Steric effects macrocyclic ligands

Schiff base 69 and sulfur-linked 70 ferrocene bjs-crown ether ligands have also been prepared and both were shown to be potassium ion selective, especially the S-linked macrocycle 70 [89]. Compound 69 did not behave well electrochemically and somewhat unexpectedly addition of to 70 resulted in a cathodic shift of the ferrocene redox couple, possibly due to conformational steric effects involving the electron lone pairs on sulfur, but certainly reminiscent of Sato s thia-ferrocenophanes discussed earlier. 

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