Manganese Analogue Research Articles

Attachment to manganese or cobalt of a bulky tri(organosilyl)methyl ligand containing an NMe 2 or an OMe donor group

The organolithium compound L i(THF) 2{C(SiMe 3) 2(SiMe 2N Me 2)} reacted with one equivalent of MnCl 2 to give [ Mn(μ-Cl){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 4) and with 0.5 equivalent of MnCl 2 to give Mn{C(SiMe 3) 2(SiMe 2NMe 2)} 2 together with a small amount of the Mn III compound [ Mn(μ-O){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 6) formed by adventitious admission of air. With CoBr 2, the compound [ Co(μ-Br){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 7) was obtained. The reaction between the lithium compound Li(THF) 2{C(SiMe 3) 2(SiMe 2O Me)} and MnCl 2 in THF gave [ Mn(THF)(μ-Cl){C(SiMe 3) 2(SiMe 2O Me)}] 2 ( 5). The crystal structures of compounds 4, 5, 6 and 7 were determined. Compounds 4 and 5 are the first manganese analogues of Grignard reagents containing MnC σ-bonds to be characterised in the solid state.

Synthesis and molecular structures and oxidation catalysis of mixed alkyl, fluoroalkyl pyrazolylborate metal complexes

First row transition metal complexes of partly fluorinated tris- and bispyrazolylborate complexes are synthesized and structurally characterized. Both the red cobalt complex, [{η 3-HB(3-CF 3-5-CH 3pz) 3}Co(η 2-NO 3)(NCCH 3)] ( 1a) and the colorless manganese analogue, [{η 3-HB(3-CF 3-5-CH 3pz) 3}Mn(η 2-NO 3)(NCCH 3)] ( 1b), exhibit a N 4O 2 donor set which defines a distorted octahedral geometry. For the blue–purple complex Cu[η 2-H 2B(3-CF 3-5-CH 3pz) 2] 2 ( 2), the N 4 donor set defines a symmetry-imposed tetragonal geometry. The ligand(s) in 1 and 2 define relatively open and closed fluorine-lined cavities around their metal centers, respectively. The cavity of 1a and 1b allows additional facial coordination by small ions and neutral molecules such as NO 3 − and MeCN. In contrast, the metal in 2 is in a more saturated, quasi-octahedral environment, defined by two non-bonding axial Cu⋯H contacts and the N 4 donor set. Catalytic oxidation of cyclohexane using 1a and cumene hydroperoxide as oxygen donor yields a 1:1 mixture of cyclohexanol and cyclohexanone, and occurs 50% faster compared with the non-fluorinated analogous complex.

Hydrothermal Synthesis and Characterization ofM2Te3O8(M=Mn, Co, Ni, Cu, Zn): A Series of Compounds with the Spiroffite Structure

Several compounds isotypic to the mineral spiroffite were obtained as high quality single crystals via hydrothermal reactions. These materials, which have the general formulaM2Te3O8, crystallize in the monoclinic space groupC2/cand contain divalent transition metal ions and tellurite building blocks. Typical synthetic conditions for the preparation of these materials are 375°C for 3–5 days in an aqueous NH4Cl solution. This structure type is based on slabs containing Te2O6groups joined byMcations. These Te2O6groups are made up of two edge-sharing TeO3+1polyhedra. The metal tellurite slabs are connected to one another through tellurium(IV) atoms, which are coordinated by four oxygen atoms in a regular TeO4trigonal bipyramidal configuration. A detailed structural characterization via single crystal X-ray diffraction was performed on four compounds (Co2Te3O8:a=12.690(1) Å,b=5.211(2) Å,c=11.632(2) Å,β=98.98(1)°,V=759.7(3) Å3,R(Rw)=0.023 (0.046); Ni2Te3O8:a=12.407(1) Å,b=5.207(1)Å,c=11.509(1) Å,β=98.723(9)°,V=735.0(2) Å3,R(Rw)=0.025 (0.033); Cu2Te3O8:a=11.8368(8) Å,b=5.266(2) Å,c=12.2419(8) Å,β=100.316(6)°,V=750.7(2) Å3,R(Rw)=0.025 (0.032); Zn2Te3O8:a=12.681(2) Å,b=5.200(2) Å,c=11.786(2) Å,β=99.60(1)°,V=766.3(3) Å3,R(Rw)=0.031 (0.041)). The manganese analog (a=12.896(5) Å,b=5.398(2) Å,c=11.907(5) Å,β= 98.14(4)°) was identified via powder diffraction patterns. The cobalt, nickel, and copper compounds were observed to have an antiferromagnetic transition by DC magnetic susceptibility measurements. The band gaps were obtained by optical diffuse reflectance spectroscopy and show that these compounds are all wide band gap materials.

