Synthesis of dumbbell-shaped bis-(pyrazolino[60]fullerene)-oligophenylenevinylene derivatives

Regioselective preparation of a bis-pyrazolinofullerene by a macrocyclization reaction

A single isomer of a pyrazolinofullerene bis-adduct was prepared by tether-directed remote functionalization. This bis-adduct has a lower LUMO than C₆₀.

Fulleropyrrolidine molecular dumbbells act as multi-electron-acceptor triads. Spectroscopic, electrochemical, computational and morphological characterizations

Three novel fulleropyrrolidine dumbbells consisting three electron acceptor moieties joined by alkyl linker displaying tunable electrical and morphological properties were synthesized and characterized.

Tunable optical properties of chromophores derived from oligo(p-phenylene vinylene)

A series of 11 symmetric push-pull chromophores consisting of electron-accepting groups connected through a central pi-conjugated system derived from oligo(p-phenylene vinylene) (OPV) were designed and synthesized. Electronic and spectroscopic properties were investigated by UV-visible absorption, fluorescence spectroscopy, and cyclic voltammetry. By finely tuning the electron-withdrawing ability of the acceptors as well as the length of the pi-conjugated spacer, a wide range of dyes exhibiting strong absorption and emission were obtained.

Conjugated oligoyne-bridged [60]fullerene molecular dumbbells: syntheses and thermal and morphological properties

A series of linear and star-shaped pi-conjugated oligomer hybrids (2-5) composed of an oligoyne core, ranging from 1,3-butadiyne to 1,3,5,7,9,11-dodecahexayne, and fullerenyl end-capping groups has been synthesized and studied. The molecular structures of these fullerene-oligoyne hybrids were assembled through three key reactions: Pd-catalyzed cross-coupling, Cu-catalyzed oxidative homocoupling, and an in situ alkynylation reaction on [60]fullerene. The properties of these compounds were investigated by UV-vis spectroscopy, differential scanning calorimetry (DSC), and atomic force microscopy (AFM) with the purpose of understanding the thermal reactivity arising from the oligoyne moieties as well as the morphological properties on surface. Our study shows that these fullerene-oligoyne hybrids tend to aggregate in different morphologies, including nanospheres, nanoflakes, and continuous thin films, while the morphological properties appear to be subject to the influence of molecular factors such as oligomer chain length, solubilizing alkylphenyl groups, and the thermal reactivity of the oligoyne unit. The correlation between molecular property and interfacial aggregation behavior evinced by these fullerene-oligoyne hybrids suggests a viable approach to exert bottom-up control over the structures and properties of fullerene based nanomaterials.

Photophysical Properties of the Newly Synthesized Triad Based on [70]Fullerene Studies with Laser Flash Photolysis

N,N-Dimethylaniline-pyrazolinoC70-ferrocene has been prepared with the 1,3-dipolar cycloaddition reaction of a nitrile imine with C70. Although three regioisomers regarding the position of the pyrazolino group on the C70 were identified in the reaction products, molecular orbital calculations indicate that the stabilities and electronic properties of the three isomers are almost the same, which was confirmed by the sharp redox peaks. The photophysical properties of the triads have been investigated by measuring the time-resolved emission and transient absorption spectra showing that charge separation takes place efficiently via the photoexcited singlet state of the C70 moiety with accepting an electron from the donor moieties. It was found that the pyrazolino ring mediates a charge separation between the donor moieties and the photoexcited C70 moiety.

Molecular and supramolecular C60–oligophenylenevinylene conjugates

Fullerene derivatives are attractive building blocks for the preparation of molecular and supramolecular photoactive devices. As a part of this research, combination of C60 with oligophenylenevinylene (OPV) subunits has generated significant research efforts. These results are summarized in the present account to illustrate the current state-of-the-art of fullerene chemistry for the development of new photoactive materials.

Cooperative Recognition of C60-Ammonium Substrates by a Ditopic Oligophenylenevinylene/Crown Ether Host

A new fullerene derivative with an ammonium subunit has been prepared. Its ability to form supramolecular complexes with oligophenylenevinylene derivatives bearing one or two crown ether moieties has been evidenced by electrospray mass spectrometry, and UV-visible and luminescence spectroscopy experiments. Interestingly, the assembly of the C60-ammonium cation with the oligophenylenevinylene derivative bearing two crown ether moieties leads to the cooperative formation of the 2:1 complex owing to intramolecular fullerene-fullerene interactions.

Pyrazolino[60]fullerene-Oligophenylenevinylene Dumbbell-Shaped Arrays: Synthesis, Electrochemistry, Photophysics, and Self-Assembly on Surfaces

Symmetrically substituted oligophenylenevinylene (OPV) derivatives bearing terminal p-nitrophenylhydrazone groups have been prepared and used for the synthesis of dumbbell-shaped bis(pyrazolino[60]fullerene)-OPV systems. In these triad arrays, the OPV-type fluorescence is dramatically quenched as a consequence of ultrafast OPV-->C60 singlet energy transfer. In its turn the fullerene singlet state is quenched by pyrazoline-->C60 electron transfer, in line with the behavior of the corresponding reference fullerene molecule. The occurrence of electron transfer in the multicomponent arrays is evidenced by recovery of fullerene fluorescence at 77 K in CH2Cl2 and in toluene at 298 K. Under these conditions the OPV-->C60 energy transfer is unaffected. The rate of this process turns out to be higher for the OPV trimer than for the corresponding pentameric OPV arrays, in agreement with energy-transfer theory expectations. Scanning tunneling microscopy (STM) and scanning force microscopy (SFM) revealed that the bis(pyrazolino[60]fullerene)-OPV can self-assemble into ordered layered crystalline architectures on the basal plane of highly oriented pyrolitic graphite.

One-Pot Sequential Synthesis of Acetoxylated [60]Fullerene Derivatives

[reaction: see text] The reaction of [60]fullerene with 4-substituted phenylhydrazine hydrochlorides in refluxing chlorobenzene under aerobic conditions afforded 1-(4-substituted phenyl)-1,2-dihydro[60]fullerenes, which could be subsequently oxidized to 1-acetoxyl-4-aryl-1,4-dihydro[60]fullerenes by manganese(III) acetate dihydrate in one pot. The transformation of ArC(60)-H to ArC(60)-OAc has been realized with Mn(OAc)(3).2H(2)O for the first time.

The Structure of Two 1-(Nitrophenyl)-Δ2-pyrazolines: a Crystallographic and Theoretical Study

The crystal and molecular structures of two nitrophenylpyrazolines have been determined. The geometries have been used as starting geometries for density functional theory (DFT) calculations. The differences in conformation between both molecules and between the solid state and gas phase are explained in terms of steric effects. An attractive intramolecular N···N interaction between the nitro group and the pyrazoline N2 nitrogens has been found. Absolute shieldings have been calculated (GIAO) and compared with experimental 1H and 13C chemical shifts.