Syntheses,crystal structures,and electrochemical properties of transition metal complexes with new tetrathiafulvalene-derivatized acetylacetonate ligands

Two new tetrathiafulvalene (TTF) derivatives of acetylacetone, namely, 3-[{6,7-benzo-2-(methylthio)-TTF-3-yl}-thio]-2,4-pentanedione (L₁) and 3-[{6,7-(ethylenedithio)-2-(methylthio)-TTF-3-yl}-thio]-2,4-pentanedione (L₂), have been synthesized. Four transition metal(II) complexes of these ligands, of general formulae [Zn(L₁)₂(THF)₂] and [M(L₂)₂(THF)₂] (M = Zn, Mn, and Ni), have been prepared and structurally characterized. The redox properties of both the ligands and their complexes were investigated by cyclic voltammetry. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Peng Zheng and Yun-Jun Guo contributed equally to this work.     

Complexing ability of the versatile,redox-active, 3-[3-(diphenylphosphino)propylthio]-3',4,4'-trimethyl-tetrathiafulvalene ligand

The synthesis of a ligand containing as an electroactive core a tetrathiafulvalene moiety, 3-[3-(diphenylphosphino)propylthio]-3',4,4'-trimethyl-tetrathiafulvalene, is reported. Its versatile ability to act as a bidentate or a monodentate ligand, as demonstrated by the metal carbonyl complexes obtained, is described. The novel cis-Mo(CO)(4)(P-TTF)(2) 4 and cis-W(CO)(4)(P,S-TTF) 6 complexes have been characterized by X-ray diffraction analyses and cyclic voltammetry measurements. Within complex 4, no significant influence of the two electroactive ligands on the molybdenum center was detected, whereas, in complex 6, a weak influence of the TTF redox-active core can be observed on the redox behavior of the metal center.     

Tetrathiafulvalene crowns: redox-switchable ligands

A series of redox-responsive ligands that associate the electroactive tetrathiafulvalene core with polyether subunits of various lengths has been synthesized. X-ray structures are provided for each of the free ligands. The requisite structural criteria for reaching switchable ligands are satisfied for the largest macrocycles, that is, planarity of the 1,1',3,3'-tetrathiafulvalene (TTF) pi system and correctly oriented coordinating atoms. The ability of these ligands to recognize various metal cations as a function of the cavity size has been investigated by various techniques (LSIMS, 1H NMR, and UV/Vis spectroscopy, cyclic voltammetry). These systems exhibit an unprecedented high coordination ability among TTF crown ethers. Their switchable ligating properties have been confirmed by cyclic voltammetry, and metal-cation complexation has been illustrated by X-ray structures of three of the corresponding metal complexes (Pb2+, Sr2+, and Ba2+). Solid-state structures of these complexes display original packing modes with channel-like arrangements.     

meso-Dithiole and tetrathiafulvalene dipyrromethanes a route to metal dithiole-dipyrrin complexes and to fluorescent tetrathiafulvalene-BODIPY

A series of meso-dithiole and tetrathiafulvalene (TTF) dipyrromethanes have been prepared via the reaction of the appropriate aldehyde with either pyrrole or 3-ethyl-2,4-dimethyl-pyrrole under acid catalysis. Oxidation to the corresponding meso-dithiole dipyrrins is reported together with the formation of the metal chelate complexes (M=Zn, Cu, Ni) as well as the meso-dithiole boron-dipyrromethene (BODIPY). The molecular structures of these metal (Cu, Ni) and boron complexes are presented and discussed. According to a similar strategy the meso-TTF BODIPY is prepared and its photophysical properties are presented and compared with those of the meso-dithiole BODIPY.     