Syntheses, structures and magnetism of α-Mn(dca)2, [Mn(dca)2(H2O)2]·H2O, [Mn(dca)2(C2H5OH)2]·(CH3)2CO, [Fe(dca)2(CH3OH)2] and [Mn(dca)2(L)2], where L = pyridine, CH3OH or DMF and dca− = dicyanamide, N(CN)2− †

The dicyanamide anion has been observed to adopt two bridging co-ordination modes (µ and µ3) in α-Mn(dca)2, [Mn(dca)2(H2O)2]·H2O, [Mn(dca)2(C2H5OH)2]·(CH3)2CO, [Fe(dca)2(CH3OH)2] and [Mn(dca)2(L)2] [L = py, CH3OH or DMF; dca = dycanamide N(CN)2–], and generates weak ligand fields thus stabilising high spin configurations. The N- or O-bonded ligands L play an important role in the stabilisation of both the molecular structures and the three dimensional structure, via hydrogen bonding. The unsolvated α-Mn(dca)2 adopts a rutile-like single network structure, based on the near orthogonal packing of ‘ribbons’ of . . . Mn(NC–N–CN)2Mn . . ., similar to that found for the isomorphous analogues of Co, Ni, Fe and Cu. Magnetisation measurements confirmed a high spin manganese d5 system displaying antiferromagnetic coupling (θ = –25 K) above 25 K and undergoing long range magnetic ordering (TN = 16 K) to a spin-canted antiferromagnet (weak ferromagnet). Magnetisation and heat capacity measurements on some samples of α-Mn(dca)2 indicated a possible second transition at ≈6 K, the nature of which is under investigation. From the hysteresis data at 2 K (remnant magnetisation of 29 cm3 Oe mol–1 and coercive field of 406 Oe) a canting angle of 0.05° is estimated for this soft magnet. Other samples gave a higher value for the coercive field. The α-M(dca)2 series has a diverse range of ground states; CuII (d9) is a paramagnet, NiII (d8) and CoII (d7) are ferromagnets and FeII (d6) and MnII (d5) are canted antiferromagnets. Reasons for this diversity are given on the basis of the nature of exchange coupling pathways within the rutile structure and a mechanism for the long range magnetic ordering is proposed. A range of 1-D chain complexes of type [Mn(dca)2(L)2], containing ‘ribbons’ of doubly bridged Mn(NC–N–CN)2Mn have been structurally characterised. The complex [Fe(dca)2(CH3OH)2] is isostructural with the manganese analogue. 2-D Square grids are found in crystals of [Mn(dca)2(C2H5OH)2]·(CH3)2CO and in [Mn(dca)2(H2O)2]·H2O, the latter displaying, in addition, penetration of ribbons of trans-Mn(dca)2(H2O)2 through the grids. Dehydration or desolvation results in formation of the α-Mn(dca)2 phase. The Lewis-base adducts all display very weak antiferromagnetic coupling (J ≈ –0.12 cm–1) and no magnetic long-range order. Dissolution of the compounds in protic solvents leads to complete dissociation of the dicyanamide, and the axially co-ordinated ligands, L, can readily be exchanged by reaction or recrystallisation in different co-ordinating solvents.

Canted Ferromagnetism and Other Magnetic Phenomena in Square-Planar, Neutral Manganese(II) and Iron(II) Octaethyltetraazaporphyrins

Iron(II) octaethyltetraazaporphyrin has been discovered to exist as two polymorphs at room temperature, α- and β-Fe(OETAP). This has been established by X-ray powder diffraction and scanning electron microscopy. Both ac and dc SQUID magnetometry show that the α phase is a soft molecular ferromagnet with TCurie = 2.8 K. The β phase possesses the same number of unpaired spins and a similar g value, but it does not order above ∼1 K. Zero-field splitting is likely competing with ferromagnetic coupling in this compound. 57Fe Mössbauer spectroscopy has been used to support the local structural similarity between the two phases and to study the ferromagnetic transition. The isomorphous manganese analogue of α-Fe(OETAP), α-Mn(OETAP), expected to be a ferromagnet with a higher TCurie, exhibits many characteristics of ferromagnetism, notably hysteresis at 1.8 K with Hcoer = 2.5 kG and Mrem = 4 kemu-G/mol. However, in contrast to ferromagnetic α-Fe(OETAP), α-Mn(OETAP) shows strongly frequency-dependent ac susceptibility in the range from 1 to 1000 Hz, indicating that it exists in a spin-glass-like state. This result underscores the need for frequency-dependent ac magnetometry to fully characterize ferromagnetic molecular materials.

