Vogtle studies

The incorporation of arenes in small cyclophanes hinders rotation around certain bonds and can afford isolable enantiomers with appropriately substituted backbones, e.g., planar-chiral 11 (Liittringhaus) or helical-chiral 12 (Vogtle). Studies of the dynamic properties of small cyclophanes with intraannular substituents X (13) provided insight into the space occupancy of atoms or functional groups. ... 

The bulk of the work which has been performed on open-chained crown ether and cryptand equivalents, especially for application to general cation binding studies has been accomplished by Vogtle and his coworkers. Vogtle has reviewed both his own and other work in this field . 

The materials shown and described above were generally prepared from the nucleophilic phenoxide or alkoxide and the appropriate bromide. The syntheses of a variety of such compounds were detailed in a report which appeared in 1977. In the same report, complex stability and complexation kinetics are reported. Other, detailed studies, of a similar nature have recently appeared" . Vogtle and his collaborators have also demonstrated that solid complexes can be formed even from simple polyethylene glycol ethers . Crystal structures of such species are also available... 

The history of dendrimer chemistry can be traced to the foundations laid down by Flory [34] over fifty years ago, particularly his studies concerning macro-molecular networks and branched polymers. More than two decades after Flory s initial groundwork (1978) Vogtle et al. [28] reported the synthesis and characterization of the first example of a cascade molecule. Michael-type addition of a primary amine to acrylonitrile (the linear monomer) afforded a tertiary amine with two arms. Subsequent reduction of the nitriles afforded a new diamine, which, upon repetition of this simple synthetic sequence, provided the desired tetraamine (1, Fig. 2) thus the advent of the iterative synthetic process and the construction of branched macromolecular architectures was at hand. Further growth of Vogtle s original dendrimer was impeded due to difficulties associated with nitrile reduction, which was later circumvented [35, 36]. This procedure eventually led to DSM s commercially available polypropylene imine) dendrimers. 

In the early 1990s Hunter [49] and Vogtle [50,51] discovered independently the possibility of using hydrogen bonding interactions displayed by amide groups to template the formation of [2 ] catenanes. While studying the reaction between the... 

Vogtle and co-workers first reported a photoswitchable dendrimer [33] with six peripheral azobenzene groups, which took advantage of the efficient and fully reversible photoisomerization reaction of azobenzene-type compounds (Scheme 7). In a follow-up study [34], polypropylene imine) dendrimers bearing azobenzene moieties (p-Im-Gn, n = 1-4) on the periphery were synthesized. These dendrimers displayed similar photoisomerization properties as the azobenzene monomers. Irradiation of the all-E azobenzene dendrimers at 313 nm led to the Z-form dendrimers, while irradiation at 254 nm or heating could convert the Z-form dendrimers back to the E-form dendrimers. The observation that the... 

After the synthesis of the first amide-linked [2]rotaxanes, Vogtle et al. set out to study the limits of molecular recognition, which in terms of Emil Fischer means to discover if the lock (macrocycle) is specific to a certain key, or if several keys (monoamide threads) fit. It turned out that - in contrast to catenane formation - rotaxane synthesis is very tolerant towards the variation of the building... 

Balzani and Vogtle et al. studied the complexation of neodymium(III) and other rare earth metal ions by a luminescent second-generation polylysine den-... 

Principles and Applications, VCH Publishers, New York-Weinheim 1994 H.R. Christen, F. Vogtle, Circular Dichroismus, in Organische Chemie, Von den Grundla-gen zur Forschung, Vol. II, Salle, Frankfurt am Main 1990, pp. 301-334 N. Har-ada, K. Nakanishi, Circular Dichroic Spectroscopy - Exciton Coupling in Organic Stereochemistry, Oxford University Press 1983 S.F. Mason, Optical Activity and Chiral Discrimination, Reidel, Dordrecht, Nato Advances Study Institutes Series, Series C, Vol. 48, 1978 E. Charney,... 

