Gotowa bibliografia na temat „Transition Metals - Poly-dentate Ligands”

A variety of transition metal complexes involving picolylcyanoacetamides (pica = NCCH2CONH-R; R = 2-picolyl- (2pica), 3-picolyl- (3pica), 4-picolyl- (4pica)) and thiocyanate have been synthesised and their solid-state structures have been determined. The complexes were all obtained from reactions between the corresponding metals salts and pica ligands with sodium thiocyanate under ambient conditions. Both 3pica and 4pica coordinate to the metal solely through the nitrogen atom of the picolyl group and form discrete tetrahedral [M(NCS)2(pica)2] (3pica; M = Mn, Zn; 4pica; M = Co) and octahedral [M(NCS)2(3pica)4] (M = Co, Fe, Ni) complexes. In addition, one-dimensional N,S-thiocyanate-bridged coordination polymers poly-[M(µ-NCS)2(pica)2] (3pica; M = Cd; 4pica; M = Co, Cd) were obtained. The ligand 2pica gave the discrete octahedral complexes [Co(NCS)2(2pica)2] and [Cd(NO3)2(2pica)2] in which 2pica chelates in a bidentate fashion through its picolyl and carbonyl groups. Magnetic susceptibility measurements on the cobalt(ii) complexes were performed and showed short-range antiferromagnetic coupling for the [Co(NCS)2(4pica)2]n 1D polymer.

From the viewpoint of crystal engineering, the construction of crystalline polymeric materials requires a rational choice of organic bridging ligands for the self-assembly process. Multicarboxylate ligands are of particular interest due to their strong coordination activity towards metal ions, as well as their various coordination modes and versatile conformations. The structural chemistry of dicarboxylate-based coordination polymers of transition metals has been developed through the grafting of N-containing organic linkers into carboxylate-bridged transition metal networks. A new luminescent two-dimensional zinc(II) coordination polymer containing bridging 2,2-dimethylsuccinate and 4,4′-bipyridine ligands, namely poly[[aqua(μ2-4,4′-bipyridine-κ2N:N′)bis(μ3-2,2-dimethylbutanedioato)-κ4O1,O1′:O4:O4′;κ5O1:O1,O4:O4,O4′-dizinc(II)] dihydrate], {[Zn2(C6H8O4)2(C10H8N2)(H2O)]·2H2O}n, has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and elemental, IR and thermogravimetric analyses. In the structure, the 2,2-dimethylsuccinate ligands link linear tetranuclear ZnIIsubunits into one-dimensional chains along thecaxis. 4,4′-Bipyridine acts as a tethering ligand expanding these one-dimensional chains into a two-dimensional layered structure. Hydrogen-bonding interactions between the water molecules (both coordinated and free) and carboxylate O atoms strengthen the packing of the layers. Furthermore, the luminescence properties of the complex were investigated. The compound exhibits a blue photoluminescence in the solid state at room temperature and may be a good candidate for potential hybrid inorganic–organic photoactive materials.

N-heterocyclic carbenes (NHCs) have generated much interest for use as versatile metal-coordinating groups, since they were first synthesized by Arduengo and coworkers in 1991. NHC molecules can be considered as L-type ligands, because they share their non-bonding electron pairs with the σ-accepting orbital of transition metals, and this endows them with strong coordination interactions. NHC-appended molecules have recently been actively exploited as potentially effective ligands for the surface passivation of various colloidal nanomaterials. We investigate the coordination interactions between a few representative colloidal nanocrystals, including gold nanoparticles (AuNPs) and luminescent quantum dots (QDs), and a NHC-based polymer ligand. The latter presents multiple NHC groups and several short poly (ethylene glycol) (PEG) chains as solubilizing blocks. We find that our NHC-decorated ligands rapidly coordinate onto both sets of nanocrystals, which we attribute to their soft Lewis base nature. These ideally match the soft Lewis acid character of transition metal colloid surfaces, promoting strong coordination bonding through soft‐soft interaction. We combine NMR spectroscopy, fluorescence spectroscopy, high-resolution transmission electron microscopy supplemented with dynamic light scattering to characterize the nature of the binding interactions. Furthermore, the long-term stability of the NHC-stabilized nanocolloids have been tested after phase transfer to water, a highly challenging chemical venue for such groups, due to the moisture sensitive nature of NHC molecules. Data show that our NHC-polymer-stabilized AuNPs and QDs exhibit long-term colloidal stability in buffer media while preserving their optical and fluorescing properties, with no sign of degradation or aggregation build up for at least one year of storage. We will discuss the ligand design and synthesis, characterization of the polymer-stabilized nanocrystals under various conditions, with a particular focus on the beneficial effects of ligand multi-coordination interactions onto the nanocolloid surfaces.

