary testing in OLED devices Excellent film-forming properties (doping in PVK matrix)  <ul><li>Collaboration Dr. Pa...
Heterometallic iridium-europium complexes
Indirect excitation using  d-transitional metals  by   inter-metallic  communication Sensitization of europium by d-metals...
Heterometallic complex - strategy and ligand design <ul><li>terpyridine-tetrazolate motif for lanthanide complexation </li...
Synthesis of iridium-based ligand
<ul><li>1 H NMR and X-ray diffraction studies prove the retention of Ir conformation during the synthesis </li></ul>Synthe...
Synthesis of the heterometallic complex 1 H NMR indicates a similar structure  to the mono-metallic lanthanide complexes [...
Protophysical properties of the heterometallic complex 300 400 500 600 700 800 0,0 0,5 1,0 1,5 2,0 2,5 intensity / a.u. wa...
Final conclusions and perspectives <ul><li>combining stability with tuning  </li></ul><ul><li>of absorption and emission p...
Acknowledgements Dr. Marinella MAZZANTI Dr. Renaud DEMADRILLE Dr. Daniel IMBERT Dr. Jacques PECAUT Prof. Luisa DE COLA, Pr...
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Andreiadis PhD Presentation

The main objective of my PhD research at CEA Grenoble (M. Mazzanti, R. Demadrille) was related to a better understanding of the structure-property relationship in emissive lanthanide complexes with potential applications in opto-electronic devices. This was achieved by a careful design of lanthanide antennas based on either organic chromophores or transition metals as ligands, followed by a study of the structural and photophysical properties of the resulting complexes, in order to estimate and further predict the sensitization efficiencies.

In a first line of research, we have described and patented the incorporation of tetrazole groups as carboxylic acid replacements for the sensitization of lanthanide emission. We were able to show how the variation of ligand substituents influences the photophysical properties, allowing us to draw predictions and to adapt the structures for improving the emission efficiency. Some of the compounds have been successfully tested in OLED devices.

We also became interested in designing and studying new types of polymetallic architectures based on iridium complexes for the sensitization of lanthanide emission, as well as preliminary investigating the grafting of lanthanide complexes on silicon surfaces.

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Andreiadis PhD Presentation

  1. 2. The organic (optoelectronic) revolution What is optoelectronics? The study and application of electronic devices that source, detect and control light LEDs solar cells lasers PM <ul><li>the classical devices use inorganic materials: Si, GaN, Y 2 O 2 S:Eu, YAG:Nd </li></ul>CRT <ul><li>1987: Tang and van Slyke demonstrate the first organic optoelectronic device </li></ul><ul><li>nowadays: </li></ul>
  2. 3. Advantages of organic versus inorganic LEDs <ul><li>tuning of chemical structure  different optical and electronic properties </li></ul><ul><li>(potentially) very cheap production </li></ul><ul><ul><li>- low temperature </li></ul></ul><ul><ul><li>- scalable to large area </li></ul></ul><ul><li>(potentially) very energy efficient </li></ul><ul><li>synthetic flexibility </li></ul><ul><ul><li>ultra-thin and lightweight </li></ul></ul><ul><ul><li>self-luminescent  no backlighting </li></ul></ul><ul><ul><li>the substrates can be flexible or transparent </li></ul></ul><ul><li>new paradigm in the field </li></ul>
  3. 4. Classes of organic emitters for OLEDs <ul><li>purely organic dyes </li></ul><ul><ul><li>- fluorescent (limited to 25% efficiency) </li></ul></ul><ul><ul><li>- broad emission bands </li></ul></ul><ul><ul><li>- photo-bleaching </li></ul></ul><ul><li>organometallic complexes </li></ul><ul><ul><li>- phosphorescent </li></ul></ul><ul><ul><li>(theoretical 100% efficiency) </li></ul></ul><ul><ul><li>- broad emission bands </li></ul></ul><ul><ul><li>- sensitivity to oxygen </li></ul></ul><ul><li>lanthanide complexes with organic ligands </li></ul><ul><ul><li>- first example: Kido, 1990 </li></ul></ul>
