Towards the stereoselective synthesis of inherently chiral pseudorotaxanes

Herein is reported an investigation towards the stereoselective synthesis of inherently chiral pseudorotaxanes. Chiral ammonium threads were readily prepared in five steps from racemic or enantiopure (M or P) salts of di-n-propyl-1,13-dimethoxyquinacridinium cation. Their self-assembly with DB24C8 or disymmetrically oriented DB24C8F6 rings formed pseudorotaxanes as shown by 1H and 19F NMR spectroscopy as well as MS measurements. A determination of the association constants (Ka) was afforded. The crucial role played by the ammonium counter-ion in the threading process was further demonstrated as salts of TRISPHAT (tris(tetrachlorobenzenediolato)phosphate(V)) anion were quite more effective than their PF6− analogues (× 7.3). A general lack of diastereoselectivity (de ≤ 8%) was unfortunately observed

Synthesis of a [2]Catenane around a Ru(diimine)32+ Scaffold by Ring-Closing Metathesis of Olefins

The synthesis of a ruthenium[2]catenane is described. One ring includes two 1,10-phenanthroline moieties, the other a bipyridinic unit. The interlocking ring system was formed by using a double ring closing metathesis reaction. Under irradiation, a rapid and selective decoordination of the bipyridinic fragment was observed, leading to a new catenane in which the metal is only coordinated to the bis-phenanthroline moiety

Titanium oxo-clusters derivatized from the Ti10O12(cat)8(py)8 complex: structural investigation and spectroscopic studies of light absorption

A series of deep-red colored nano-sized titanium oxo-clusters bearing catecholato ligands is reported. These architectures are produced via post-synthetic modification of the Ti10O12(cat)8(py)8 (cat = catecholato, py = pyridine) complex through quantitative substitution of labile pyridine ligands by three substituted pyridines (pico, 4-Phpy and pyrald). The crystal structure analysis reveals a common Ti10O12(cat)8 backbone for the three isolated molecular architectures. Partial charge analysis indicates two types of titanium atoms within these complexes with one resembling titanium(IV) found in TiO2. These complexes strongly absorb visible light in solution (λmax = 411 nm, ε = 10 800 for Ti10O12(cat)8(py)8 in CHCl3) and in the solid-state. The band gaps estimated from the reflectance spectra are between 1.85 eV and 1.97 eV. The present work also details the HOMO and LUMO representations obtained via DFT calculation for Ti10O12(cat)8(py)8 and a virtual Ti10O12(cat)8 complex as well as the DOS (density of states) plots calculated for those structures. This computational study highlights an impact of the pyridine ligand on the DOS plots

Identification of Zr(IV)-based architectures generated from ligands incorporating the 2,2′-biphenolato unit

The structural identification in solution of the Zr(IV) complexes involving two 2,2-biphenol-based proligands is reported. The proligand L1H2 contains one 2,2-biphenol unit whereas L2H4 incorporates two 2,2-biphenol units linked by a para-phenylene bridge. Diffusion Ordered Spectroscopy (DOSY) combined with electrospray mass spectrometry analysis and density functional theory (DFT) allowed for determining the molecular structures of such Zr(IV)-based architectures. It is proposed that [Zr(OPri)4(HOPri)] in the presence of L1H2 generates an octahedral complex formulated as [ZrL13H2]. Concerning the self-assembled architecture incorporating the L2 ligand, the analytical data highlight the formation of an unprecedented neutral Zr(IV) triple-stranded helicate ([Zr2L23H4]). Insight into the geometry of these complexes is obtained via DFT calculations. Remarkably, the helicate structure characterized in solution strongly contrasts with the triple-stranded structure of the complex that crystallizes

Monomeric Ti(IV)-based complexes incorporating luminescent nitrogen ligands: synthesis, structural characterization, emission spectroscopy and cytotoxic activities

