Synthesis of novel viscosity sensitive pyrrolo-quinaldine based styryl dyes: Photophysical properties, electrochemical and DFT study

Synthesis of A2-D2-A1-D1 type red-emitting unsymmetrical squaraine dye: Influence of additional pyridine moiety on photophysical, electrochemical, photo and thermal stability

We have synthesized a π-conjugated acceptor-donor-acceptor-donor (A²-D²-A¹-D¹) type of unsymmetrical squaraine dye, signified by USQ-1 based on 1-ethyl-2,3,3,8-tetramethyl-2,3-dihydro-1H-pyrrolo[3,2-h] quinoline moiety to improve the absorption as well as emission spectra to the red-emitting region. The influence of pyridine as a subsidiary electron acceptor unit on various properties in USQ-1 dye was compared with their close relative dye (USQ-2). The synthesized dyes were examined by FT-IR, HR-MS, ¹H, and ¹³C NMR spectroscopy. This novel unsymmetrical squaraine dye shows a strong absorption with high molar absorptivity (˃10⁵ L mol^-1 cm^-1) in the range of 676-661 nm from non-polar to polar solvents. The intramolecular charge transfer (ICT) process from donor to the acceptor moiety in a non-polar to polar solvent has been investigated with the help of oscillator strengths (f), as well as transition dipole moments (μ_eg). These dyes showed a negative solvatochromic shift from non-polar to polar solvent. The quantitative analysis of charge transfer from the ground to the excited state of these squaraine dyes was calculated by Reichardt's E_T (30) scale plot. The comparative electrochemical, as well as the thermal study of these unsymmetrical squaraines, were studied with the aid of cyclic voltammetry and thermogravimetric analysis (TGA), respectively. Additionally, A²-D²-A¹-D¹ type dye (USQ-1) showed an improved photo-stability compared to D²-A¹-D¹ type dye (USQ-2). The computational (theoretical) study of these dyes was supported with the assistance of density functional theory (DFT) together with time-dependent density functional theory (TD-DFT).

Pyrroloquinoline Based Styryl Dyes Doped PMMA, PS, and PS/TiO2 Polymer for Fluorescent Applications

This article presents two highly fluorescent donor-π-acceptor (D-π-A) moieties containing an electron-donating carbazole and phenothiazine donors fused with electron-withdrawing pyrrolo-quinoline acceptor dyes, PQC and PQPT. We also discussed the polymerization and film-forming process of dye PQC and PQPT doped in poly (methyl methacrylate) (PMMA) and polystyrene (PS) polymer to find their optical applications in polymer-based technology. We investigated the fluorescent properties of dyes PQC and PQPT from 0.01 to 1 wt% in poly(methyl methacrylate) (PMMA). We also investigated the changes in the spectrum shape and shift in wavelength with changes in poly(methyl methacrylate) (PMMA), polystyrene (PS), and TiO₂ doped in polystyrene (PS/TiO₂). The analysis of surface morphology of prepared polymer samples was done with the help of a scanning electron microscope. The thermal and photostability of synthesized dyes in poly (methyl methacrylate) (PMMA), polystyrene (PS), and TiO₂ doped in polystyrene (PS/TiO₂) were investigated to get detailed information owing to the application of fluorescent polymers in the field of optoelectronic, nanohybrid coatings in solar concentrators, etc.