Metallocyclodextrins of 6A-(2-Aminoethylamino)-6A-deoxy-ß-cyclodextrin: Their Formation and Complexation of (R)- and (S)-Tryptophanate in Aqueous Solution

Abstract

The binary metallocyclodextrins formed by 6^A-(2-aminoethylamino)-6^A-deoxy-β-cyclodextrin ([M(βCDen)]²⁺ where M²⁺ = Co²⁺ , Ni²⁺ , Cu²⁺ and Zn²⁺) are characterized by log(K/dm³ mol^–1) = 12.000.05, 7.810.01, 8.370.03 and 8.520.07, respectively, in aqueous solution at 298.2 K and I = 0.10 mol dm^–3 (NaClO₄), where K is the stability constant. The ternary metallocyclodextrins formed by [M(βCDen)]²⁺ and (R)- and (S)-tryptophanate, [M(βCDen)(R)-Trp]⁺ and [M(βCDen)(S)-Trp]⁺ , are characterized by log(K/dm³ mol^–1) = 8.710.06 and 8.540.07, 5.380.06 and 5.410.04, 8.200.04 and 7.860.02, and 5.790.01 and 5.790.05, respectively, when M²⁺ = Co²⁺ , Ni²⁺ , Cu²⁺ and Zn²⁺. These data are discussed together with those characterizing the less stable metallocyclodextrins formed by 6^A-(3-aminopropylamino)-6^A-deoxy-β-cyclodextrin.