Self-assembly from the gas-phase: Design and implementation of small-molecule chromophore precursors with large nonlinear optical responses

David Frattarelli, Michele Schiavo, Antonio Facchetti, Mark A. Ratner, Tobin J. Marks

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Efficiently organizing molecular nonlinear optical (NLO) chromophores having large first-order hyperpolarizabilities (β) into acentric microstructures for electro-optic (EO) applications represents a significant materials synthesis and processing challenge, in part due to interchromophore dipolar interactions that promote centrosymmetric organization. Here we report the computational modeling, synthesis, and characterization of a series of eight heteroaromatic organic chromophores, designed to self-organize from the vapor phase via directed hydrogen-bond networks, into acentric thin films. Introduction of α,ω-donor-acceptor hydrogen-bonding substituents along the molecular long axes tunes properties such as hyperpolarizability, volatility, thermal stability, film-forming properties, and macroscopic NLO response (χ(2)). DFT-level molecular modeling, INDO/S optical property analysis, and sum-overstates computation indicate that molecular-core fluorination and hydrogen-bond donor incorporation can increase βvec up to 40x versus that of typical fluorine-free chromophores. Furthermore, inclusion of sterically induced biphenyl conjugative decoupling between chromophore π-donor substituents and the hydrogen-bonding donor sites increases β by ∼50%. Experimental thin-film second harmonic generation (SHG) spectroscopy confirms these trends in calculated responses, with χ(2) increasing 7.5x upon chromophore core fluorination and 15x with hydrogen-bonding donor substitution, thereby achieving macroscopic responses as high as 302 pm/V at ωo = 1064 nm. In addition to response trends, cluster calculations also reveal linear additivity in βvec with catenation for all benzoic acid-containing chromophores up to longitudinally aligned trimers. Linear scaling of SHG response with film thickness is observed for benzoic acid-containing chromophores up to 1.0 μm film thickness.

Original languageEnglish
Pages (from-to)12595-12612
Number of pages18
JournalJournal of the American Chemical Society
Volume131
Issue number35
DOIs
Publication statusPublished - Sep 9 2009

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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