Investigation of the oxygen affinity of manganese(II), cobalt(II) and nickel(II) complexes with some tetradentate Schiff bases

Oxygen absorption–desorption processes for square planar Mn(II), Co(II) and Mn(II) complexes of tetradentate Schiff base ligands in DMF and chloroform solvents were investigated. The tetradentate Schiff base ligands were obtained by condensation reaction of ethylenediamine with salcyldehyde, o-hydroxyacetophenone or acetylacetone in the molar ratio 1:2. The square planar complexes were prepared by the reaction of the Schiff base ligands with Mn(II) acetate, Co(II) nitrate and Ni(II) nitrate in dry ethanol under nitrogen atmosphere. The sorption processes were undertaken in the presence and absence of (pyridine) axial-base in 1:1 M ratio of (pyridine:metal(II) complexes). Complexes in DMF indicate significant oxygen affinity than in chloroform solvent. Cobalt(II) complexes showed significant sorption processes compared to Mn(II) and Ni(II) complexes. The presence of pyridine axial base clearly increases oxygen affinity.     

Tetrathiafulvalene hydrazone an efficient precursor of various chelating electroactive ligands

Novel bidentate electroactive ligands containing one or two tetrathiafulvalene (TTF) cores as redox active unit have been synthesized thanks to the condensation of various carbonyl derivatives with TTF hydrazone. The electron donating ability of these redox active ligands determined by cyclic voltammetry is described together with the investigations of their molecular structures by X-ray diffraction studies. The chelating ability of these ligands has been exemplified through the coordination to molybdenum carbonyl fragment or the complexation to difluoroboron moiety.     

Ligands derived from tetrathiafulvalene: building blocks for multifunctional materials

The last decade has witnessed many advances in the coordination chemistry of tetrathiafulvalene (TTF). Various ligands, in which a metal-binding functionality is attached to the TTF unit, have been synthesized and used for the preparation of metal complexes. This Perspective summarizes the main types of TTF-containing ligands and their metal complexes and outlines the potential for the use of these building blocks in the design and assembly of multifunctional molecular materials.     

Spectral, thermal and X-ray studies on some new bis-hydrazine metal glyoxylates and bis-hydrazine mixed metal glyoxylates

Bis-hydrazine complexes of metal glyoxylates and mixed metal glyoxylates of 3d-metal ions of the formula M(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Co, Ni, Cu, Zn or Cd and M_1/3Co_2/3(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Ni, Zn or Cd, respectively, have been prepared and studied. The compositions of the complexes have been determined by chemical analyses. The magnetic moments and electronic spectra suggest a high-spin octahedral geometry for the metal complexes. Infrared spectral data indicate the bidentate bridging by hydrazine molecules and monodentate coordination by glyoxylate ions in both the metal and mixed metal compounds. Thermogravimetry and differential thermal analyses in air have been used to study the thermal behaviour of the complexes. The simultaneous TG-DTA traces of all the complexes show multi-step degradation and the final products are found to be the respective metal oxides in the case of metal complexes and metal cobaltites in the case of mixed metal complexes. The final residues were identified by their X-ray powder diffraction patterns. X-ray powder diffraction patterns of the complexes including mixed metal complexes are almost superimposable with in each of the series indicating isomorphism. The metal cobaltites MCo₂O₄, where M = Mg, Mn, Ni, Zn or Cd were also prepared by decomposing the respective mixed metal complex in a pre-heated silica crucible at about 300 °C, and their identities were confirmed by chemical analyses, infrared spectra and X-ray powder diffraction.     

Synthesis,structural studies and bio-activity of some metal(II) complexes with glyoxal salicylaldehyde acyldihydrazones

Complexes of the type [M(gssdh)]Cl and [M(gspdh)]Cl, where M?=?Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), Hgssdh?=?glyoxal salicylaldehyde succinic acid dihydrazone and Hgspdh?=?glyoxal salicylaldehyde phthalic acid dihydrazone, have been synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR and IR spectra and X-ray powder diffraction studies. The metal complexes are insoluble in common organic solvents and are 1?:?1 electrolytes. The magnetic moment values and electronic spectra indicate a spin–free octahedral geometry for all Co(II), Ni(II) and Cu(II) complexes. ESR spectral parameters of Cu(II) complexes suggest an elongated tetragonally–distorted octahedral stereochemistry around copper. Both ligands are monobasic hexadentate ligands coordinating through three >C=O, two >C=N– and a deprotonated phenolate group to the metal. X-ray powder diffraction parameters for three of the complexes correspond to an orthorhombic crystal lattice. The complexes show appreciable activity against various fungi and bacteria.     

