Hydroxyamidinates et polymères de coordination : suspicions et valences mixtes

Dans un contexte où l’énergie représente un enjeu majeur pour les pays et organisations à économies émergentes et développées, la recherche de nouvelles sources renouvelables et la démocratisation des vecteurs énergétiques permettant l’approvisionnement mondial de façon durable constitue un devoir pour la communauté scientifique internationale. D’ailleurs, il serait essentiel que les nombreuses disciplines de la chimie concertent leurs efforts. Plus particulièrement, la croissance de la recherche en chimie de coordination orientée vers la photosynthèse artificielle ainsi que le développement de matériaux fonctionnels démontre l’importance indéniable de ce champ de recherche. Ce travail présente dans un premier temps l’étude des différentes voies de synthèse d’hydroxyamidines, un ligand chélatant aux propriétés de coordination prometteuses ne recevant que très peu d’attention de la part de la communauté scientifique. Dans un deuxième temps, nous présenterons le développement d’une stratégie d’assemblage de leurs complexes supramoléculaires impliquant des métaux de transition abondants et peu dispendieux de la première rangée. Dans un troisième temps, il sera question de l’investigation de leurs propriétés photophysiques et électrochimiques à des fins d’applications au sein de matériaux fonctionnels. Pour ce faire, les différentes voies de synthèse des hydroxyamidines et de leurs amidines correspondantes qui ont précédemment été étudiées par les membres du groupe seront tout d’abord perfectionnées, puis investiguées afin de déterminer leur versatilité. Ensuite, les propriétés de complexation des amox résultantes comportant des motifs sélectionnés seront déterminées pour enfin étudier les propriétés photophysiques et électrochimiques d’une série de complexes de métaux de transition de la première rangée. En somme, plusieurs designs qu’offrent les amox et bis-amox sont étudiés et les propriétés des architectures résultantes de leur auto-assemblage sont déterminées.

Hydroxyamidinates et polymères de coordination : suspicions et valences mixtes

Dans un contexte où l’énergie représente un enjeu majeur pour les pays et organisations à économies émergentes et développées, la recherche de nouvelles sources renouvelables et la démocratisation des vecteurs énergétiques permettant l’approvisionnement mondial de façon durable constitue un devoir pour la communauté scientifique internationale. D’ailleurs, il serait essentiel que les nombreuses disciplines de la chimie concertent leurs efforts. Plus particulièrement, la croissance de la recherche en chimie de coordination orientée vers la photosynthèse artificielle ainsi que le développement de matériaux fonctionnels démontre l’importance indéniable de ce champ de recherche. Ce travail présente dans un premier temps l’étude des différentes voies de synthèse d’hydroxyamidines, un ligand chélatant aux propriétés de coordination prometteuses ne recevant que très peu d’attention de la part de la communauté scientifique. Dans un deuxième temps, nous présenterons le développement d’une stratégie d’assemblage de leurs complexes supramoléculaires impliquant des métaux de transition abondants et peu dispendieux de la première rangée. Dans un troisième temps, il sera question de l’investigation de leurs propriétés photophysiques et électrochimiques à des fins d’applications au sein de matériaux fonctionnels. Pour ce faire, les différentes voies de synthèse des hydroxyamidines et de leurs amidines correspondantes qui ont précédemment été étudiées par les membres du groupe seront tout d’abord perfectionnées, puis investiguées afin de déterminer leur versatilité. Ensuite, les propriétés de complexation des amox résultantes comportant des motifs sélectionnés seront déterminées pour enfin étudier les propriétés photophysiques et électrochimiques d’une série de complexes de métaux de transition de la première rangée. En somme, plusieurs designs qu’offrent les amox et bis-amox sont étudiés et les propriétés des architectures résultantes de leur auto-assemblage sont déterminées.