This manuscript describes the synthesis of a series of neutral titanium(IV) monomeric complexes constructed around a TiO4N2 core. The two nitrogen atoms that compose the coordination sphere of the metallic center belong to 2,2′-bipyrimidine ligands homo-disubstituted in the 4 and 4′ positions by methyl (2a), phenylvinyl (2b), naphthylvinyl (2c) or anthrylvinyl (2d) groups. The crystal structures of these complexes named [Ti(1)2(2a)], [Ti(1)2(2b)], [Ti(1)2(2c)] and [Ti(1)2(2d)] (where 1 is a 2,2′-biphenolato ligand substituted in the 6 and 6′ positions by phenyl groups) are reported. The hydrolytic stability of the four complexes is evaluated by monitoring the evolution of the free 2a–d signals by 1H NMR spectroscopy. For the conditions tested (6 mM, DMSO-d6/D2O: 8/1), a rather good stability with t1/2 ranging from 180 to 300 min is determined for the complexes. In the presence of an acid (DCl), the hydrolysis of [Ti(1)2(2a)] is faster than without an acid. The cytotoxic activity against gastric cancer cells of the titanium-based compounds and the free disubstituted 2,2′-bipyrimidine ligands is tested, showing IC50 ranging from 6.2 ± 1.2 μM to 274 ± 56 μM. The fluorescence studies of the ligands 2a–d, and the complexes [Ti(1)2(2a–d)] reveal an important fluorescence loss of the ligands 2c and 2d upon coordination with the Ti(1)2 fragment. Frontier orbitals obtained by DFT calculations permit us to explain this fluorescence quenching.Other supports : Centre National pour la Recherche Scientifique (CNRS, France), ARC, Ligue contre le Cancer, European action COST CM1105 (C. G.

Caténanes construits sur un métal octaédrique (Mise en mouvement sous l'action de la lumière)

Ce travail de thèse s'inscrit dans le domaine des machines moléculaires. Il décrit l'élaboration de nouveaux [2]-caténanes de ruthénium (II), dont l'un des deux anneaux est mis en mouvement sous l'action de la lumière puis de la chaleur.Dans une première partie est exposée la synthèse de deux nouveaux macrocycles bis-phénanthrolines de taille différente, M50 et M63. Ces anneaux M50 et M63 sont aptes à complexer des métaux à sphère de coordination octaédrique. Le macrocycle M50 ne permet de former des complexes de symétrie C2, qu'avec des métaux non labiles (rhodium (III), ruthénium (II)). Le macrocycle M63 de taille supérieure permet de former également un complexe avec le fer (II) (métal labile).Cette aptitude des macrocycles à site bis-phénanthroline M50 et M63 à complexer le ruthénium (II) avec une symétrie C2, a permis d'aller vers la synthèse de nouveaux [2]-caténanes de ruthénium (II). Deux approches ont été étudiées. L'une consistant à synthétiser les caténanes de ruthénium via une seule réaction de fermeture de cycle par métathèse des oléfines. La seconde approche, "la voie directe", passe par une double réaction de fermeture de cycle.Puis il a été démontré, en s'appuyant sur les propriétés photophysiques particulières du ruthénium (II), qu'il était possible de "mettre en mouvement" ces [2]-caténanes de ruthénium. La décoordination sélective d'un des deux anneaux, et son retour thermique ont été mis en évidence.Enfin, l'aptitude du macrocycle M50 à former avec le rhodium (III) un complexe de symétrie C2 a été utilisée pour réaliser la synthèse d'un [2]-caténane de rhodium (III). Le deuxième anneau étant formé dans le "dos" de la troisième unité coordinante.This work, which is part of the field of molecular machines, entails the synthesis of a [2]-catenane, in which one ring can be set into motion under the action of light.In the first part, the synthesis of two new macrocycles M50 (a 50 membered ring) and M63 (a 63 membered ring) bearing two phenanthrolines is described.Macrocycles M50 and M63 are able to coordinate octahedral transition metals. The macrocycle M50 forms complexes with a C2 symetry with only second transition metals (such as ruthenium (II) or rhodium (III)), whereas the macrocycle M63 forms a stable C2 symetry complex even with iron (II) (first row transition metal).Three different [2]-catenanes were synthesized, for the first time, around an octahedral ruthenium (II) complex, taking advantage of the ability of the bis-phenanthroline backbone of each macrocycle to coordinate to this metal.Two different synthetic strategies were used; one is based on a single ring closing metathesis reaction, while the other involves the formation of the catenane using a double ring closing metathesis reaction.Next, it was demonstrated, that by using the unique photophysical properties of the ruthenium (II), it is possible to set these molecules into motion. The selective decoordination of one ring, and the thermal back reaction have been performed.Finally, a new [2]-catenane constructed around a rhodium (trisdiimine) complex was built, where the second ring was formed at the "rear" of the coordination unit.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF