1. Putting Fluorous Tails to Work. From Catalysis to Optoelectronics Gianluca Pozzi CNR - Istituto di Scienze e Tecnologie Molecolari via Golgi 19, 20133 Milano gianluca.pozzi@istm.cnr.it

2. Fluorous = of, relating to, or having the characteristic of highly fluorinated saturated organic materials, molecules or molecular fragments (J.A. Gladysz, D.P. Curran Tetrahedron 2002, 58, 3823)

3. Biomedical technologies SynthesisMaterials Life Science Fluorous Nanoparticles Metabolomics Microaarray Surface coating Proteomics Imaging Drug delivery Blood substituents Reagents High- throughput techniques PG Crystal engineering Catalysis Biphasic Organocatalysis Asymmetric ….. Organic (opto)electronics A Cinderella in the Fluorous World ?

4. Bordeaux (France) 2005 Jackson Hole (USA) 2009 Yokohama (Japan) 2007 Fluorous catalysis and synthesis with a pinch of other topics. Organic electronics never cited. Catalysis and synthesis still well represented. Increased attention to other fluorous applications, but organic electronics. Fluorous materials take the lead (self-assembly, nanostructures). Fluorous molecules for organic electronics are mentioned at last (S. Gorun ).

5. Mainly conjugated oligomers and polymers with aromatic and vinylic C-F bonds Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022 Emissive layer in OLEDsp-type semiconductor (OFETs) …but also compounds with fluorous tails, including monomeric species n-type semiconductors (OFETs)

6. Increased thermal and oxidative stability Enhanced hydrophobicity and lipophobicity Lower LUMO and HOMO energy levels Charge mobility along preferred directions (self-assembled molecular architectures ) Improved processability Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022

7. Mainly conjugated oligomers and polymers with aromatic and vinylic C-F bonds Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022 …but also compounds with fluorous tails, including monomeric species Emissive layer in OLEDsp-type semiconductor (OFETs) n-type semiconductors (OFETs)

9. High-Performance n-Type Organic Thin-Film Transistors Based on Solution Processable Perfluoroalkyl-Substituted C60 Derivatives M. Chikamatsu, A. Itakura, Y. Yoshida, R. Azumi, K. Yase Chem. Mater. 2008, 20, 7365-7367 Excellent field-effect electron mobility  e = 0.25 cm 2 V -1 s -1 TFTs still operating when exposed to air

10. Functionalized Perylenes: Origin of the Enhanced Electrical Performances C. Piliego, F. Cordella, D. Jarzab, S. Lu, Z. Chen, A. Facchetti, M. A. Loi Appl. Phys. A 2009, 95, 303-308. Solution processable (spin coating) Electron mobility  e = 0.15 cm 2 V -1 s -1 High degree of co-facial arrangement and smooth morphology

12. Self-organized Buffer Layers in Organic Solar Cells Q. Wei, T. Nishizawa, K. Tajima, K. Hashimoto Adv. Mater. 2008, 20, 1-6 PCBMF-PCBM PCBM P3HT F-PCBM Al PEDOT:PSS ITO + - Donor Acceptor

13. Self-organized Buffer Layers in Organic Solar Cells Q. Wei, T. Nishizawa, K. Tajima, K. Hashimoto Adv. Mater. 2008, 20, 1-6 PCBM P3HT F-PCBM Al PEDOT:PSS ITO + - Donor Acceptor Decreased hole-electron recombination loss at the P3HT / Al interface Reduced energy barrier for electron injection and collection decreased metal work function ? increased HOMO and LUMO energy levels of the organic layer ?