  4. 5. Properties of lanthanide ions <ul><li>Shielding of 4f orbitals  </li></ul><ul><ul><li>similar chemical properties </li></ul></ul><ul><ul><li>electrostatic bonding </li></ul></ul><ul><ul><li>variable geometry and CNs </li></ul></ul><ul><ul><li>hard acid behaviour </li></ul></ul>Lu Yb Tm Er Ho Dy Tb Gd Eu Sm Pm Nd Pr Ce La <ul><li>Fascinating optical properties: </li></ul><ul><ul><li>luminescence from f-f transitions </li></ul></ul><ul><ul><li>characteristic emission for each ion </li></ul></ul><ul><ul><li>narrow emission bands </li></ul></ul><ul><ul><li>long excited-states lifetimes </li></ul></ul>Ln III ground state [Xe]4f n , n = 0..14 blue  NIR Applications in optoelectronics and bio-medicine
  5. 6. Advantages of lanthanide complexes in optoelectronics <ul><li>one ligand, different emission colors (even NIR) </li></ul><ul><li>no oxygen sensitivity and no photo-bleaching </li></ul><ul><li>sharp emission  pure colors (no filters) </li></ul><ul><li>easier coordination chemistry </li></ul>f-f transitions are forbidden the excited states cannot be efficiently populated directly
  6. 7. Sensitization of lanthanide ions Indirect excitation by energy transfer from a suitable antenna to the lanthanide ion <ul><li>Antenna requirements: </li></ul><ul><li>excellent energy harvester </li></ul><ul><li>efficient inter-system crossing </li></ul><ul><li>matching electronic levels </li></ul><ul><li>Deactivation: </li></ul><ul><li>radiative processes ( fluorescence , phosphorescence ) </li></ul><ul><li>non-radiative processes ( vibration-induced ) </li></ul><ul><li>electronic processes ( energy back-transfer ) </li></ul>Antenna Ln III 1 S 3 T absorption ISC ET Antenna excitation Energy transfer Light emission
  7. 8. Antennas for lanthanides organic chromophores (pyridines, phenantroline) d-metal complexes (Ru II , Pt II , Ir III ) matrixes (PVK, CBP)
  8. 9. The design of lanthanide complexes <ul><li>Connecting the antenna to negatively charged groups (carboxylate) </li></ul><ul><li>Associating the antenna to diketonate complexes </li></ul><ul><li>low stability </li></ul><ul><li>few structure-property relationships </li></ul><ul><li>difficult optimization </li></ul>Grenthe, J. Am. Chem. Soc. 1961 Bunzli, Spectrosc. Lett. 2007 Bunzli, Dalton Trans. 2000 Latva, J. Lumin. 1997 Mazzanti, Angew. Chem. Int. Ed. 2005
  9. 10. Luminescent lanthanide architectures for optoelectronics <ul><li>synthesize new stable lanthanide architectures </li></ul><ul><li>tuned absorption and emission properties by ligand design </li></ul><ul><li>investigate their potential for applications in optoelectronics </li></ul><ul><li>high denticity ligands with negatively charged groups </li></ul><ul><li>sensitizing antenna: - organic chromophores </li></ul><ul><li> - d-metal complexes </li></ul>
  10. 11. The tetrazole motif in coordination chemistry <ul><li>carboxylate often used for lanthanide coordination </li></ul><ul><li>no luminescent lanthanides </li></ul><ul><li>no comparative studies </li></ul><ul><li>Tetrazole-based complexes of d-metals: </li></ul><ul><li>high thermodynamic stability </li></ul><ul><li>interesting properties </li></ul>Very few examples in lanthanide coordination chemistry! <ul><li>tetrazole - highly acidic, aromatic </li></ul><ul><li>tetrazolate could replace carboxylate </li></ul><ul><li>tuning of absorption wavelength </li></ul>Aime, Tetrahedron Lett. 2002 , 43 , 783 Facchetti, Chem. Commun. 2004 , 1770
  11. 12. Lanthanide complexes based on pyridine-tetrazolates
