A new lead(II) inorganic–organic hybrid of the P,P′-diphenylmethylene-diphosphinate ligand: synthesis and X-ray characterization of the [Pb(CH2(P(Ph)O2)2)] complex

By reaction of lead(II) nitrate with P,P^′-diphenylmethylenediphosphinic acid in water solution a new inorganic–organic hybrid of formula [Pb(CH₂(P(Ph)O₂)₂)] has been synthesized and structurally characterized. The complex displays a polymeric columnar structure, the column being formed by two intersecting sinusoidal ribbons of lead(II) ions bridged by bifunctional phosphinate ligands. The intersections of the ribbons are constituted by dimeric units of pentacoordinated lead(II) ions.     

A novel copper(II) complex identified as a potent drug against colorectal and breast cancer cells and as a poison inhibitor for human topoisomerase IIα

A novel complex, [Cu(acetylethTSC)Cl]Cl·0.25C₂H₅OH 1 (where acetylethTSC = (E)-N-ethyl-2-[1-(thiazol-2-yl)ethylidene]hydrazinecarbothioamide), was shown to have anti-proliferative activity against various colon and aggressive breast cancer cell lines. In vitro studies showed that complex 1 acted as a poison inhibitor of human topoisomerase IIα, which may account for the observed anti-cancer effects.     

Stepwise synthesis of a pentanuclear copper(II)–manganese(II) cluster by using a versatile Schiff base ligand derived from 3-formylsalicylic acid

The Schiff base 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H₂L) is a useful ligand for the design of heteronuclear complexes. A pentanuclear copper(II)–manganese(II) cluster was synthesized by using H₂L as a ligand. The compound was characterised by analytical and spectral methods. Cryomagnetic investigations over the temperature range 1.9–300 K reveal antiferromagnetic interactions between the copper(II) and manganese(II) ions.     

Facile separation of diastereo-chiral N,N′-diamine ligand via fractional crystallization and demetalation of corresponding Zn(II) complex

Enantiopure N,N-diamine has been obtained in an economical manner via demetalation of its corresponding dichloro Zn(II) complex, which is separated by fractional crystallization of two diastereomeric Zn(II) complexes. Polymerization of rac-lactide (rac-LA) initiated by diisopropoxide derivative proceeds rapidly at room temperature in a living fashion to yield heterotactic polylactide (PLA) with P_r = 0.90.     

Tris(N,N′-dimethylurea)bis(nitrato-O,O′)manganese(II), the first example of a seven-coordinate manganese(II) complex with a monodentate organic ligand

Employing a variety of solvents and molar ratios, the reactions of Mn(NO₃)₂·6H₂O with N,N′-dimethylurea (DMU) afforded the adduct [Mn(NO₃)₂(DMU)₃] (1). X-ray analysis shows that the high-spin complex has a pentagonal bipyramidal geometry with two DMU oxygen atoms in axial positions and with two types of monodentate O-bonding for the DMU molecules, one of them being very unusual. The spectroscopic properties of the prepared complex are also discussed.     

Synthesis,structure and properties of the first dinuclear copper(II) complex as a structural model for the phenolic intermediate in tyrosinase–cresolase activity

The synthesis, X-ray crystal structure and spectroscopic and electrochemical properties of the new dinuclear copper(II) complex [Cu₂(Hbtppnol)CH₃COO](ClO₄)₂ (1), employing the novel unsymmetric dinucleating ligand N-(2-hydroxybenzyl)-N,N′,N′-tris(2-pyridylmethyl)-1,3-diaminopropan-2-ol (H₂btppnol), are presented. This complex could be a relevant model for the axial interaction of a phenolic substrate to tyrosinase during cresolase activity.     

Application of nickel(II) complexes to the efficient synthesis of α- or β-amino acids

Nonproteinogenic α- or β-amino acids have attracted tremendous attention, as they are widely utilized for biological, biochemical, pharmaceutical, and asymmetric chemical investigations. Recently, we developed a series of new strategies for preparing achiral and chiral nickel(ii) complexes for the synthesis of amino acids. We applied these new methods utilizing chiral nickel(ii) complexes for the asymmetric Mannich reaction to synthesize enantiopure α,β-diamino acids, the enantioselective tandem conjugate addition-elimination reaction to prepare glutamic acid derivatives, the Suzuki coupling reaction to yield β(2)-amino acid derivatives, the asymmetric Mannich reaction to synthesize 3-aminoaspartate, the asymmetric Michael addition reaction to give β-substituted-α,γ-diaminobutyric acid derivatives, the asymmetric alkylation reaction to prepare linear ω-trifluoromethyl containing amino acids, and the asymmetric Michael addition reaction to synthesize syn-β-substituted tryptophans.     

