Metallocyclodextrins of 6A-(2-amino-ethyl-amino)-6A-deoxy-b-cyclodextrin: their formation and complexation of (R)- and (S)-tryptophanate in aqueous solution

Abstract

<jats:p> The binary metallocyclodextrins formed by 6A-(2-aminoethylamino)-6A-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 6A-(3-aminopropylamino)-6A-deoxy-β-cyclodextrin.</jats:p>