A New Type of Dendritic [60]Fullerene–Metallo-tetraphenylporphyrin Diads (M = Zn, Co)

Supramolecular Self-Associations of Amphiphilic Dendrons and Their Properties

This review presents precisely defined amphiphilic dendrons, their self-association properties, and their different uses. Dendrons, also named dendritic wedges, are composed of a core having two different types of functions, of which one type is used for growing or grafting branched arms, generally multiplied by 2 at each layer by using 1→2 branching motifs. A large diversity of structures has been already synthesized. In practically all cases, their synthesis is based on the synthesis of known dendrimers, such as poly(aryl ether), poly(amidoamine) (in particular PAMAM), poly(amide) (in particular poly(L-lysine)), 1→3 branching motifs (instead of 1→2), poly(alkyl ether) (poly(glycerol) and poly(ethylene glycol)), poly(ester), and those containing main group elements (poly(carbosilane) and poly(phosphorhydrazone)). In most cases, the hydrophilic functions are on the surface of the dendrons, whereas one or two hydrophobic tails are linked to the core. Depending on the structure of the dendrons, and on the experimental conditions used, the amphiphilic dendrons can self-associate at the air-water interface, or form micelles (eventually tubular, but most generally spherical), or form vesicles. These associated dendrons are suitable for the encapsulation of low-molecular or macromolecular bioactive entities to be delivered in cells. This review is organized depending on the nature of the internal structure of the amphiphilic dendrons (aryl ether, amidoamine, amide, quaternary carbon atom, alkyl ether, ester, main group element). The properties issued from their self-associations are described all along the review.

Nucleophilic cyclopropanation of [60]fullerene by the addition-elimination mechanism

Information on the synthesis of monofunctionalized methanofullerenes C60 obtained by the addition-elimination mechanism is generalized. The main reagents for cyclopropanation, mechanisms and optimal conditions for the processes, and the prospects for practical application of the products are considered.

Synthesis and Atropisomerism of Cascaded Tetraphenylporphyrin-[60]Fullerene Hybrids

Flexible, linked dendritic tetraphenylporphyrin (TPP)-fullerene hybrids were synthesized. They were designed to gain insight into and mimic the primary events in the natural photosynthetic reaction center. These multiporphyrin moieties are based on a light-harvesting concept. Moreover, they incorporate multiple redox components aligned along a redox gradient. Newkome-type dendrons were added to these TPP-fullerene hybrids. In principle they can mediate pH-dependent water solubility, which, however, could not be observed in this case. A protecting-group strategy using tert-butyldiphenylsilyl groups allows convergent synthesis of the dendritic compounds. The dendritic multiporphyrins were synthesized separately and can be used as individual building blocks. Atropisomerism was observed in the dendritic compounds, and single atropisomers could be assigned to the corresponding peaks of a characteristic pattern in the NMR spectra. Deprotection of the Newkome-type dendrons was shown to be feasible under mild conditions that leave the redox gradient intact.

Layer-by-layer deposition of molecular oligoelectrolytes-investigation of assembling and degradation behaviour

The assembly and degradation behavior of oligoelectrolyte multilayer films (OEMs) self assembled by layer-by-layer deposition of positively and negatively charged oligoelectrolytes 1-6 was investigated. Next to colorless oligoelectrolytes we have employed representatives involving chromophores, in particular porphyrins. This allows for the systematic observation of both assembly and disassembly of the OEMs using optical spectroscopy, where chromophore containing building blocks serve as reporter electrolytes. The OEMs investigated in this study were built in a consistent, monomolecular matter and show linear correlation between the absorption and the number of layers. Using the concept of reporter electrolytes we have introduced for the first time also the use of non-chromophoric oligoelectrolytes, such as the new synthesized cationic system 2 as building blocks for OEMs. Moreover, we have investigated for the first time the degradation behavior of OEMs. We demonstrated that two different mechanisms of degradation proceed at the same time. The direct degradation is accompanied by a second release mechanism.