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.