Trinuclear and Dinuclear Manganese Complexes of 2/4-Formylbenzoic Acid Oxime Ligands： Syntheses and Crystal Structures

Two manganese complexes, [Mn3（2-cba）6（phen）2] 1 （2-cba = 2-cyanobenzoic acid, phe11 = 1,10-phenanthroline） and [MnE（4-fbaO）E（phen）4]（PF6）E.EHEO 2 （4-fbao = 4-formylbenzoic acid oxime）, have been synthesized by the reaction of 2-formylbenzoic acid oxime （2-fbao, HELl） or 4-formylbenzoic acid oxime （4-fbao, HELE） with phen and manganese acetate in ethanol or methanol solution. A translation from the oximino （-CHN=OH） of HELl to cyano （-C-N） was found in the formation of complex 1 at room temperature. The complexes were structurally determined by single-crystal X-ray diffraction. The crystal of compound I belongs to monoclinic, space group C2/c, with a = 17.983（6）, b = 23.364（7）, c =14.589（5） A, β = 92.401（5）° V = 6124（3） A^3, Z = 4, C72H40Mn3N10O12, Mr= 1401.96, Dc = 1.521 g/cm^3, F（000） = 2852.0, Rint = 0.0372, T= 293（2） K,μ = 0.686 mm^-1, the final R = 0.0644 and wR = 0.1813 for 5803 observed reflections with I 〉 2δ（I）. The crystal of compound 2 is of monoclinic system, space group P21/n, with a = 13.050（4）, b = 20.577（5）, c = 13.323（4）A,β = 113.578（3）°, V = 3227.2（14）A3, Z = 2, C64H48F12Mn2N10O8P2, Mr = 1484.94, Dc = 1.528 g/cm^3, F（000） = 1508.0, Rint= 0.0295, T= 293（2） K,μ = 0.539 mm^-1, the final R = 0.0629 and wR = 0.1789 for 5298 observed reflections with I 〉 2σ（I）. Compounds 1 and 2 are linear trinuclear and dinuclear manganese complexes respectively, which are both bridged by carboxylate groups of the ligands.     

Syntheses and Magnetism of μ-1, 3, 5-Benzenetricarboxylato Trinuclear Manganese(Ⅱ) and Nickel(Ⅱ)Complexes

IntroductionThestudyofmagneticexchangeinteractionbetweenparamagneticcenterspropagatedbymulti-atombridgesisofcurrentinterestduetounderstandingthepathwayofelectrontransferinbio1ogicalsystemandobtainingsomeusefulin-formationaboutdesigningmolecule-basedmagnets.Manypapers['-'Jdealingwithphthalato,isophthalatoandterephthalatoligandsasamulti-atombridgeshavebeenpublished.1thasbeenrevealedbythevariable-temperaturemagneticsusceptibilityinvestigationthatlong-rangemagneticcouplingoccursbetweentwoparamagne…     

Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis,Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear FeIII Triplesalen Complexes

The chiral triplesalen ligand H₆chand provides three chiral salen ligand compartments in a meta‐phenylene arrangement by a phloroglucinol backbone. The two diastereomeric versions H₆chand^RR and H₆chand^rac have been used to synthesize the enantiomerically pure chiral complex [(FeCl)₃(chand^RR)] ( 3^RR ) and the racemic complex [(FeCl)₃(chand^rac)] ( 3^rac ). The molecular structure of the free ligand H₆chand^rac exhibits at the terminal donor sides the O‐protonated phenol–imine tautomer and at the central donor sides the N‐protonated keto–enamine tautomer. The trinuclear complexes are comprised of five‐coordinate square‐pyramidal Fe^III ions with a chloride at the axial positions. The crystal structure of 3^rac exhibits collinear chiral channels of ～11 Å in diameter making up 33.6 % of the volume of the crystals, whereas the crystal structure of 3^RR exhibits voids of 560 ų. Mössbauer spectroscopy demonstrates the presence of Fe^III high‐spin ions. UV/Vis spectroscopy is in accordance with a large delocalized system in the central backbone evidenced by strong low‐energy shifts of the imine π–π* transitions relative to that of the terminal units. Magnetic measurements reveal weak intramolecular exchange interactions but strong magnetic anisotropies of the Fe^III ions. Complexes 3^rac and 3^RR are good catalysts for the sulfoxidation of sulfides providing very good yields and high selectivities with 3^RR being enantioselective. A comparison of 3^RR and [FeCl(salen′)] provides higher yields and selectivities but lower enantiomeric excess values (ee values) for 3^RR relative to [FeCl(salen′)]. The low ee values of 3^RR appeared to be connected to a strong ligand folding in 3^RR , opening access to the catalytically active high‐valent Fe–O species. The higher selectivity is assigned to a cooperative stabilization of the catalytically active high‐valent Fe–O species through the phloroglucinol backbone in the trinuclear complexes.     

