Efficient Charge Separation in Li⁺@C₆₀ Supramolecular Complexes with Electron Donors

Abstract

Lithium-ion-encapsulated fullerene (Li(+) @C60 ) exhibits greatly enhanced reactivity in photoinduced electron-transfer reduction with electron donors compared with pristine C60 . The enhanced reactivity of Li(+) @C60 results from the more positive one-electron reduction potential of Li(+) @C60 (+0.14 V versus a standard calomel electrode (SCE)) than that of C60 (-0.43 V versus SCE), whereas the reorganization energy of electron transfer of Li(+) @C60 (1.01 eV) becomes larger than that of C60 (0.73 eV) because of the change in electrostatic interactions of encapsulated Li(+) upon electron transfer. Li(+) @C60 can form strong supramolecular complexes with various anionic electron donors through electrostatic interactions. Li(+) @C60 can also form strong supramolecular π complexes with various electron donors, such as cyclic porphyrin dimers, corannulene, and crown ether fused monopyrrolotetrathiafulvalenes. Photoinduced electron transfer from electron donors to Li(+) @C60 afforded long-lived charge-separated states of supramolecular complexes between electron donors and Li(+) @C60 . A photoelectrochemical solar cell composed of supramolecular nanoclusters of Li(+) @C60 and zinc sulfonated meso-tetraphenylporphyrin exhibits significant enhancement in the photoelectrochemical performance than that of the reference system containing only a single component.

Understanding the Reactivity of Ion‐Encapsulated Fullerenes

“…For instance, this cationic fullerene is reported to form the highly stable donor-acceptorL i + @C 60 &[10]CPP supramolecular nanocarbon structure (CPP = cycloparaphenylene) due to the strongc hargetransfer interaction between [10]CPP and Li + @C 60 . [11] Diels-Alder (DA) cycloaddition reactions between cyclopentadiene or 1,3-cyclohexadiene and Li + @C 60 were reported to be significantly faster than the analogous processes involving the parentC 60 fullerene. [8] The presence of the lithiumc ation also modifies the exohedral reactivityo ft he C 60 moiety.…”

“…[9,10] Indeed, Li + @C 60 shows greatly enhanced reactivity in photoinduced electron-transfer reductionsw ithe lectron donors compared to hollow C 60 . [11] Diels-Alder (DA) cycloaddition reactions between cyclopentadiene or 1,3-cyclohexadiene and Li + @C 60 were reported to be significantly faster than the analogous processes involving the parentC 60 fullerene. [10] Thus, the observed activation barrierf or the DA reactiono fL i + @C 60 and C 6 H 8 (11.0 kcal mol À1 )w as about6kcalmol À1 lower than that for the reaction involving empty C 60 (16.8 kcal mol À1 ).…”

Singlet oxygen generation from Li+@C60nano-aggregates dispersed by laser irradiation in aqueous solution

“…[1][2][3][4][5][6] Fullerenes, especially [60]fullerene (C 60 ), are known as efficient photosensitisers to generate the triplet excited state and ROS with high quantum yields (F( 3 C 60 *) = 0.98; F( 1 O 2 *) = 0.96 in C 6 D 6 ). 23 However, neither solubilisation of Li + @C 60 , C 60 or C 70 in water nor the photoinduced singlet oxygen generation efficiency has been studied. 8 However, pristine C 60 is hardly soluble in water (0.4 mg mL À1 at 298 K) 9 and biological media to prevent expression of the photoactivity and PDT efficiency.…”

Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li+@C60

“…0.3 ms) reported previously. 63 The lifetime of 1.2 ms for H 2 Pc·2 4− /(Li + @C 60 ) 2 is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes reported so far. In the case of ZnPc·4 4− /Li + @C 60 , the lifetime of the CS state was 100 μs, which is one digit shorter than those of the other supramolecular complexes ( Figure S25 in the Supporting Information).…”