@article{ae79bd687470494499bf55be1302fec4,
title = "Effect of the electron donating group on the excited-state electronic nature and epsilon-near-zero properties of curcuminoid-borondifluoride dyes",
abstract = "Epsilon-near-zero (ENZ) properties have been reported in organic molecular films. In particular, cyanine and squaraine films have been shown to exhibit ENZ properties in the visible spectral region with a strong 3rd order nonlinear optical response near the ENZ spectral region. Noting both cyanine and squaraine belong to the polymethine family, a series of six curcuminoid borondifluoride (Curc) derivatives were developed to examine whether such a polymethine character is positively correlated with the ENZ property of the organic films. Those Curc derivatives possess a Donor-Acceptor-Donor (D-A-D) architecture with acceptor, AcacBF2, located at the molecular center. The backbone of Curc is designed such that the donor strength can be tuned to transit between charge transfer (CT) and polymethine character. This balance between CT and polymethine character of the Curc series is examined based on the Lippert-Mataga plot. As donor strength in the D-A-D structure increases, CT character is less marked resulting in a more dominant polymethine character. The structural and optical properties of the Curc films with a thickness in the order of 30 nm were examined to correlate the polymethine character with the ENZ response. The results obtained in isotropic Curc thin films demonstrate that an increase of polymethine character associated with a stronger donor strength leads to an appearance/enhancement of the ENZ property in the visible spectrum range from 500 to 670 nm. Overall, this study provides useful guidelines to engineer new organic materials showing ENZ properties in a desired spectral range.",
author = "Choi, {Kyu Ri} and Kim, {Dae Hyeon} and Lee, {Yeon Ui} and Virginie Placide and Steven Huynh and Dandan Yao and Gabriel Canard and Elena Zaborova and Fabrice Mathevet and Lo{\"i}c Mager and Beno{\^i}t Heinrich and Ribierre, {Jean Charles} and Wu, {Jeong Weon} and Fr{\'e}d{\'e}ric Fages and Anthony D'Al{\'e}o",
note = "Funding Information: This work is supported by funding of the Ministry of Science, ICT & Future Planning, Korea (2014M3A6B3063708, 2017R1E1A1A01075394). YUL acknowledges National Research Foundation for funding (2021R1F1A1062916). This work was carried out in the framework of CNRSUMI2002 2B-FUEL {"}Building Blocks for Future Electronics Laboratory{"}. We further thank Pohang Accelerator Laboratory (PAL) for giving us the opportunity to perform the GIWAXS measurements, MEST and POSTECH for supporting these experiments, Dr Hyungju Ahn for adjustments and help, and other colleagues from the 9A USAXS beamline for assistance. Part of this work was also supported by the CNRS (PICS No 8085), France. Funding Information: This work is supported by funding of the Ministry of Science, ICT & Future Planning, Korea (2014M3A6B3063708, 2017R1E1A1A01075394). YUL acknowledges National Research Foundation for funding (2021R1F1A1062916). This work was carried out in the framework of CNRSUMI2002 2B-FUEL “Building Blocks for Future Electronics Laboratory”. We further thank Pohang Accelerator Laboratory (PAL) for giving us the opportunity to perform the GIWAXS measurements, MEST and POSTECH for supporting these experiments, Dr Hyungju Ahn for adjustments and help, and other colleagues from the 9A USAXS beamline for assistance. Part of this work was also supported by the CNRS (PICS No 8085), France. Publisher Copyright: {\textcopyright} The Royal Society of Chemistry.",
year = "2021",
month = nov,
day = "29",
doi = "10.1039/d1ra08025c",
language = "English",
volume = "11",
pages = "38247--38257",
journal = "RSC Advances",
issn = "2046-2069",
publisher = "Royal Society of Chemistry",
number = "60",
}