Unveiling the nature of supramolecular crown ether-C60 interactions

A series of exTTF-(crown ether)(2) receptors, designed to host C-60, has been prepared. The size of the crown ether and the nature of the heteroatoms have been systematically changed to fine tune the association constants. Electrochemical measurements and transient absorption spectroscopy assisted in corroborating charge transfer in the ground state and in the excited state, leading to the formation of radical ion pairs featuring lifetimes in the range from 12 to 21 ps. To rationalize the nature of the exTTF-(crown ether)(2).C-60 stabilizing interactions, theoretical calculations have been carried out, suggesting a synergetic interplay of donor-acceptor, pi-pi, n-pi and CH center dot center dot center dot pi interactions, which is the basis for the affinity of our novel receptors towards C-60.