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

doi:10.1021/jacs.8b04320

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

Chemistry

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

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 language	English (US)
Pages (from-to)	8746-8755
Number of pages	10
Journal	Journal of the American Chemical Society
Volume	140
Issue number	28
DOIs	https://doi.org/10.1021/jacs.8b04320
State	Published - Jul 18 2018

Funding

This work was supported by AFOSR MURI grant FA9550_14_1_0040 and made use of the IMSERC facility at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the State of Illinois and International Institute for Nanotechnology (IIN). A. J.-T.L. thanks NDSEG for a Graduate Research Fellowship. A.M. and C.Z. thank PRIN 2015 (20154 × 9ATP 004) for financial support. The University of Perugia and MIUR are also acknowledged for financial support to the project AMIS through the program “Dipartimenti di Eccellenza-2018−2022”. We also thank Dr. C. Malliakas for assistance in solving the crystal structure of B0TMC-2.

ASJC Scopus subject areas

General Chemistry
Biochemistry
Catalysis
Colloid and Surface Chemistry

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10.1021/jacs.8b04320

Cite this

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title = "Unprecedented Large Hyperpolarizability of Twisted Chromophores in Polar Media",

abstract = " 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.",

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AU - Macchioni, Alceo

AU - Marks, Tobin J.

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Unprecedented Large Hyperpolarizability of Twisted Chromophores in Polar Media

Abstract

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CCDC 1859724: Experimental Crystal Structure Determination

CCDC 1859725: Experimental Crystal Structure Determination

CCDC 1859726: Experimental Crystal Structure Determination

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Unprecedented Large Hyperpolarizability of Twisted Chromophores in Polar Media

Abstract

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ASJC Scopus subject areas

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CCDC 1859724: Experimental Crystal Structure Determination

CCDC 1859725: Experimental Crystal Structure Determination

CCDC 1859726: Experimental Crystal Structure Determination

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