Generation of σ-Aryl Platinum(IV) Complexes in Mechanically Activated Reaction of K2PtCl6 with Arenes

Mechanical activation of K₂PtCl₆ in the presence of gaseous arenes RH (where R = Ph, MeC₆H₄) gives rise to the corresponding -aryl platinum(IV) complexes, whose formation is confirmed by the ¹H NMR and IR spectra and chemical testing. The reaction with toluene gives a statistical mixture of the corresponding meta- (66%) and para-isomeric complexes (33%) with an overall energy yield of 0.08 µmol/J. According to the results of ab initio calculations, the energies of the isomers are fairly similar; therefore, their formation is equally probable from the viewpoint of thermodynamics.     

DNA Binding Properties and Cytotoxic Activities of Two Trinuclear Ruthenium（Ⅱ） Polypyridyl Complexes

The interactions between two trinuclear Ru（II） complexes and calf thymus DNA（CT DNA） were studied via absorption spectroscopy, reverse salt titrations, binding stoichiometry, DNA melting experiments, as well as viscosity measurement. The results indicate that complexes 1 and 2 bind to DNA via the interaction of the planar π-delocalized system of the complexes with intrinsic binding constants of 4.18 × 10^5 and 3.85 × 10^6 L/tool, respectively, and non-electrostatic binding free energy makes a predominant contribution to the binding free energy. The in vitro cytotoxic activity of complexes 1 and 2 was evaluated by the MTT[3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl- 2H-tetrazolium bromide] method. Complex I shows higher anticancer potency than complex 2 against four tumor cell lines. Further mechanism study indicates that complexes 1 and 2 can cause cell cycle arrest in the G2/M phase.     

Crystal Structures and Magnetic Properties of Cu(II) Complexes with Pyrazole‐Substituted Iminonitroxyl Radicals: New Trinuclear Heterospin Complexes

The paper describes the crystal structures and magnetic properties of complexes of copper(II) hexafluoroacetate (Cu(hfac)₂) with stable pyrazolesubstituted iminonitroxyl radicals containing the pyrazole substitutuent in the second position of the 2imidazoline cycle (L). A new group of [Cu(hfac)₂]₃(L)₂ complexes is found, in which L performs a bidentatebridge function due to the coordination of the imine N atoms of the pyrazole and imidazoline cycles. It is shown that in the solid complexes there are Cu²⁺—N = C—N—O exchange routes with highenergy ferromagnetic interactions (60–100 cm^-1).     

The Electronic Structures and Chemical Bonding of Some Dinuclear and Trinuclear Low－valence Molybdenum Complexes Containing Thiolate Bridges

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Investigation on Magnetic Properties of Exchange Coupled Transition Metal Complexes Ⅱ．Theoretical Model for Trinuclear Complexes

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Synthesis and Сharacterization of Soft-Bridged Iminopyridyl Iron and Cobalt Complexes and Their Catalytic Behavior toward Ethylene Oligomerization

Russian Journal of Physical Chemistry A - Two kinds of soft-bridged iminopyridyl ligands and their metal (iron and cobalt) complexes were synthesized. All soft-bridged iminopyridyl ligands and...     