Preparation of cationic non-metallated or zinc-porphyrin-oligonucleotide fluorescent conjugates

Abstract The preparation of cationic non-metallated or zinc-porphyrin-oligonucleotide conjugates is described and is compared to the synthesis of the corresponding cationic manganese analogs. Possible side-reactions during metalloporphyrin coupling are also discussed.

Catalytic oxidation with hydrogen peroxide catalyzed by ‘sandwich’ type transition metal substituted polyoxometalates

The oxidation of organic substrates catalyzed by ‘sandwich’ type transition metal substituted polyoxometalates of the general formula, Na x M 2Zn 3W 19O 68, (M = Ru, Mn, Zn, Pd, Pt, Co, Fe, Rh) was examined in three different reaction media. The manganese analog was dissolved in a 1,2-dichloroethane phase using a lipophilic quaternary ammonium counter cation. Various organic substrates were oxidized with 30% aqueous H 2O 2. Alkenes reactivity increased as a function of the nucleophilicity of the double bond, but decreased as a function of steric crowding in the cyclohexene series. Alkenols with primary hydroxyl groups reacted chemo- and stereoselectively to form the corresponding epoxy alcohols. On the other hand, alkenols with secondary hydroxyl units did not react chemoselectively; both ketones and epoxy alcohols were formed. Diols were oxidized in most cases to ketols, except for 1,4-butanediol which yielded γ-butyrolactone. Secondary amines yielded hydroxyl amines except for piperidine which reacted with the solvent. A manganese containing catalyst supported on a functionalized silica particle was as active and selective as the organic solvent containing biphasic system for the oxidation of alkenes and alkenols. Reactions were also carried out by dissolving Na x M 2Zn 3W 19O 68 in aqueous solutions of 30% H 2O 2, 70% t-butylhydroperoxide or 0.02 M potassium persulfate in the absence of solvent. Hydrogen peroxide degraded all the TMSP compounds. One degradation product was an effective and chemo- and stereoselective catalyst for the epoxidation of primary alkenols. In alcohol oxidation only the ruthenium precursor was active. For oxidations with 70% t-butylhydroperoxide all compounds were stable but only the Na 11Ru 2Zn 3W 19O 68 compound was active. Alcohols were oxidized selectively, however, alkenols yielded a mixture of products. With persulfate, some catalytic effects were observed in double bond oxidation.

Synthetic, Spectroscopic, and Electrochemical Studies of the Isomerically-Rich [M(CO)(2)(P(2)P')X](+/0) (M = Mn, Re; X = Cl, Br; P(2)P' = eta(3)-Ph(2)P(CH(2))(2)P(Ph)(CH(2))(2)PPh(2)) System: Structural Characterization of a Novel Pair of Diastereoisomers of cis,mer-Re(CO)(2)(P(2)P')Cl.

