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Diquat Derivatives: Highly Active, Two-Dimensional Nonlinear Optical Chromophores with Potential Redox Switchability

Coe, Benjamin J. and Fielden, John and Foxon, Simon P. and Harris, James A. and Helliwell, Madeleine and Brunschwig, Bruce S. and Asselberghs, Inge and Clays, Koen and Garín, Javier and Orduna, Jess (2010) Diquat Derivatives: Highly Active, Two-Dimensional Nonlinear Optical Chromophores with Potential Redox Switchability. Journal of the American Chemical Society, 132 (30). pp. 10498-10512. ISSN 0002-7863. http://resolver.caltech.edu/CaltechAUTHORS:20100818-080217906

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Abstract

In this article, we present a detailed study of structure−activity relationships in diquaternized 2,2′-bipyridyl (diquat) derivatives. Sixteen new chromophores have been synthesized, with variations in the amino electron donor substituents, π-conjugated bridge, and alkyl diquaternizing unit. Our aim is to combine very large, two-dimensional (2D) quadratic nonlinear optical (NLO) responses with reversible redox chemistry. The chromophores have been characterized as their PF_6^− salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Their visible absorption spectra are dominated by intense π → π^* intramolecular charge-transfer (ICT) bands, and all show two reversible diquat-based reductions. First hyperpolarizabilities β have been measured by using hyper-Rayleigh scattering with an 800 nm laser, and Stark spectroscopy of the ICT bands affords estimated static first hyperpolarizabilities β_0. The directly and indirectly derived β values are large and increase with the extent of π-conjugation and electron donor strength. Extending the quaternizing alkyl linkage always increases the ICT energy and decreases the E_(1/2) values for diquat reduction, but a compensating increase in the ICT intensity prevents significant decreases in Stark-based β_0 responses. Nine single-crystal X-ray structures have also been obtained. Time-dependent density functional theory clarifies the molecular electronic/optical properties, and finite field calculations agree with polarized HRS data in that the NLO responses of the disubstituted species are dominated by ‘off-diagonal’ β_(zyy) components. The most significant findings of these studies are: (i) β_0 values as much as 6 times that of the chromophore in the technologically important material (E)-4′-(dimethylamino)-N-methyl-4-stilbazolium tosylate; (ii) reversible electrochemistry that offers potential for redox-switching of optical properties over multiple states; (iii) strongly 2D NLO responses that may be exploited for novel practical applications; (iv) a new polar material, suitable for bulk NLO behavior.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ja103289a DOIArticle
http://pubs.acs.org/doi/full/10.1021/ja103289aPublisherArticle
ORCID:
AuthorORCID
Coe, Benjamin J.0000-0002-5998-3895
Fielden, John0000-0001-5963-7792
Brunschwig, Bruce S.0000-0002-6135-6727
Additional Information:© 2010 American Chemical Society. Received April 19, 2010. Publication Date (Web): July 9, 2010. We thank the EPSRC for support (Grants EP/E000738 and EP/D070732) and also the Fund for Scientific Research-Flanders (FWO-V, G.0297.04), the University of Leuven (GOA/2006/3), MCyT-FEDER (CTQ2005-01368, CTQ2008-02942), the NSF (Grant CHE-0802907, ‘Powering the Planet: an NSF Center for Chemical Innovation’) and Gobierno de Aragon-Fondo Social Europeo (E39). We thank Dr. Emma C. Fitzgerald for assistance with obtaining the data for Figure 4, Kurt De Mey for assistance with the HRS studies, and Dr. John E. Warren (Synchrotron Radiation Source, CCLRC, Daresbury Laboratory, Warrington WA4 4AD, U.K.) for assistance with the data collection for [16][NapSO3]2 ·2H2O and [18][PF6]2 ·2Me2CO.
Group:CCI Solar Fuels
Funders:
Funding AgencyGrant Number
Engineering and Physical Sciences Research Council (EPSRC)EP/E000738
Engineering and Physical Sciences Research Council (EPSRC)EP/D070732
Fonds Wetenschappelijk Onderzoek - Vlaanderen (FWO)G.0297.04
University of LeuvenGOA/2006/3
Ministerio de Ciencia y Tecnología (MCyT)CTQ2005-01368
Ministerio de Ciencia y Tecnología (MCyT)CTQ2008-029
NSFCHE-0802907
Gobierno de Aragon-Fondo Social EuropeoE39
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Record Number:CaltechAUTHORS:20100818-080217906
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20100818-080217906
Official Citation:Diquat Derivatives: Highly Active, Two-Dimensional Nonlinear Optical Chromophores with Potential Redox Switchability Benjamin J. Coe, John Fielden, Simon P. Foxon, James A. Harris, Madeleine Helliwell, Bruce S. Brunschwig, Inge Asselberghs, Koen Clays, Javier Garn, Jess Orduna Journal of the American Chemical Society 2010 132 (30), 10498-10512
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19485
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:18 Aug 2010 16:48
Last Modified:06 Oct 2017 22:35

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