A dinuclear Ni(II) complex with two types of intramolecular magnetic couplings: Ni(II)-Ni(II) and Ni(II)-TTF*+

A dinuclear Ni(II) complex involving tetrathiafulvalene (TTF) radicals as ligands has been prepared and characterized, [Ni2(mu-Cl)2(L*+)2(I3)4(I2)3.(H2O)2.(C4H8O)3 (1), L = 4,5-bis(2-pyridylmethylsulfanyl)-4',5'-ethylenedithiotetrathiafulvalene. There are two types of intramolecular magnetic exchange interactions, namely one ferromagnetic Ni(II)-Ni(II) and one antiferromagnetic Ni(II)-TTF*+. This study is new in the respect of revealing a magnetic exchange interaction between a TTF*+ radical and a paramagnetic transition metal ion. This is due to the fact of a direct binding of the transition metal ion to the skeleton of the TTF*+ radical.     

Reinvestigation of the M(II) (M = Ni, Co)/tetrathiafulvalenetetracarboxylate system using high-throughput methods: isolation of a molecular complex and its single-crystal-to-single-crystal transformation to a two-dimensional coordination polymer

A high-throughput methodology combined with X-ray powder diffraction measurements was used to investigate the reactivity of the TetraThiaFulvalene TetraCarboxylic acid ((TTF-TC)H(4)) with divalent metals (M = Ni, Co) under various reaction conditions (stoichiometry, pH, temperature). Two new crystalline phases were identified and then studied by single crystal X-ray diffraction. Whereas the first one appears to be a simple salt, the second one, formulated {[M(H(2)O)(4)](2)(TTF-TC)}·4H(2)O, is built of 2:1 M:TTF-TC molecular complexes and labeled MIL-136(Ni, Co) (MIL stands for Materials Institute Lavoisier). The combination of thermogravimetric analysis and thermodiffraction studies reveals that MIL-136(Ni) exhibits a complex dehydration behavior. Indeed, a partial dehydration/rehydration process led to the single-crystal-to-single-crystal transformation of the molecular compound in a two-dimensional coordination polymer formulated {[Ni(2)(H(2)O)(5)(TTF-TC)]}·H(2)O (MIL-136'(Ni)). Magnetic and redox properties of MIL-136(Ni, Co) were investigated. Magnetic measurements indicate that all the magnetic coupling, intra- and intermolecular, are very weak; thus, the magnetic data of MIL-136(Ni, Co) have been interpreted in term of single-ion spin orbit coupling. Solid state cyclic voltammetry of MIL-136(Ni, Co) presents three reversible waves which were assigned to the redox activity of the TTF core and the metallic cations. In contrast to solids based on TTF linkers and alkaline ions, the MIL-136(Ni, Co) complexes do not act as excellent positive electrode materials for Li batteries, but present two reversible electron oxidation of the TTF core. These observations were tentatively related to the strength of the metal-carboxylate bond.     

