New N-pyrimidinyl stilbazolium crystals for second-order nonlinear optics. (December 2022)

• Record Type: Journal Article
• Authors: Shin, Bong-Rim; Kim, Se-In; Kim, Dongwook; Jazbinsek, Mojca; Yoon, Woojin; Yun, Hoseop; Yu, In Cheol; Rotermund, Fabian; Kwon, O-Pil
• Is Part Of: Optics & laser technology. Volume 156(2022)
• Publication Date: 2022-12
• Subjects: Nonlinear optics -- Chromophores -- Organic crystals -- Stilbazolium; Optics -- Periodicals; Lasers -- Periodicals; Electronic journals; 621.366
• DOI: 10.1016/j.optlastec.2022.108454
• Languages: English
• ISSNs: 0030-3992

Abstract

Graphical abstract: New cationic chromophore HPR (4-(4-hydroxy-3-methoxystyryl)-1-(pyrimidin-2-yl)pyridin-1-ium), with large first hyperpolarizability of up to 264 × 10 −30 esu, exhibits large off-diagonal macroscopic optical nonlinearity, which is approximately four times higher than that of the benchmark stilbazolium crystals. Highlights: New cationic HPR chromophore based on N -pyrimidinyl stilbazolium was developed. New HPR cationic chromophore exhibits large microscopic optical nonlinearity (264 × 10 −30 esu). HPR-based crystals exhibit large off-diagonal macroscopic optical nonlinearity, approximately four times higher than that of benchmark stilbazolium crystals. Abstract: We report a new π-conjugated cationic chromophore based on phenolic N -pyrimidinyl stilbazolium and its corresponding non-centrosymmetric crystals. The new cationic chromophore, HPR (4-(4-hydroxy-3-methoxystyryl)-1-(pyrimidin-2-yl)pyridin-1-ium), consists of a strong electron donor, the 4-hydroxy-3-methoxyphenyl group based on two electron-donating groups, and a strong electron acceptor, the N -pyrimidinyl pyridinium group based on two electron-withdrawing groups. The HPR chromophore possesses large molecular optical nonlinearity with first hyperpolarizability of up to 264 × 10 −30 esu, which is significantly larger than that of the benchmark stilbazolium chromophores. In solution, the HPR chromophore showed co-existence of phenol- and phenolate-like forms with two absorption bands (∼460 and ∼610 nm, respectively). In the crystalline state, all HPR-based derivatives with three different counter anions, N2S (naphthalene-2-sulfonate), VBS (4-vinylbenzenesulfonate), and NBS (3-nitrobenzenesulfonate), exhibit a macroscopic second-order nonlinear optical response. HPR-N2S crystals exhibit non-centrosymmetric monoclinic Pn space group symmetry and large off-diagonal effective macroscopic optical nonlinearity (94 × 10 −30 esu), which is approximately four times higher than that of the benchmark stilbazolium crystals. Therefore, the newly developed HPR-based crystals are highly promising materials for second-order nonlinear optical applications.