Spectroscopic Behaviour of Two Novel Azobenzene Fluorescent Dyes and Their Polymeric Blends

Abstract

Two novel symmetrical bis-azobenzene red dyes ending with electron-withdrawing or donor groups were synthesized. Both chromophores display good solubility, excellent chemical, and thermal stability. The two dyes are fluorescent in solution and in the solid-state. The spectroscopic properties of the neat crystalline solids were compared with those of doped blends of different amorphous matrixes. Blends of non-conductive and of emissive and conductive host polymers were formed to evaluate the potential of the azo dyes as pigments and as fluorophores. Both in absorbance and emission, the doped thin layers have CIE coordinates in the spectral region from yellow to red. The fluorescence quantum yield measured for the brightest emissive blend reaches 57%, a remarkable performance for a steadily fluorescent azo dye. A DFT approach was employed to examine the frontier orbitals of the two dyes.

Trans–Cis Kinetic Study of Azobenzene-4,4′-dicarboxylic Acid and Aluminium and Zirconium Based Azobenzene-4,4′-dicarboxylate MOFs

“…The excited state decay of the cis and trans isomers of azobenzenes in DMSO are generally in the ps timescale [34]. It was, however, found that bulky substituents close to the N=N linker or intramolecular hydrogen bonding slowed down the rotation around the nitrogen-carbon bond during photo-isomerisation, increasing the fluorescence performance of azobenzene compounds in solution [35]. In this study, both the free ligand and crystalline MOFs did not display fluorescent behaviour in solid-state; hence, the samples were suspended in DMF.…”

Photo-Tunable Azobenzene-Anthraquinone Schiff Base Copper Complexes as Mediators for Laccase in Biofuel Cell Cathode

“…For a measurement of the angle-dependent polarized UV-vis absorption spectra at 320 nm, cast films were prepared by mixing a 5 wt% polymethyl methacrylate (PMMA) in DMF solution (PMMA: complex = 2:1). To evaluate the Weigert effect, we employed the R parameter to describe the degree of the photo-induced optical anisotropy [39][40][41][42]. Figure 7 exhibits the change of UV-vis spectra due to the transto cis-photoisomerization of azobenzene moiety of 1, which displays a shift of π-π* bands to a shorter wavelength [37].…”

“…For a measurement of the angle-dependent polarized UV-vis absorption spectra at 320 nm, cast films were prepared by mixing a 5 wt% polymethyl methacrylate (PMMA) in DMF solution (PMMA: complex = 2:1). To evaluate the Weigert effect, we employed the R parameter to describe the degree of the photo-induced optical anisotropy [39][40][41][42]. For a measurement of the angle-dependent polarized UV-vis absorption spectra at 320 nm, cast films were prepared by mixing a 5 wt% polymethyl methacrylate (PMMA) in DMF solution (PMMA: complex = 2:1).…”

The Polychromatic Woodburytype—Colour Tracking in Translucent, Patterned Gelatin/Pigment Films

“…The chromaticity values or CIE coordinates can be plotted on the CIE 1931 color space chromaticity diagram to provide a general overview of the varying colorimetric properties [37]. The values for step-wedge prints of cyan, magenta and yellow can be seen in Figure 7, for a weak ink set of 0.00108 wt%, 0.00176 wt% and 0.00176 wt%, respectively.…”