Cyclodextrins sequential complexation

Sequential complexation was confirmed in reference 97, where it was reported that P-CD addition decreases the R value and increases the intensity of the two vibronic bands. Solutions of P-CD containing 13 always exhibited a biexponential decay the shortest, t, = 130 ns, has the same lifetime of 13 in water, the largest, Tj = 300 ns, indicates that 13 experiences a hydrophobic environment. The ratio of the preexponentials /42Mi grew monotonically with [/ -CD]. The data are consistent with a sequential complexation, as in the complexation of 13 with a-CD. In the 1 1 complex, the included pyrene has the same lifetime as 13 in water because a substantial portion of the molecule is still exposed to the solvent when 13 is encapsulated by two cyclodextrins, it experiences a low-polarity microenvironment and its lifetime consequently increases. In the same paper, the complexing ability of a polymer-supported P-CD of the general formula... 

Figure 8 Sequential complexation of cucurbituril-6 (CB-6, green barrel depiction) and -cyclodextrin (j8-CD, yellow torus) onto dicyclohexylammonium (DHA) or hexylammonium (HA) guests in 50 mM aqueous NaCl solution, pH 3, at 298 K. (Reproduced from Ref. 71. American Chemical Society, 2006.)...

Figure 3. ITC-measurement of the complexation of (-)camphor by a-cyclodextrin in water. Left Primary heat pulse trace (CFB = cell feedback current) the saw-tooth shape arises from changing the aliquots of titrand solution. Right The time integral of the heat pulses furnishes the titration curve. The solid line represents the best fit to a 2 1 host-guest sequential binding model.

Figure 9-1 H, N-HSQC spectrum of the amide signals of a 45-kDa maltose binding protein / 3-cyclodextrin complex. With the help of a deuterated relabeled sample, all backbone signals could be sequentially assigned (reproduced with permission from [6] Copyright 1997 American Chemical Society).

---