10.1021/ja020253n.s001
Koji Kano
Koji
Kano
Ryuhei Nishiyabu
Ryuhei
Nishiyabu
Takuji Asada
Takuji
Asada
Yasuhisa Kuroda
Yasuhisa
Kuroda
Static and Dynamic Behavior of 2:1 Inclusion Complexes of
Cyclodextrins and Charged Porphyrins in Aqueous
Organic Media
American Chemical Society
2002
C 6 H 4
binding constants
rate constants
TPPS 4
TPPOC 3Py
van der Waals interaction
Aqueous Organic Media
cationic TPPOC 3Py Formation
cationic TPPOC 3Py
cavity
PorSub 4
k 1
TCPP
TMe
k 2 values
CO
3PS
complex
2002-07-26 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Static_and_Dynamic_Behavior_of_2_1_Inclusion_Complexes_of_Cyclodextrins_and_Charged_Porphyrins_in_Aqueous_Organic_Media/3640779
Two heptakis(2,3,6-tri-<i>O</i>-methyl)-β-cyclodextrin (TMe-β-CD) molecules strongly include the
peripheral substituents at the 5- and 15-positions of the charged meso-tetrasubstituted porphyrins, PorSub<sub>4</sub>
[TPPS<sub>4</sub> (Sub = <i>p</i>-C<sub>6</sub>H<sub>4</sub>-SO<sub>3</sub><sup>-</sup>), TPPOC3PS (<i>p</i>-C<sub>6</sub>H<sub>4</sub>-O-(CH<sub>2</sub>)<sub>3</sub>-<i>p</i>-C<sub>6</sub>H<sub>4</sub>-SO<sub>3</sub><sup>-</sup>), TCPP (Sub = <i>p</i>-C<sub>6</sub>H<sub>4</sub>-CO<sub>2</sub><sup>-</sup>),
and TPPOC3Py (<i>p</i>-C<sub>6</sub>H<sub>4</sub>-O-(CH<sub>2</sub>)<sub>3</sub>-Py<sup>+</sup>Br<sup>-</sup>), where Py<sup>+</sup> = <i>N</i>-alkylpyridinium] in aqueous ethylene glycol.
The binding constants (<i>K</i><sub>1</sub> and <i>K</i><sub>2</sub>) and the rate constants (<i>k</i><sub>1</sub> and <i>k</i><sub>2</sub>) for formation of the 1:1 and 2:1
complexes of TMe-β-CD and PorSub<sub>4</sub> were determined. Both the binding constants and the rate constants
for anionic TPPS<sub>4</sub>, TCPP, and TPPOC3PS were much larger than those for cationic TPPOC3Py. The
smaller <i>k</i><sub>1</sub> and <i>k</i><sub>2</sub> values for TPPOC3Py indicate a higher barrier for penetration of a cationic guest into the
TMe-β-CD cavity. The methyl groups at the rims and the cavity wall of the host are positively polarized due
to the inductive effect of the ethereal oxygens. The positively polarized rims and interior of the host cavity
should prevent the penetration of the cationic substituent of TPPOC3Py into the TMe-β-CD cavity. The 2:1
TMe-β-CD−PorSub<sub>4</sub> complexes are extraordinary stable in aqueous solutions, even in the case of cationic
TPPOC3Py. Formation of both 1:1 and 2:1 complexes is promoted by negative and large enthalpy changes,
suggesting a strong van der Waals interaction as the main binding force.