14. Phase Separation and Affinity between a Fluorinated Perylene Diimide Dye and an Alkyl-Substituted Hexa-peri- Hexabenzocoronene G. De Luca, A. Liscio, M. Melucci, T. Schnitzler, W. Pisula, C. G. Clark, L. Monsù Scolaro, V. Palermo, K. Müllen, P. Samorì J. Mater. Chem. 2010, 20, 71–82 n-type semiconductor (acceptor) p-type semiconductor (donor) Strong intermolecular interaction in the blends (C–H …. F–C interactions +  -stacking) Control of the phase separation at different scales

15. Semiperfluoroalkyl Polyfluorenes for Orthogonal Processing in Fluorous Solvents J.-K. Lee, H. H. Fong, A. A. Zakhidov, G. E. McCluskey, P. G. Taylor, M. Santiago-Berrios, H. D. Abruna, A. B. Holmes, G. G. Malliaras, C. K. Ober Macromolecules 2010, 43, 1195-1198 Light emitting polymers Increased band gap (blue emission) Photolitographic conditions compatible with fluorous solvents HFE-7500

16. Catalysis (Opto)electronics Dyes Liquid Crystals Photo- litography Photodynamic therapy Phthalocyanine derivatives (Pcs)

17. Catalysis Phthalocyanine derivatives (Pcs) (Aerobic) Oxidation of hydrocarbons, alcohols, organic sulfides Photooxidations (photodegradation of pollutants) Degradation of lignin ….

18. Catalysis Phthalocyanine derivatives (Pcs) Separation from products Site isolation Bleaching …. A fluorous approach can help

19. Harsh reaction conditions Number and location of R F = ? Fluorous Pcs I. Rábai in Handbook of Fluorous Chemistry, Wiley-VCH 2004, Ch. 14 Functionalization of preformed Pcs

20. Eur. J. Org. Chem. 2001, 181 Milder reaction conditions Better control on substitution pattern Cyclization of fluorous building-blocks Fluorous Pcs

21. Catalyst Substrate Organic phase Fluorous phase Recycling Catalyst Product Reaction O2O2

22. M. Özer et al. Appl. Organometal. Chem. 2009, 23, 55 FB oxidation of benzylic alcohol Spacers matter time = 9h P O2 = 2 atm Conv. = 6.5% time = 24h P O2 = 6 atm Conv. = 6.5% Fluorous Pcs

23. (Opto)electronics Phthalocyanine derivatives (Pcs) Nonlinear optical materials Electrochromic devices TFT Dye Sensitized Solar Cells (DSC) ….

24. -- Red Ox - - TCO FTO TCO FTO Mesoporous semiconductor film Nanostructured metal oxide (TiO 2, 100-300 nm) Thickness = 2 – 10  m Sensitizer Ru polypyridyl complexes Organic dyes, other metal complexes (extended) conjugated  -systems Working electrode (Photoanode) TCO = Trasparent conducting oxide FTO = Fluorine-doped SnO 2 Charge carrier Electrolyte with a redox shuttle (I - /I 3 - ) Organic hole transporter Counterelectrode (Cathode) Pt = catalyst for the electrochemical reduction of the charge carrier Pt SemiconductorSensitizer

25. (1) Light absorption and photoexcitation S + h  S* (2) Electron injection S* S + + e - TiO 2 (3) Dye regeneration 2 S + + 3 I - 2 S + I 3 - (4) Carrier regeneration I 3 - + 2 e - Pt 3 I - (5) Recombination S + + e - TiO 2 S (6) Dark current I 3 - + 2 e - TiO 2 3 I - Photocurrent generation Side Processes V vs NHE -0.5 -- e-e- e-e- HOMO LUMO S* S/S + e-e- E CB EFEF (1) (2) (3) I3-I3- e-e- e-e- I-I- (4) (5)(6) 0 0.5 1.0 Maximum voltage

26. Electron injection Proper energy levels / location of MO; good electronic contact with TiO 2 Light harvesting Elevated  over visible and NIR regions Dye functions Stability (in the ground, excited and oxidized states) Reduced e - recombination (and dark current) incidence Non-aggregating properties Hydrophobicity Further requirements TiO 2 D A  e-e-

27. Electron injection Energy levels / location of MO ? Electronic contact with TiO 2 ? Stability (in the ground, excited and oxidized states) Reduced e - recombination (and dark current) incidence Non-aggregating properties Hydrophobicity Further requirements Light harvesting Intense absorption  in the red / NIR, transparency over a large portion of the Vis Dye functions

