A coordination polymer of manganese (III) porphyrinate with right-handed helicity and opticity

A first example of 1D coordination polymer [MnTHPP·H₂O·(DMF)₂ (1)] with right-handed helicity and opticity was successfully assembled. Crystal analyses indicate that the right-handed helical assembly is based on coordination bonds from peripheral to center, associating with the saddle distortion of the molecular planes. In its crystal architecture, MnTHPP [manganese (III) ion coordinated by 5,10,15,20-tetra(4-hydroxyphenyl) porphyrin] molecules were ligated each other via the axial coordination between –PhO^? → Mn^III (peripheral to center model, from the peripherally deprotonated hydroxyphenyl to the central metal of the neighbor molecule) to construct the right-handed helices, and the helices are sustained by plentiful hydrogen bonding. Meanwhile DMF molecules are entrapped within the voids among the helices. This is a rare example of the multiporphyrin arrays with right-handed helices bearing opticity.     

pH-sensitive fluorescent sensors based on europium(III) complexes

New europium(III) complexes Eu(TTA)(2)-DSQ and Eu(TTA)(3)-DR1 were designed and synthesized as new fluorescent pH probes (where HDSQ = 5-(dimethylamino)-N-(4-(2-((8-hydroxyquinolin-2-yl)methylene)hydrazinecarbonyl)phenyl)naphthalene-1-sulfonamide, DR1 = N(1)-(4-(dimethylamino)benzylidene)-N(2)-(rhodamine-6G) lactamethylene-diamine and TTA = thiophentrifluoroacetone). Eu(TTA)(2)-DSQ exhibited high sensitivity in monitoring pH changes in neutral aqueous solution with negligible background fluorescence. Eu(TTA)(3)-DR1 comprised a green light emitting Rhodamine 6G fluorophore and a Eu(III) moiety as the origin of red light. These pH-sensitive emitter components have pK(a) values of 5.0 and 7.2 respectively, and exhibit isolated protonated steps within one molecule. Luminescence titrations demonstrate that Eu(TTA)(3)-DR1 was able to detect pH values at both near neutral pH and acidic pH ranges, and was also able to detect pH in both cultured cells and in vivo.     

New spot-test for silver(I) based on double iodide formation with bismuth(III)

The formation of an intense brownish-maroon or maroon-red product by the interaction of silver(I) and bismuth(III) solution in the presence of iodide forms the basis of a new and specific spot-test procedure for silver. The test is conducted on a spot plate with 2 or 3 drops of 2% potassium iodide solution, 1 drop of 1% bismuth(III) nitrate solution, and 1 drop of test solution. Limit of detection is 0.01 mug; limit of dilution is 1:5 x 10(6). Most cations and anions do not interfere. Only Tl(I), Cs, S(2)O(2-)(3), EDTA, pyridine, excess of thiourea, oxidizing ions (NO(-)(2), IO(-)(3), IO(-)(4), MnO(-)(4), BrO(-)(3), and S(2)O(2-)(8)) and ions such as Cl(-), Br(-), I(-), SCN(-), and N(-)(3) which cause precipitation of silver, interfere. The product formed is most probably Ag(2)BiI(5).     

Synthesis, structures, and magnetic properties of carboxylate-bridged trinuclear complexes based on low-spin manganese(III)/iron(III) building blocks

Four linear trinuclear transition metal complexes have been prepared and characterized. The complexes [M^II(MeOH)₄][Fe^III(L)₂]₂·2MeOH (M = Fe (1) or Ni (2)), [Co^II(EtOH)₂(H₂O)₂][Fe^III(L)₂]₂·2EtOH (3), and [Mn^II(phen)₂][Mn^III(L)₂]₂·4MeOH (4) (H₂L = ((2-carboxyphenyl)azo)-benzaldoxime, phen = 1,10-phenanthroline) possesses a similar syn–anti carboxylate-bridged structure. The terminal Fe(III) or Mn(III) ions are low spin, and the central M(II) ions are high spin. Magnetic measurements show that antiferromagnetic interactions were present between the adjacent metal ions via the syn–anti carboxylate bridges. The antiferromagnetic coupling between low-spin Fe(III) and Ni(II) is unusual, which has been tentatively assigned to the structural distortion of Fe(III).     

Structure and properties of cobalt(III) porphyrinate molecular complexes

By combined calculation and spectral methods the structure and properties of the molecular complexes of cobaltoctaalkylporphyrin in benzene were studied. Geometric and energy characteristics of the optimized molecules of cobalt porphyrinate and its molecular complexes were calculated. Their stability and degree of deformation were evaluated. It was established that the process of axial coordination is accompanied by the reduction of cobalt. Interrelation between the stability of the cobalt porphyrinate complexes and the nature of the base was noted. A change in the degree of deformation of the porphyrin ligand in the course of reaction was shown. Correlations between the calculation data and the value of the equilibrium constant of the axial coordination reaction were obtained.     

