Ever since the first experimental evidence of the existence of endohedral metallofullerenes (EMFs) was obtained, the search for carbon cages with encapsulated metals and small molecules has become a very active field of research. EMFs exhibit unique electronic and structural features, with potential applications in many fields. Furthermore, functionalized EMFs offer additional potential applications because of their higher solubility and their ease of characterization by X-ray crystallography and other techniques. Herein we review the general field of EMFs, particularly of functionalized EMFs. We also address their structures and their (electrochemical) properties, as well as applications of these fascinating compounds.

The first pyrrolidine adduct on Sc(3)N@C(80) was synthesized and fully characterized. Addition of the N-ethylazomethine ylide occurs regioselectively on a [5,6] double bond on the surface of the icosahedral symmetry Sc(3)N@C(80), exactly in the same position as that described previously for a Diels-Alder adduct of the same compound.(11a,b) This addition pattern results in symmetric pyrrolidine carbons and unsymmetric geminal hydrogens on the pyrrolidine ring, as confirmed by (1)H and (13)C NMR spectroscopy, especially by HMQC. The shielding environment experienced by these geminal hydrogens differs by 1.26 ppm, indicative of pronounced ring current effects on the surface of this endohedral fullerene. This represents the first fully characterized pyrrolidine adduct on an endohedral metallofullerene.

Aromatic triazoles have been frequently used as π-conjugated linkers in intramolecular electron transfer processes. To gain a deeper understanding of the electron mediating function of triazoles, we have synthesized a family of new triazole-based electron donor-acceptor conjugates. We have connected porphyrins and fullerenes through a central triazole moiety – (ZnP-Tri-C60) – each with a single change in their connection through the linker. An extensive photophysical and computational investigation reveals that the electron transfer dynamics – charge separation and charge recombination – in the different ZnP-Tri-C60 conjugates reflect a significant influence of the connectivity at the triazole linker. Except for m4m-ZnP-Tri-C60 17, the conjugates exhibit through-bond electron transfer with varying rate constants. Since the through-bond distance is nearly equal in the ZnP-Tri-C60 conjugates, the variation in charge separation and charge recombination dynamics is mainly associated with the electronic properties of the conjugates, including orbital energies, electron affinity, and the energies of the excited states. The changes of the electronic couplings are, in turn, a consequence of the different connectivity patterns at the triazole moieties.

Sensitizers with high triplet quantum yields are useful for generating photovoltaics, photocatalysts and photodynamic therapy agents with increased efficiency. In this study, the heavy atom effect was used to optimize the triplet and singlet oxygen quantum yields of 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin (1-TCM4PP). The triplet quantum yields, determined using delayed fluorescence, was calculated as 0.35 for 1-TCM4PP, 0.75 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-bromophenyl)porphyrin (2-TBCM3PP) and 0.88 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-iodophenyl)porphyrin (3-TCM3IPP). Chemical quenching of 1,3-diphenylisobenzofuran and singlet oxygen emission studies rendered an average singlet oxygen quantum yield of 0.51, 0.75, and 0.90 for TCM4PP, TBCM3PP and TCM3IPP respectively. These photophysical properties indicate that a single halogen atom is capable of transforming TCM4PP into a sensitizer with strong triplet character. This is useful for generating singlet oxygen for photodynamic therapy, creating a long lasting reactive species for catalysis and for extending diffusion lengths in photovoltaic applications while retaining three molecular modification points for further functionalization.

Seit dem ersten Fund von endohedralen Metallofullerenen (EMFs) hat sich die Suche nach Kohlenstoffkäfigen mit eingeschlossenen Metallen oder kleinen Molekülen rasch zu einem sehr aktiven Forschungsgebiet entwickelt. EMFs weisen besondere elektronische und Struktureigenschaften auf und finden vielfache Anwendungsmöglichkeiten. Noch mehr Potenzial bieten funktionalisierte EMFs, die besser löslich sind und durch Röntgenkristallographie und andere Techniken leicht charakterisiert werden können. Wir geben hier eine Übersicht über das allgemeine Gebiet der EMFs und insbesondere der funktionalisierten EMFs. Wir befassen uns in diesem Aufsatz mit der Struktur und den (elektrochemischen) Eigenschaften dieser faszinierenden Verbindungen und werden auch auf Anwendungen eingehen.

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The effects of molecular arrangement and orientation on the singlet exciton diffusion properties of carboalkoxyphenylporphyrins were investigated in solution-cast thin films.

The singlet exciton diffusion properties of solution-cast thin films prepared from mixed substituent monoiodophenyl or monobromophenyl derivatives of 5,10,15,20-tetrakis(4-carbomethoxyphenyl) porphyrin (TCM4PP) were investigated for use in solar energy conversion applications. The photoluminescent singlet decay lifetime PL(t) of pristine porphyrin films and films lightly doped (0.1 -0.6% wt.) with [6,6]-phenyl-C61-butryic acid methyl ester (PCBM) were used to obtain relative quenching efficiencies (Q). The exciton diffusion coefficient (D) and exciton diffusion length (LD) for each derivative were obtained by modeling the quenching efficiency and PL lifetime decay data using a 3D exciton Monte Carlo diffusion simulation. Although the three TCMPP derivatives showed nearly identical absorbances and electrochemical properties, the monobromophenyl or monoiodophenyl substituted porphyrins exhibited significantly lower steady-state emission intensities and fluorescent lifetimes in solution. Amorphous thin films of the halogenated derivatives also exhibited a decrease in the PL decay lifetimes, relative quenching efficiencies, and reduced singlet exciton diffusion lengths. The singlet exciton diffusion length for TCM4PP was calculated to be 15 nm and decreased by 71% to 4.4 nm for TCM3IPP with the addition of a single iodo substituent. Photocurrent-voltage measurements of the derivatives in a PCBM bulk heterojunction device suggest that lowered exciton diffusion and enhanced singlet to triplet exciton conversion, due to the heavy atom effect, decreases photoconversion efficiency.