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THE ROLE OF THE METAL AND OF THE SOLVENT ON THE SECOND ORDER NLO RESPONSE OF

THE ROLE OF THE METAL AND OF THE SOLVENT ON THE SECOND ORDER NLO RESPONSE OF [5-[[4’-(DIMETHYLAMINO)PHENYL]ETHYNYL]-15- [(4’’-NITROPHENYL)ETHYNYL]-10,20- DIPHENYLPORPHINATO]M(II) (M = Ni, Zn): A DFT, TDDFT AND EFISH INVESTIGATION. Francesca Tessore

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THE ROLE OF THE METAL AND OF THE SOLVENT ON THE SECOND ORDER NLO RESPONSE OF

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  1. THE ROLE OF THE METAL AND OF THE SOLVENT ON THE SECOND ORDER NLO RESPONSE OF [5-[[4’-(DIMETHYLAMINO)PHENYL]ETHYNYL]-15- [(4’’-NITROPHENYL)ETHYNYL]-10,20- DIPHENYLPORPHINATO]M(II) (M = Ni, Zn): A DFT, TDDFT AND EFISH INVESTIGATION Francesca Tessore Dip. Chimica Inorganica Metallorganica e Analitica UdR INSTM Centro di Eccellenza CIMaINa dell’Università degli Studi di Milano VI Convegno INSTM Perugia, 12-15 giugno 2007

  2. A LITTLE BIT OF HYSTORY… Therien, M. J. et al. J. Am. Chem. Soc. 1996, 118, 1497 M = Cu(II), Zn(II) Second order NLO response by Hyper Rayleigh Scattering (HRS) at 1064 nm M = Zn M = Cu bHRS, 1064 = 1501 x 10-30 esu bHRS, 1064 = 4933 x 10-30 esu

  3. A LITTLE BIT OF HYSTORY… Therien, M. J. et al. J. Am. Chem. Soc. 1998, 120, 2660 Second order NLO response by both absorption and electroabsorption (Stark effect) data Lower! b1064 = 1710 x 10-30 esu

  4. A LITTLE BIT OF HYSTORY… Ng, D. K. P. et al. J. Org. Chem. Soc. 1998, 63, 7143 Second order NLO response by Electric Field Induced Second Harmonic (EFISH) generation at 1907 nm Even lower! bEFISH, 1907 = 124 x 10-30 esu bEFISH, 1907 = 66 x 10-30 esu

  5. A LITTLE BIT OF HYSTORY… Pizzotti, M. et al. J. Porph. And Phtal. 2004, 8, 1311 Second order NLO response by Electric Field Induced Second Harmonic (EFISH) generation at 1907 nm Good agreement! bEFISH, 1907 = 73.2 x 10-30 esu

  6. Large difference on the order of magnitude of b measured by various experimental techniques (value of incident wavelength!) Overestimation of bHRS due to fluorescent emission At 1064 nm, resonance enhancement between the SH (532 nm) and the B and Q bands of the chromophores Not totally negligible contribution of the cubic term g(-2w; w, w, 0) in the EFISH response Role of the metal IN SUMMARY… Pay attention when comparing results!

  7. To compare data obtained under similar and well defined conditions To better understand the role of the metal and of the solvent on the second order NLO response OUR FOCUS

  8. OUR OBJECTS M = Cu(II), Zn(II), Ni(II)

  9. DFT and TDDFT theoretical investigations (collaboration with the research group of Prof. A. Sgamellotti in Perugia) EFISH and UV-vis experimental investigation (only on Zn(II) and Ni(II) complexes): Incident wavelength = 1907 nm (not resonant!) Range of concentration = 10-4M – 10-6M Solvents = CHCl3 (non polar); DMF (polar and donor); CHCl3 + pyridine OUR “WEAPONS”

  10. SYNTHESIS OF THE CHROMOPHORES-1 Ni(II)

  11. SYNTHESIS OF THE CHROMOPHORES-2 Zn(II)

  12. DFT RESULTS - GEOMETRY For all calculations: Gaussian03 program package For DFT calculation: B3LYP exchange-correlation functional For Zn(II) and Ni(II): closed shell singlet ground state For Cu(II): open shell doublet configuration Optimized molecular structure for Zn(II) complex (planar configuration, favoured over the twisted by 3.4 Kcal/mol) De Angelis, F. et al. umpublished results

  13. No influence of the metal on the length of the triple C-C bond (values close to that of free acetilene (1.21Å)). Influence of the metal on the metal-ring nitrogen distance (the shortening from Zn(II), d10, to Ni(II), d8 shows the increased bonding of the metal) DFT RESULTS - GEOMETRY De Angelis, F. et al. umpublished results

  14. TD-HF TD-DFT data in vacuo Good agreement between theory and experiment TDHF AND TDDFT RESULTS – ABSORPTION SPECTRA De Angelis, F. et al. umpublished results

  15. TDHF AND TDDFT RESULTS – ABSORPTION SPECTRA De Angelis, F. et al. umpublished results

  16. HOMO: on donor moiety and on porphyrin N and meso atoms LUMO: on acceptor moiety and porphyrin pyrrole C atom and meso C atom to which donor and acceptor are connected LUMO: energy almost constant HOMO: energy slightly decreases in going from Zn to Ni TDHF AND TDDFT RESULTS – HOMO-LUMO De Angelis, F. et al. umpublished results

  17. The nature of the metal does not influence the second order NLO response of the complexes (similar values of blzzz). Significant resonance enhancement at 1064 nm! TDHF AND TDDFT RESULTS – QUADRATIC HYPERPOLARIZABILITY

  18. EFISH TECHNIQUE gEFISH = mbl/5kT+g0(-2w; w, w, 0)

  19. EFISH RESULTS ON Zn(II) COMPLEX

  20. b values lower than those previously reported • values in DMF and CHCl3 with pyridine are very close to the theoretical one • depends upon the solvent: it is higher in non polar CHCl3 and lower in a polar and donor solvent such as DMF or in CHCl3 with pyridine aggregation processes! • reaches comparable values in DMF and CHCl3 with pyridine b of the pentacoordinated “naked” complex (no aggregation) EFISH RESULTS ON Zn(II) COMPLEX

  21. UV-VIS SPECTRA OF Zn(II) COMPLEX

  22. similar values of b in CHCl3 and DMF, at 5x10-5M b values increase with increasing dilution aggregation? EFISH RESULTS ON Ni(II) COMPLEX mtheor = 13.2 D

  23. UV-VIS SPECTRA OF Ni(II) COMPLEX

  24. CONCLUSIONS CONCLUSIONS Both theoretical and experimental investigation show that there is no role of the metal in tuning the second order NLO response of the kind of porphyrinic chromophores here considered. An interesting role seems on the contrary to be played by aggregation processes (different for Zn(II) and Ni(II) complexes and related to the solvent), which surely deserve further investigation. Porphyrins are interesting substrates for optical limiting.

  25. MIUR, Project FIRB 2003 “Molecular compounds and hybrid nanostructured materials with resonant and non resonant optical properties for photonic devices” CNR Research group of Prof. Renato Ugo and Prof. Maddalena Pizzotti @ Unimi Research group of Prof. Antonio Sgamellotti @ Unipg ACKNOWLEDGMENTS

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