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Supramolecular polymers are described that are derived from the association of two homoditopic heterocomplementary monomers through sextuple hydrogen‐bonding arrays. They form fibers and a variety of different materials depending on the conditions. The strong affinity of the DAD–DAD (D=donor, A=acceptor) hydrogen‐bonding sites for double‐faced cyanuric acid type wedges drives the supramolecular polymeric assembly in apolar and chlorinated organic solvents. The marked influence of stoichiometry, as well as end‐capping and cross‐linking agents upon fiber formation is revealed in solution and by electron microscopy (EM). The results further contribute to the development of a supramolecular polymer chemistry that comprizes reversible polymers formed through recognition‐controlled noncovalent connections between the molecular components. Such materials are, by nature, dynamic and present adaptive character in view of their ability to respond to external stimuli.

Helically preorganized oligopyridine‐dicarboxamide strands are found to undergo dimerization into double helical supramolecular architectures. Dimerization of single helical strands with five or seven pyridine rings has been characterized by NMR and mass spectrometry in various solvent/temperature conditions. Solution studies and stochastic dynamic simulations consistently show an increasing duplex stability with increasing strand length. The double helical structures of three different dimers was characterized in the solid phase by X‐ray diffraction analysis. Both aromatic stacking and hydrogen bonding contribute the double helical arrangement of the oligopyridine‐dicarboxamide strand. Inter‐strand interactions involve extensive face‐to‐face overlap between aromatic rings, which is not possible in the single helical monomers. Most hydrogen bonds occur within each strand of the duplex and stabilize its helical shape. Some inter‐strand hydrogen bonds are found in the crystal structures. Dynamic studies by NMR as well as by molecular modeling computations yield structural and kinetic information on the double helices and on monomer–dimer interconversion. In addition, they reveal the presence of a spring‐like extension/compression as well as rotational displacement motions.

Molecular strands composed of alternating 2,6‐diaminopyridine and 2,6‐pyridinedicarbonyl units have been designed to self‐organize into single stranded helical structures upon forming intramolecular hydrogen bonds. Pentameric strands 11, 12, and 14, heptameric strands 1and 20, and undecameric strand 15have been synthesized using stepwise convergent strategies. Single helical conformations have been characterized in the solid state by single crystal X‐ray diffraction analysis for four of these compounds. Helices from pentameric strands 12and 14extend over one turn, and helices from heptameric 20and undecameric 15species extend to one and a half and two and a half turns, respectively. Intramolecular hydrogen bonds are responsible for the strong bending of the strands. 1H NMR shifts both in polar and nonpolar organic solvents indicate intramolecular overlap between the peripheral aromatic groups. Thus, helical conformations also predominate in solution. Molecular stochastic dynamic simulations of strand folding starting from a high energy extended linear conformer show a rapid (600 ps at 300 K) conversion into a stable helical conformation.

Ligand 3has been shown to self‐assemble under coordination of copper(II) cations in a 1:1 ratio in acetonitrile to give equilibrating mixtures of a [2×2] grid‐type tetranuclear structure 1and a hexanuclear achitecture of hexagonal shape 2. The latter was confirmed by determination of the crystal structure which further indicated that 2contained acetonitrile molecules and hydroxo groups bound to the copper(II) centers, which are therefore five‐coordinate. The structures assigned to 1and 2were further supported by the spectral (mass, UV/Vis) data. The self‐assembly process is strongly dependent on the conditions of the medium. An increase in concentration in acetronitrile increases the relative amount of hexamer 2, which appears to be the favored entity at the highest concentrations that can be reached before precipitation occurs. On the other hand, in nitromethane only the tetranuclear complex 1was detected by mass spectrometry. Replacement of nitromethane by acetonitrile and vice versa indicated the reversible switching between a solution containing either 1alone or an equilibrium mixture of 1and 2, respectively. In conclusion, the system described presents several remarkable features: 1) self‐assembly with substrate binding, 2) dynamic combinatorial structure generation, and 3) environment‐induced structural switching amounting in effect to a process of adaptive self‐assembly.

The condensation of the two oligoheterocyclic aldehydes 8and 16with the bis‐hydrazine 17gives the bis‐hydrazones 1and 2. These molecular strands are shown to adopt helical conformations of 1.5 and 2.5 turns, respectively. The helical shape of 1has been confirmed and structurally characterized by X‐ray crystallography. The results indicate that the pyrimidine‐hydrazone unit is a satisfatory helicity codon, so that the facile hydrazone formation provides an efficient procedure for generating helical structures. This greatly widens the scope of the methodology based on designed heterocyclic sequences for enforcing helicity in molecular strands, and opens interesting routes towards a variety of derived structures.

Benzoporphyrins 5and 6are the major products obtained from the cycloaddition reactions of β-fused metallo-pyrroloporphyrins 1and 2with dimethyl acetylenedicarboxylate. In the presence of excess dienophile a bis-adduct is also obtained which undergoes retro-Diels-Alder reaction to produce 5. Benzoporphyrin 5was converted into the first reported β-fused benzochlorins 9–11, and the free-base benzoporphyrin 12was regioselectively brominated to afford 13. Exhaustive bromination also yields hexabromobenzoporphyrin 14.

