Synthesis and Chirality of Ferrichrome Mimicking C₃-Symmetric Fe³⁺ Complexes Based on α-Cyclodextrin

Abstract

The C₃-symmetric tripodal ferrichrome model that contains three MeCON (OH) (CH₂)₂CONH sidechains attached to the smaller rim of α-cyclodextrin (α-CyD) as the rigid platform has been prepared and its structural features have been investigated by UV- and CD- spectroscopy. The linking of the side-chains to the CyD results in a twisting of the octahedral chromophore around the Fe³⁺ center, giving a Δ-cis, cis complex in water with a right-handed screw propeller, but the chirality is found to decrease with decreasing solvent polarity. Meanwhile, the binuclear tripodal complex with three MeCON (OH) (CH₂)₂ CONH(CH₂)₂ CON(OH) (CH₂)₂ CONH side-chains exhibits a significantly different solvent effect. The origin of the chirality will be discussed.