Physico-Chemical nanomaterials science

Synthesis and photophysical properties of indolenine styrylcyanine dye and its carboxyl-labeled derivative 
Svitlana Chernii1,2, Roman Selin1, Iryna Tretyakova1, Yan Dovbiy1, 
Viktor Chernii1, Vasyl Pekhnyo1, Vladyslava Kovalska1,2

1V.I. Vernadsky Institute of General and Inorganic Chemistry NASU, 32/34 Palladin Ave, 03-142 Kyiv, Ukraine
2Institute of Molecular Biology and Genetics NASU, 150 Zabolotnogo Street, 03143 Kyiv, Ukraine 
*corresponding author chernii.sv@gmail.com

Organic fluorescent dyes are widely used as a working medium in dye lasers, in analytical chemistry to determine the various trace elements, in photodynamic therapy, in tissue optics, in the analysis of cells, etc. Depending on the sphere of application of fluorophores their various properties: quantum yield and photostability, pH dependence, and fluorescence lifetime are essential [1]. 
Herein, two indolenine-based styrylcyanine dyes functionalized by the carboxyl group at the indolenine ring were synthesized and characterized. UV-VIS absorption and fluorescence spectra of these dyes in organic solvents (DMSO, ACN, MeOH) were studied.
The absorption maxima of the studied dyes in organic solvents are located in the range of 544-563 nm, and the molar extinction values were moderate in the range (5.3-7.7)×104 M-1cm-1 depending on solvent and dye structure.  Dyes’ fluorescence intensity in DMSO was 4-5 times higher than in MeOH and ACN. The emission maximum was shifted to the short-wavelength region for both dyes in MeOH (compared to DMSO and ACN). Depending on the solvent, the excitation was located in the range of 547-564 nm, with the emission in the range of 593-609 nm. The introduction of a carboxyl group in the indolenine ring leads to a bathochromic shift of the absorption maximum. These dyes can be further characterized as potential probes for biological application.
Acknowledgments. S.Ch. and R.S. are grateful for the grant of a group of young scientists no. 0122U002204 (2022–2023) and for the grant for young scientists № 0121U112233 (2021-2022) NAS of Ukraine.

1.	Kurtaliev, E. N. Spectroscopic study of interaction of styrylcyanine dye Sbt and its derivatives with bovine serum albumin // Journal of Luminescence. -2012. -132, N 9. -P. 2281–2287.