Copper(II), nickel(II) and cobalt(II) complexes of 4-cyanobenzonic acid: syntheses, crystal structures and spectral properties

Three new metal complexes, Cu(4-Hcba)₂(4-cba)₂(Py)₂ (4-Hcba=4-cyanobenzoic acid) 1 and M[H(4-cba)₂]₂(Py)₂ (M=Ni 2, Co 3), have been prepared by the treatment of 4-Hcba with the respective metal nitrate M(NO₃)₂ (M=Cu, Ni, Co) in the presence of pyridine (Py). Single-crystal X-ray diffraction analyses (3 is isostructural to 2) show that the obtained complexes are of isolated mononuclear and the metal atoms have distorted octahedral coordination environment. Two different types of intramolecular hydrogen bonds exist: asymmetrical O–HO for 1 and symmetrical OHO for 2 and 3. The crystal packing between the molecular complexes is controlled mainly by T-shaped C–Hπ interactions between pyridine and phenyl rings. Preliminary discussions on IR, UV–VIS and fluorescent spectra have also been carried out.     

四硫富瓦烯(TTF)衍生物的配位组装

四硫富瓦烯（tetratiafulvalenc,TTF)衍生物和二硫纶（dithiolene)化合行等有机富硫分子作为有机光电磁的功能化合物,一直受到了人们的重视,近年来一类融合了TTF和二硫纶结构的扩展TTF衍生物引起人们很大的兴趣,这类八硫共轭体系具有较好的电子授受特性,展示出潜在的应用价值。有目的地利用它与与金属离子间较强的配位能力对这些化合物进行晶体或分子设计已成为配位化学在富硫有机配合物研究中的一个热点。本文重点介绍这方面的研究的最新进展。主要包括以卤化亚铜基本骨架为基础的四烷基硫取代四硫富瓦烯（[(RS)2TTF(SR)2])的配位组装;二烷基硫取代的TTF融合二硫纶离子（[(RS)2TTF(S2)]^2-)和TTF融合双二硫纶离子（[(S)2TTF(S)]^4-金属配位衍生物的分子设计和空间构筑。通过配位修饰或组装,这类TTF金属衍生物显示了多变的结构,有的已发展具有较好的物理性质。     

Spin-crossover behavior and electrical conduction property in iron(II) complexes with tetrathiafulvalene moieties

Iron(II) complexes with neutral and oxidized tetrathiafulvalene (TTF) moieties were prepared and X-ray crystallographic analyses, magnetic and electrical resistivity measurements suggested an interaction of spin transition and electrical conductivity.     

Trinuclear Zn(II) and Cu(II) homo and heterotrimetallic complexes involving D-glucopyranosyl and biscarboxylate bridging ligands. A substrate binding model of xylose isomerases

Reactions of MCl(2).nH(2)O with N,N'-bis(D-glucopyranosyl)-1,4,7-triazacyclononane ((D-Glc)(2)-tacn), which was formed from D-glucose and 1,4,7-triazacyclononane (tacn) in situ, afforded a series of mononuclear divalent metal complexes with two beta-D-glucopyranosyl moieties, [M((D-Glc)(2)-tacn)Cl]Cl (M = Zn (11), Cu (12), Ni (13), Co (14)). Complexes 11-14 were characterized by analytical and spectroscopic measurements and X-ray crystallography and were found to have a distorted octahedral M(II) center ligated by the pentacoordinate N-glycoside ligand, (beta-D-glucopyranosyl)(2)-tacn, and a chloride anion. Each D-glucose moiety is tethered to the metal center through the beta-N-glycosidic bond with tacn and additionally coordinated via the C-2 hydroxyl group, resulting in a lambda-gauche five-membered chelate ring. When L-rhamnose (6-deoxy-L-mannose) was used instead of D-glucose, the nickel(II) complex with two beta-L-rhamnopyranosyl moieties, [Ni((D-Man)(2)-tacn)(MeOH)]Cl(2) (15), was obtained and characterized by an X-ray analysis. Reactions of 11 (M = Zn) with [Zn(XDK)(H(2)O)] (21) or [Cu(XDK)(py)(2)] (22) (H(2)XDK = m-xylylenediamine bis(Kemp's triacid imide)) yielded homo and heterotrimetallic complexes formulated as [Zn(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Zn (31), Cu (32)). The similar reactions of 12 (M = Cu) with complex 21 or 22 afforded [Cu(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Cu (33), Zn (34)). An X-ray crystallographic study revealed that complexes 31 and 34 have either Zn(II)(3) or Cu(II)Zn(II)Cu(II) trimetallic centers bridged by two carboxylate groups of XDK and two D-glucopyranosyl residues. The M...M' separations are 3.418(3)-3.462(3) A (31) and 3.414(1)-3.460(1) A (34), and the M...M'...M angles are 155.18(8) degrees (31) and 161.56(6) degrees (34). The terminal metal ions are octahedrally coordinated by the (D-Glc)(2)-tacn ligand through three nitrogen atoms of tacn, two oxygen atoms of the C-2 hydroxyl groups of the carbohydrates, and a carboxylate oxygen atom of XDK ligand. The central metal ions sit in a distorted octahedral environment ligated by four oxygen atoms of the carbohydrate residues in the (D-Glc)(2)-tacn ligands and two carboxylate oxygen atoms of XDK. The deprotonated beta-D-glucopyranosyl unit at the C-2 hydroxyl group bridges the terminal and central ions with the C-2 mu-alkoxo group, with the C-1 N-glycosidic amino and the C-3 hydroxyl groups coordinating to each metal center. Complexes 31-34 are the first examples of metal complexes in which D-glucose units act as bridging ligands. These structures could be very useful substrate binding models of xylose or glucose isomerases, which promote D-glucose D-fructose isomerization by using divalent dimetallic centers bridged by a glutamate residue.     

