Abstract
A novel azo-dye was isolated by a diazo-coupling reaction and characterized by the elemental analysis, mass spectra, IR and UV-VIS spectroscopy. The processes of complex formation of H4L with some mono-, bis-, and trivalent metal cations were studied by spectrophotometric titration and theoretical modeling. The NBO effective charge calculations indicate a strong covalent character of the coordination bonds at complexation.
Highlights
About half of the dyes in industrial use today are azo dyes [3, 4]. They are good complexing agents, and their metal complexes are used as dyes and pigments, but their thermal and optical properties provide their applications as optical recording media [5], toners [6] ink-jet printing [7], in non-linear and photoelectronics [8, 9], especially in optical information storage [10,11,12,13]
The types of tautomeric equilibria at complex formation is studied by the theoretical B3LYP calculations
In the case of trivalent metals such as Cr3+ and Fe3+, the shoulder at around 580 nm appears in the UV-VIS spectrum (Fig. 1a)
Summary
About half of the dyes in industrial use today are azo dyes [3, 4]. They are good complexing agents, and their metal complexes are used as dyes and pigments, but their thermal and optical properties provide their applications as optical recording media [5], toners [6] ink-jet printing [7], in non-linear and photoelectronics [8, 9], especially in optical information storage [10,11,12,13]. Introduction of one or two hydroxy-groups into the ortho- or para-positions of the aryl-substituents at the azogroup increases the complexing abilities of the organic dye and leads to the possibility of the proton migration that is reflected as the azo-hydrazone tautomerism and different ionization processes. The direct structure determination is in most times unavailable because of the high dispersity of azo-dyes. In this case, the only one possibility to assign the spectral changes at ionization or at complex formation with the corresponding tautomeric or ionic transformation of the organic species is quantum chemical modeling of the process. The types of tautomeric equilibria at complex formation is studied by the theoretical B3LYP calculations
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