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Two yellow bis-azo dyes containing anthracene and two azodiphenylether groups (BPA and BTA) were prepared, and an extensive investigation of their physical, thermal and biological properties was carried out. The chemical structure was confirmed by the FTIR spectra, while from the UV–Vis spectra, the quantum efficiency of the laser fluorescence at the 476.5 nm was determined to be 0.33 (BPA) and 0.50 (BTA). The possible transitions between the energy levels of the electrons of the chemical elements were established, identifying the energies and the electronic configurations of the levels of transition. Both crystals are anisotropic, the optical phenomenon of double refraction of polarized light (birefringence) taking place. Images of maximum illumination and extinction were recorded when the crystals of the bis-azo compounds rotated by 90° each, which confirms their birefringence. A morphologic study of the thin films deposited onto glass surfaces was performed, proving the good adhesion of both dyes. By thermal analysis and calorimetry, the melting temperatures were determined (~224–225 °C for both of them), as well as their decomposition pathways and thermal effects (enthalpy variations during undergoing processes); thus, good thermal stability was exhibited. The interaction of the two compounds with collagen in the suede was studied, as well as their antioxidant activity, advocating for good chemical stability and potential to be safely used as coloring agents in the food industry.

Seven new complexes of 2-pyridyl ketone Schiff bases N,N 0 -bis-(pyridin-2-yl-benziliden)-propan-1,3diamine (bpbpd) and N,N 0 -bis-[1-(pyridin-2-yl)-etiliden]propan-1,3-diamine (bpepd) with Co(II), Ni(II), Zn(II) and Cd(II) nitrates and perchlorates were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV-Vis-NIR) as well as magnetic and conductometric measurements. The structure of a cadmium(II) complex was accomplished by single-crystal X-ray diffraction. The Schiff base ligands act as NNNN tetradentate ligands coordinating through pyridine nitrogens and azomethine nitrogens to transition metal ions. The metal ions are six-coordinate for Co(II) and Ni(II), fourcoordinate in the case of Zn(II) and eight-coordinate for Cd(II) ions. The coordination sphere of cobalt and nickel complexes is completed by two water molecules, resulting a distorted octahedron. In the case of zinc(II) complexes has been proposed a distorted tetrahedral geometry. The Cd(II) ions are surrounded by a tetradentate Schiff base ligand and two bidentate nitrate anions, leading to a dodecahedral coordination environment. Thermal decomposition of these compounds is a multistage process. Generally, water elimination occurs in the first step and the decomposition of nitrate groups and organic ligands in the next stages. The last step of decomposition for all complexes is strong exothermic and corresponds to oxidative combustion of the Schiff base ligand.