Luminescence has already been considered in general terms in Chapter 5. Luminescent POPAM dendrimers of various generations with peripheral dansyl units were studied by Balzani and Vogtle et al. as sensor model systems with regard to the fundamental suitability of dendritic structures for multiplication of signalling groups (multi-labelling) [48]. 

Grimme S, Pischel I, Vogtle F, Niegers M (1995) Experimental and theoretical study of dithia [njmetacyclophanes syntheses, chiroptical properties, and conformational analysis. J Am Chem Soc 117 157-162... 

Grimme S, Peyerimhoff SD, Bartram S, Vogtle F, Breest A, Hormes J (1993) Experimental and theoretical study of the circular dichroism spectra of oxa- and thia-[2.2]metacyclophane. Chem Phys Lett 213 32-40... 

Wortmann-Saleh D, Grimme S, Engels B, Miiller D, Vogtle F (1995) A study of the N-inversion barrier and the circular dichroism spectra of l-thia-10-aza[2.2]metacyclophane. J Chem Soc Perkin Trans 2 1185-1189... 

Grinune S, Mennicke W, Vogtle F, Nieger M (1999) Experimental and theoretical studies of a chiral azulenophane synthesis, structure and circular dichroism spectra of 14,17-dimethyl[2]... 

Vogtle et al. have demonstrated the formation of solid 1 1 adducts between terpy and MSCN (M = Li or Na) in contrast, [NH4][SCN] forms a 2 1 adduct with terpy. Although stability constants were not reported, it was shown by Na NMR studies that terpy is superior to bipy, but inferior to phen, as a ligand for the sodium cation 455). Presumably, the metal-nitrogen interaction is predominantly ionic in character. 

A simple possibility for the synthesis of esters, the reaction of an acid chloride with an alcohol, was used by Schrage and Vogtle [58] for a two-step synthesis of the macrocycle 63 from the alcohol 61 and the acid chloride 62. Compound 63, an example from the field of host/guest chemistry, forms a cavity, as studied with CPK-models, which could include planar, aromatic guests. Crystals obtained from benzene/ -heptane point to a 1 2 stoichiometry of 63 and benzene according to NMR-spectroscopic data. However, whether this is a molecular inclusion complex or just a clathrate is not yet known. 

Vogtle and Mayenfels studied the influence of the bases cesium hydroxide and sodium hydroxide on twofold aldol condensations leading to macrocyclic dichal-cones 4 [24] ... 

C.A. Schalley, K. Beizai, F. Vogtle, On the Way to Rotaxane-Based Molecular Motors Studies in Molecular Mobility and Topological Chirality , Acc. Chem. Res., 34, 465 (2001)... 

Vogtle, F. Lindner, P. Distribution of end groups within a dendritic structure a SANS study including contrast variation. Macromolecules 2002, 35, 8098-8105. 

The binding of various nucleobases by a molecular tweezer has been studied by Vogtle and coworkers [107]. They found that this receptor (Figure 81) bound 2,6-diaminopurine and adenine with of the order of 10 M . 2-Aminopurine, cytosine, guanine and 2,4-dihydroxypteridine did not show any observable binding. 

Some metallodendrimers with one or more stereogenic centers have been prepared without control of the chirality. Vogtle and Balzani [74] have tried several strategies to prepare dendrimers in which a ruthenium cation is the core of the final compound. In these compounds, the only centre of chirality is that of the metal, but as it was not controlled racemic mixtures were obtained. Controlling the stereochemistry of the starting complex would have allowed the authors to prepare a optically pure metallodendrimer. Denti, Campagna, Balzani, and their co-workers have studied polymetallic dendrimers based on bipyridine and 2,3- 7s -(2-pyridyl)pyrazine (2,3-... 

Schalley, C. A., Beizai, K. and Vogtle, F., On the way to rotaxane-based molecular motors Studies in molecular mobility and topological chirality , Acc. Chem. Res. 2001, 34, 465-476. 

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