Reduction of VCl3(THF)3(THF is tetrahydrofuran) and NbCl4(THF)2by alkali metal pyrene radical anion salts in THF affords the paramagnetic sandwich complexes bis[(1,2,3,3a,10a,10b-η)-pyrene]vanadium(0), [V(C16H10)2], and bis[(1,2,3,3a,10a,10b-η)-pyrene]niobium(0), [Nb(C16H10)2]. Treatment of tris(naphthalene)titanate(2−) with pyrene provides the isoelectronic titanium species, isolated as an (18-crown-6)potassium salt, namelycatena-poly[[(18-crown-6)potassium]-μ-[(1,2-η:1,2,3,3a,10a,10b-η)-pyrene]-titanate(−I)-μ-[(1,2,3,3a,10a,10b-η:6,7-η)-pyrene]], {[K(C12H24O6)][Ti(C16H10)2]}n. The first two compounds have very similar packing, with neighboring molecules arranged orthogonally to one another, such that aromatic donor–acceptor interactions are likely responsible for the specific arrangement. The asymmetric unit contains a half-occupancy metal center η6-coordinated to one pyrene ligand, with the fullM(pyrene)2molecule generated by a crystallographic inversion center. In the titanium compound, the cations and anions are in alternating contact throughout the crystal structure, in one-dimensional chains along the [101] direction. As in the other two compounds, the asymmetric unit contains a half-occupancy Ti atom η6-coordinated to one pyrene ligand. Additionally, the asymmetric unit contains one half of an (18-crown-6)potassium cation, located on a crystallographic inversion center coincident with the K atom. The full formula units are generated by those inversion centers. In all three structures, the pyrene ligands are eclipsed and sandwich the metals in one of two inversion-related sites. These species are of interest as the first isolable homoleptic pyrene transition metal complexes to be described in the scientific literature.

Introduction: In recent years, there has been considerable interest in dithiocarbamate complexes because of its diverse biological roles, very few reports have been made on polymeric bis- dithiocarbamate compounds with carbon chain of n-propyl or hexamethelene with transition metals in addition of the absence of any report of organosilicone or tellurium halides with such compounds Our interest in this report based on the preparation of new series of polymers with an expected activity as a fungi side compounds followed by the using of prepared amino compound as a hardners for epoxy paints Materials and Methods: A new polymers of the general structures –(MS2CNH(CH2)6NHCS2M-)n where [M= Cu, Cd, Mn and Zn] and –(M(R)2S2CNH(CH2)nNHCS2MR2-)m where [M= Si,R=CH 3 , n= 2 ,3 and 6 ; M=Te , R= Br , n= 2 ,3 and 6 ; M=Co, Ni R=Cl ; n= 6] have been prepared by reaction of MX2 where M= Ni ,Co, Cd , Mnor Zn , X= Cl ; M=Cu , X= SO4 , and dimethyl dichloro silane, tellurium tetrabromide with the corresponding sodium salts of bis-dithiocarbamateligands. Results and Discussion: Dimethyldichloro silane is a very sensitive material to O-H group, in addition to that, TeBr4 decomposed rapidlyin water so, a series solvents may be useful with such sensitive chemicals to water , in the other hand, dithiocarbamate ligands which is usually prepared in aqueous and alcoholic solution , must be prepared and isolated carefully to apply the other steps of synthesis using a chloroform solution as a solvent. It seems for the first view for dithiocarbamato ligands it may act as a bi dentate ligands using two sulphur donating atoms that is clearly appeared in common complexes such as diethyl dithiocarbamato or pipyridyl, morpholino dithiocarbamato with representation metal elements, even in such type of elements a sulfur bridges may formed. In this study, it showed clearly that Zinc and Cadimium polymers are diamagnetic polymers that is mean that these polymers are with oxidation state equal to (II) and a tetrahedral configuration Conclusions: The study showed that the new silicone polymers act as a stable polymers compared with others. All new polymers are of a high stability with large values of char contain with commercial epoxy. Among silicone polymers, the polymerwith carbon chain equal to 3 is more stable than that with 2 carbon atoms while the silicone polymer with 6 carbon atoms is the less stable one, may thermal treatment caused decomposition combined.