Solvatochromism and Preferential Solvation of 4-Pentacyanoferrate 4′-Aryl Substituted Bipyridinium Complexes in Binary Mixtures of Hydroxylic and Non-hydroxylic Solvents

The intense solvatochromic behavior of several pentacyanoferrate complexes with aryl substituted 4,4′-bipyridines acting as ligands, was investigated in six hydroxylic and non hydroxylic solvents using UV-Visible spectroscopy. The metal-to-ligand-charge-transfer bands of the visible spectra of these compounds proved to be markedly affected by solvent polarity. In order to quantify the extent of the observed solvatochromism and reveal the dominant interactions which take place in the cybotactic region, resulting in solvatochromism, the Kamlet-Taft equation was used. This is a multiparametric linear-solvation-energy-relationship (LSER) widely used for the study of solvent effects on various physicochemical properties. Through this analysis it was proved that both specific and non specific interactions contribute to the observed solvatochromism. Furthermore, the preferential solvation of the complex salts was studied in binary solvent mixtures. Solvatochromism was used as the key approach to rationalize solvent-solute and solvent-solvent interactions in the binary solvent mixtures studied.     

Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor(CSTR)over a Fe-Mn catalyst.The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),Mφssbauer spectroscopy,and CO_2 temperature-programmed desorption(TPD).The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas,and decreased the catalyst surface basicity.At the same time,the addition of small amounts of sulfate improved the activities of Fischer- Tropseh synthesis(FTS)and water gas shift(WGS),shifted the product to light hydrocarbons(C_1-C_(11)) and suppressed the formation of heavy products(C_(12 )).Addition of SO_4~(2-)to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe,and S-05 catalyst gave the highest CO conversion(62.3%),and beyond this sulfur level the activity of the catalyst decreased.     

Bonding Situation of σ-E−H Complexes in Transition Metal and Main Group Compounds

The ambiguous bonding situation of σ-E−H (E=Si, B) complexes in transition metal compounds has been rationalized by means of Density Functional Theory calculations. To this end, the combination of the Energy Decomposition Analysis (EDA) method and its Natural Orbital for Chemical Valance (NOCV) extension has been applied to representative complexes described in the literature where the possible η¹ versus η² coordination mode is not unambiguously defined. Our quantitative analyses, which complement previous data based on the application of the Quantum Theory of Atoms in Molecules (QTAIM) approach, indicate that there exists a continuum between genuine η¹ and η² modes depending mainly on the strength of the backdonation. Finally, we also applied this EDA-NOCV approach to related main-group species where the backdonation is minimal.     

Synthesis of Nonionic Oligomeric Manganese(Ⅱ) Complexes and Investigation of Their Toxicity and Τ1-Relaxation Enhancement

Six nonionic oligomeric manganese(Ⅱ) complexes with oligomeric phosphate-polyglycol-EDTA ester ligands were synthesized and characterized. The longitudinal relaxivities of these complexes were measured. One of these complexes, which showed the highest relaxivity, was chosen to be used in the acute toxicity test and the Τ1-weighted imaging experiment. It has been found that compared to Gd-DTPA, this nonionic oligomeric Mn(Ⅱ) complex exhibits no acute toxicity, generates highly enhanced MRI signals and increases the intention time in the rat liver tissue.     

Synthesis of Nonionic Oligomeric Manganese（ Ⅱ ） Complexes and Investigation of Their Toxicity and T1 -Relaxation Enhancement

Six nonionic oligomeric manganese （ Ⅱ ） complexes with oligomeric phosphate-polyglycol-EDTA ester ligands were synthesized and characterized. The longitudinal relaxivities of these complexes were measured. One of these complexes, which showed the highest relaxivity, was chosen to be used in the acute toxicity test and the T1-weighted imaging experiment. It has been found that compared to Gd-DTPA, this nonionic oligomeric Mn（ Ⅱ ） complex exhibits no acute toxicity, generates highly enhanced MRI signals and increases the intention time in the rat liver tissue.     

