Synthesis and characterization of a new tetradentate ligand for Cu(II) metal ions

The synthesis and characterization of a tailor-made ligand 1 is described. Self-assembly of 1 on a GaAs surface was studied by FT-IR spectroscopy. The IR spectrum of the thin film points to the conclusion that the monolayer adsorbs to the surface via both carboxylates of the malonic acid derivative. The distinction between the possible binding modes is discussed.     

Synthesis,characterization, and catalytic application of a zinc(II) complex bearing a pyrazole-based ligand

The reaction between ZnCl₂ and N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-1-phenylethylamine (bdmppea) affords [(bdmppea)ZnCl₂], whose structure has been determined by X-ray crystallography. The [(bdmppea)ZnEt₂] complex in situ prepared by the reaction between [bdmppea] and ZnEt₂ exhibited high activity toward the polymerization reaction of rac-lactide at room temperature. However, its activity decreased sharply with decreasing temperature. Stereospecificity of this catalyst characterized by heterotacticity (P_r) was determined by homonuclear decoupled NMR spectroscopy, which value was ∼0.58.     

Synthesis, characterization, and catalytic application of a new chiral P,N-indene ligand derived from (R)-BINOL

Lithiation of 2-dimethylaminoindene followed by quenching with [(R)-(1,1′-binaphthalene-2,2′-diyl)]chlorophosphite and treatment with triethylamine afforded the crystallographically characterized enantiopure P,N-indene 3 in 71% isolated yield. In the course of rhodium coordination chemistry studies involving 3, the formation of the isolable complex [(κ²-P,N-3)(κ¹-P,N-3)RhCl] (7) (81%) was observed, thereby confirming the propensity of this new ligand to form L_nRh(3)₂ complexes. Such coordination chemistry behavior may contribute in part to the generally poor catalytic performance exhibited by mixtures of 3 and rhodium precursor complexes in the asymmetric hydrogenation and hydrosilylation studies described herein.     

Synthesis and structural characterization of tris(2-seleno-1-mesitylimidazolyl) hydroborato complexes: a new type of strongly electron donating tripodal selenium ligand

A new tripodal ligand that features three selenium donors, namely the tris(2-seleno-1-mesitylimidazolyl)hydroborato ligand, [Tse(Mes)], has been constructed via the reaction of KBH(4) with 1-mesitylimidazole-2-selone; comparison of the IR spectroscopic data of [Tse(Mes)]Re(CO)(3) with those of a variety of related LRe(CO)(3) complexes demonstrates that the [Tse(Mes)] ligand is more strongly electron donating than Cp, Cp*, [Tp], [Tp(Me(2))] and [Tm(Mes)] ligands.     

A new tripodal ligand system based on the iminophosphorane functional group. Part 1: Synthesis and characterization

Two tripodal alcohols, viz., 1,1,1-tris(hydroxymethyl)ethane and α,α,α-tris(hydroxymethyl)toluene were converted by an efficient multi-step pathway involving azide formation into the corresponding tris(iminophosphorane) scaffolds bearing cyclopentyl (Cp) or phenyl groups on their phosphorus atoms, R-C(CH₂-NPR′₃)₃ (R=Me or Ph, R′=Cp or Ph). The synthesis of some representative transition-metal complexes of Cu(I), Cu(II), Ni(II), and Pd(II) bearing these new tridentate ligands is also reported.     

Synthesis, characterization and structural analysis of new copper(II) complexes incorporating a pyridoxal-semicarbazone ligand

The reaction between 3-hydroxy-5-hydroxymethyl-2-methyl-4-pyridinecarboxaldehyde semicarbazone (pyridoxal-semicarbazone or PLSC) and appropriate chloride, sulfate, nitrate or thiocyanate Cu(II) salts in water/alcohol mixtures resulted in the formation of new copper(II) complexes: [Cu(PLSC)Cl₂] (1), [Cu(PLSC)(H₂O)(SO₄)]₂·3H₂O (2), [Cu₂(PLSC)₂(NCS)₂](NCS)₂ (3), [Cu(PLSC)(NO₃)₂(CH₃OH)] (4) and [Cu(PLSC-2H]NH₃·H₂O (5). The complexes were characterized by elemental analysis, conductometric measurements and IR spectroscopy, while complexes 1, 2, 3 and 4 were further characterized by single crystal X-ray diffraction.     

Synthesis,crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

A new copper(II) complex of an unsymmetrical tripodal ligand (NN₂O222) derived from tris(2-aminoethylamine)amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN₂O222)Cu(ImH)](ClO₄)₂·0.5H₂O (NN₂O222?=?2-[bis(2-aminoethyl)amino]ethanol; ImH?=?imidazole). Crystals of the complex are orthorhombic, space group Pna2₁, with a?=?29.983(10), b?=?15.568(5), c?=?8.127(3)?Å. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu^II/Cu^I redox behavior at +44?mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO₄)₂·6H₂O.     