One of most interesting systems of coordination polymers constructed from the first-row transition metals is the porous ZnIIcoordination polymer system, but the numbers of such polymers containingN-donor linkers are still limited. The title double-chain-like ZnIIcoordination polymer, [Ag2Zn(CN)4(C10H10N2)2]n, presents a one-dimensional linear coordination polymer structure in which ZnIIions are linked by bridging anionic dicyanidoargentate(I) units along the crystallographicbaxis and each ZnIIion is additionally coordinated by a terminal dicyanidoargentate(I) unit and two terminal 1-benzyl-1H-imidazole (BZI) ligands, giving a five-coordinated ZnIIion. Interestingly, there are strong intermolecular AgI...AgIinteractions between terminal and bridging dicyanidoargentate(I) units and C—H...π interactions between the phenyl rings of BZI ligands of adjacent one-dimensional linear chains, providing a one-dimensional linear double-chain-like structure. The supramolecular three-dimensional framework is stabilized by C—H...π interactions between the phenyl rings of BZI ligands and by AgI...AgIinteractions between adjacent double chains. The photoluminescence properties have been studied.

Poly (vinyl ethers) are compounds with great value in the coating industry due to exhibiting properties such as high viscosity, soft adhesiveness, resistance to saponification and solubility in water and organic solvents. However, the main challenge in this field is the synthesis of vinyl ether monomers that can be synthetized by methodologies such as vinyl transfer, reduction of vinyl phosphate ether, isomerization, hydrogenation of acetylenic ethers, elimination, addition of alcohols to alkyne species etc. Nevertheless, the most successful strategy to access to vinyl ether derivatives is the addition of alcohols to alkynes catalyzed by transition metals such as molybdenum, tungsten, ruthenium, palladium, platinum, gold, silver, iridium and rhodium, where gold-NHC catalysts have shown the best results in vinyl ether synthesis. Recently, the hydrophenoxylation reaction was found to proceed through a digold-assisted process where the species that determine the rate of the reaction are PhO-[Au(IPr)] and alkyne-[Au(IPr)]. Later, the improvement of the hydrophenoxylation reaction by using a mixed combination of Cu-NHC and Au-NHC catalysts was also reported. DFT studies confirmed a cost-effective method for the hydrophenoxylation reaction and located the rate-determining step, which turned out to be quite sensitive to the sterical hindrance due to the NHC ligands.