Coordination chemistry of a pi-extended, rigid and redox-active tetrathiafulvalene-fused Schiff-base ligand

A pi-extended, redox-active tetradentate tetrathiafulvalene-fused salphen [salphen = N,N'-phenylenebis(salicylideneimine)] compound (L) was prepared via a direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde. Its chelating coordination ability has been demonstrated by the formation of the corresponding transition metal complexes in the presence of M(OAc)2.nH2O (M = Co(II), Ni(II), Cu(II)) and FeCl3.6H2O. Three complexes have been characterized by single-crystal X-ray diffraction analysis showing that the TTF-salphen ligand coordinates to the metal ions in a planar mode through the nitrogen and oxygen atoms in a N2O2 cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III) complex is formed. These paramagnetic complexes are promising building blocks for the construction of dual functional materials due to their unique structural features (planarity and rigidity) as well as their inherent redox properties.     

Fine tuning of the oxidation locus, and electron transfer, in nickel complexes of pro-radical ligands

A large number of complexes of the first-row transition metals with non-innocent ligands has been characterized in the last few years. The localization of the oxidation site in such complexes can lead to discrepancies when electrons can be removed either from the metal center (leading to an M((n+1)+) closed-shell ligand) or from the ligand (leading to an M(n+) open-shell ligand). The influence of the ligand field on the oxidation site in square-planar nickel complexes of redox-active ligands is explored herein. The tetradentate ligands employed herein incorporate two di-tert-butylphenolate (pro-phenoxyl) moieties and one orthophenylenediamine spacer. The links between the spacer and both phenolates are either two imines ([Ni(L1)]), two amidates ([Ni(L3)]2-), or one amidate and one imine ([Ni(L2)]-). The structure of each nickel(II) complex is presented. In the noncoordinating solvent CH2Cl2, the one-electron-oxidized forms are ligand-radical species with a contribution from a singly occupied d orbital of the nickel. In the presence of an exogenous ligand, such as pyridine, a Ni(III) closed-shell ligand form is favored: axial ligation, which stabilizes the trivalent nickel in its octahedral geometry, induces an electron transfer from the metal(II) center to the radical ligand. The affinity of pyridine for the phenoxylnickel(II) species is correlated to the N-donor ability of the linkers.     

