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Tunable Chiral Second-Order Nonlinear Optical Chromophores Based on Helquat Dications

Buckley, Laura E. R. and Coe, Benjamin J. and Rusanova, Daniela and Joshi, Vishwas D. and Sánchez, Sergio and Jirásek, Michael and Vávra, Jan and Khobragade, Dushant and Severa, Lukáš and Císařová, Ivana and Šaman, David and Pohl, Radek and Clays, Koen and Depotter, Griet and Brunschwig, Bruce S. and Teplý, Filip (2017) Tunable Chiral Second-Order Nonlinear Optical Chromophores Based on Helquat Dications. Journal of Physical Chemistry A, 121 (31). pp. 5842-5855. ISSN 1089-5639.

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Fourteen new dipolar cations have been synthesized, containing methoxy or tertiary amino electron donor groups attached to helquat (Hq) acceptors. These Hq derivatives have been characterized as their TfO^– salts by using various techniques including NMR and electronic absorption spectroscopies. UV–vis spectra show intense, relatively low energy absorptions with λ_(max) ≈ 400–600 nm, attributable to intramolecular charge-transfer (ICT) excitations. Single-crystal X-ray structures have been solved for two of the chromophores, one as its PF_6^– salt, revealing centrosymmetric packing arrangements (space groups Pbca and P1̅). Molecular quadratic nonlinear optical (NLO) responses have been determined directly by using hyper-Rayleigh scattering (HRS) with a 800 nm laser, and indirectly via Stark (electroabsorption) spectroscopy for the low energy absorption bands. The obtained static first hyperpolarizabilities β_0 range from moderate to large: (9–140) × 10^(–30) esu from HRS in MeCN and (44–580) × 10^(–30) esu from the Stark data in PrCN. The magnitude of β_0 increases upon either extending the π-conjugation length or replacing a methoxy with a tertiary amino electron donor substituent. Density functional theory (DFT) and time-dependent DFT calculations on selected tertiary amino chromophores confirm that the low energy absorptions have ICT character. Relatively good agreement between the simulated and experimental UV–vis absorption spectra is achieved by using the CAM-B3LYP functional with the 6-311G(d) basis set. The β_(tot) values predicted by using DFT at the same level of theory are large ((472–1443) × 10^(–30) esu in MeCN). Both the theoretical and experimental results show that para-conjugation between Hq and electron donor fragments is optimal, and enlarging the Hq unit is inconsequential with respect to the molecular quadratic NLO response.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Coe, Benjamin J.0000-0002-5998-3895
Brunschwig, Bruce S.0000-0002-6135-6727
Additional Information:© 2017 American Chemical Society. Received: June 20, 2017; Revised: July 12, 2017; Published: July 13, 2017. This work was supported by ASCR (RVO: 61388963, M200551208 to F.T.), the Czech Science Foundation (13-19213S to F.T.), Ministry of Health of the Czech Republic (16-31156A to F.T.), the Fund for Scientific Research-Flanders (Research Grant 1510712N), the University of Leuven (GOA/2011/03), and the EPSRC (grants EP/G020299/1 and EP/J018635/1 to B.J.C.). B.S.B. acknowledges the Beckman Institute of the California Institute of Technology for support. The authors declare no competing financial interest.
Funding AgencyGrant Number
Academy of Sciences of the Czech Republic61388963
Academy of Sciences of the Czech RepublicM200551208
Czech Science Foundation13-19213S
Ministry of Health (Czech Republic)16-31156A
Fonds Wetenschappelijk Onderzoek - Vlaanderen (FWO)1510712N
University of LeuvenGOA/2011/03
Engineering and Physical Sciences Research Council (EPSRC)EP/G020299/1
Engineering and Physical Sciences Research Council (EPSRC)EP/J018635/1
Issue or Number:31
Record Number:CaltechAUTHORS:20170714-133626347
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Official Citation:Tunable Chiral Second-Order Nonlinear Optical Chromophores Based on Helquat Dications Laura E. R. Buckley, Benjamin J. Coe, Daniela Rusanova, Vishwas D. Joshi, Sergio Sánchez, Michael Jirásek, Jan Vávra, Dushant Khobragade, Lukáš Severa, Ivana Císařová, David Šaman, Radek Pohl, Koen Clays, Griet Depotter, Bruce S. Brunschwig, and Filip Teplý The Journal of Physical Chemistry A 2017 121 (31), 5842-5855 DOI: 10.1021/acs.jpca.7b06057
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79112
Deposited By: Tony Diaz
Deposited On:14 Jul 2017 21:10
Last Modified:03 Oct 2019 18:16

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