Owing to the growing hardware capabilities and the enhancing efficacy of computational methodologies, computational chemistry approaches have constantly become more important in the development of novel anticancer metallodrugs. Besides traditional Pt-based drugs, inorganic and organometallic complexes of other transition metals are showing increasing potential in the treatment of cancer. Among them, Au(I)- and Au(III)-based compounds are promising candidates due to the strong affinity of Au(I) cations to cysteine and selenocysteine side chains of the protein residues and to Au(III) complexes being more labile and prone to the reduction to either Au(I) or Au(0) in the physiological milieu. A correct prediction of metal complexes’ properties and of their bonding interactions with potential ligands requires QM computations, usually at the ab initio or DFT level. However, MM, MD, and docking approaches can also give useful information on their binding site on large biomolecular targets, such as proteins or DNA, provided a careful parametrization of the metal force field is employed. In this review, we provide an overview of the recent computational studies of Au(I) and Au(III) antitumor compounds and of their interactions with biomolecular targets, such as sulfur- and selenium-containing enzymes, like glutathione reductases, glutathione peroxidase, glutathione-S-transferase, cysteine protease, thioredoxin reductase and poly (ADP-ribose) polymerase 1.

Because of their versatile coordination modes and strong coordination ability for metals, triazole ligands can provide a wide range of possibilities for the construction of metal–organic frameworks. Three transition-metal complexes, namely bis(μ-1,2,4-triazol-4-ide-3-carboxylato)-κ3 N 2,O:N 1;κ3 N 1:N 2,O-bis[triamminenickel(II)] tetrahydrate, [Ni2(C3HN3O2)2(NH3)6]·4H2O, (I), catena-poly[[[diamminediaquacopper(II)]-μ-1,2,4-triazol-4-ide-3-carboxylato-κ3 N 1:N 4,O-[diamminecopper(II)]-μ-1,2,4-triazol-4-ide-3-carboxylato-κ3 N 4,O:N 1] dihydrate], {[Cu2(C3HN3O2)2(NH3)4(H2O)2]·2H2O} n , (II), (μ-5-amino-1,2,4-triazol-1-ide-3-carboxylato-κ2 N 1:N 2)di-μ-hydroxido-κ4 O:O-bis[triamminecobalt(III)] nitrate hydroxide trihydrate, [Co2(C3H2N4O2)(OH)2(NH3)6](NO3)(OH)·3H2O, (III), with different structural forms have been prepared by the reaction of transition metal salts, i.e. NiCl2, CuCl2 and Co(NO3)2, with 1,2,4-triazole-3-carboxylic acid or 3-amino-1,2,4-triazole-5-carboxylic acid hemihydrate in aqueous ammonia at room temperature. Compound (I) is a dinuclear complex. Extensive O—H...O, O—H...N and N—H...O hydrogen bonds and π–π stacking interactions between the centroids of the triazole rings contribute to the formation of the three-dimensional supramolecular structure. Compound (II) exhibits a one-dimensional chain structure, with O—H...O hydrogen bonds and weak O—H...N, N—H...O and C—H...O hydrogen bonds linking anions and lattice water molecules into the three-dimensional supramolecular structure. Compared with compound (I), compound (III) is a structurally different dinuclear complex. Extensive N—H...O, N—H...N, O—H...N and O—H...O hydrogen bonding occurs in the structure, leading to the formation of the three-dimensional supramolecular structure.

The preparation of coordination polymers (CPs) based on either transition metal centres or rare-earth cations has grown considerably in recent decades. The different coordination chemistry of these metals allied to the use of a large variety of organic linkers has led to an amazing structural diversity. Most of these compounds are based on carboxylic acids or nitrogen-containing ligands. More recently, a wide range of molecules containing phosphonic acid groups have been reported. For the particular case of Ca2+-based CPs, some interesting functional materials have been reported. A novel one-dimensional Ca2+-based coordination polymer with a new organic linker, namely poly[[diaqua[μ4-(4,5-dicyano-1,2-phenylene)bis(phosphonato)][μ3-(4,5-dicyano-1,2-phenylene)bis(phosphonato)]dicalcium(II)] tetrahydrate], {[Ca2(C8H4N2O6P2)2(H2O)2]·4H2O}n, has been prepared at ambient temperature. The crystal structure features one-dimensional ladder-like∞1[Ca2(H2cpp)2(H2O)2] polymers [H2cpp is (4,5-dicyano-1,2-phenylene)bis(phosphonate)], which are created by two distinct coordination modes of the anionic H2cpp2−cyanophosphonate organic linkers: while one molecule is only bound to Ca2+cationsviathe phosphonate groups, the other establishes an extra single connectionviaa cyano group. Ladders close pack with water molecules through an extensive network of strong and highly directional O—H...O and O—H...N hydrogen bonds; the observed donor–acceptor distances range from 2.499 (5) to 3.004 (6) Å and the interaction angles were found in the range 135–178°. One water molecule was found to be disordered over three distinct crystallographic positions. A detailed solution-state NMR study of the organic linker is also provided.

