Production, Separation, Isolation, and Spectroscopic Study of Dysprosium Endohedral Metallofullerenes

The first successful production and chromatographic isolation of dysprosium endohedral metallofullerenes are reported. A series of 18 endohedral fullerenes have been separated and isolated having mainly two dysprosium metals engaged in a range of fullerene cages from C80 up to C94. All these newly synthesized metallofullerenes are characterized by LD-TOF mass spectrometry and UV−vis−NIR absorption spectroscopy. Their possible molecular symmetry, HOMO−LUMO band gap, and electronic structure are discussed in terms of their absorption spectra and HPLC elution time. Their separation and isolation procedure by multistage high-performance liquid chromatography is discussed in detail

Organic Chemistry with Heterofullerenes: Photosensitized Oxygenation of Alkenes

Heterofullerenes C59HN and (C59N)2 sensitize the reaction of olefins with molecular oxygen under photolytic conditions. 2-Methyl-2-butene and α-terpinene undergo ene and Diels−Alder photooxygenation reactions, respectively, even in the presence of minute amounts of azafullerenes to produce the corresponding peroxides

Fluorene–Perylene Diimide Arrays onto Graphene Sheets for Photocatalysis

A facile approach for introducing photoactive poly­(fluorene–perylene diimide) arrays (PFPDI) onto graphene sheets was accomplished. Noncovalent PFPDI/graphene ensembles formed via π–π stacking interactions between the two components and covalent PFPDI–graphene hybrids realized upon a Stille polycondensation reaction between an iodobenzyl-functionalized graphene, a 9,9-dialkyl substituted fluorene diboronic acid, and a 1,7-dibromo-PDI derivative were prepared. The morphology of PFPDI/graphene and PFPDI–graphene was evaluated by high-resolution transmission electron microscopy (HR-TEM), revealing the presence of even monolayered graphene sheets. Moreover, their photophysical and redox properties as assessed by electronic absorption spectroscopy and steady-state as well as time-resolved photoluminescence assays and electrochemistry, respectively, disclosed charge-transfer characteristics owing to the high photoluminescence quenching of PFPDI in the presence of graphene and the fast component attributed to the decay of the emission intensity of the singlet excited state of PFPDI in both PFPDI/graphene and PFPDI–graphene. Next, testing their ability to operate in energy conversion schemes, the PFPDI–graphene was successfully employed as catalyst for the reduction of 4-nitrophenol to 4-aminophenol. Notably, the kinetics for the reduction were enhanced by visible light photoirradiation as compared to dark conditions as well as the presence of PFPDI–graphene, contrasting the case where only PFPDI, in the absence of graphene, was employed. Finally, recycling of the catalyst PFPDI–graphene was achieved and reutilization in successive reduction reactions of 4-nitrophenol was found to proceed with the same efficiency

<i>N</i>-(Iodopropenyl)-octahydrobenzo[<i>f</i>]- and -[<i>g</i>]quinolines: Synthesis and Adrenergic and Dopaminergic Activity Studies

A series of N-(iodopropenyl)-octahydrobenzo[f]- and -[g]quinolines was synthesized and assayed in vitro for their dopaminergic and α-adrenergic activity. Structure−activity relationship (SAR) analysis revealed that the tested benzoquinolines exhibited activity at the D1 rather than the D2 receptor sites in contrast to the D2 receptor subfamily activity reported for their aminotetralin congeners. N-Iodopropenyl substitution was apparently a decisive factor for D1 activity independent of ring substitution pattern. Considering the structural factors influencing α-adrenergic activity, in a general trend, N-iodopropenyl analogues were α1-active, with the ring-hydroxylated congeners exhibiting the highest affinity. Affinity to the α2 receptor was even higher with no detectable trend of SAR. However, a combination of the linear arrangement of the [g]-ring system, combined with the ring hydroxyl and the N-iodopropenyl substitution in compound 5c, resulted in a significant enhancement of α2 activity in this series as demonstrated by an IC50 value of 0.5 nM. A new synthetic approach to the [g]benzoquinoline system is also described

Theoretical Study of Fulleropyrrolidines by Density Functional and Time-Dependent Density Functional Theory

Density functional theory (DFT) calculations have been employed in a study of various fulleropyrrolidines in order to determine their electronic structure and in particular the effect on the chemical properties of the pyrrolidine nitrogen atom of fullerene as well as of additional substituents. It is found that fullerene causes a large chemical shift in the calculated N 1s binding energy, while further substitution at N has smaller effect independent of the type of substituent. Time-dependent DFT calculations have been employed for the calculation of the energy of the lower-lying electronic states of fulleropyrrolidines, as well as on higher-lying states, in view of the intense interest related to photoinduced charge-transfer processes in these systems. The TDDFT calculations on the lower-lying states converge on the same lowest excitation energy for most of the substituted fulleropyrrolidines, favoring excitations from occupied orbitals localized on C60 even when the highest occupied molecular orbital (HOMO) is localized on the substituent groups. Good agreement is found with the experimental lowest excitation energy in fullerene and in the fulleropyrrolidine−porphyrin system. Finally, an excitation to a higher-lying state, related to the charge-transfer process, has been determined by TDDFT calculations on a porphyrin−fulleropyrrolidine system, where it is found that the absorption characteristics of the individual substituent are transferable to the combined system

Novel Synthesis and Characterization of Five Isomers of (C₇₀)₂ Fullerene Dimers

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV−vis−NIR absorption and mass spectroscopy

Novel Synthesis and Characterization of Five Isomers of (C₇₀)₂ Fullerene Dimers

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV−vis−NIR absorption and mass spectroscopy

Electrostatic Association of Ammonium-Functionalized Layered-Transition-Metal Dichalcogenides with an Anionic Porphyrin

Ammonium-modified MoS₂ and WS₂ were prepared and characterized by complementary spectroscopic, thermal, and microscopic means. The positive charges on functionalized MoS₂ and WS₂, due to the presence of ammonium units, were exploited to electrostatically bring in contact an anionic porphyrin bearing a carboxylate moiety, yielding porphyrin/MoS₂ and porphyrin/WS₂ ensembles, <b>5a</b> and <b>5b</b>, respectively. Efficient photoluminescence quenching of porphyrin’s emission by MoS₂ and WS₂ within nanoensembles <b>5a</b> and <b>5b</b>, in combination with time-resolved photoluminescence assays, revealed transduction of energy from the photoexcited porphyrin to MoS₂ or WS₂

Photooxidation of Olefins Sensitized by Bisazafullerene (C₅₉N)₂ and Hydroazafullerene C₅₉HN: Product Analysis, Emission of Singlet Oxygen, and Transient Absorption Spectroscopy

The photooxidation reactions of olefins sensitized by the excited triplet states of bisazafullerene (C59N)2 and hydroazafullerene C59HN have been studied. Oxidation yields were compared with those of pristine C60. The singlet oxygen yields are also determined directly from the emission intensities, which are in good agreement with the oxidation yields. The triplet states of (C59N)2 and C59HN have been identified by the time-resolved spectroscopic method by observing the triplet−triplet absorption spectra, which decay in the presence of oxygen. It has been proven that (C59N)2 and C59HN have the ability to sensitize the reactions via singlet oxygen in about half of the efficiency of that of pristine C60. For both azafullerenes, the triplet lifetimes are shorter than that of pristine C60, which may be related to the nitrogen atom embedded in the C60 moiety

Cone-End Functionalization of Carbon Nanohorns

Cone-End Functionalization of Carbon Nanohorn