The syntheses, characterizations, X-ray crystal structures and properties of Cu(I) complexes of a bis-bidentate schiff base ligand

Bis-bidentate Schiff base ligand L and its two mononuclear complexes [CuL(CH3CN)(2)]ClO4 (1)and [CuL(PPh3)(2)]ClO4 (2)have been prepared and thoroughly characterized by elemental analyses, IR, UV-Vis, NMR spectroscopy and X-ray diffraction analysis. In both the complexes the metal ion auxiliaries adopt tetrahedral coordination environment. Their reactivity, electrochemical and photophysical behavior have been studied. Complex 1 shows reversible Cu-II/I couple with potential 0.74 V versus Ag/AgCl in CH2Cl2. At room temperature L is weakly fluorescent in CH2Cl2, however in Cu(I)complexes 1 and 2 the emission in quenched. (C) 2009 Elsevier B. V. All rights reserved.

Sequential C-H and C-Ru bond formation and cleavage during the thermally induced rearrangement of aryl ruthenium(II) complexes with [C6H3(CH2NMe2)(2)-2,6](-) as a bidentate eta(2)-C,N coordinated ligand. The crystal structures of the isomeric pairs [RuCl{eta(6)-C10H14}{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,n}] (n = 4 or 6) and [Ru(eta(5)-C5H5){(eta(2)-C,N-C6H3(CH2NMe2)(2)-2,n} (PPH3)] (n = 4 or 6)

New air-stable ruthenium(II) complexes that contain the aryldiamine ligand [C6H3(CH2-NMe2)(2)-2,6](-) (NCN) are described. These complexes are [RuCl{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,6}(eta(6)-C10H14)] (2; C10H14 = p-cymene = C6H4Me-Pr-i-4), [Ru{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,6}(eta(5)-C5H5)(PPh3)] (5), and their isomeric forms [RuCl{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,4}(eta(6)-C10H14)] (3) and [Ru{eta(2)-C,N-C6H3(CH2NMe2)(2)-2,4}(eta(5)-C5H5)(PPh3)] (6), respectively. Complex 2 has been prepared from the reaction of [Li(NCN)](2) with [RuCl2(eta(6)-C10H14)](2), whereas complex 5 has been prepared by the treatment of [RuCl{eta(3)-N,C,N-C6H3(CH2NMe2)(2)-2,6}(PPh3)] (4) with [Na(C5H5)](n). Both 2 and 5 are formally 18-electron ruthenium(II) complexes in which the monoanionic potentially tridentate coordinating ligand NCN is eta(2)-C,N-bonded, In solution (halocarbon solvent at room temperature or in aromatic solvents at elevated temperature), the intramolecular rearrangements of 2 and 5 afford complexes 3 and 6, respectively. This is a result of a shift of the metal-C-aryl bond from position-1 to position-3 on the aromatic ring of the NCN ligand. The mechanism of the isomerization is proposed to involve a sequence of intramolecular oxidative addition and reductive elimination reactions of both aromatic and aliphatic C-H bonds. This is based on results from deuterium labeling, spectroscopic studies, and some kinetic experiments. The mechanism is proposed to contain fully reversible steps in the case of 5, but a nonreversible step involving oxidative addition of a methyl NCH2-H bond in the case of 2. The solid-state structures of complexes 2, 3, 5, and 6 have been determined by single-crystal X-ray diffraction. A new dinuclear 1,4-phenylene-bridged bisruthenium(II) complex, [1,4-{RuCl(eta(6)-C10H14)}(2){C-6(CH2NMe2)(4)-2,3,5,6-C,N,C',N'}] (9) has also been prepared from the dianionic ligand [C-6(CH2NMe2)(4)-2,3,5,6](2-) (C2N4). The C2N4 ligand is in an eta(2)-C,N-eta(2)-C',N'-bis(bidentate) bonding mode. Compound 9 does not isomerize in solution (halocarbon solvent), presumably because of the absence of an accessible C-aryl-H bond. Complex 9 could not be isolated in an analytically pure form, probably because of its high sensitivity to air and very low solubility, which precludes recrystallization.

