Synthesis and Characterization of Supramolecules of Li~+@C_(60) and Fluorinated Porphyrins

摘要

Metal endohedral [60]fullerenes (M@C_(60)) have a unique structure encapsulating a metal atom (M) inside the π-conjugated spherical C_(60) cage. Lithium cation endohedral fullerene (Li~+@C_(60)) is a commercially available M@C_(60) and has a potential for application in nano material fields. The cationic Li~+@C_(60) crystallizes with weakly coordinated anions such as SbCl_6~-, PF_6~-, Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion (TFPB~-), and bis(trifluoromethanesulfonyl)imide anion (TFSI~-). Due to the inside Li~+ cation, the first reduction potential of Li~+@C_(60) is shifted to positive direction by 0.7 eV than that of pristine C_(60). As a result, Li~+@C_(60) has larger electron acceptability than C_(60). Li~+@C_(60) also forms a guest-host type supramolecule with [10]cycloparaphenylene ([10]CPP) and π-π stacking supramolecules with porphyrins or phthalocyanines. A supramolecule of Li~+@C_(60) and 5,10,15,20-tetrakis(4-sulfonatophenyl) zinc porphyrin anion (ZnTPPS~(4-)), [Li~+@C_(60)- ZnTPPS~(4-)] with the binding constant of ca. 10~5 M~(-1) shows a long-lived electron charge separation state by photoinduced electron transfer and can be used in photovoltaic cells. The [Li~+@C_(60) - ZnTPPS~(4-)] based photovoltaic cell shows maximum incident photon-to-photocurrent efficiency (IPCE) value of 78% under the certain condition. The performance of the photovoltaic cells would be changed by the chemical modification of porphyrins.