Unprecedented Large Hyperpolarizability of Twisted Chromophores in Polar Media

Alexander J.T. Lou, Stefania Righetto, Christopher Barger, Cristiano Zuccaccia, Elena Cariati, Alceo Macchioni, Tobin J. Marks*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Twisted intramolecular charge transfer (TICT) chromophores exhibit uniquely large second-order optical nonlinearities (μβ). However, their promise as electro-optic (E-O) materials is yet untapped, reflecting a strong tendency to aggregate in low-polarity media, leading to a dramatic fall in μβ. Until now, TICT chromophores in deaggregating polar solvents suffered decreased response due to polarity-driven changes in electronic structure. Here we report a new series of benzimidazolium-based TICT chromophores with interaryl torsional angles in the range of 64-77°. The most twisted, B2TMC-2, exhibits a large μβ vec = -26,000 × 10 -48 esu (at 1907 nm) in dilute nonpolar CH 2 Cl 2 solution, which is maintained in polar DMF (μβ vec = -20,370 × 10 -48 esu) as measured by DC electric field-induced second harmonic generation (EFISH). Sterically enforced interaryl torsional angles are confirmed by single-crystal X-ray diffraction and solution phase Nuclear Overhauser Effect (NOE) NMR, and spectroscopic characterization reveals a zwitterionic/aromatic ground state electronic structure associated with the high μβ. We show that increasingly disrupted conjugation is correlated with increased μβ even at intermediate twist angles. The excellent performance and reduced aggregation in polar solvents opens new avenues for bridging microscopic and macroscopic chromophore performance.

Original languageEnglish (US)
Pages (from-to)8746-8755
Number of pages10
JournalJournal of the American Chemical Society
Issue number28
StatePublished - Jul 18 2018

ASJC Scopus subject areas

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


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