28. Electron injection Stability (in the ground, excited and oxidized states) Reduced e - recombination (and dark current) incidence Non-aggregating properties Hydrophobicity Further requirements Light harvesting Dye functions D A  e-e- E. Palomares et al. Chem. Commun. 2004, 2112

29. Electron injection Stability (in the ground, excited and oxidized states) Reduced e - recombination (and dark current) incidence Non-aggregating properties Hydrophobicity Further requirements Light harvesting Dye functions D A  e-e- P. Y. Reddy et al. Angew. Chem. Int. Ed. 2007, 46, 373. H. Imahori et al. Acc. Chem. Res. 2009, 42, 1809

30. Electron injection Stability (in the ground, excited and oxidized states) Reduced e - recombination (and dark current) incidence Non-aggregating properties Hydrophobicity …at least we hope so! Light harvesting Unsymmetrical Fluorous Pcs D A  e-e-

31. = Bulky fluorous electron-donating moiety ???? M = Zn = (COOH) n

32. B. A. Bench et al. Angew. Chem. Int. Ed. 2002, 41, 748 S. P. Keizer et al. J. Am. Chem. Soc. 2003, 125, 7067 C. Keil et al. Thin Solid Films 2009, 517, 4379 Gorun’s ZnPc Does not aggregate Stable Active (photo) oxygenation catalyst … R. Gerded et al. Dalton Trans. 2009, 209, 1098 EW –CF(CF 3 ) 2 groups

33. Spacers matter A lesson learned from catalysis

34. Dipole Vector 3.04 Debye

35. LUMO  E HOMO-LUMO = 2 eV ( abs 620 nm)

36. LUMO PcCOO-Ti(IV).

37. H.Weitman et al. Photochem. Photobiol. 2001, 73, 473 Does not aggregate Stable enough to be used as a photosensitizer CF 3 CH 2 O- = EW character Does not aggregate Acceptable photosensitivity CF 3 CH 2 O- = positive mesomeric effect M. R. Reddy et al. Angew. Chem. Int. Ed. 2006, 45, 8163

38. No intramolecular electron and/or charge transfer Pc = donor; fullerene = acceptor in standard Pc-fullerene dyads CF 3 CH 2 O- EW effect prevails D. Sukeguchi et al. J. Fluorine. Chem. 2009, 130,361

39. Unsymmetrical Fluorous Pcs M = Zn = (COOH) n =

40. Unsymmetrical Fluorous Pcs Statistical condensation affords mixtures of Pcs (mainly A 4 and A 3 B products) Chromatographic separation of A 4, A 3 B, A 2 B 2,…. is possible X = H products A 3 B are obtained as mixtures of regioisomers Chromatographic separation of regioisomers is not feasible A3BA3B A B

41. F 81 -ZnPc(COOH) n Unsymmetrical Fluorous Pcs UV-Vis, IR, MALDI-TOF

42. Fluorous Phthalonitriles

44. Template tetracyclization fails to afford the corresponding Pc

45. Fluorous Phthalonitriles Template tetracyclization affords the corresponding Pc

46. Unsymmetrical Fluorous Pcs Faintly soluble in PFCs F 68 -ZnPcCOOH Aggregation in organic solvents F 27 -ZnPc(COOH)2 Soluble in OS + freon F 54 -ZnPc(COOH) 2

47. F 81 -ZnPc(COOH) 2 Unsymmetrical Fluorous Pcs F 81 -ZnPcCOOH Soluble in OS, addition of amphiphilic solvents (BTF, freon…) helps Processable for DSC

48. Unsymmetrical Fluorous Pcs Light harvesting Intense absorption  in the red / NIR, transparency over a large portion of the Vis F81-ZnPcCOOH (Et 2 O) 1.7 x 10 -5 M3.4 x 10 -6 M 664 nm675 nm 603 nm 344 nm ( nm) A

49. Unsymmetrical Fluorous Pcs Light harvesting Intense absorption  in the red / NIR, transparency over a large portion of the Vis F81-ZnPc(COOH) 2 (Et 2 O/CCl 2 FCF 2 Cl 3/1) 1.6 x 10 -5 M3.2 x 10 -6 M 664 nm681 nm 633 nm 344 nm ( nm) A

50. Unsymmetrical Fluorous Pcs Light harvesting Intense absorption  in the red / NIR, transparency over a large portion of the Vis ( nm) A (a.u.) 400500600700800 F81-ZnPc(COOH) 2 (Et 2 O/CCl 2 FCF 2 Cl 3/1)F81-ZnPc(COOH) 2 on TiO 2 681 nm695 nm ( nm) A (a.u.)