  12. 13. Design of tetrazole-based ligands terpyridine ligands – pentadentate bipyridine ligands – tetradentate pyridine ligands – tridentate <ul><li>influence of tetrazolate on the properties of the complexes </li></ul><ul><li>direct comparison with carboxylate analogues </li></ul>
  13. 14. Organic synthesis of terpyridine-based ligands Andreiadis et al, submitted ; patent pending
  14. 15. Organic synthesis of bipyridine-based ligands
  15. 16. Organic synthesis of pyridine-based ligands Easy access to tetrazole-based ligands
  16. 17. Lanthanide complexes with terpyridine-based ligands Giraud, Inorg. Chem. 2008 , 47 , 3952-3954 the tetrazole-based ligands are well adapted to lanthanide complexation [Ln( L ) 2 ] - , Ln = Nd, Eu, Tb
  17. 18. Lanthanide complexes with bipyridine-based ligands Andreiadis et al, submitted [Ln( L ) 2 ] - , Ln = Eu, Tb
  18. 19. Lanthanide complexes with pyridine-based ligands Andreiadis et al, submitted [Ln( L ) 3 ] 3- , Ln = Nd, Eu, Tb
  19. 20. Increasing the solubility in chlorinated solvents isolated as an oil <ul><li>ligand functionalization </li></ul><ul><li>change of counterion </li></ul>Solubility – strong advantage for the applications in OLED devices (wet process)
  20. 21. Stability of tetrazolate-based complexes logβ 2 = 10.5(5) logβ 2 = 11.8(4) [Eu L ] + [Eu L 2 ] - L 2- [Eu L ] + [Eu L 2 ] - L 2- Comparable stability to carboxylate analogues <ul><li>stable without dissociation in air and wet methanol solutions </li></ul><ul><li>quantitative study by UV titration </li></ul>
  21. 22. Absorption properties of pyridine-based complexes 250 275 300 325 350 0 1 2 3 4 Wavelength / nm ε / 10 4 cm -1 M -1 aromatic tetrazolate  increase of absorption wavelength and intensity [Ln( L ) 3 ] 3-
  22. 23. Absorption properties of bipyridine-based complexes 250 275 300 325 350 375 400 0 1 2 3 4 Wavelength / nm ε / 10 4 cm -1 M -1 [Ln( L ) 2 ] -
  23. 24. Absorption properties of terpyridine-based complexes 250 300 350 400 450 500 0 2 4 6 8 10 Wavelength / nm ε / 10 4 cm -1 M -1 substituents  tuning of absorption wavelength and intensity [Ln( L ) 2 ] -
  24. 25. Photophysical properties of terpyridine-based complexes Modulation of ligand triplet state Ligand triplet states
  25. 26. Photophysical properties of terpyridine-based complexes Emission quantum yields Eu: 35% Tb: 6% Nd: 0.22% Eu: 36% Tb: 35% Nd: 0.09 % Eu: 29% Tb: 0.1% Eu: 28% Eu: 5% Nd: 0.29% Nd: 0.19%  Tuning of emission quantum yields Modulation of ligand triplet state [Ln( L ) 2 ] - Very good QY for Eu (35%) and Nd (0.29%)
  26. 27. Photophysical properties of terpyridine-based complexes Emission quantum yields Eu: 35% Tb: 6% Nd: 0.22% Eu: 36% Tb: 35% Nd: 0.09 % Eu: 29% Tb: 0.1% Eu: 28% Eu: 5% Nd: 0.29% Nd: 0.19% Terbium QY function of triplet state Latva, J. Lumin. 1997 [Ln( L ) 2 ] -
  27. 28. Photophysical properties of bipyridine-based complexes Eu: 45% Tb: 27% Eu: 54% Tb: 13% Eu: 63% Tb: 6% Measured after drying [Ln( L ) 2 ] - Similar tuning of emission quantum yields
  28. 29. Photophysical properties of pyridine-based complexes Eu: 61% Tb: 65% Nd: 0.21% Eu: 39% Eu: 24% * Tb: 22% * * Chauvin, Spectr. Lett. 2007 , 40, 193 <ul><li>excellent quantum yields </li></ul><ul><li>for pyridine-tetrazole complexes </li></ul>[Ln( L ) 3 ] 3- <ul><li>solubility in chlorinated solvents </li></ul>Possible applications in OLEDs
  29. 30. Neutral lanthanide diketonate complexes
  30. 31. New approach towards neutral lanthanide complexes <ul><li>Lanthanide complexes employed in optoelectronics </li></ul><ul><li>neutral (vacuum processing) </li></ul><ul><li>based on the β -diketonate motif </li></ul><ul><li>additional soft, neutral ligands </li></ul>Replacing neutral chromophores with negatively charged ones for increasing the stability of the complex Preliminary testing in OLED devices <ul><li>low stability </li></ul><ul><li>dissociation during processing </li></ul>