Synthesis and characterization of a tripodal amide ligand and its binding with anions of different dimensionality

Synthesis and crystal structure of a tren-based amide, L(1), N,N',N'-tris[(2-amino-ethyl)-3-nitro-benzamide] is reported. The crystallographic results show intramolecular hydrogen bonding and aromatic pi...pi stacking among tripodal arms which prevent opening of the receptor cavity. Intermolecular hydrogen bonding in L1 generates the sheetlike network in the solid state. The structural aspects of binding halides (1 and 2), nitrate (3), perchlorate (4), and hexafluorosilicate (5) with the protonated L1 are examined crystallographically. Protonation at the apical nitrogen of L1 in the presence of anions shows a structural transformation from sheet to bilayer network. Anion binding with multiple receptor units is observed via amide N-H...anion and aryl C-H...anion hydrogen-bonding interactions in all the complexes. The aryl group having nitro functionality that contributes to anion binding in complexes 1-5 through CH...anion interactions (either para or meta to nitro C-H) is noteworthy. These studies also show higher anion coordination of chloride (8) and hexafluorosilicate (14) with L1H+.     

Synthesis and structural characterization of tris(2-oxo-1-tert-butylimidazolyl) and tris(2-oxo-1-methylbenzimidazolyl)hydroborato complexes: a new class of tripodal oxygen donor ligand

A new class of tripodal L(2)X ligands that feature three oxygen donors, namely the tris(2-oxo-1-tert-butylimidazolyl) and tris(2-oxo-1-methylbenzimidazolyl)hydroborato ligands, [To(Bu(t))] and [To(MeBenz)], has been synthesized via the reactions of NaBH(4) with the respective imidazolone. Structural and spectroscopic studies indicate that both [To(Bu(t))] and [To(MeBenz)] are significantly more sterically demanding but less electron donating than the related [O(3)] donor ligand, [CpCo{P(O)(OEt)(2)}(3)].     

Synthesis and crystal structure of a copper(II) complex of the tripodal tetradentate ligand tris(2-benzimidazolylmethyl)amine

A mononuclear copper complex [Cu(NTB)Cl]Cl·3CH₃CH₂OH (1) (NTB?=?tris(2-benzimidazolylmethyl)amine) was synthesized and its structure was determined by single crystal X-ray diffraction. In this complex, copper(II) is five-coordinate with NTB serving as a neutral tetradentate ligand. Three tertiary nitrogen atoms of benzimidazole groups of NTB formed the base of the trigonal bipyramidal geometry. One axial position was occupied by the apical nitrogen atom of NTB and the other was occupied by chloride. The ESR spectrum of complex 1 in ethanol at 101?K was recorded and the well-defined ESR parameters (g _∥?=?2.02, g _⊥ =?2.16 and A _∥ ^?=?109?G) indicated that the Cu(II) has a distorted trigonal-bipyramidal environment, in good agreement with crystal structure determination for complex 1.     

Synthesis of an asymmetrical tripodal tetraamine ligand and its five-coordinate copper(II) complex

A simple synthesis has been devised for the tripodal 3,3,4-tetraamine ligand N{(CH2)3NH2}2{(CH2)4NH2} (L). This ligand forms a copper(II) complex, [Cu (LH)Cl2]ClO4 (7), the structure of which has been determined by X-ray diffraction. The cation contains a five-coordinate copper atom, bonded to two chloride ions, the two propylamine groups and the tertiary nitrogen atom of the ligand; the arrangement is a distorted trigonal bipyramid, in which the two primary amine groups occupy the axial positions. The butylamine group of the ligand does not coordinate to copper but is protonated. It is involved in hydrogen bonding to the perchlorate ion. The e.p.r. spectrum of [Cu(dpt)Cl2] is very similar to that of (7), suggesting that it also has a trigonal bipyramidal structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ion-selective carbon paste electrode based on new tripodal ligand for determination of cadmium (II)

A new chemically modified carbon paste electrode for Cd(II) ions based on 3,5-dinitro-N-(tri-2-pyridyl methyl) benzamide (DNTPMBA) as an ionophore was prepared. The electrode exhibits a Nernstian response for Cd(II) ions over a wide concentration range (2.16 × 10^?7–1.00 × 10^?1 mol L^?1) with a slope of 30 ± 1 mV per decade. It has a response time of about 50 s and can be used for a period of 3 months with good reproducibility. Detection limit obtained in the optimal conditions was 1.82 × 10^?7 mol L^?1. The electrode was successfully used for potentiometric determination of Cd(II) in well water. The pH influence and interference of some cations were also studied.     