Potentiometric pH sensors based on chemically modified electrodes with electropolymerized metal-tetraaminophthalocyanine

Potentiometric pH sensors based on polymer film were prepared by electropolymerization of the monomer nickel(II)-4,4',4',4'-tetraaminophthalocyanine (NiTAPc) or copper(II)-4,4',4',4'-tetraaminophthalocyanine (CuTAPc) on glassy carbon (GC) electrodes. The polymer of metal tetraaminophthalocyanine (p-MTAPc) film coated electrodes show a slope of 55 +/- 1 mV/pH (at 20 degrees C) and nearly Nernstain potentiometric response to pH over the range of pH 1-13. The electrodes possess good potential reproducibility and high selectivity, and are useful sensing devices in pH determination and end-point indication of acid-base potentiometric titration.     

Dispersions, novel nanomaterial sensors and nanoconjugates based on carbon nanotubes

Nanomaterials are structures with dimensions characteristically much below 100 nm. The unique physical properties (e.g., conductivity, reactivity) have placed these nanomaterials in the forefront of emerging technologies. Significant enhancement of optical, mechanical, electrical, structural, and magnetic properties are commonly found through the use of novel nanomaterials. One of the most exciting classes of nanomaterials is represented by the carbon nanotubes. Carbon nanotubes, including single-wall carbon nanotubes, multi-wall carbon nanotubes, and concentric tubes have been shown to possess superior electronic, thermal, and mechanical properties to be attractive for a wide range of potential applications They sometimes bunch to form “ropes” and show great potential for use as highly sensitive electronic (bio)sensors due to the very small diameter, directly comparable to the size of single analyte molecules and that every single carbon atom is in direct contact with the environment, allowing optimal interaction with nearby molecules. Composite materials based on integration of carbon nanotubes and some other materials to possess properties of the individual components with a synergistic effect have gained growing interest. Materials for such purposes include conducting polymers, redox mediators and metal nanoparticles. These tubes provide the necessary building blocks for electronic circuits and afford new opportunities for chip miniaturization, which can dramatically improve the scaling prospects for the semiconductor technologies and the fabrication of devices, including field-effect transistors and sensors. Carbon nanotubes are one of the ideal materials for the preparation of nanoelectronic devices and nanosensors due to the unique electrical properties, outstanding electrocatalytic properties, high chemical stability and larger specific surface area of nanotubes. Carbon nanotubes are attractive material for supercapacitors due to their unique one-dimensional mesoporous structure, high specific surface area, low resistivity and good chemical stability. Nanoscaled composite materials based on carbon nanotubes have been broadly used due to their high chemical inertness, non-swelling effect, high purity and rigidity. The integration of carbon nanotubes with organics, biomaterials and metal nanoparticles has led to the development of new hybrid materials and sensors. Hybrid nanoscale materials are well established in various processes such as organic and inorganic compounds, nucleic acid detachment, protein separation, and immobilization of enzymes. Those nanostructures can be used as the building blocks for electronics and nanodevices because uniform organic and metal coatings with the small and monodisperse domain sizes are crucial to optimize nanoparticle conductivity and to detect changes in conductivity and absorption induced by analyte adsorption on these surfaces. The highly ordered assembly of zero-dimensional and one-dimensional nanoparticles is not only necessary for making functional devices, but also presents an opportunity to develop novel collective properties.     

All-solid-state Cr(III)-selective potentiometric sensor based on Cr(III)-imprinted polymer nanomaterial/MWCNTs/carbon nanocomposite electrode

A novel potentiometric sensor, based on carbon paste electrode (CPE), modified with ion-imprinted polymer (IIP) and multi-walled carbon nanotubes (MWCNTs), is introduced for detection of chromium (III). The IIP nanomaterial was synthesised and characterised by using scanning electron microscopy and Fourier Transform Infrared. The modification of the CPE with the IIP (as a ionophore) resulted in an all-solid-state Cr(III)-selective sensor. However, the presence of appropriate amount of MWCNTs in the electrode composition was found to be necessary to observe Nernstian response. The optimised electrode composition was 76.7% graphite, 14.3% binder, 5% IIP, and 4% CNT. The proposed sensor exhibited Nernstian slope of 20.2 ± 0.2 mV decade^?1 in the working concentration range of 1.0 × 10^?6?1.0 × 10^?1 mol L^?1 (52 µg L^?1–5.2 g L^?1), with a detection limit of 5.9 × 10^?7 mol L^?1 (30.68 µg L^?1) and a fast response time of less than 40 s. It displayed a stable potential response in the pH range of 2–5. It exhibited also high selectivity over some interfering ions. The proposed sensor was successfully applied for the determination of Cr(III) in real samples (sea, river water and soil).     

