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Experimental Demonstration of the Dependence of the First Hyperpolarizability of Donor-Acceptor-Substituted Polyenes on the Ground-State Polarization and Bond Length Alternation

Bourhill, Grant and Brédas, Jean-Luc and Cheng, Lap-Tak and Marder, Seth R. and Meyers, Fabienne and Perry, Joseph W. and Tiemann, Bruce G. (1994) Experimental Demonstration of the Dependence of the First Hyperpolarizability of Donor-Acceptor-Substituted Polyenes on the Ground-State Polarization and Bond Length Alternation. Journal of the American Chemical Society, 116 (6). pp. 2619-2620. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20180529-154153450

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Abstract

It has been suggested that optimizing the first hyperpolarizability, β, of donor-acceptor compounds requires a specific donor-acceptor strength for a given conjugated bridge. For donor-acceptor polyenes, β can be maximized when an optimal degree of mixing between neutral and charge-separated canonical resonance forms This degree of mixing is related to the donor-acceptor strength and a molecular parameter, bond length alternation (BLA), defined as the difference between the average carbon-carbon single and double bond lengths in the polymethine backbone. The degree of BLA arises from the linear combination, or mixing, of the two-limiting charge-transfer resonance forms of the molecule (Figure 1).4 For unsubstituted polyenes or chromophores with weak donors-acceptors, the neutral canonical form is the dominant contributor to the ground state, resulting in large positive BLA. As the donor-acceptor strength increases, the charge-separated resonance structure contributes more to the ground state, resulting in smaller BLA, until both resonance forms contribute equally and the ground-state structure possesses essentially zero BLA, analogous to a symmetrical cyanine. Increasing the ground-state polarization further results in the charge-separated canonical form dominating the ground-state structure, leading to negative BLA.


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https://dx.doi.org/10.1021/ja00085a052DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/ja00085a052PublisherSupporting Information
Additional Information:© 1994 American Chemical Society. Received November 23, 1993. The research described in this paper was performed in part by the Jet Propulsion Laboratory (JPL), California Institute of Technology, and was supported by the Advanced Research Projects Agency and the Ballistic Missiles Defense Initiative Organization, Innovative Science and Technology Office, through a contract with the National Aeronautics and Space Administration (NASA). Support from the National Science Foundation (Grant No. CHE-9106689) and the North Atlantic Treaty Organization is gratefully acknowledged. G.B. thanks the National Research Council and NASA for a Resident Research Associateship at JPL. The work by F.M. is carried out within the framework of the Belgium Prime Minister Office of Science Policy "Pole d'Attraction Interuniversitaire en Chimie Supramoleculaire et Catalyse". The authors would like to thank Dr. Brian M. Pierce for helpful discussions and Matthew J. Perry and Ging Lee for experimental assistance.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Ballistic Missile Defense OrganizationUNSPECIFIED
NSFCHE-9106689
North Atlantic Treaty Organization (NATO)UNSPECIFIED
National Research CouncilUNSPECIFIED
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20180529-154153450
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180529-154153450
Official Citation:Experimental Demonstration of the Dependence of the First Hyperpolarizability of Donor-Acceptor-Substituted Polyenes on the Ground-State Polarization and Bond Length Alternation Grant Bourhill, Jean-Luc Bredas, Lap-Tak Cheng, Seth R. Marder, Fabienne Meyers, Joseph W. Perry, and Bruce G. Tiemann Journal of the American Chemical Society 1994 116 (6), 2619-2620 DOI: 10.1021/ja00085a052
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86688
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:29 May 2018 23:21
Last Modified:03 Oct 2019 19:46

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