Reaction of Mn(CO)(5)X (X = Cl, Br) with Ph(2)P(CH(2))(2)P(Ph)(CH(2))(2)PPh(2) (P(2)P') in refluxing xylene led to the formation of isomerically pure cis,mer-Mn(CO)(2)(eta(3)-P(2)P')X. Cyclic voltammograms in dichloromethane (0.1 M Bu(4)NPF(6)) show a reversible one-electron oxidation (process 1, E(1/2) = 0.142 V) to give cis,mer-[Mn(CO)(2)(P(2)P')X](+). However, in acetone (0.1 M Bu(4)NPF(6)) at room temperature, process 1 is not reversible and an additional redox process 4 (E(1/2) = 0.048 V) is observed. Process 4 is not observed at low temperatures, and at higher temperatures in acetone it merges with process 1 and also a new reversible redox couple (process 5, E(1/2) = -0.411 V) appears. A combination of electrolyses, chemical oxidation, and subsequent reduction, coupled with IR and (31)P NMR spectroscopies and electrospray mass spectrometry (ESMS), is used to show that processes 1, 4, and 5 are all associated with redox and interconversion reactions of different isomers of Mn(CO)(2)(P(2)P')X and [Mn(CO)(2)(P(2)P')X](+). Other irreversible processes due to oxidation of the different isomers of [Mn(CO)(2)(P(2)P')X](+) are observed at very positive potentials. Reaction between Re(CO)(5)X and P(2)P' in refluxing mesitylene gives a soluble product and a small amount of precipitate. The major soluble product was identified as cis,mer-Re(CO)(2)(P(2)P')X, and the oxidative chemistry is similar to that of the manganese analogues. The precipitate consists of five compounds, one of which was cis,mer-Re(CO)(2)(P(2)P')X. The new compounds A-D were identified as follows: A is cis,mer-{Re(CO)(2)(P(2)P')X}(2), a dimeric species with bridging P(2)P' ligands. The spectroscopic data for B indicated that it was a form of cis,mer-Re(CO)(2)(P(2)P')X, but not the same as the major product. Compound C is cis,fac-Re(CO)(2)(P(2)P')X, and compound D was shown to be fac-[Re(CO)(3)(P(2)P')]X. The crystal structures of cis,mer-Re(CO)(2)(P(2)P')Cl(I) and cis,mer-Re(CO)(2)(P(2)P')Cl(II) show the compounds to be diastereoisomers with the same mer geometry of the P(2)P' ligand, which of necessity generates a cavity formed by three phenyl rings on one side of the rhenium atom. The coordination geometry of the two compounds differ only by the interchange of the mutually trans chloro and carbonyl ligands. In (I) the carbonyl ligand is within the cavity and in (II) the chloro ligand is within the cavity.

Alkyl chain dynamics in perovskite bilayers and their variation with structural phase as studied by powder and single crystal NMR

A single crystal magnetic resonance study of C4Cd, [(C4H9NH3)2Cd]Cl4, specifically deuterated at a variety of positions is reported. This class of compound forms bilayered structures and C4Cd itself undergoes at least three phase transitions over the temperature range studied, 120 to 350 K. The experimental results yield a detailed picture of the variation of molecular ordering in the butyl chain with temperature and structural phase and bear substantial resemblance to 2H NMR results reported for lipid membranes. In the high and intermediate phases, complete order tensors are determined in the bilayer frame which are compared (unsuccessfully) with the disordered high temperature x-ray structure of the isomorphous manganese analog, C4Mn. On the time scale of 10−5 s, the butyl chain is nearly stationary at 120 K where it is found to occupy the expected all-trans configuration which runs parallel to the bilayer normal. At temperatures between the intermediate phase and 120 K, a mosaic structure is observed in which the C–D bonds occupy for long times (≳10−3 s) a distribution of orientations. A qualitative model for the high and intermediate phases based on gauche–trans isomerization is presented. To explain the measured order tensors, we assume that (a) gauche–trans isomerization is coupled to molecular reorientation and (b) the configurations are distorted from ideal diamond lattice configurations so as to make molecular packing more compact. It is suggested that in the mosaic structure, configurations containing gauche sequences remain populated but the isomerization rate is dramatically slowed.

Vibrational Spectra of Magnesium Hydrogenphosphate Trihydrate and of its Manganese Analogue

Abstract The infrared (IR) and Raman spectra of MgHPO4. 3H2O and of a series of partially deuterated analogues as well as the IR spectra of MnHPO4. 3H2O have been recorded and interpreted. The analysis of the IR spectra in the HOD bending region rules out the possibility of existence of H3OC+ ions in the structure.

Noélbensonite, a new BaMn silicate of the lawsonite structure type, from Woods mine, New South Wales, Australia

