Halogen-bonded one-dimensional chains of functionalized ditopic bipyridines co-crystallized with mono-, di-, and triiodofluorobenzenes

A series of halogen-bonded (XB) discrete, one-dimensional (1D) linear and zigzag supramolecular architectures by co-crystalizing a sterically hindered class of homologous ditopic para-xylenes bearing bipyridyl moieties at peripheries with mono-, di-, and triiodofluorobenzene as XB donor components were prepared. The solid-state structures investigated by X-ray diffraction on single crystals show that the molecular geometry of the tectons and halogen bond directionality translates into corresponding XB co-crystals and display a conformational twist at the planes of para-xylene with the adjacent aromatic rings. The bipyridine tectons grafted with photo-responsive azobenzene (–N=N–) side-group, once integrated into the halogen-bonded chains, can be remotely modulated by light, thus being applicable for controlling structure and innovative applications possibilities

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms

The self‐assembly of a nickel‐porphyrin derivative (Ni‐DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni‐DPPyP onto Au(111) gave rise to a close‐packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two‐dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close‐packed network and post‐deposition annealing at 423 K led to the formation of a Co‐coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal‐ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni‐DPPyP molecule

Synthetic polyamines stimulate in vitro transcription by T7 RNA polymerase.

The influence of nine synthetic polyamines on in vitro transcription with T7 RNA polymerase has been studied. The compounds used were linear or macrocyclic tetra- and hexaamine, varying in their size, shape and number of protonated groups. Their effect was tested on different types of templates, all presenting the T7 RNA promoter in a double-stranded form followed by sequences encoding short transcripts (25 to 35-mers) either on single- or double-stranded synthetic oligodeoxyribonucleotides. All polyamines used stimulate transcription of both types of templates at levels dependent on their size, shape, protonation degree, and concentration. For each compound, an optimal concentration could be defined; above this concentration, transcription inhibition occurred. Highest stimulation (up to 12-fold) was obtained by the largest cyclic compound called [38]N6C10.comparative studyjournal articleresearch support, non-u.s. gov't1994 Jul 25importe

Synthèse et étude de tourniquets moléculaires et conception de MOFs à base de Pt (II)

Le contrôle du mouvement à l échelle d une simple molécule est un sujet actuellement florissant et intensément exploré par des chimistes de tous horizons. Le travail présenté dans ce manuscrit s inscrit dans ce cadre. La conception ainsi que l étude en solution et à l état cristallin de tourniquets moléculaires, espèces composées d un rotor et d un stator comportant plusieurs sites d interaction, y sont décrites.Dans une première partie, la synthèse ainsi que le fonctionnement de tourniquets à charnière de Pt(II) sont décrits. La fermeture et l ouverture de ces systèmes ainsi que les essais de passage d une station à une autre y sont étudiés. Les sites d interactions ont été variés sur le rotor et le stator, pour aboutir à des systèmes variant par la dynamique de leur comportement.Dans une seconde partie, une synthèse optimisée de tourniquets à charnière organique est décrite. Les états ouverts et fermés de ces tourniquets ont été caractérisés.Tous les processus décrits pour les tourniquets ont été étudiés par des études RMN mono- et bi-dimensionnelles en solution.Dans un dernier chapitre, des MM OFs basés sur un tecton comportant un centre Pt(II) et deux sites coordinant de type pyridine sont exposés. Leur utilisation en tant que tecton organométallique avec divers centres métalliques conduit à la formation de réseaux hétérobimétalliques. Un ligand incluant deux centres Pt(II) et un centre Fe(II) entouré par deux terpyridines est décrit.The control of intramolecular movements has been a topic of high interest for chemists over two decades. Investigations described in this PhD manuscript aim at the design and study, both in solution and in the crystalline state, of molecular turnstiles. These entities are composed of a rotor and a stator, each of these constituents equipped with recognition sites.In the first part, the synthesis and behavior of Pt(II)-based molecular turnstiles are described. The switching between their open and closed states and the migration process between stations are discussed. The recognition sites on both the stator and rotor have been varied, leading to different behaviors, particularly in terms of their dynamics.In solution, 1- and 2-D NMR have been used for the characterization of the dynamic processes.In the last chapter, the use of a Pt(II)-bispyridyl based tecton for the synthesis of MM OFs is reported. The use of various metal salts as secondary center has led to the construction of networks varying by their geometry and dimensionality. A ligand including two Pt(II) and one Fe(II) complexed by two terpyridyl units is described.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Pre-organization of clefts for Ag–π interactions in Zn( ii ) bisdipyrrin helicates for the construction of heterometallic networks

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La tectonique moléculaire : des molécules à l’organisation hiérarchique de la matière complexe

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