Potentiometric Investigation of the Metal Complexes of 1-(2-Pyridylazo)-2-naphthol and 4-(2-Pyridylazo)resorcinol.

Molar absorption coefficients and stability constants of metal complexes of 4-(2-pyridylazo)resorcinol (PAR): Revisiting common chelating probe for the study of metalloproteins

“…These data are highly convergent, which demonstrates the lack of concentration-dependence of the deprotonation processes. Comparisons of these data with the values that were previously determined in 50%-50% dioxane-water revealed significant differences, especially regarding the second deprotonation, which differed by~1.5 log units (Table 2) [65,66]. Similar observations were made regarding methanol-water mixtures in which the pK a2 values varied by 1.3 log units as the concentration of methanol was increased from 0 to 90% [67].…”

“…This eliminates the possibility of the potentiometry use to study metal ion complexation by PAR. In a very early study, Corsini et al applied a 50% water solution of dioxane for potentiometric studies [65,66]. In these conditions, metal complexes are easily soluble in a wide range of pH.…”

Development of a sol–gel optical sensor for analysis of zinc in pharmaceuticals

“…In acetate medium (pH 3.0-6.0) PAR forms a red-orange 1:2 (metal:ligand) complex with zinc which can be monitored spectrophotometrically [8,14,15]. The molar absorptivity reported for the PAR-Zn(II) complex (ε = 7.7 × 10 4 l mol −1 cm −1 [16]) is considerably greater than for other reagents, which makes PAR a superior chelating agent for zinc analysis [17].…”

Absorption-Modulated Crossed-Optical Fiber-Sensor Platform for Measurements in Liquid Environments and Flow Streams

“…Pyridylazo-naphthol (PAN) is a well-known azo dye that forms colored complexes with metal ions, including copper, cobalt, cadmium, nickel, and zinc [24][25][26][27]. The structures and absorbance spectra of PAN and the Zn-PAN 2 complex are given in Figure 2.…”