Projects per year
Abstract
Currently, there is immense interest in the chemistry of push–pull heptamethines containing a strong acceptor of 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF). This class of compounds is important as second-order nonlinear optical (NLO) chromophores for electro-optic (EO) applications. The crystal packing of TCF-based NLO chromophores is generally dominated by intermolecular π–π stacking and non-classical C–H···N(cyano) hydrogen bonding interactions, considerably limiting the bulk NLO properties of chromophores in solid films. In this paper, we report a series of TCF-based push–pull heptamethines bearing the substituent of 4,5-diphenyl-oxazol-2-ylsulfanyl group at the central position of the π-conjugated bridge. Crystallographic studies show a very uncommon crystal packing mode of one-dimensional chain structure with vanished C–H···N(cyano) contacts and negligible π–π stacking. Such reduced intermolecular interactions and fine-tuned bond length alternation lead to NLO performance breakthrough of these chromophores in poled polymeric films, including much better EO coefficients up to 465% in improvement, higher polar order, and larger molecular hyperpolarizabilities (up to 4,135 × 10–30 esu at 1304 nm), over the results from the simple chloro-substituted heptamethines. Our study indicates that the interplay of steric effect, non-classical C–H···N hydrogen bonding, and intermolecular π–π stacking is critically important in optimizing the supramolecular assembly and NLO properties of TCF-based heptamethines for photonic applications.
Original language | English |
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Pages (from-to) | 3702-3711 |
Number of pages | 10 |
Journal | Chemistry of Materials |
Volume | 33 |
Issue number | 10 |
Online published | 5 May 2021 |
DOIs | |
Publication status | Published - 25 May 2021 |
Bibliographical note
Information for this record is supplemented by the author(s) concerned.Research Keywords
- Noncovalent interactions
- Chromophores
- Molecular interactions
- Thin films
- Nonlinear optics, materials
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- 1 Finished
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GRF: Ultra-Efficient Supramolecular Organic Electro-Optic Materials for Hybrid Graphene Organic Platform
LUO, J. (Principal Investigator / Project Coordinator)
1/01/21 → 5/06/25
Project: Research