AbstractNoélbensonite, a new mineral, is the barium manganese analogue of lawsonite. It is described from the Woods ornamental rhodonite mine, 30 km NNE of Tamworth, New South Wales, Australia, where it occurs as aggregates of blocky to sometimes lamellar crystals ranging from a few micrometres to (rarely) 100 µm in length. It replaces NaMn amphibole, namansilite, and pectolite, and also occurs as tiny monomineralic veinlets 0.05–0.25 mm thick. Rare euhedral crystals are dominated by {100} and {011}, with (011) ^ = 68°. The mineral is orthorhombic, space group apparently Cmcm; a = 6.325(1), b = 9.120(1), c = 13.618(1) Å, V = 785.6(1) Å3, with a : b : c = 0.694 : 1 : 1.493. Noélbensonite is brittle, fracture irregular, Mohs hardness about 4, cleavage and twinning not observed, colour dark brown, streak paler yellow-brown, lustre earthy on some veinlet surfaces to brilliantly vitreous, calculated density 3.87 g/cm3, refractive indices α = 1.82(1),β (calculated from 2V) = 1.835(10), γ = 1.85(1), biaxial negative 2Vα = 46°(3°), strong dispersion r > v, straight extinction to plane of flattening, {100}, α ∥ c, β ∥ b, γ ∥ a with pleochroism in very thin sections: α = orange yellow, β = orange, γ = brownish orange, absorption γ > β ⇐p; α. The average of 23 electron microprobe analyses (wt.%) is SiO2 26.02, Al2O3 0.17, TiO2 0.01, Fe2O3 0.19, Mn2O3 34.76, CaO 0.31, Na2O 0.14, BaO 29.08, SrO 1.51, H2Ocalc 7.87, total 100.06, leading to the simplified formula . Up to 15% Sr and 9% Ca substitute for Ba in the large-cation sites. The strongest lines in the X-ray powder diffraction pattern are [(Iobs) dobs/Å hkl] (100) 4.85 111; (50) 4.557 020; (59) 4.322 021; (77) 3.416 113,004; (80) 2.869 202; (47) 2.849 114; (82) 2.729 024; (45) 2.543 132; (48) 2.428 222; (38) 2.255 223,041. The name is for William Noél Benson (1885–1957), in honour of his classic researches in the New England Fold Belt and of his tenure of the Chair of Geology at the University of Otago.

Reactions of electrophiles with [ButN)2ReVI(µ-NBut)]2

The interaction of [(ButN)2ReVI(µ-NBut)]21 with trifluoromethanesulfonic acid gave the amido complex [(ButN)(ButHN)Re(µ-NBut)2Re(NBut)2][CF3SO3], where the cation has a structure very similar to that of its manganese(VI) analogue. The interaction of 1 with silver triflate differs from the similar reaction with [(ButN)2MnVI(µ-NBut)]2 in that a silver complex {[(ButN)Re(µ-NBut)]2(µ-NBut)2Ag(µ-O3SCF3)}2 that has NBut groups bridging both rhenium and silver atoms with the latter having µ-O3SCF3 bridges is formed. A similar complex [(ButN)Re(µ-NBut)]2(µ-NBut)2Cu2(O3SCF3)2 was obtained by interaction of 1 with Cu(O3SCF3)·0.5C6H6 but this has Re(µ-NBut)Cu(O3SCF3) groups. Interaction of 1 with Al(O3SCF3)3·nCF3SO3H in CH2Cl2 gave a linear molecule (ButN)2Re(µ-NBut)2Re(NBut)(µ-OH)2Al(O3SCF3)3(H2O). The crystal structures of four compounds have been determined. An improved synthesis of 1 involving Na/Hg reduction of Re(NBut)3I was elaborated.

Alkane hydroxylation by a manganese analogue of the iron core from methane monooxygenase

A binuclear manganese (II/II) complex with a µ-hydroxo bridging ligand catalyses the hydroxylation of cyclohexane in the presence of tart-butyl hydroperoxide (TBHP).

Non-oxo chemistry of manganese in high oxidation states. Part 1. Mononuclear tert-butylimido compounds of manganese-(VII) and -(VI)

