Towards a Real Knotaxane

Two classes of mechanically interlocked molecules, [3]rotaxanes and knotted [1]rotaxanes, were the subject of this investigation. The necessary building blocks, alkyne-terminated axles containing two ammonium ions and azide-terminated stoppers, and azide-containing substituted macrocycles, have been synthesized and characterized. Different [3]rotaxanes were synthesized by copper-catalyzed “click” reactions between the azide stoppers and [3]pseudorotaxanes formed from the dialkyne axles and crown ethers (DB24C8). Methylation of the triazoles formed by the “click” reaction introduced a second binding site, and switching via deprotonation/protonation was investigated. In preliminary tests for the synthesis of a knotted [1]rotaxane, pseudorotaxanes were formed from azide-containing substituted macrocycles and dialkyne substituted diammonium axles, and copper-catalyzed “click” reactions were carried out. Mass spectral analyses showed successful double “click” reactions between two modified macrocycles and one axle. Whether a knotted [1]rotaxane was formed could not be determined

Second Generation Self‐Assembling Dendrimer Combining Supramolecular and Dynamic Covalent Chemistry

A monodisperse second generation self-assembled dendrimer has been obtained combining supramolecular chemistry and dynamic covalent chemistry as orthogonal binding moieties. A branching unit 18 and a core 5 were connected via a heteroleptic terpyridine zinc complex exploiting the sterical hindrance of mesitylene units in the 6,6’’-position of one of the terpyridines as the distinction between the ligands. Solubility problems could be solved by introduction of an ethylhexyl ether. The final sphere of the dendrimer was connected via imines, hydrazones and oximes, whereby the oxime made from O-methylhydroxylamine (22) led to a complete turnover of all aldehyde functions. Furthermore, no amine signal was left and also no signals for a diffusion constant of the hydroxylamine 22 were observed. The successful formation of the dendrimers was analyzed by 1 H NMR and DOSY NMR spectroscopy. Furthermore both, the first and second generation dendrimers could be detected by ESI HRMS

Substituted 1,3,5-Triazine Hexacarboxylates as Potential Linkers for MOFs

Hexacarboxylates are promising linkers for MOFs such as NU-109 or NU-110, which possess large values for surfaces and pore volumina. Starting from 2,4,6-tris(bromoaryl)-1,3,5-triazines, palladium-catalyzed cross coupling reactions (Suzuki-Miyaura, Sonogashira-Hagihara) form elongated hexacarboxylate linkers. Eight new 2,4,6-tris(biphenyl) and 2,4,6-tris(phenylethynylphenyl) 1,3,5-triazines have been prepared in quantities ranging from 40 mg to 1.1 g. In five cases, one of the arms of the linker carries an additional functionality (NO2 or OMe)

Synthesis and crystal structure of allyl 7-(diethylamino)-2-oxo-2H-chromene-3-carboxylate

The title compound, C17H19NO4, was synthesized by the reaction of 7-(di-ethyl-amino)-2-oxo-2H-chromene-3-carb-oxy-lic acid with allyl bromide and purified by flash column chromatography on silica gel. Crystals suitable for single-crystal X-ray diffraction were obtained by recrystallization from acetone. The aromatic core of the mol-ecule is not planar with the di-ethyl-amino group and with the carboxyl group that are rotated out of the 2-oxo-2H-chromene plane by 6.7 (2)° and 11.4 (2)°. The NC2 unit of the di-ethyl-amino group is planar with an angle sum close to 360°. Inter-molecular Car-H⋯Ocarbon-yl inter-actions lead to the formation of chains parallel to the b axis. X-ray powder diffraction analysis proves that the title compound was obtained as a pure phase

Metal induced folding: Synthesis and conformational analysis of the lanthanide complexes of two 44-membered hydrazone macrocycles

Six new lanthanide complexes of two 44-membered macrocycles have been prepared and characterised in solution. An analysis of the conformations of the free macrocycles and their lanthanide complexes both in solution (2D NMR) and in solid state (X-ray crystallography) demonstrate that the complexation induces changes in folding of the macrocycles

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

A bi-macrocycle with an incorporated isophthalamide substructure was synthesized by double amide formation between an isophthaloyl dichloride and two equivalents of a bis(alkenyloxy)aniline, followed by ring-closing metathesis and hydrogenation. In contrast to many related isophthalamides, the concave host exhibits a better binding for oxides, such as DMSO or pyridine-N-oxide, than for halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated K ass of pyridine-N-oxide of ca. 40 M−1, NMR titration confirms 25 M−1

Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

New triazine-based tricarboxylic acid linkers were prepared as elongated relatives of triazinetribenzoic acid (TATB). Additionally, functional groups (NO2, NH2, OMe, OH) were introduced for potential post-synthetic modification (PSM) of MOFs. Functionalized tris(4-bromoaryl)triazine “cores” (3a,3b) were obtained by unsymmetric trimerization mixing one equivalent of an acid chloride (OMe or NO2 substituted) with two equivalents of an unsubstituted nitrile. Triple Suzuki coupling of the cores 3 with suitable phenyl- and biphenylboronic acid derivatives provided elongated tricarboxylic acid linkers as carboxylic acids 17 and 20 or their esters 16 and 19. Reduction of the nitro group and cleavage of the methoxy group gave the respective amino and hydroxy-substituted triazine linkers

Chiral Concave Imidazolinium Salts as Precursors to Chiral Concave N-Heterocyclic Carbenes

Imidazolinium moieties have been incorporated into bimacrocycles to generate precursors for concave N-heterocyclic carbenes (NHCs). By using one symmetrically substituted benzene bridgehead and one naphthalene bridgehead devoid of local C2-symmetry, axially chiral concave imidazolinium ions have been obtained. Starting from 2,7-dihydroxy-1-nitronaphthalene (7), the phenol groups have been transformed to 4-pentenyl ethers 8, and the nitro group was then reduced to the corresponding amine 9. Next, 9 and a 2,6-bis(alkenyloxy)aniline 10 were connected by an oxalic acid linker. After reduction of the diamide 13 to diamine 14, a bridge was installed with triethyl orthoformate to give a tetraalkenyl-substituted imidazolinium salt 15. Ring-closing metathesis of 15 followed by hydrogenation of the products 16 yielded the bimacrocyclic salts 17 in 9-18 % overall yield (based on 7), giving amounts up to >300 mg. The configurational stability of 17 was investigated by NMR using chiral enantiopure anions TRISPHAT 18 and BINPHAT 19 as stereodynamic probes

Business Chemistry: The successful establishment of an interdisciplinary field

The article presents the development of Business Chemistry at seven German and one Swiss universities. Besides highlighting the course of study in general and it's development, the respective universities present benefits but also specific challenges they had to face when introducing Business Chemistry. Followed by a short introduction of Business Chemistry itself, its development and the status quo, every university presented their individual perspectives on the course of study. Overall, the article should provide our readers with an overview of Business Chemistry and sensitize them for the differences in the study programs, even though the courses of study were developed in ac cordance with all respective universities