[Cr(C6H18N4)(SbS3)], a chromium complex containing an unusual bidentate SbS33- ligand

A new chromium-antimony-sulfide, [Cr(C6H18N4)(SbS3)], has been synthesised under solvothermal conditions from CrCl3. 6H(2)O, Sb2S3 and S in the presence of triethylenetetramine at 433 K and characterised by single-crystal X-ray diffraction, thermogravimetry, elemental analysis and SQUID magnetometry. The structure of [Cr(C6H18N4)(SbS3)] consists of neutral mononuclear chromium-centred complexes, in which the Cr3+ is chelated by one tetradentate triethylenetetramine molecule and a bidentate SbS33- ligand, yielding distorted octahedral coordination. Intermolecular hydrogen bonds link individual molecules into layers within the ac plane. Within a layer, molecules occur in pairs with each member related by a centre of inversion. The Cr...Cr separation within a pair is approximately 6.5 Angstrom. Magnetic susceptibility data reveal Curie-Weiss behaviour with mu(eff) = 3.819(3)/mu(B) and a negligible Weiss constant, indicative of non-interacting Cr3+ ions. (C) 2003 Elsevier Science Ltd. All rights reserved.

Mixed-Ligand Complexes of Technetium and Rhenium with Tridentate Benzamidines and Bidentate Benzoylthioureas

Mixed-ligand complexes of technetium(V) or rhenium(V) containing tridentate N-[(dialkylamino)(thiocarbonyl)]benzamidine (H(2)L(1)) and bidentate N,N-dialkyl-N`-benzoylthiourea (HL(2)) ligands were formed in high yields when (NBu(4))[MOCl(4)] (M = Tc or Re) or [ReOCl(3)(PPh(3))(2)] was treated with mixtures of the proligands. Other approaches for the synthesis of the products are reactions of [MOCl(L(1))] complexes with HL(2) or compounds of the-composition [ReOCl(2)(PPh(3))(L(2))] with H(2)L(1). The resulting air-stable [MO(L(1))(L(2))] complexes possess potential for the development of metal-based radiopharmaceuticals. [TcO(L(1))(L(2))] complexes are readily reduced by PPh3 with formation of [Tc(L(1))(L(2))(PPh(3))]. The resulting Tc(III) complexes undergo two almost-reversible oxidation steps corresponding to one-electron transfer processes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Theoretical and experimental spectroscopic studies of the first highly luminescent binuclear hydrocinnamate of Eu(III), Tb(III) and Gd(III) with bidentate 2,2 '-bipyridine ligand

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis, Characterization and Biological Activities of a Bidentate Schiff Base Ligand: N,N '-Bis(1-phenylethylidene)ethane-1,2-diamine and its Transition Metals (II) Complexes

Schiff base ligand: N,N'-bis(1-phenylethylidene)ethane-1,2-diamine (L), was derived from acetophenone and ethylenediamine by condensation and its complexes (1-5) were prepared with Pb2+, Ni2+, Co2+, Cu2+ and Cd2+ metal ions. Their structures were characterized by FAB-MS, IR spectra, elemental analyses and molar conductance. The octahedral geometry of the complexes was proposed by electronic spectra and magnetic moment data. The conductivity data showed that the complexes have non-electrolytic nature. The complexes (1-5) have higher in vitro antimicrobial activity than the Schiff base ligand (L). In the nuclease activity, the complexes cleave DNA as compared to control DNA in the presence of H2O2.

Dynamic axial ligand-site exchange in facially discriminated ruthenium(II) carbonyl and rhodium(III) halide metalloporphyrins

For a series of six-coordinate Ru(II)(CO)L or Rh(III)(X–)L porphyrins which are facially differentiated by having a naphthoquinol- or hydroquinol-containing strap across one face, we show that ligand migration from one face to the other can occur under mild conditions, and that ligand site preference is dependent on the nature of L and X–. For bulky nitrogen-based ligands, the strap can be displaced sideways to accommodate the ligand on the same side as the strap. For the ligand pyrazine, we show 1 H NMR evidence for monodentate and bidentate binding modes on both faces, dependent on ligand concentration and metalloporphyrin structure, and that inter-facial migration is rapid under normal conditions. For monodentate substituted pyridine ligands there is a site dependence on structure, and we show clear evidence of dynamic ligand migration through a series of ligand exchange reactions.