Synthesis of polymer having β,β-triketone unit in the main chain and its copper (II) complex

Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl₃, DMF, and DMSO. The structure of the polymer was confirmed by ¹H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex. Received: 20 March 1998/Accepted: 17 April 1998     

A 3D Mesomeric Supramolecular Structure of a Cu(II) Coordination Polymer with 1,1′-Biphenyl-2,2′,3,3′-tetracarboxylic Acid and 5,5′-Dimethyl-2,2′-bipyridine Ligands

A novel metal–organic framework {[Cu(H₂bptc)(cbpy)(H₂O)]·(H₂O)} _n (1) has been hydrothermally synthesized through reaction of 1,1′-biphenyl-2,2′,3,3′-tetracarboxylic acid (H₄bptc) with Cu(II) salt in the presence of ancillary nitrogen ligand 5,5′-dimethyl-2,2′-bipyridine (cbpy), and its structure was determined by X-ray diffraction and characterized by elemental analysis, and IR spectrum. The title compound crystallizes in monoclinic space group P2₁/c. Both right- and left-handed helices are detected in the structure. In the ab-plane, adjacent chains are homochiral and parallel to each other, which are connected together by hydrogen bonds to form a 2D supramolecular structure. The supramolecular layers with opposite chirality are arranged alternatively along the c-axis to form a 3D mesomeric supramolecular structure through π···π interactions. The thermal stability of the complex 1 was studied by thermal gravimetric and differential thermal analysis.     

Catalytic Cu(II)–polymer complexes as recyclable catalysts for the synthesis of poly(2,6-dimethyl-1,4-phenylene oxide)s in water

Water-soluble polymers comprising itaconic amide acid with acrylic acid or acrylamide, which contain carboxylic acid and amide groups capable of coordinating to the copper catalyst, were synthesized by radical polymerization using an azobisisobutyronitrile initiator. These polymers were used as polymer ligands to prepare copper complexes, which were subsequently analyzed by UV–Vis spectroscopy. The complexes were then used as catalysts for the oxidative polymerization of 2,6-dimethylphenol (DMP) to synthesize poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) under oxygen and in the presence of a surfactant in alkaline water. The polymerization conditions were optimized by varying the amounts of polymer ligands and copper precursors, the concentrations of surfactant and hydrogen chloride, and the temperature, resulting in PPO with a maximum yield of 93%, a number-average molecular weight (M _n) of 3700, and a molecular weight distribution (M _w/M _n) of 2.12. This yield is higher than that previously achieved using arginine ligand in water (72%). Furthermore, the optimum conditions were applied in the copolymerization of DMP and 2-allyl-6-methylphenol to obtain a thermally crosslinkable copolymer in 95% yield (M _n = 3000, M _w/M _n = 2.5). In addition, the catalyst complex of the copper–polymer ligand was recovered and reused after the polymerization of DMP. The catalyst maintained its activity even after being recycled five times, without the addition of copper precursor or polymer ligand, thereby demonstrating an environmentally friendly process wherein environmental emissions and production costs can be substantially reduced.     

Structural analysis and electronic properties of a homodinuclear erbium(III) complex bridged by the polyazine ligand 2,2′-bipyrimidine

Structural analysis of the previously reported homodinuclear complex [Er(tfa)₃]₂bpm (where tfa = 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione and bpm = 2,2′-bipyrimidine) synthesized by reaction of two equivalents of ErCl₃ with six equivalents of tfa and one equivalent of bpm in a basic ethanol solution is presented. X-ray quality crystals were grown by slow evaporation of concentrated methanol solution containing the complex. The complex crystallizes in the monoclinic space group P2₁/n, with a planar bpm ligand. The erbium…erbium distance is 6.715(5) Å. Each erbium center is eight coordinate from six tfa oxygens and two bpm nitrogens. Electronic transitions of concentrated solutions of the complex reveal three sharp lines corresponding to the 4f–4f1 transitions at 486 nm, 520 nm and 657 nm with the lowest energy transition corresponding to ⁴I_15/2 → ⁴F_9/2.     

