Sulfonatocalixarenes and cyclodextrins display
different affinity for cationic and anionic porphyrins. The binding
constants for the formation of the complexes TMPyP/CD,
TMPyP/sulfonatocalixarene and TPPS/CD range between 103-105
The electrostatic nature of the interaction
between TMPyP and calixarene is well visualized by comparison of complexing
properties and effects of ionic strength.
The effects of complexation on Ffluo,
FT and lifetimes of the triplet states of the porphyrins
depend on the size and the type of the receptor cavity. The comple-xation
with calixarenes leads to considerable decrease of FT
while interaction with cyclodextrins does not. This is due to different
binding modes, i.e. Coulombic attraction for calixarenes and hydrophobic
interactions for inclusion
complexes of the porphyrins with CD.
Sulfonatocalixarenes and cyclodextrins serve as
hosts for binding redox active compounds. This arrangement leads to
photoinduced electron transfer between the porphyrin in the excited singlet
state and the electron acceptors.