The interaction of manganese(III) chloride in acetonitrile with NHR(SiMe3)(R = But or CMe2CH2Me) gave the manganese(VII) species Mn(NR)3Cl as thermally and air-stable green crystals. The chlorine atom in Mn(NBut)3Cl 1 has been substituted by Br, OC(O)R (R = Me or CF3). OC6X5(X = F or Cl), OCH(CF3)2′ SC6F5′ C6F5 or NHBut by use of SiMe3Br and the silver, thallium or lithium salts of other reagents. Interaction of compound 1 with Ag(O3SCF3) or AgPF6 and NH2But gave the salts of the cation [Mn(NBut)3(NH2But)]+, with Li(NHBut) under selected conditions gave the paramagnetic manganese(VI) analogues of the manganate(VI) anion, [LiL]2[Mn(NBut)4][L = 1,2-dimethoxyethane (dme) or N,N,N′,N′-tetramethylethylenediamine (tmen)], and with HCl gave Mn(NBut)2(NHBut)Cl2, the reaction being reversed by addition of pyridine. Unstable compounds, e.g Mn(NBut)3(C6F5) and Mn(NBut)3(NHBut), were characterised spectroscopically. The mechanism of the formation of 1 is discussed together with a mechanism accounting for the instability of compounds where the X-group has β-H atoms as in Mn(NBut)3[OCH(CF3)2]. β-Hydrogen transfer to a NBut group to give a manganese(V) dimer [Mn(NBut)2(NHBut)]2 occurs with the formation of ketones from alkoxides; for alkyls decomposition appears to involve homolysis of the Mn–C bond and a radical pathway. The crystal structures of the compounds Mn(NBut)3X, X = OC(O)Me, OC6F5, SC6F5, [Mn(NBut)3(NH2But)]Y, Y = CF3SO3 or PF6 and [Li(dme)]2[Mn(NBut)4] have been determined. In all the compounds the manganese atom has distorted tetrahedral geometry. In the first three the Mn–N(imido) bond lengths are 1.664(3)–1.673(9)Å and the Mn–N–C angles 139.9(2) to 144.6(3)°, indicating partial multiple-bond character. The Mn–X distances, 1.91(3), 1 896(2) and 2.289(1)Å respectively indicate single bonds. In the cationic compounds the Mn–N(imido) distances are 1.531 (8)–1.655(8)Å, with Mn–N–C angles of 1 35.8(6)–170.2(9)°, suggesting more uneven distribution of the Mn–N multiple bonding, although these structures were less precisely determined due to disorder. In the manganate(VI) anion the Mn–N(imido) lengths are longer, 1.746(3)–1.749(3)Å, as expected.

Electrocatalytic properties of chemically polymerized films of cobalt, iron and manganese tetrakis( o-aminophenyl)porphyrins

Polymeric films of tetrakis( o-aminophenyl)porphyrins (abbreviated H 2( o-NH 2)TPP) and their cobalt, iron and manganese analogs were obtained by reacting the aniline groups with nitrite ions in an acidic medium. The electrocatalytic properties of the chemically polymerized (CP) Co( o-NH 2)TPP films towards O 2 reduction and CP-Fe( o-NH 2)TPP towards the reduction of nitrite ions are described and compared with those reported in the literature for the reduction of dioxygen by electropolymerized (EP) films of Co( o-NH 2)TPP and for nitrite reduction by dissolved and electropolymerized iron porphyrins. It is also shown that CP-Mn( o-NH 2)TPP films mediate the electro-oxidation of glucose oxidase. Amperometric measurements conducted with glucose electrodes based on these films show that the current is linearly proportional to glucose concentrations up to 6 × 10 −2 M. This linearity range is two orders of magnitude higher than that previously reported for Mn( o-NH 2)TPP and enzyme both immobilized in colloidal graphite.

Metal phenoxyalkanoic acid interactions—36. The preparation and crystal structures of tetraaquabis(2-phenoxybenzoato)nickel(ii) dihydrate, diaquabis(4-fluorophenoxyacetato)zinc(ii), catena-diaquabis(phenoxyacetato)cobalt(ii) and tetrakis-μ-[(pentafluorophenoxy)acetato(o,o′)] bis[aquacopper(ii)

The structures of four complexes involving divalent first-row transition metals and phenoxy substituted carboxylic acids have been determined by X-ray diffraction. These are tetraaquabis(2-phenoxybenzoato)nickel(II) dihydrate (1), diaquabis(4-fluorophenoxyacetato)zinc(II) (2), diaquabis(phenoxyacetato)cobalt(II) (3) and tetrakis-μ-(pentafluorophenoxyacetato)bis[aquacopper(II)] (4). Complex 1 is regular octahedral with trans-related unidentate carboxylate [Ni—O (carboxylate) 2.031(1) Å] and four waters [Ni—O 2.049, 2.104(2) Å]. Complex 2 has a skew trapezoidal bipyramidal stereochemistry, involving four oxygens from two asymmetric bidentate carboxylates [Zn—O 2.107, 2.332(3) Å] and two waters [Zn—O 1.989(4) Å]. The polymeric complex 3 is isomorphous and isostructural with the manganese(II) analogue, with centrosymmetric octahedral CoO 6 stereochemistry comprising four bonds to carboxylate oxygens (both bridging) [Co—O 2.076, 2.087(3) Å] and two to waters [Co—O 2.134(3) Å]. Complex 4 is a pseudo-centrosymmetric tetracarboxylate bridged dimer of the copper(II) acetate hydrate type with a Cu—Cu separation of 2.644(4) Å. Bond distances to copper are 1.96(1) (average, equatorial) and 2.15(1) Å (average, axial, to water).