Synthesis and Evaluation of N,N′-dimethyl-N,N′-dicyclohexyl-Malonamide (DMDCMA) as an Extractant for Actinides

A malonamide based extractant, i.e., N,N′-dimethyl-N,N′-dicyclohexyl-malonamide (DMDCMA) was synthesized in a single step and tested for the extraction of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV), Pu(VI), etc., from nitric acid medium. The extractant was soluble in phenyltrifluoromethylsulphone (PTMS or FS-13) unless stated otherwise. The effect of various experimental parameters, such as the aqueous phase acidity (0.01–3 M HNO₃), nature of the acid, oxidation states of the metal ions, ligand concentration, nature of the diluent and temperature on the extraction behavior of metal ions was studied. The extracted Am(III) species was determined from slope analysis method as [Am(NO₃)₃(DMDCMA)₂]. The extraction of the metal ions was found to increase with the aqueous phase acidity. The temperature variation studies allowed the calculation of the heat of the two-phase extraction reaction as well as the corresponding extraction constants. These studies revealed that DMDCMA showed good extraction for all the actinide metal ions investigated, and have the advantage of single stage synthesis and easier purification protocol.     

Synthesis,X-ray structure and catalytic properties of a copper(II) Schiff base complex modeling the activity of the CuB site of dopamine β-hydroxylase

The copper(II) complex [Cu(salgly)(bpy)]·4H₂O (1), where salgly is a tridentate glycinatosalicylaldimine Schiff base ligand, is prepared and structurally characterized. The complex is found to be catalytically active in the oxidation of ascorbic acid by dioxygen and the process is also effective in the presence of benzylamine giving benzaldehyde as a product, thus modeling the activity of the Cu_B site of dopamine β-hydroxylase.     

A novel chelate-assisted C−C bond formation on a Cd(II) complex of an asymmetric heptadentate(N7) tripodal Schiff base ligand

Cadmium(II) complexes of some potentially heptadentate tripodal Schiff base ligands with the general formula N{(CH₂)_nNCHC₅H₄N}₂{(CH₂)_mNCHC₅H₄N}) (where n = m = 2, L₂₂₂; n = 2, m = 3, L₃₂₂; n = 3, m = 2, L₃₃₂) have been studied. These ligands are products of the full condensation of a number of tripodal tetraamines with 2-pyridinecarboxaldehyde. An unusual reaction of an additional 2-pyridine-carboxaldehyde with a methylene group adjacent to the imine bond only during template preparation of [Cd(L₃₃₂)]²⁺ was observed. The latter reaction is a novel chelate-assisted C?C bond formation because it is occurred only where a rigid five-membered chelate ring is present.     

The unexpected synthesis of rhodium(I) complexes with the 1-(2′-pyridyl)-3-oxo-1-propenoxide anionic ligand

The enaminone compound 1-(2^′-pyridyl)-3-dimethylamine-1-propenone (1) reacts with [{Rh(μ-OY)(COD)}₂] (OY=OMe, OH) dimers in the presence of water to form a mononuclear square-planar rhodium(I) complex 2, which incorporates the unexpected 1-(2^′-pyridyl)-3-oxo-1-propenoxide ligand (N, O). The mediation of the metal in this ligand transformation is demonstrated. The crystal structure of [Rh(N,O)(COD)] (2) reveals the coordination of the new propenoxide ligand as a N,O-bidentate with the presence of an additional non-coordinated aldehyde group. Complex 2 reacts with CO by displacement of the COD molecule, but maintaining the N,O-coordination of the chelate propenoxide ligand.     

Interplay of coordination and hydrogen bonding modes in the self-assembly of the supramolecular network in copper(II) phthalate–trimethoprim complex (0.5:1:1)

Trimethoprim cations forming self complementary hydrogen-bonded DADA arrays interact with the copper–phthalate supramolecular frameworks through extensive hydrogen bonding.     

A luminescent pH sensor based on a diruthenium(II) complex: `off–on–off' switching via the protonation/deprotonation of an imidazole-containing ligand

Complex [(bpy)₂Ru(bpibH₂)Ru(bpy)₂](ClO₄)₄·3H₂O (1) (bpy=2,2′-bipyridine and bpibH₂=1,4-bis([1,10]phenanthroline[5,6-d]imidazol–2-yl)benzene), which contains two metallolumophores and a two receptor system, acts as an `off–on–off' luminescent pH sensor through protonation and deprotonation in MeOH–H₂O (1:1 v/v) solution at room temperature.     

The synthesis and characterization of a mesomorphic brush type polycarbosilane: poly[1,1-bis(4′-biphenyl)silabutane]

Summary Poly[1,1-bis(4-biphenyl)silabutane] (II) has been prepared by the anionic ring opening polymerization of 1,1-bis(4-biphenyl)silacyclobutane. II shows mesomorphic behavior by DSC. The¹³C NMR T₁ relaxation times have been measured. These are found to be smaller than those of poly(1,1-dimethylsilabutane)by an order of magnitude. This may result from interaction of the highly rigid biphenyl side chain moieties. The thermal stability of II is higher than that for other 1,1-disubstituted polysilabutanes.