Azo complexons

MOLECULAR INCLUSION REACTIONS BETWEEN METAL COMPLEXES OF AZO COMPLEXONS AND a-CYCLODEXTRIN IN AQUEOUS SOLUTION... 

ABSTRACT. Kinetics of the molecular inclusion reactions of the azo complexons and their metal complexes with a- and 3-cyclodextrins (a- and 3-CD ) were studied in aqueous solution by means of a spectrophotometric and a stopped-flow method. The acid dissociation of the azo complexons was regulated by the inclusion with CD. Two-step process was observed for the interaction of a-cyclodextrin with LH species of the azo complexons and with the metal complexes. 

The azo complexons, 3-IDA-5-R-HAB (Fig. 1), which have a coordinating iminodiacetate group, show the conformational change in the acid dissociation and the complexation with metal ions.3 The stability of the inclusion complexes of the azo complexons with a-cyclodextrin (oMX)j ) depends on the complementary geometry between the diameter of hydrophobic cavity of a-cyclodextrin and the shape and the size of guest molecule. ... 

Fig. 1. Structural formula of the azo complexons, p-(3-carboxyroethyl-ami nome thy 1 - 4 - hydr oxy- 5 - a Iky Ipheny 1-azo)benzenesulfonic acid (3-IDA-5-Pr-HAB)...

The azo complexons, 3-IDA-5-R HAB (R = Me and Pr), were synthesized by Mannich condensation5 of p-hydroxyphenylazo derivatives of sulfanilic acid (HAB) with iminodiacetic acid (IDA) and formaldehyde. The crude samples of the synthesized 3-IDA-5-R-HAB were purified by cellulose column chromatography (Avicel Microcrystalline Cellulose, 1-butanol ... 

Fig. 2), were found to form 1 1 inclusion complexes with a- and 3-CD from the spectrophotometric measurements. Figure 3 shows the spectral change in the formation of the inclusion compound of NiLH - (R = Pr) with a-CD Table 1 shows the stability constants of the inclusion complexes of the azo complexons and their metal complexes with a- and 3-CD ... 

Table I. The Stability Constants of the Inclusion Complexes of the Azo Complexons and their Metal Complexes with o- and B-CO...

Unpublished data the azo complexons form stable and colored 1 1 protonated complexes with bivalent metal ions, Ni(II), Zn(II), and Cu(Il), in a weakly acidic solution. 

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