51. V vs NHE -0.5 -- e-e- e-e- HOMO LUMO S* S/S + e-e- E CB EFEF (1) (2) (3) I3-I3- e-e- e-e- I-I- (4) (5)(6) 0 0.5 1.0 E* Ox = E Ox – E 0-0 E* Ox = Excited state oxidation potential E Ox = Ground state oxidation potential (measured by cyclic or DP voltammetry) E 0-0 = Vibrational transition energy (estimated form the intersection of normalized Absorption and Emission spectra) Electron injection

52. Differential Pulse Voltammetry E peak = 0.59 V I (  A) E peak = 0.71 V 0.00.20.40.60.81.00.00.20.40.60.81.0 0.80.35 V (vs SCE) 0.1 I (  A) 0.05 F81-ZnPcCOOH F81-ZnPc(COOH) 2 E Ox = E peak +  E/2 Pulse amplitude = 20 mV

53. Unsymmetrical Fluorous Pcs abs (nm) em (nm) E 0-0 (eV )E ox (V vs SCE)E* ox (V vs SCE) F81-ZnPcCOOH 349 664 675 6871.80+0.60-1.20 F81-ZnPc(COOH)2 344 633 664 681 6941.79+0.72-1.07 Electron injection Energy levels E CB = -0.6 / -0.7 V vs SCE E 0 I - /I 3 - = +0.25 V vs SCE

54. Unsymmetrical Fluorous Pcs in DSC Photocurrent/voltage curve (J/V curve) open-circuit voltage (Voc) short-circuit photocurrent density (Jsc) fill factor (ff) Solar energy to electricity conversion yield (η). Influenced by all the cell components (type of electrode, electrolyte, …) Incident Photon-to-Current Conversion Efficiency (IPCE) depends mostly on the dye Opaque TiO 2 (DSL 18NR-AO - Dyesol) Electrolyte = 1-Methyl-3-Propylimidazolium Iodide (MPI-I) 0.6 M, LiI 0.1 M, I 2 = 0.02 M in methoxypropionitrile (MPN)

55. Unsymmetrical Fluorous Pcs in DSC Photocurrent/voltage curve (J/V curve) J (mA/cm 2 ) V (V) 0.0 0.20.3 0.4 0.1 0.0 1.0 2.0 3.0 4.0 Open-circuit voltage (V oc ) = 0.39 V Short-circuit photocurrent density (J sc ) = 3.65 mA/cm 2 Fill factor (ff) = (V mp J mp ) / (V oc J sc ) = 0.34 Voc Jsc F81-ZnPcCOOH η =  J sc V oc ff = 0.43% Simulated solar irradiation I 0 = 110 mW/cm 2 Cell configuration = not optimized

56. Unsymmetrical Fluorous Pcs in DSC Photocurrent/voltage curve (J/V curve) F81-ZnPc(COOH)2 Open-circuit voltage (V oc ) = 0.40 V Short-circuit photocurrent density (J sc ) = 6.92 mA/cm 2 Fill factor (ff) = (V mp J mp ) / (V oc J sc ) = 0.50 Simulated solar irradiation I 0 = 110 mW/cm 2 η =  J sc V oc ff = 1.32% Cell configuration = not optimized