The nature of ligands coordinated to the metal ion mostly determines the properties of the inorganic, organometallic or bioinorganic model compounds. The pyrazole is one of the most studied heterocyclic aromatic compounds in coordination chemistry as single ligand or incorporated in polidentate ligands, such as in poly(pyrazolyl)borates (‘scorpionates'), poly(pyrazolyl)alkanes, etc. The great versatility of the pyrazole allows the formation of several ligands with different functionalizations, which mainly influence the geometry and nuclearity of the diverse coordination complexes afforded by the reaction of the pyrazole-based chelating ligands and a metal ion. Another of the most studied heterocyclic aromatic compounds in coordination chemistry is an analogue of pyrazole with two non-adjacent nitrogen atoms, the imidazole, which represents the main structure of the most common and studied N-Heterocyclic carbenes (NHCs), in particular the imidazol‐2‐ylidenes. These general informations arouse curiosity in main features and reactivity, synthesis and coordination modes, potential and ensured applications of various N-donor ligands, such as poly(pyrazolyl)borates or scorpionates, their isoelectronic and isosteric neutral analogues poly(pyrazolyl)alkanes and N-heterocyclic carbenes, presented, thus, in detail, in Chapter 1. The focus on the electronic and steric properties, the coordinating behaviour and several applications of scorpionates metal complexes, the state-of-art on coordination chemistry and reactivity of the poly(pyrazolyl)alkanes derivatives, the advantages of NHCs over phosphines, including ease of handling, minimal toxicity and powerful electron-donating properties, as enhanced stability of their transition metal complexes, which lead to the synthesis of highly active derivatives in homogeneous catalysis, anticipate the research work of this thesis on the nitrogen pyrazole- and imidazole-based ligands and their organometallic compounds. Beginning from Chapter 2, which describes the aims of the research work, all the chapters are divided in four sub-chapters. In the first sub-chapter differently halogen substituted bis- and tris-(pyrazolyl)borate ligands (BpBr3, TpBr3 and TpiPr,4Br) are compared in terms of electron-donor character through their interactions with various ruthenium(II) arene dimers, as also through electrochemical studies. Interestingly, an unexpected dinuclear ionic compound accounted for by its low thermodynamic stability, confirmed by theoretical calculations at the DFT level, due to steric reasons. The second sub-chapter is centered on the synthesis, characterization and crystal structure of the complexes of the second-lowest steric hindrance scorpionate ligand, TpTn, towards CuI, CuII, ZnII and CdII acceptors. A remarkable coordinative aspect of this ligand is pointed out, as well as the thermal and air stability of the relative complexes, confirmed by thermogravimetric and differential thermal analysis (TGA-DTA). By contrast, the interaction between TpTn and PtI2 proceeded through ligand decomposition, affording a monomeric complex. In the third sub-chapter, the varying, different stoichiometries and the N,N-chelating coordination modes of the bis(pyrazolyl)methanes, in particular of the two indazolyl-based regio-isomeric ligands, L1, bis(1H-indazol-1-yl)methane, and L2, bis(2H-indazol-2-yl)methane, toward XI group metal centers are studied. The synthesis and full characterization of analogous adducts of both regio-isomers allow a systematic comparison of their structural and spectral features, depending on the regio-isomeric ligand and counter-ion used, and the reaction conditions employed. The synthesis and characterization of a new series of stable, cationic gold(I/III) NHC complexes, as well as their catalytic activity in five well-established organic gold-mediated transformations, performed at the University of Strasbourg, under guidance of Director of Research Pierre Braunstein and coworkers (Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universita'© de Strasbourg, France) is described in the fourth sub-chapter. Interestingly, various attempts to synthesize gold(III) NHC bis- or tris-pyridine complexes, as also the comparative behaviour of NHCs respect to phosphine ligands, are presented. Going further on the thesis structure, all the general procedures and experimental data are reported in Chapter 3, while the discussion and elaboration of the results are described in Chapter 4. Concluding remarks and future perspectives are discussed in Chapter 5, whereas all the references and some notes are given in Chapter 6. In Annexes section, the Curriculum Vitae, the List of Pubblications and the Contributions to Congresses are presented.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006.
Prof. Will Rees, Committee Member ; Prof. Charles Liotta, Committee Member ; Prof. David Collard, Committee Member ; Prof. Marcus Weck, Committee Chair ; Prof. Kent Barefield, Committee Member.

