Shu-Hui Li

Hydroxide-initiated conversion of aromatic nitriles to imidazolines: fullerenes vs TCNE.

Transformation of aromatic nitriles to imidazolines has been achieved under basic conditions with the electron-deficient C60 and C70 fullerenes, but not with the electron-deficient olefin of tetracyanoethylene (TCNE). In situ UV-vis-NIR indicates that the ability of RC60(-) to undergo single-electron transfer (SET) to C60 is crucial for the reaction.

Oxazolination of 1,4-(PhCH2)2C60: toward a better understanding of multiadditions of heteroaddends.

Multiadditions of heteroaddends to C(60) are achieved via the oxazolination reaction of 1,4-(PhCH(2))(2)C(60) with OH(-) and PhCN, which exhibit a unique regioselectivity regarding the addition sites of the heteroatoms.

Base-Promoted Consecutive Enolate Addition Reaction of [60]Fullerene with Ketones

[60]Fullerene derivatives with novel 1,4,9,25- and 1,4,9,12-configurations were obtained by reactions of C60 with aliphatic ketones and benzyl bromide under basic conditions. The structures of the products were determined by X-ray single-crystal diffraction and spectroscopic characterization. The reactions were rationalized by a monoenolate addition experiment and in situ vis-NIR spectroscopy.

Oxazoline and imidazoline functionalization of a C60 dimer via the reaction of C60HBn and aromatic nitriles with a bifunctional hydroxide.

Oxazoline and imidazoline functionalization of a singly bonded C60 dimer is achieved via a one-pot reaction of C60HBn with OH(-) and aromatic nitriles, where the OH(-) not only functions as a Brønsted base that deprotonates C60HBn but also as a nucleophile that initiates the nucleophilic addition to the fullerene cage. The structures of the obtained oxazolinated and imidazolinated C60 dimeric compounds have been established by HRMS, UV-vis, and (1)H, (13)C, and HMBC NMR characterizations and computational calculations. The reaction mechanism is studied with the in situ vis-near-IR spectra, which shows that the use of I2 is crucial for the functionalization of the C60 dimer, indicating that it is likely the dimeric molecule rather than the fragment of the dimer that is involved in the reaction.

Approach to high open-circuit voltage in organic solar cells utilizing a structural change of the oxazolino-C70 derivative.

Reactions of 2,5-Bn2 C70 (Bn=CH2 Ph) with hydroxide and ArCN (Ar=Ph, m-ClPh) followed by quenching with I2 and BnBr afforded dibenzylated and tetrabenzylated oxazolino[70]fullerenes, respectively. The latter has a novel structural configuration, in which the addends are positioned from the polar to the transequatorial region. A key structural feature of this compound is that the oxygen atom of the oxazoline ring is bound to the equatorial belt region of C70 , giving structural change in its reduced state. This enables stabilization of the reduced state, suppressing charge recombination dynamics in organic solar cells to give a high open-circuit voltage (0.85, 0.93, and 1.11 V in devices using P3HT, PTB7, and DPP(TBFu)2 , respectively).

Reactions of C-70(2-) with Organic Halides Revisited: Unusual Magnetic Equivalence for the Diastereotopic Methylene Protons in 2,5-(PhCH2)(2)C-70

The reactions of C70(2-) with organic halides result in several isomeric products. However, the structures of the isomers have not been identified unambiguously and the reactions still remain elusive even though the first report of the reaction appeared more than ten years ago. Herein, the reactions of C70(2-) with ArCH2Br (Ar = Ph, o-, m-, and p-BrC6H4) are revisited. Two types of isomeric para-adducts of 2,5- and 7,23-(ArCH2)2C70 are obtained and characterized with the X-ray single-crystal diffractions, HRMS, (1)H and (13)C NMR, and UV-vis spectroscopies. An unusual singlet resonance instead of the typical AB quartet resonance is shown for the C2 diastereotopic methylene protons in (1)H NMR spectrum of 2,5-(PhCH2)2C70 recorded at ambient temperature. The unexpected magnetic equivalence is studied with the variable-temperature (VT) NMR and density functional theory (DFT) calculations. The results show that the greater local curvature in the C70 polar region is likely responsible for the unusual magnetic equivalence exhibited by the C2 diastereotopic methylene protons of 2,5-(PhCH2)2C70, indicating that under certain cases, it is improbable to elucidate the spectral data of fullerene derivatives with a less symmetrical carbon cage in analogy with those of the C60 derivatives.

