2,1,3-Benzothiadiazole dyes conjugated with benzothiazole and benzoxazole: Synthesis, solvatochromism and solid-state properties

• Published in: Journal of molecular liquids 2020-12, Vol.319, p.114277, Article 114277
• Main Authors: Maliszewsk Paczkowski, Ingrid, Lange Coelho, Felipe, Franciscato Campo, Leandra
• Format: Article
• Language: English
• Subjects: Benzothiazole dyes; Benzoxazole dyes; BTD dyes; Fluorescence; Solid-state emitters
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2020.114277

Benzothiadiazole (BTD) dyes are an important class of N,S-containing heterocycles that have remarkable optical properties. In this work, two new 2,1,3-benzothiadiazole dyes conjugated with benzothiazole and benzoxazole moieties were synthesized and the optical properties in solutions and in the solid state were investigated. The BTD dyes were synthesized in a single step from cyclization of ortho-diamino benzothiazole and ortho-diamino benzoxazole dyes. The photophysical behavior of BTD precursor's benzoxazole and benzothiazole dyes were also investigated. The dyes present absorption in the UVB (280–315 nm) and UVA (315–400 nm) wavelength and fluorescence in the blue-green visible region. The solvatochromic properties of the dyes were investigated in different solvents taking into account the solvent orientation polarizability (Δf) and ET (30) polarity solvent parameter. The ground and excited state dipole moments were determined by applying Bakshiev's and Kawaski-Chamma-Viallet's formulations. Furthermore, the spectroscopic properties of thin films and powders of BTD dyes were explored. [Display omitted] •Synthesis of 2,1,3-BTD dyes in two simple steps and with good yield•Insertion of benzothiazole and benzoxazole chromophoric and fluorogenic units in the structure of 2,1,3-BTD dyes•The ground and excited state dipole moments of dyes were determined by Bakshiev’s and Kawaski-Chamma-Viallet’s formulations•The new 2,1,3-BTD dyes are solid-state fluorescence emitters