Poly-N-isopropylacrylamide (PNIPAM) gels grafted to redox-active metal monomers undergo sudden expansion-contraction activity in response to change in environmental conditions, such as temperature, pH, ion concentration, and oxidation states of the metal. The relevance of these conditions to biological systems has garnered attention for PNIPAM-based polymer as potential biomedical materials. Candidate transition metal monomers containing ruthenium and nickel cores were designed and synthesized for copolymerization with NIPAM and cross-linker methylene-bis-acrylamide in order to attain metallopolymer microspheres with a high percentage of metal incorporation. Synthesis of 4-vinyl-4'-methyl-2,2'-bipyridine (vmbpy) was optimized from literature procedures for usage in the metal-containing monomers. Metal-containing monomers were then synthesized, purified, and characterized using electrospray ionization mass spectrometry (ESI-MS), proton nuclear magnetic resonance ( 1 H-NMR), X-ray diffraction, Ultraviolet-Visible light (UV-Vis) spectroscopy, and spectrofluorometry. While the Ru complex was pure and exhibited interesting photochemical properties, lability of the ligands on the Ni monomers resulted in complication of their synthesis. Polymer microspheres of poly(NIPAM-co-vmbpy), the cross-linked copolymer constructed from NIPAM and vmbpy monomers, were synthesized from modified emulsion polymerization procedures. Experimental setup parameters and conditions—such as the methods of injection of initiator and stirring, the time duration for incubating the emulsion, and the initiation temperature—were varied to assess their influences on the material properties of the final product. The polymers were tested for size and morphological uniformity by dynamic light scattering (DLS) and scanning electron microscopy (SEM). While varying the method of initiator injection had no measurable effect on the product, strong mechanical stirring and incubation of the polymer emulsion for 15-25 minutes at 71 °C procured similar polymer products. Consistent properties ensured the polymers' suitability for further material development. Preliminary morphological and spectroscopic characterization was conducted of metallopolymers made from Ru and Ni grafted to PNIPAM. Metallopolymers containing polypyridyl Ru cores exhibited desirable spectroscopic properties and spherical morphology.

In this study we synthesized and characterized new complexes containing ((isophthalohyrazide ) N,N (1,3-dithioformylphthalamide)) ligand which prepared from reaction between phathalic acid with thiosemicarbazied in the rate of (2:2) presence of the hydraulic acid with some transition metal (Cr(III),Mn(II),Fe(II), Co(II),Ni(II), Cu(II), Zn(II)). Elemental analyses, FTIR (Fourier transform infrared) and UV-vis spectral investigations, magnetic measurement, conductivity measurement, and 1HNMR for the ligand (L) and some of the complexes have all been used to characterize the complexes. The complexes' stoichiometry has been determined from analytical data to be (1:2) (metal: ligand), and conductance results show that they are (1:2) electrolyte.The electronic spectra and magnetic measurements indicate that the type of complexes [M(L)]Cl2 and [M(L)]Cl3 have a tetrahedral environment around the metal ions.