Reaction of the 5,15-di-(2-alkylamidophenyl)-etioporphyrin 3 (α,α-atropisomer) with the ‘self-trans-diprotected’ dioxocyclam 4 leads easily, in only two steps, to a new symmetrical dioxocyclam porphyrin 5 in an overall 41% yield. This ligand is a precursor of models of cytochromes. All the compounds have been fully characterized by elemental analysis, mass spectrometry and UV-vis, 1HNMR, 13CNMRand 1H–13Cheteronuclear correlation NMRspectroscopies. X-ray structural data are presented for the Zn(II)porphyrin 6 confirming that the porphyrin and the dioxocyclam adopt cofacial orientations.

Eine dimere, auch in Lösung stabile Struktur, die auf Wasserstoffbrückenbindungen beruht, charakterisiert das Chloridsalz des abgebildeten expandierten Corrols. Die Synthese, die Röntgenstrukturanalyse sowie die NMR- und UV/Vis-Absorptionsspektren der neuen Spezies bestätigen die Strukturzuordnung sowohl in Lösung als auch im festen Zustand.

Alle vier Porphyrineinheiten auf der gleichen Seite‐ das ist die überraschende Konformation, die das Calixaren 1einnimmt. Die Verbindung liegt im Kristall in einer dimeren “Zahnradstruktur” vor, in der π‐Stapelung das dominierende strukturprägende Merkmal ist.

Reaction of (2-nitro-5,10,15,20-tetraphenylporphyrinato)nickel(II) 3 or its copper(II) complex 4 with α-isocyanoacetic esters in the presence of 1,8-diazabicyclo[5.4.O]undec-7-ene accomplishes the first syntheses of β-fused pyrroloporphyrins (e.g. 5–10). The removal of the fused pyrrole ester protecting groups to give the di-α-free pyrroloporphyrins 2a and 13 is described, as well as some pyrrole-type chemistry. Unsymmetrical fused dipyrromethanoporphyrins (16–18) were synthesized by reacting 5-acetoxymethylpyrrole-2-carboxylates (14,15) with mono-α-free pyrroloporphyrins (5–8) in the presence of Montmorillonite clay. A symmetrical bis-porphyrinyl dipyrromethane 19 was also prepared by condensation of the β-fused methyl ester pyrroloporphyrin 7 with dimethoxymethane in ethanol and concentrated hydrochloric acid.© 1997 John Wiley & Sons, Ltd.

Reaction of (2-nitro-5,10,15,20-tetraphenylporphyrinato)nickel(II) 3or its copper(II) complex 4with α-isocyanoacetic esters in the presence of 1,8-diazabicyclo[5.4.O]undec-7-ene accomplishes the first syntheses of β-fused pyrroloporphyrins (e.g. 5–10). The removal of the fused pyrrole ester protecting groups to give the di-α-free pyrroloporphyrins 2aand 13is described, as well as some pyrrole-type chemistry. Unsymmetrical fused dipyrromethanoporphyrins (16–18) were synthesized by reacting 5-acetoxymethylpyrrole-2-carboxylates (14,15) with mono-α-free pyrroloporphyrins (5–8) in the presence of Montmorillonite clay. A symmetrical bis-porphyrinyl dipyrromethane 19was also prepared by condensation of the β-fused methyl ester pyrroloporphyrin 7with dimethoxymethane in ethanol and concentrated hydrochloric acid.

All four porphyrin units on the same side—that is the surprising conformation adopted by calixarene 1. A “cogwheel” dimeric structure was identified for the compound in the solid state, in which p–p aggregation is the dominating structural feature.

Reaction of the 5,15-di-(2-alkylamidophenyl)-etioporphyrin 3 (α,α-atropisomer) with the ‘self-trans-diprotected’ dioxocyclam 4 leads easily, in only two steps, to a new symmetrical dioxocyclam porphyrin 5 in an overall 41% yield. This ligand is a precursor of models of cytochromes. All the compounds have been fully characterized by elemental analysis, mass spectrometry and UV-vis, ¹H NMR, ¹³C NMR and ¹H–¹³C heteronuclear correlation NMR spectroscopies. X-ray structural data are presented for the Zn(II) porphyrin 6 confirming that the porphyrin and the dioxocyclam adopt cofacial orientations. © 1998 John Wiley & Sons, Ltd.

TetraNRpyridinium4ylporphyrin and tetraNRpyridinium3ylporphyrin derivatives were synthesized with R 3, 6, and 8 carbon alkene, alcohol and carboxylic acid chains. Selfaggregation of these systems was studied at I 0.1 using visible spectroscopy. NAlkyl chain length and functionality were determined to play the dominant role in aggregation of the cationic porphyrins. Position of peripheral charge meta vs. para also influenced spectral changes and the nature of the aggregate.

A dimeric structure that is held together by hydrogen bonds and is stable in solution is adopted by the hydrochloride salt of the expanded corrole shown. The synthesis, X-ray structure, and NMR and electronic absorption spectra of the new species all confirm the structural assignment in solution and in the solid state.

The cover picture showsa perspective view of the crystal structure of a double helix formed from two oligomeric molecular strands of pyridine heterocycles connected through carboxamide functions. The color coded strands are shown in stick representations with solvent accessible surfaces. The folding of these oligomers into single helical conformations and their association into double helices held by hydrogen bonds and stacking interactions are described in detail by Lehn and Huc et al. on p. 2810 ff. (We thank C. Caroli from the Visual Design Softwareentwicklungs GmbH, Karlsruhe, for assistance in the preparation of the cover picture.)

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.