Syntheses and in vitro evaluation of water-soluble "cationic metalloporphyrin-ellipticine" molecules having a high affinity for DNA

The synthesis of hybrid "cationic metalloporphyrin-intercalator" molecules is reported. These molecules are based on 9-methoxyellipticine as intercalator and tris-(4-N-methylpyridiniumyl)metalloporphyrins having a 4-aminophenyl or a 4-hydroxyphenyl group for the attachment of the linker. The effect of the length of linker (7-13 bonds), the chemical nature of the linking group (with a carboxamido or an ether function), the position of amino group between the two parts of hybrid molecules, the number of intercalator moieties (ellipticinium) covalently attached to the metalloporphyrin, and the nature of the central metal atom (Mn, Fe, Zn) on the biological activity of these hybrid molecules were studied. In addition, these molecules have a high affinity for double-stranded DNA (affinity constant of hybrid molecule 9Mn,Me = 2.3 x 10(9) M-1 for poly[d(A-T)] and 2.8 x 10(8) M-1 for poly[d(G-C)] and are cytotoxic against murine leukemia cells L1210 in vitro (IC50 of 9Mn,Me = 0.8 microM). Their cytotoxicities are dependent on the nature of central atom. Iron derivatives are less active than manganese analogues and the corresponding zinc derivatives are nearly inactive despite their same affinity for nucleic acids. These highly water-soluble hybrid molecules could be considered as efficient bleomycin models based on a cationic metalloporphyrin.

The interactions of superoxide ion(O2-.) with metallo-porphyrins [(C1(8)TPP)M, M = Fe,Mn,Co Zn]; models for biological systems and superoxide dismutases.

In dimethylformamide superoxide ion forms a 1:1 adduct with tetrakis (2,6-dichlorophenyl) porphinato-iron, (C1(8)TPP)FeOO-, as well as with its manganese analogue, (C1(8)TPP)MnOO-. On the basis of their electrochemical, spectroscopic, and magnetic properties these adducts have a metal-oxygen covalent bond (PorM-OO-), oxygen-centered redox chemistry, and reactivities that are similar to the hydroperoxide ion (HOO-). Addition of -OH to a solution of PorFe and O2 results in the formation of PorFe(OH)(OO-), which can be electrochemically oxidized to PorFeOH plus O2 (-0.2 V vs SCE). Addition of protons to the PorM-OO- adducts promotes their rapid decomposition to PorM, HOOH, and O2. This chemistry provides insight to the reactions of biological superoxide and superoxide dismutases.

The EPR spectrum of CpCr(CO) 3 in a single crystal of CpMn(CO) 3 at 20 K

The EPR spectrum of cyclopentadienylchromium tricarbonyl has been detected in single crystals of the diamagnetic manganese analog at temperatures below 25 K. Its g and 53Cr hyperfine matrices have been assembled in the crystal-axis system of the host. Both tensors are orthorhombic and their principal axes are almost coincident: g = (1.9969, 2.0353, 2.1339); a 53 = (3, 27, 44) MHz. The proximity of the principal directions of the maximum and intermediate values of these tensors to certain directions in the host crystal shows that the chromium center substitutes for CpMn(CO) 3 with little or no deformation. The single unpaired electron in CpCr(CO) 3 is believed to occupy an a′ orbital (in C s symmetry) which is composed of d x 2− y 2 and d yz chromium atomic orbitals, z being the molecular axis which connects Cr to the centers of Cp and the three CO ligands.

ChemInform Abstract: TRINUCLEAR METAL(III) TRIFLUOROACETATES

Durch Reaktion von frisch gefällten Metalloxiden und Trifluoressigsäure wurden mono-hydratisierte (85-87% Ausb.) und wasserfreie dreikernige Verbindungen M3O(O-CO-CF3)7 (M: Fe, Cr) dargestellt, während man die entsprechenden Mn-Komplexe (95 und 97% Ausb.) aus den Acetatanalogen über Säureaustausch erhielt.