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.

HPLC Resolution of Chiral [4]Heterohelicenium Dyes on Chiral Stationary Phases

[4]Heterohelicenium cations la-c adopt a twisted helical structure that renders them chiral. They are configurationally stable and their enantiomers have been resolved, for the first time, by HPLC on Chiralcel OD-RH and Chirobiotic TAG chiral stationary phases (CSPs). Chiral cations la-c have been resolved by HPLC using water-based eluents containing KPF6 as additive. The elution order of the analyte enantiomers was determined by on-line CD detection, and was found to be opposite on the two CSPs. The effect of mobile phase composition and analyte: structure on retention and enantioselectivity was investigated

A robust Ti(IV)-based mesogen constructed around a TiO4N2 core

International audienceStable complexes [Ti(1a)(2)2] and [Ti(1b)(2)2], where 2 is the 6,6′-diphenyl-2,2′-biphenolato ligand and 1a and 1b ligands are 2,2′-bipyrimidine derivatives, are synthesized. The complex [Ti(1b)(2)2] containing a diimine ligand substituted with long alkyl chains (C16) exhibits a liquid crystal behaviour. This property and self-assembling in the crystalline state are explained by the particular molecular conformation of the complexes

Modified pyridine–triazole and 2,2′-bipyrimidine ligands generating robust titanium complexes constructed around a TiO4N2 core

International audienceThe synthesis and characterization of novel chelate nitrogen ligands with phasmidic tails (pyridine-triazole ligand 1b; 2,2'bipyrimidine ligands 2b and 3b) is reported, as well as their titanium (IV) coordination complexes. The analogous ligands 1a, 2a and 3a with methoxy substituents instead of the tails were also synthesized, together with titanium complexes that could be crystallographically characterized. A good agreement is noticed between analytical data of the complexes in solution (NMR) and in the solid state (X-ray diffraction). The complexes are overall stable on phases like alumina or silica, so that they could be characterized by TLC and sometimes chromatographied. Supramolecular architectures were generated from an equimolar solution of titanium (IV) isopropoxide, ligand 1a and a polyphenol ligand 5-H4, leading to a double-stranded helicate characterized by MS, NMR and crystallography, which was then converted into a trinuclear complex as shown by MS and NMR DOSY data. The liquid-crystalline behaviour of the ligands 1b, 2b and 3b incorporating the long alkyl tails, and of the complexes derived from these ligands, has been investigated