  31. 32. Terpyridine carboxylic acid leads to stable homoleptic mono- or poly-metallic complexes [Ln (LnL 2 ) 6 ](OTf) 9 ∩ [Ln(L) 2 ](OTf) Ln= Eu, Gd, Tb, Nd The terpyridine-monocarboxylate ligand Bretonnière, J. Am. Chem. Soc., 2002 , 124 , 9012 Chen, Inorg. Chem ., 2007 , 46 , 625 formation of heteroleptic complexes with β -diketonate units:
  32. 33. Synthesis and properties of the complexes QY = 41% QY = 13% Investigate potential applications in OLED devices <ul><li>complexes stable in air and solution </li></ul><ul><li>good quantum yields </li></ul>
  33. 34. Preliminary testing in OLED devices Excellent film-forming properties (doping in PVK matrix) <ul><li>Collaboration Dr. Pascal Viville (Univ. Mons) </li></ul><ul><li>testing in OLED devices (spin-coating) </li></ul><ul><li>classical device architecture </li></ul><ul><li>the OLED devices display promising results </li></ul><ul><li>rather low current intensities: 5.4 mA/cm 2 at 25V (Eu) </li></ul><ul><ul><ul><li>45 mA/cm 2 at 20V (Tb) </li></ul></ul></ul>device optimization in progress + – – Al (cathode) ITO (anode ) glass substrate Cs 2 CO 3 PVK : Ln complex PEDOT:PPS
  34. 35. Heterometallic iridium-europium complexes
  35. 36. Indirect excitation using d-transitional metals by inter-metallic communication Sensitization of europium by d-metals Ir III complexes - modulation of emission energy by the coordinated ligands Thompson et al. Inorg Chem 2005, 44 , 7992 <ul><li>absorption at visible wavelength </li></ul><ul><li>sensitization of NIR emitting lanthanides </li></ul><ul><li>europium sensitization requires high energy </li></ul>Coppo, Angew. Chem. Int. Ed., 2005 , 44 , 1806 use blue-emitting Ir complexes
  36. 37. Heterometallic complex - strategy and ligand design <ul><li>terpyridine-tetrazolate motif for lanthanide complexation </li></ul><ul><li>several target ligands investigated </li></ul>Connecting the metal ions by a completely covalent structure (stability)
  37. 38. Synthesis of iridium-based ligand
  38. 39. <ul><li>1 H NMR and X-ray diffraction studies prove the retention of Ir conformation during the synthesis </li></ul>Synthesis of iridium-based ligand
  39. 40. Synthesis of the heterometallic complex 1 H NMR indicates a similar structure to the mono-metallic lanthanide complexes [Eu( L ) 2 ] -
  40. 41. Protophysical properties of the heterometallic complex 300 400 500 600 700 800 0,0 0,5 1,0 1,5 2,0 2,5 intensity / a.u. wavelength / nm η Ir-Eu = 85-90% QY = 0.96% ex 400 nm selective excitation of Ir moiety <ul><li>iridium  europium energy transfer </li></ul><ul><li>residual emission from iridium </li></ul><ul><li>very good energy transfer efficiency </li></ul><ul><li>Eu emission due exclusively to Ir </li></ul>promising architecture
  41. 42. Final conclusions and perspectives <ul><li>combining stability with tuning </li></ul><ul><li>of absorption and emission properties </li></ul><ul><li>improving the stability of neutral diketonate </li></ul><ul><li>complexes by using charged chromophores </li></ul><ul><li>polyvalent stable heterometallic architecture </li></ul><ul><li>with very high Ir  Eu transfer efficiency </li></ul> extending the work to other architectures (podates) <ul><li>tetrazole-based antennas for lanthanide </li></ul> applications in OLEDs and surface grafting  applications in OLEDs  improving europium emission efficiency  extending the chemistry to other metals
  42. 43. Acknowledgements Dr. Marinella MAZZANTI Dr. Renaud DEMADRILLE Dr. Daniel IMBERT Dr. Jacques PECAUT Prof. Luisa DE COLA, Prof. Jean WEISS, Prof. Muriel HISSLER, Dr. Guy ROYAL Yann KERVELLA, Dr. Bruno JOUSSELME, Prof. Alexander FISYUK Colette LEBRUN, Pierre-Alain BAYLE European Community Marie Curie EST “CHEMTRONICS” MEST-CT-2005-020513 Dr. Pascal VIVILLE (Mons University), Prof. Jean-Claude BUNZLI (EPFL) my colleagues and friends

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