The structures of the isomorphous potassium and rubidium salts of 4-nitrobenzoic acid and an overview of the metal complex stereochemistries of the alkali metal salt series with this ligand

The structures of the isomorphous potassium and rubidium polymeric coordination complexes with 4-nitrobenzoic acid, poly[mu2-aqua-aqua-mu3-(4-nitrobenzoato)-potassium], [K(C7H4N2O2)(H2O)2]n, (I) and poly[mu3-aqua-aqua-mu5-(4-nitrobenzoato)-rubidium], [Rb(C7H4N2O2)(H2O)2]n, (II) have been determined. In (I) the very distorted KO6 coordination sphere about the K+ centres in the repeat unit comprise two bridging nitro O-atom donors, a single bridging carboxyl O-atom donor and two water molecules, one of which is bridging. In the the Rb complex (II), the same basic MO6 coordination is found in the repeat unit but is expanded to RbO9 through a slight increase in the accepted Rb-O bond length range and includes an additional Rb-O(carboxyl) bond, completing a bidentate O,O'-chelate interaction, and additional bridging Rb-Onitro) and Rb-O(water) bonds. The comparative K-O and Rb-O bond length ranges are 2.738(3)-3.002(3)Ang. (I) and 2.884(2)-3.182(2)Ang. (II). The structure of (II) is also isomorphous as well as isostructural with the known structure of the nine-coordinate caesium 4-nitrobenzoate analogue, [Cs(C7H4N2O~2~)(H~2~O)2]n, (III) in which the Cs---O range is 3.047(4)-3.338(4)Ang. In all three complexes, common basic polymeric extensions are found, including two different centrosymmetric bridging interactions through both water and nitro groups as well as extensions along c through the p-related carboxyl group, giving a two-dimensional structure in (I). In (II) and (III), three-dimensional structures are generated through additional bridges through the nitro and water O-atoms. In all structures, both water molecules are involved in similar intra-polymer O-H...O hydrogen-bonding interactions to both carboxyl as well as water O-atom acceptors. A comparison of the varied coordination behaviour of the full set of Li-Cs salts with 4-nitrobenzoic acid is also made.

Cobalt(II), nickel(II) and copper(II) complexes of bidentate bibenzimidazoles

Complexes of cobalt(II), nickel(II) and copper(II) with novel bidentate bibenzimidazoles, [M(L-L)Cl2], where L-L are methylenebis(1, 1prime-benzimidazole), methylenebis(2, 2prime-benzimidazole) and dimethylenebis(2, 2prime-benzimidazole) are described and characterized by different physical measurements. The four coordinate complexes have distorted tetrahedral or square coplanar structures. The bridging entity between the two donor groups apparently influences the ligand field strength and the ligands occupy a higher position than that of benzimidazole in the spectrochemical series.

Synthesis and crystal structure of copper (II) uracil ternary polymeric complex with 1,10-phenanthroline along with the Hirshfeld surface analysis of the metal binding sites for the uracil ligand

The study of models for ``metal-enzyme-substrate'' interaction has been a proactive area of research owing to its biological and pharmacological importance. In this regard the ternary copper uracil complex with 1,10-phenanthroline represents metal-enzyme-substrate system for DNA binding enzymes. The synthesis of the complex, followed by slow evaporation of the reaction mixture forms two concomitant solvatomorph crystals viz., {Cu(phen)(mu-ura)(H2O)](n)center dot H2O (1a)} and {Cu(phen)(mu-ura)(H2O)](n)center dot CH3OH (1b)}. Both complexes are structurally characterized, while elemental analysis, IR and EPR spectra were recorded for 1b (major product). In both complexes, uracil coordinates uniquely via N1 and N3 nitrogen atom acting as a bidentate bridging ligand forming a 1-D polymer. The two solvatomorphs were quantitatively analyzed for the differences with the aid of Hirshfeld surface analysis. (C) 2014 Elsevier B.V. All rights reserved.

