Metallo-β-cyclodextrins of 6^A-(2-(2-(2-Aminoethylamino)-ethylamino)ethylamino)-6 ^A-deoxy-β-cyclodextrin 6^A-Deoxy-6 ^A-(1,4,7,10-tetraazacyclododecan-1-yl)-β-cyclodextrin: Their formation and complexation of (R)- and (S)-tryptophan and tryptophanate in aqueous solution

The binary metallo-β-cyclodextrins formed by 6^A-(2-(2-(2-aminoethylamino)ethylamino)ethylamino)-6 ^A-deoxy-β-cyclodextrin, [M(βCDtrien)]²⁺, where M²⁺ = Ni²⁺, Cu²⁺ and Zn²⁺, are characterized by log(K/dm³ mol^-1) = 11.50±0.02,10.70±0.07 and 9.40±0.01, respectively, in aqueous solution at 298.2 K and I = 0.1 mol dm^-3 (NaClO₄), where K is the stability constant. For those formed by 6^A-deoxy-6 ^A-(1,4,7,10-tetraazacyclododecan-1-yl)-β-cyclodextrin, [M(βCDcyclen)]²⁺, where M²⁺ = Cu²⁺ and Zn²⁺, log(K/dm³ mol^-1) = 13.6±0.02 and 11.62±0.04, respectively. The ternary metallo-β-cyclodextrins formed by [M(βCDtrien)]²⁺ and (R)- and (S)-tryptophanate, [M(βCDtrien)((R)-Trp)]⁺ and [M(βCDtrien)((S)-Trp)]⁺ are characterized by log(K/dm³ mol^-1) = 6.90±0.04 and 6.79±0.04, 8.2±0.3 and 7.9±0.2, and 6.64±0.08 and 7.01±0.07, respectively, where M²⁺ = Ni²⁺, Cu²⁺ and Zn²⁺. For the ternary metallo-β-cyclodextrins formed by [M(βCDcyclen)]²⁺ and (R)- and (S)-tryptophanate, [M(βCDcyclen)((R)-Trp)]⁺ and [M(βCDcyclen)((S)-Trp)]⁺, log(K/dm³ mol^-1) = 6.84±0.06 and 6.85±0.06, and 4.95±0.05 and 4.94±0.04, respectively, where M²⁺ = Cu²⁺ and Zn²⁺. Other binary and ternary metallo-β-cyclodextrins are also formed. Binary complexes formed by the substituted β-cyclodextrins are exemplified by βCDcyclen (R)-Trp^- and βCDcyclen (S)-Trp^- for which log(K/dm³ mol^-1) = 3.69±0.04 and 3.95±0.03, respectively. These data are discussed together with those from the literature characterizing other metallo-β-cyclodextrin and substituted β-cyclodextrin systems.