Twisted π-electron system electrooptic chromophores. Structural and electronic consequences of relaxing twist-inducing nonbonded repulsions

Yiliang Wang, David L. Frattarelli, Antonio Facchetti, Elena Cariati, Elisa Tordin, Renato Ugo, Cristiano Zuccaccia, Alceo Macchioni, Staci L. Wegener, Charlotte L. Stern, Mark A. Ratner, Tobin J. Marks

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31 Citations (Scopus)

Abstract

The synthesis, structural and spectroscopic characterization, and nonlinear optical response properties of a "slightly" twisted zwitterionic 4-quinopyran electrooptic chromophore FMC, 2-{4-[1-(2-propylheptyl)-1H-pyridine- 4-ylidene]cyclohexa-2,5-dienylidene}malononitrile, are reported. X-ray diffraction data and density functional theory (DFT) minimized geometries confirm that deletion of the four o-, o′-, o″-, and o‴-methyl groups in the parent chromophore TMC-2, 2-{4-[3,5-dimethyl-1-(2-propylheptyl)- 1H-pyridin-4-ylidene]-3,5-dimethylcyclohexa-2,5-dienylidene}malononitrile, relaxes the arene-arene twist angle from 89.6 to 9.0°. These geometrical changes result in a significantly increased contribution of the quinoidal structure to the molecular ground state of FMC (versus TMC-2), reduced solvatochromic shifts in the optical spectra, and a diminished electric-field-induced second-harmonic (EFISH) generation derived molecular hyperpolarizability (μβ = -2340 × 10-48 esu of DFMC, the dendrimer derivative of FMC, vs -24000 × 10-48 esu of TMC-2) in CH2Cl2 at 1907 nm. Pulsed field gradient spin-echo (PGSE) NMR spectroscopy and EFISH indicate that the levels of FMC aggregation in solution are comparable to those of TMC-2 (monomers and dimers) in CH2Cl2 solution. B3LYP and INDO/S computation of chromophore molecular structure, aggregation, and hyperpolarizability trends are in good agreement with experiment.

Original languageEnglish
Pages (from-to)8005-8015
Number of pages11
JournalJournal of Physical Chemistry C
Volume112
Issue number21
DOIs
Publication statusPublished - May 29 2008

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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    Wang, Y., Frattarelli, D. L., Facchetti, A., Cariati, E., Tordin, E., Ugo, R., Zuccaccia, C., Macchioni, A., Wegener, S. L., Stern, C. L., Ratner, M. A., & Marks, T. J. (2008). Twisted π-electron system electrooptic chromophores. Structural and electronic consequences of relaxing twist-inducing nonbonded repulsions. Journal of Physical Chemistry C, 112(21), 8005-8015. https://doi.org/10.1021/jp8003135