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Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

Metallo-β-cyclodextrins of 6A-(2-(2-(2-Aminoethylamino)-ethylamino)ethylamino)-6A-deoxy-β-cyclodextrin and 6A-Deoxy-6A-(1,4,7,10-tetraazacyclododecan-1-yl)-β-cyclodextrin: Their Formation and Complexation of (R)- and (S)-Tryptophan and Tryptophanate in Aqueous Solution

Suzanna D. Kean, Christopher J. Easton and Stephen F. Lincoln

Australian Journal of Chemistry 53(5) 375 - 381
Published: 2000

Abstract

The binary metallo-β-cyclodextrins formed by 6A-(2-(2-(2-aminoethylamino)ethylamino)ethylamino)-6A-deoxy-β-cyclodextrin, [M(βCDtrien)]2+, where M2+ = Ni2+, Cu2+ and Zn2+, are characterized by log(K/dm3 mol-1) = 11.500.02, 10.700.07 and 9.400.01, 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 6A-deoxy-6A-(1,4,7,10-tetraazacyclododecan-1-yl)-β-cyclodextrin, [M(βCDcyclen)]2+, where M2+ = Cu2+ and Zn2+, log(K/dm3 mol-1) = 13.610.02 and 11.620.04, 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) = 6.900.04 and 6.790.04, 8.20.3 and 7.90.2, and 6.640.08 and 7.010.07, 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) = 6.840.06 and 6.850.06, and 4.950.05 and 4.940.04, respectively, where M2+ = Cu2+ and Zn2+. Other binary and ternary metallo-β-cyclo-dextrins are also formed. Binary complexes formed by the substituted β-cyclodextrins are exemplified by βCDcyclen.(R)-Trp- and βCDcyclen.(S)-Trp- for which log(Kd/m3 mol-1) = 3.690.04 and 3.950.03, respectively. These data are discussed together with those from the literature characterizing other metallo-β-cyclodextrin and substituted β-cyclodextrin systems.

Keywords: Copper; cyclodextrin; nickel; stability constant; tryptophan; tryptophanate; zinc.

https://doi.org/10.1071/CH00052

© CSIRO 2000

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