Highly 3,4-Selective Polymerization of Isoprene with NPN Ligand Stabilized Rare-Earth Metal Bis(alkyl)s. Structures and Performances

Deprotonation of (ArNHPPh2NAr2)-N-1 (H[NPN](n), n = 1 - 10) by Ln(CH2SiMe3)(3)(THF)(2) (Ln = Lu, Y, Sc, Er) generated a series of rare-earth metal bis(alkyl) complexes [NPN](n)Ln(CH2SiMe3)(2)(THF)(2) (1-10), which under activation with [Ph3C][B(C6F5)(4)] and AliBu(3) were tested for isoprene polymerization. The correlation between catalytic performances and molecular structures of the complexes has been investigated. Complexes 1-5 and 8, where Ar-1 is nonsubstituted or ortho-alkyl-substituted phenyl, adopt trigonal-bipyramidal geometry. The Ar-1 and Ar-2 rings are perpendicular in 1-4 and 8 but parallel in 5. When Ar-1 is pyridyl, the resultant lutetium and yttrium complexes 9a and 9b adopt tetragonal geometry with the ligand coordinating to the metal ions in a N,N,N-tridentate mode, whereas in the scandium analogue 9c, the ligand coordinates to the Sc3+ ion in a N,N-bidentate mode. These structural characteristics endow the complexes with versatile catalytic performances, With increase of the steric bulkiness of the ortho-substituents Ar-1 and Ar-2, the 3,4-selectivity increased stepwise from 81.6% for lutetium complex 1 to 96.8% for lutetium complex 6 and to 97.8% for lutetium complex 7a. However, further increase of the steric bulk of the ligand led to a slight drop of 3,4-selectivity for the attached complex 5 (95.1%).

Rare earth metal complexes bearing thiophene-amido ligand: Synthesis and structural characterization

2,6-Diisopropyl-N-(2-thienylmethyl) aniline ( H2L) has been prepared, which reacted with equimolar rare earth metal tris( alkyl)s, Ln( CH2SiMe3)(3)( THF)(2), afforded rare earth metal mono( alkyl) complexes, LLn(CH2SiMe3)(THF)(3) ( 1: Ln = Lu; 2: Ln = Y). In this process, H2L was deprotonated by one metal alkyl species followed by intramolecular C-H activation of the thiophene ring to generate dianionic species L2- with the release of two tetramethylsilane. The resulting L2- combined with three THF molecules and an alkyl unit coordinates to Y3+ and Lu3+ ions, respectively, in a rare N,C-bidentate mode, to generate distorted octahedron geometry ligand core. Whereas, with treatment of H2L with equimolar Sc(CH2SiMe3)(3)( THF)(2), a heteroleptic complex ( HL)( L) Sc( THF) ( 3) was isolated as the main product, where the dianionic L2- species bonds to Sc3+ via chelating N, C atoms whilst the monoanionic HL connects to Sc3+ in an S,N-bidentate mode. All complexes 1-3 have been characterized by NMR spectroscopy and X-ray diffraction analysis.

PEG-supported dipyridyl ligand for palladium-catalyzed Suzuki and Suzuki-type reactions in PEG and aqueous media

An air- and water-stable PEG-supported bidentate nitrogen ligand is prepared and its applications in the palladium-catalyzed Suzuki reaction of aryl halides with arylboronic acids in PEG and Suzuki-type reaction of aryl halides with sodium tetraphenylborate in aqueous media are reported. The homogeneous catalyst system is environmentally friendly and offers the advantages of high activity, reusability and easy separation.