Vis-Near-IR Spectroscopic and Time-Dependent DFT Study of Reduced Singly Bonded C60 Species.

Reduced fullerenes and fullerene derivatives exhibit intense absorptions in the vis-near-IR (vis-NIR) region. The absorptions are sensitive toward the addition pattern, number of addends, and oxidation state of the fullerene species and are used as an important benchmark for identifying anionic fullerene species. Similar absorptions are also shown for the reduced singly bonded C60 species, which are electronically different from reduced fullerene derivatives. However, much less work has been carried out on the vis-NIR spectroscopic study of the anionic singly bonded C60 species, likely due to the difficulty in controlled production of these species. Herein, we report the vis-NIR spectroscopic study of the mono- and dianions of the singly bonded C60 species (RC60(-), R(-)C60(-), and RC60(2-•)), which are selectively generated by controlled-potential bulk electrolysis (CPE) of the singly bonded C60 dimer and C60 oxazolino heterocycles. Time-dependent density functional theory (TD-DFT) calculations were performed to rationalize the experimental results.

Reductive Benzylation of Singly Bonded 1,2,4,15-C60 Dimers with an Oxazoline or Imidazoline Heterocycle: Unexpected Formation of 1,2,3,16-C60 Adducts and Insights into the Reactivity of Singly Bonded C60 Dimers

Upon reduction, singly bonded 1,2,4,15-C60 dimers with an oxazoline or imidazoline heterocycle dissociate into monoanionic 1,2,4-C60 intermediates, which surprisingly leads to the formation of 1,2,3,16-C60 rather than 1,2,4,15-C60 adducts of the original configuration by further benzylation, even though the analogue of dibenzylated C60 oxazoline with a 1,2,4,15-configuration is stable and has been obtained. These results are corroborated by computational calculations, which rationalize the reaction and clarify the structure of the 1,2,3,16-C60 adducts, providing new insights into the intrinsic reactivity of singly bonded C60 dimers.

Controlled Synthesis of C70 Equatorial Multiadducts with Mixed Addends from an Equatorial Diadduct: Evidence for an Electrophilic Carbanion

Controlled synthesis of the equatorial tetra-, hexa-, and octaorgano[70]fullerenes with mixed addends was achieved via the reaction of equatorial 7,23-Bn2C70 with MeO- and ArCH2Br. The products were structurally characterized by single crystal X-ray diffraction. The regioselectivity of the reaction was studied by in situ vis-NIR and Fukui function analysis. A surprising electrophilic triorgano[70]fullerene carbanion was shown, and an enhanced fluorescence was observed for the mixed octaadducts.

Regiocontrolled Electrosynthesis of [60]Fullerene Bisadducts: Photovoltaic Performance and Crystal Structures of C60 o-Quinodimethane Bisadducts

C60 o-quinodimethane bisadducts [C60(QM)2] are promising electron acceptors for bulk heterojuction (BHJ) organic solar cells (OSCs). However, previous production of C60(QM)2 often resulted in excessive regioisomers, which were difficult to purify and might consequently obscure the structure-performance study of the organofullerene acceptors. Herein, the electrosynthesis of C60(QM)2 is reported. The reaction exhibits a strong regiocontrol with generation of fewer regioisomers. Pure regioisomers of cis-2, trans-3, and e C60(QM)2 are obtained, and the structures are solved with single-crystal X-ray diffraction. Interestingly, the cis-2 and trans-3 regioisomers exhibit better photovoltaic performance than the e regioisomer in the OSCs based on poly(3-hexylthiophene) (P3HT), which can be correlated with their structural difference.