Phosphorescent Trinuclear Pt–Ir–Pt Complexes: Insights into the Photophysical and Electrochemical Properties and Interaction with Guanine Nucleobase

In this study we have analysed the comparative photophysical and electrochemical properties of two isomeric heterotrinuclear Pt^II–Ir^III–Pt^II complexes 3 and 6 and the four corresponding intermediate isomeric homonuclear cyclometalated iridium(III) complexes 1 , 2 , 4 and 5 . The isomerisation originates from positional differences in the formyl, di-2-picolylamine and Pt–di-2-picolylamine moieties appended to cyclometalated or ancillary ligands. The interaction of 5′-GMP with the trinuclear complexes 3 and 6 shows that platinum centres appended to the cyclometalated ligand in 3 facilitate the binding of two 5′-GMP units per Pt^II centre in preference to a single 5′-GMP unit per Pt^II centre as observed in 6 . The 1:2 and 1:1 Pt^II–5′-GMP binding patterns probably arise from the convenient arrangements of the Pt–di-2-picolylamine units in different planes in complex 3 , which is absent in complex 6 .     

Synthesis and Crystal Structure of a Di-μ_2-phenolic Bridged Binuclear Manganese(Ⅲ) Schiff Base Complex

A new complex [Mn(L)(NCS)]2·0.5CH3CN (H2L = N,N'-bis(chlorosalicylidene)-1,2-diaminoethane) has been synthesized,and its structure (C70H51Cl8Mn4N13O8S4,Mr = 1833.84) was determined by single-crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system,space group C2/c with a = 25.883(2),b = 12.3320(13),c = 13.5951(16) ,β = 112.906(2),V = 3997.2(7) 3,Z = 2,Dc = 1.524 g/cm3,μ(MoKα) = 1.050mm-1,F(000) = 1852,S = 1.098,the final R = 0.0630 and wR = 0.1847 for 2542 reflections with Ⅰ 2σ(Ⅰ). The centrosymmetric title complex contains a dimer in which two distorted octahedral Mn(Ⅲ) centers are bridged equatorially by phenolic oxygen of the Schiff base ligand. The units of the complex are linked via weak C-H···N hydrogen bonds,leading to the formation of 1D chains along the b axis. The weak π-π packing interactions and weak intermolecular C(3)-H(3)···N(3) hydrogen bonds stabilize the crystal structure.     

Molecular and Supramolecular Structures of Manganese(Ⅱ) and Cobalt(Ⅱ) Complexes with 1-Carboxymethylpyridinium-4-carboxylate

Two complexes with a zwitterionic dicarboxylate ligand,Mn(L)2(H2O)4 1 and Co(L)2(H2O)4 2(L = 1-carboxymethylpyridinium-4-carboxylate),were synthesized and structurally characterized.Complex 1 crystallizes in monoclinic,space group P21 with a = 6.490(2),b = 19.210(7),c = 7.813(3) ,β = 92.716(5)o,V = 972.9(6) 3,Z = 2,Mr = 487.28,Dc = 1.663 g/cm3,F(000) = 502,μ = 0.749 mm-1,S = 1.060,the final R = 0.0377 and wR = 0.0893 for 3292 observed reflections with I 2σ(I).Complex 2 is isomorphous with 1,with a = 6.478(2),b = 19.052(7),c = 7.742(3) ,β = 92.690(4)o,V = 954.6(6) 3,Z = 2,Mr = 491.28,Dc = 1.709 g/cm3,F(000) = 506,μ = 0.971 mm-1,S = 1.035,the final R = 0.0425 and wR = 0.0809 for 3289 observed reflections with I 2σ(I).In the compounds,the mononuclear [M(L)2(H2O)4] units with trans-octahedral coordination geometry are linked into 3D architectures via hydrogen bonding(or second-sphere coordination) involving carboxylate groups and coordinated water molecules.The 3D networks illustrate a 3,8-connected net with Schlfli symbol(4·62)2(42·623·83).     

Synthesis of Nonionic Oligomeric Manganese(Ⅱ) Complexes and Investigation of Their Toxicity andΤ_1-Relaxation Enhancement

Introduction Non-invasive and accurate imaging of human inter-nal organs is crucial for medical diagnosis. Lauterburand Mansfield were awarded the 2003 Nobel Prize inphysiology and medicine, respectively, for their semi-nal work concerning magnetic resonance imaging(MRI)[1]. This powerful technique represents a break-through in medical diagnostics as well as in other myri-ad fields such as chemistry, physics, materials scienceand biology. Throughout the development of the MRItechnique, a g…