Tris(salicylhydroxamato)manganese(III)

Summary Hydroxamic acids show a degree of selectivity towards transition metal ions having symmetrical d-electron configuration, e.g. vanadium(V) (d⁰) and iron(III) (d⁶⁵). Hydroxamato complexes of metal ions having unsymmetrical d-electron distribution are rare. Thus for manganese(III) (d⁴) only some thiohydroxamato complexes⁽¹⁾ have been characterised so far. In this communication we report on the first synthesis of a salicylhydroxamato complex of manganese(III). Such investigations are of interest because these higher valent manganese complexes are potentially models for the water-splitting complex present in photosystem II⁽²).     

镧系乙酰丙酮-5,10,15,20-四(4-吡啶基 )卟啉配合物

制备了乙酰丙酮-5,10,15,20-四(4-吡啶基)卟啉稀土配合物Ln(TPyP)acac[In:Dy,Ho,Yb,Lu;H~2TPyP:5,10,15,20-四(4-吡啶基)卟啉;Hacac:乙酰丙酮].配合物由一 个中心稀土离子,一个乙酰丙酮和一个四(4-吡啶基)卟啉组成,乙酰丙酮以氧双卤配位,卟啉以氮四卤配位,因此配合物有六配位的结构.     

A selective Cu(II)/Fe(III)-mediated hydrogenation of steroidal haloalkenes in the presence of hydrazine

A new system for hydrogenation of haloalkenes is reported. Cu(II)/Fe(III)-mediated selective hydrogenation of steroidal haloalkenes in the presence of hydrazine proves to be a very efficient method for the synthesis of 17β-halosteroids, potential candidates as antiestrogens or androgen receptor-mediated imaging agents. The reaction stereospecifically affords β-haloalkanes without any concomitant formation of dehalogenation products.     

Chromium(III) selective membrane sensors based on Schiff bases as chelating ionophores

The two chromium chelates of Schiff bases, N-(acetoacetanilide)-1,2-diaminoethane (L₁) and N,N′-bis(acetoacetanilide)-triethylenetetraammine (L₂), have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Cr(III). The addition of lipophilic anion excluder (NaTPB) and various plasticizers viz. o-Nitrophenyloctyl ether (o-NPOE), dioctylpthalate (DOP), dibutylphthalate (DBP), tris(2-ethylhexyl)phosphate (TEHP), and benzyl acetate (BA) have found to improve the performance of the sensors. The best performance was obtained for the membrane sensor having a composition of L₁:PVC:DBP:NaTPB in the ratio 5:150:250:3 (w/w). The sensor exhibits Nernstian response in the concentration range 8.9 × 10⁻⁸ to 1.0 × 10⁻¹ M Cr³⁺ with limit of detection 5.6 × 10⁻⁸ M. The proposed sensor manifest advantages of relatively fast response (10 s) and good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The selectivity behavior of the proposed electrode revealed a considerable improvement as compared to the best previously PVC-membrane electrode for chromium(III) ion. The potentiometric response of the proposed sensor was independent of pH of the test solution in the range of 2.0-7.0. The sensor has found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 3 months. The proposed electrode was used as an indicator electrode in potentiometric titration of chromium ion with EDTA and in direct determination in different water and food samples.     

New chiral (salen)manganese(III) systems for asymmetric epoxidation of styrene

Highly enantioselelctive and repeatable epoxidation of styrene was performed by using new chiral (salen)Mn(III) catalysts, which were derived from the initial immobilization of a homogeneous (salen)Mn(III) complex on solid carriers and subsequent dispersion into ionic liquids. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Tetranuclear manganese (III) salicylaldoxime ensemble

Crystal structure of {[Mn(salicylaldoximeH)(salicylaldoxime)]₄} · 3CHCl₃ 1 formed by the interaction of MnCl₂ · 4H₂O and salicylaldoxime in a 1:1 ratio is described. The compound crystallizes in the orthorhombic space group Pbca (No 61) with the lattice parameters; a = 27.769 (3), b = 22.672 (2), c = 21.650 (2) Å, V = 13630 (2) Å³, Z = 8, R ₁ = 0.0776, wR ₂ = 0.2356, S = 1.164. The cluster with four Mn (III) centers formed by four terminal and four bridging salicylaldoxime ligands results in a central rotating wheel-like core with the Mn–Mn separation varying from 3.531 to 3.576 Å and with the diagonal distances being 4.156–4.165 Å. Four intramolecular H-bonds between a terminal oxime (NOH) group and the adjacent phenolate oxygen atom of another ligand stabilize the structure of the cluster. Spectral, magnetic, and cyclic voltammetry studies corroborate a stable Mn (III) tetramer.     

Low-temperature magnetisation study on manganese(III) porphyrins

Average magnetisation between 2 and 20 K and 10 and 50 kOe of two typical high-spin manganese(III) porphyrins, namely TPPMnCI and TPPMnCl(py), is reported for the first time. The results have been analysed in terms of spin hamiltonian formalism including both the crystal field and magnetic exchange.