Synthesis, characterization, and structures of copper(II)-thiosulfate complexes incorporating tripodal tetraamine ligands

The reaction of [Cu(L)(H(2)O)](2+) with an excess of thiosulfate in aqueous solution produces a blue to green color change indicative of thiosulfate coordination to Cu(II) [L = tren, Bz(3)tren, Me(6)tren, and Me(3)tren; tren = tris(2-aminoethyl)amine, Bz(3)tren = tris(2-benzylaminoethyl)amine, Me(6)tren = tris(2,2-dimethylaminoethyl)amine, and Me(3)tren = tris(2-methylaminoethyl)amine]. In excess thiosulfate, only [Cu(Me(6)tren)(H(2)O)](2+) promotes the oxidation of thiosulfate to polythionates. Products suitable for single-crystal X-ray diffraction analyses were obtained for three thiosulfate complexes, namely, [Cu(tren)(S(2)O(3))].H(2)O, [Cu(Bz(3)tren)(S(2)O(3))].MeOH, and (H(3)Me(3)tren)[Cu(Me(3)tren)(S(2)O(3))](2)(ClO(4))(3). Isolation of [Cu(Me(6)tren)(S(2)O(3))] was prevented by its reactivity. In each complex, the copper(II) center is found in a trigonal bipyramidal (TBP) geometry consisting of four amine nitrogen atoms, with the bridgehead nitrogen in an axial position and an S-bound thiosulfate in the other axial site. Each structure exhibits H bonding (involving the amine ligand, thiosulfate, and solvent molecule, if present), forming either 2D sheets or 1D chains. The structure of [Cu(Me(3)tren)(MeCN)](ClO(4))(2) was also determined for comparison since no structures of mononuclear Cu(II)-Me(3)tren complexes have been reported. The thiosulfate binding constant was determined spectrophotometrically for each Cu(II)-amine complex. Three complexes yielded the highest values reported to date [K(f) = (1.82 +/- 0.09) x 10(3) M(-1) for tren, (4.30 +/- 0.21) x 10(4) M(-1) for Bz(3)tren, and (2.13 +/- 0.05) x 10(3) M(-1) for Me(3)tren], while for Me(6)tren, the binding constant was much smaller (40 +/- 10 M(-1)).     

glucoBox--a new carbohydrate-based bis(oxazoline) ligand. Synthesis and first application

The synthesis of a new bis(oxazoline) ligand from D-glucosamine and its application in enantioselective copper(I) catalysed cyclopropanations of olefins is described.     

A new bis(imidazolyl)(alkylthiolate) tripodal ligand and the spontaneous formation of a disulfide-linked,hydroxo-bridged dinuclear zinc complex

The new sterically encumbered, tripodal N2S(alkylthiolate) ligand, LIm2SH, has been synthesized and used to prepare [(LIm2S)ZnCH3], which upon protonolysis under acidic conditions leads to the synthesis of a novel dinucleating ligand and a zinc dimer with an unusual structure.     

Synthesis,spectroscopic and structural characterization of new complex of ruthenium(II) with Hmtpo ligand

The [(PPh₃)₂RuHCl(CO)(Hmtpo)] complex has been prepared and studied by IR, NMR, UV–VIS spectroscopy and X-ray crystallography. The complex was prepared in reactions of [RuHCl(CO)(PPh₃)₃] with 7-hydroxy-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine in methanol. The electronic structure and UV–Vis spectrum of the obtained compound have been calculated using the TD–DFT method.     

Design and synthesis of a Pt(II) nanoscopic trigonal bipyramidal cage using a new tripodal ester-containing ligand

The formation of a Pt(II) nanoscopic trigonal bipyramidal cage (TBP) containing a new tripodal linker with ester functionality is achieved by self-assembly. The new tripod ligand and the cage were characterized by multinuclear NMR and electrospray ionization mass spectroscopy. Energy minimized simulation of the cage yielded a pseudo TBP shape with an internal diameter of 2 nm.     

Synthesis and characterization of a new iron (II)— dinitrogen compound with PDTA as ligand

A new dinitrogen complex of formula Na₂[Fe(PDTA) (N₂] (H₂O)₂ has been synthesized in aqueous solution from [Fe(H-PDTA) (H₂O)], 3/2H₂O and NaN₃. The complex has been characterized by chemical analysis, IR and electronic spectra, and magnetic measurements. The thermal decomposition process has been studied by using DTA and TG techniques. The evolution of gases was followed by Gas Chromatography.