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Daniele Fazzi Matteo Tommasini Andrea Lucotti Mirella Del Zoppo Giuseppe Zerbi

OPTICAL PROPERTIES OF ADAMANTYL END-CAPPED POLYYNES: FROM EXPERIMENTS AND FIRST PRINCIPLES SIMULATIONS. Daniele Fazzi Matteo Tommasini Andrea Lucotti Mirella Del Zoppo Giuseppe Zerbi. W. Chalifoux R. R. Tykwinski.

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Daniele Fazzi Matteo Tommasini Andrea Lucotti Mirella Del Zoppo Giuseppe Zerbi

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  1. OPTICAL PROPERTIES OF ADAMANTYL END-CAPPED POLYYNES: FROM EXPERIMENTS AND FIRST PRINCIPLES SIMULATIONS Daniele Fazzi Matteo Tommasini Andrea Lucotti Mirella Del Zoppo Giuseppe Zerbi W. Chalifoux R. R. Tykwinski

  2. Linear sp carbon chains are gathering interest for the direct investigation of the physical properties of one dimensional systems. • Adamantyl groups stabilize the highly reactive sp carbon chain. • They are possible candidates for non linear optical applications thanks to their large second order hyperpolarizability γ. γvib Largeγvalues (among the largest for conjugated systems) γelec (DOKE) γv/γestrictly related: large e-ph coupling Vibrational (Raman and IR) and electronic (UV-vis) spectroscopies are used to study the optical and structural properties of these systems

  3. NC≡C= 6 The vibrational contribution (γv) to the second order hyperpolarizability can be written as a function of absolute Raman intensities (Ii) and vibrational wavenumbers (νi) [1]: Я normal mode [1] C.Castiglioni et al., Solid State Commun.82 (1992) 13 Superlinear increase ofγv ! Breaking of mutual exclusion principle Dispersion of Raman and IR active normal mode, with the chain length Nc≡c=10 Nc≡c=5 ωIR Nc≡c=4 Nc≡c=8 ωЯ Nc≡c=6 Nc≡c=3

  4. 0-0 Fit of experimental UV-Vis spectra via Franck-Condon factors: 0-1 Nc=20 0-2 HOMO 0-3 0-4 LUMO ZINDO simulations on PBEPBE/cc-pVDZ optimized geometries From fit we obtained: ωЯg • The vibrational frequency of the excited state and its dispersion with the chain length ωЯe 2. The displacement parameter B between the ground and excited state along the Я normal mode

  5. Based on the theoretical analysis of the transition dipole moment [2] and supported by the Albrecht’s theory [3], we can obtained the following relationship: Experimental confirmation Nelec: number of electrons; ΔE: energy-gap; I: Raman intensity; B: displacement parameter; [2] M. G. Kuzyk, Optics Letters, 25, 1183 (2000) [3] A. C. Albrecht, J.Chem.Phys.34, 1476 (1961) Conclusion: • Adamantyl capped polyynes show a relevant NLO response (γ) of both electronic and vibrational nature 2. The violation of the IR-Raman mutual exclusion principle points to a bent equilibrium structure of the molecules in solution (bow-like shape) 3. The coupling of the π-π* excitation with the Я coordinate is experimentally demonstrated from the detailed analysis of the UV-Vis absorption spectra. This is also supported by the theoretical analysis of HOMO and LUMO orbitals

  6. ZINDO TD-DFT

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