57. Unsymmetrical Fluorous Pcs in DSC J SC F81-ZnPcCOOH < J SC F81-ZnPc(COOH)2 Light absorption capability (Absorption Spectroscopy) Kinetics of dye regeneration (Electrochemical Impedance Spectroscopy) Electron injection efficiency (Photocurrent Action Spectroscopy) Regeneration of the oxidized dye F81-ZnPcCOOH by I - is slower than regeneration of F81-ZnPc(COOH)2 E ox (V vs SCE) F81-ZnPcCOOH = + 0.60 E ox (V vs SCE) F81-ZnPc(COOH)2 = + 0.72 E 0 I - /I 3 - = +0.25 V vs SCE

58. Unsymmetrical Fluorous Pcs in DSC Incident Photon-to-Current Conversion Efficiency (IPCE) Number of flowing electrons per incident photons of wavelength IPCE ( ) % = x photon flux 1240 x photocurrent density IPCE ( ) = LHE ( )  inj  coll LHE ( ) = light harvesting efficiency for photons of wavelength f (Dye) f (TiO 2 film)  inj = quantum yield of electron injection  coll = efficiency of collection of the injected electron in the external circuit

59. Unsymmetrical Fluorous Pcs in DSC Incident Photon-to-Current Conversion Efficiency (IPCE) Number of flowing electrons per incident photons of wavelength Plot IPCE ( ) % vs A useful tool for the evaluation of new sensitizers IPCE ( ) = LHE ( )  inj  coll LHE ( ) = light harvesting efficiency for photons of wavelength  inj = quantum yield of electron injection  coll = efficiency of collection of the injected electron in the external circuit

60. Photocurrent Action Spectra F81-ZnPc(COOH)2 F81-ZnPcCOOH Semiconductor = Opaque TiO 2 (DSL 18NR-AO - Dyesol) Electrolyte = 1-Methyl-3-propylimidazolium iodide 0.6 M, LiI 0.1 M, I 2 = 0.02 M in MPN Additives = None Irradiation = 150 W Xe lamp + monochromator. Electron injection is more efficient for F81-ZnPc(COOH)2  (nm) IPCE %

61. Photocurrent Action Spectra F81-ZnPc(COOH)2 Semiconductor = Opaque TiO 2 (DSL 18NR-AO - Dyesol) Electrolyte = 1-Methyl-3-propylimidazolium iodide 0.6 M, LiI 0.1 M, I 2 = 0.02 M in MPN Irradiation = 150 W Xe lamp focused through a monochromator. F81-ZnPc(COOH)2 + Cheno 10 mM Co-adsorption of anti-aggregating chenodeoxycholic acid does not improve IPCE F81-ZnPc(COOH)2 + Cheno 20 mM  (nm) IPCE %

62. F81-ZnPcCOOH IPCE % max Additives S. Eu at al. Dalton Trans. 2008, 5476 4.9%TBP 24.2 6.9 Cheno + TBP None J. He at al. JACS, 2002, 124, 4922 L. Giribabu at al. Sol. Energy Mater. Sol. Cells 2007, 91, 1611 25Cheno + TBP 74Cheno + TBP 60TBP J-H Yum et al. Langmuir 2008, 24, 5636 F81-ZnPc(COOH)2 63.7None 33.9None Fluorous tails work !

63. Branched fluorous tails have been successfully used to tune the stereoelectronic and aggregation behaviour of Pcs The EW character of fluorous tails can be tamed Unsymmetrical fluorous Pcs are promising sensitizers for DSC Summary The potential of fluorous molecules as components of (opto)electronic devices is worth investigating

64. Evaluation of more unsymmetrical fluorous Pcs Dye cocktails (fluorous Pc/organic dye) in DSC D-A fluorous dyes (EW R F ) in DSC Solid state DSC based on fluorous dyes and hole transporters Fluorous molecules for bulk p-n heterojunction PV cells Molecular architectures Efficient devices Electronic features Cell setup Outlook

65. CNR project PM004.004 “Molecular, supramolecular and macromolecular components for photonics and optoelectronics”  CNR-ISTM, Milan Dr. Marco Cavazzini Dr. Silvio Quici Dr. Maria Concetta Raffo University of Ferrara (DSC) Prof. Carlo Alberto Bignozzi Dr. Stefano Caramori Fondazione CARIPLO “PRESTO project” Thanks to…