Metallomicellar Catalysis Hydrolysis of p-Nitrophenyl Picolinate Catalyzed by Copper(II), Nickel(II), and Zinc(II) Complexes of Long Alkyl Pyridine Ligands in Micellar Solution

The ternary complex kinetic model for metallomicellar catalysis has been proposed in this paper. The catalytic effects of bivalent metal ion (Cu(2+), Zn(2+), and Ni(2+)) complexes of long alkyl pyridine ligands upon the hydrolysis of p-nitrophenyl picolinate (PNPP) have been studied kinetically in aqueous buffer of pH ranging from 5.0 to 8.5 at 30 degrees C. The effect of pH on the reactivity is discussed. The results indicate that the metallomicelles formed by pyridine ligands promote the hydrolysis of PNPP, and the order is Cu(II) system>Ni(II) system>Zn(II) system. A stereochemical modification of the complex in the CTAB micelle is suggested as a likely explanation for the observed phenomena. Copyright 2000 Academic Press.     

An infrared and Raman spectroscopic study of some metal pyridine tetracyanonickelate complexes

The results of an infrared and Raman spectroscopic study are presented for seven new metal pyridine tetracyanonickelate complexes, M(py)₂Ni(CN)₄, M = Mn, Co, Fe, Ni, Cu, Zn and Cd. It is shown that the spectra are consistent with a proposed crystal structure for these complexes derived from X-ray diffraction measurements. The spectra can be clearly distinguished from those of analogous Hofmann-type clathrates with which the nickel complex had been previously confused. The copper complex has spectral features different from the other six compounds and an explanation is proposed in terms of a distortion of the general crystal structure due to the Jahn-Teller effect. Analysis of the single, sharp bands of coordinated pyridine offers a method of resolving some difficulties in earlier assignments of the normal modes of the free base. Several modes of coordinated pyridine have upward shifts in frequency compared to those in the free molecule and the shifts are metal dependent. An explanation, supported by a simple normal coordinate analysis on a model, is provided in terms of coupling with low frequency vibrations, particularly the M-N stretching frequency. Other vibrations of the Ni(CN)₄ group, which coordinates to the metals M to form a two-dimensional coordination polymer, are also metal dependent. It is similarly suggested that coupling with low frequency modes is the principal cause of the upward shifts in frequency.     

A periodic walk: a series of first-row transition metal complexes with the pentadentate ligand PY5

A series of transition metal complexes derived from the pentadentate ligand PY5, 2,6-(bis-(bis-2-pyridyl)methoxymethane)pyridine, illustrates the intrinsic propensity of this ligand to complex metal ions. X-ray structural data are provided for six complexes (1-6) with cations of the general formula [M(II)(PY5)(Cl)](+), where M = Mn, Fe, Co, Ni, Cu, Zn. In complexes 1-4 and 6, the metal ions are coordinated in a distorted-octahedral fashion; the four terminal pyridines of PY5 occupy the equatorial sites while the axial positions are occupied by the bridging pyridine of PY5 and a chloride anion. Major distortions from an ideal octahedral geometry arise from displacement of the metal atom from the equatorial plane toward the chloride ligand and from differences in pyridine-metal-pyridine bond angles. The series of complexes shows that M(II) ions are consistently accommodated in the ligand by displacement of the metal ion from the PY5 pocket, a tilting of the axial pyridine subunit, and nonsymmetrical pyridine subunit ligation in the equatorial plane. The displacement from the ligand pocket increases with the ionic radius of M(II). The axial pyridine tilt, however, is approximately the same for all complexes and appears to be independent of the electronic ground state of M(II). In complex 5, the Cu(II) ion is coordinated by only four of the five pyridine subunits of the ligand, resulting in a square-pyramidal complex. The overall structural similarity of 5 with the other complexes reflects the strong tendency of PY5 to enforce a distorted-octahedral coordination geometry. Complexes 1-6 are further characterized in terms of solution magnetic susceptibility, electrochemical behavior, and optical properties. These show the high-spin nature of the complexes and the anticipated stabilization of the divalent oxidation state.