Preparation,spectroscopic, and electrochemical properties of four novel trinuclear Ru(II) polypyridyl complexes containing diazafluorene

Four tripodal ligands 2,2′,2″-tris[4-(4,5-diazafluoren-9-ylhydrazinyl)methylenephenoxyethyl]amine (L¹), 1,1,1-tris[4-(4,5-diazafluoren-9-ylhydrazinyl)methylenephenoxymethyl]propane (L²), 1,3,5-tris[4-(4,5-diazafluoren-9-ylhydrazinyl)methylenephenoxymethyl]-2,4,6-trimethylbenzene (L³), 1,3,5-tris[4-(4,5-diazafluoren-9-ylhydrazinyl)methylenephenoxymethyl]benzene (L⁴), and corresponding Ru(II) complexes [(bpy)₆L^1–4(Ru^II)₃](PF₆)₆ (Ru-L^1–4) have been synthesized. Cyclic voltammetry of these complexes comprise one Ru(II)-centered reversible oxidation and three ligand-centered reductions. Photophysical behaviors are investigated by UV–Vis absorption and luminescence spectrometry. These complexes display metal-to-ligand charge transfer absorption at around 410 nm and emission at around 582 nm.     

The Synthesis and Characterization of s-Triazine-Cored and [Fe(III)Salen]-Capped Polymer Complexes

2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride, C₃N₃Cl₃, 1) was used as the starting material. 2-(4-Carboxyphenylamino)-4,6-dichloro-1,3,5-triazine (2) was obtained from the reaction of cyanuric chloride with 4-aminobenzoic acid in the presence of sodium bicarbonate in acetone. A mononuclear complex (4) was obtained by reacting 2 and [FeSalen]₂O (3). A series of polymeric compounds was obtained by reacting 4 with a series of diamines. The polymeric complexes were characterized by elemental analysis, AAS, FT-IR, ¹H NMR, TGA and magnetic susceptibility measurements. The complexes are low-spin, distorted octahedral Fe(III) species that are bridged by carboxylic acids. The [FeSalen]-containing compounds may have the electronic structure t_2g⁵e_g⁰. All the complexes have six coordination and are polymeric.     

A new family of trinuclear Ru(II) polypyridyl complexes acting as pH-induced fluorescence switch

Tripodal ligands 1,3,5-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}-2,4,6-trimethylbenzene (L¹), 1,1,1-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}propane (L²), 2,2′,2′′-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)ethyl}amine (L³), and corresponding Ru(II) complexes [(bpy)₆L^1–3(Ru^II)₃](PF₆)₆, shortly called (Ru–L^1–3), have been synthesized. UV–vis absorption and fluorescence spectra of these complexes are both strongly dependent on the pH of the buffer solution. These complexes act as pH-induced off–on–off fluorescence switch through protonation and deprotonation of the imidazole-containing ligands.     

Pyryliumverbindungen. 30. C-Alkylierung von 1,3,5-Triaryl-penten-1,5-dion-Enolaten: Ein einfacher Zugang zu 3-alkylsubstituierten 2,4,6-Triaryl-pyryliumsalzen

Pyrylium Compounds. 30. C-Alkylation of 1,3,5-Triaryl-pentene-1,5-dione Enolates: A Simple Approach to 3-Alkylsubstituted 2,4,6-Triarylpyrylium Salts 1,3,5-Triaryl-pentene-1,5-dione enolates ( 10 ), obtainable in crystalline form from 2,4,6-triarylpyrylium pseudobases ( 9 ) and sodium methoxide in benzene/ether, react in dipolar aprotonic solvents (e.g. DMSO, DMF) with various types of alkyl iodides to give C-alkylation products ( 11 ) which afford 3-substituted 2,4,6-triarylpyrylium salts ( 12 ) on treatment with perchloric acid. This reaction sequence proved to be a convenient synthetic route to pyrylium salts ( 12 ) having 3-oriented substituents such as normal or branched alkyl groups C_nH_2n+1 (e.g.n = 1–5), isotopically modified alkyl groups (e.g. C[²H₃], C₂[²H₅]), allyl type substituents (e.g. CH₂CHCH₂, MeCHCHCH₂, CH₂, CH₂CMeCH₂) or benzyl groups (e. g. PhCH₂, 4-Br C₆H₄CH₂). Bifunctional alkylating agents (e.g. 1,4-diiodobutane, o-xylylenediiodide) resulted in a novel type of bispyrylium salts ( 14 ) with 3,3′-linkage. The pyrylium salts obtained were characterized by their ¹H-n.m.r. and u.v. spectra as well as, in most cases, by transformation into the corresponding pyridine derivatives ( 13 ) and bispyridines ( 15 ) respectively.     

Solvent Extraction of U(VI) by Calix[6]arenes

Abstract

This paper focuses on the solvent extraction of U(VI) traces by 1,3,5‐OMe‐2,4,6‐OCH₂CONHOH‐p‐tert‐butylcalix[6]arene (LH₃). The global extraction equation of U(VI) has been established. The complex formed in the organic phase is (UO₂)(LH) with an apparent extraction constant equal to 7.1×10^?5 M (I=0.04 M). Distribution data show that LH₃ efficiently extracts U(VI) from NaNO₃ media at pH 5 and that the stripping of U(VI) can be achieved in nitric acid solutions. Finally a comparison with previous results obtained with the 1,3,5‐OMe‐2,4,6‐OCH₂COOH‐p‐tert‐butylcalix[6]arene (L′H₃) shows that the hydroxamate groups are as efficient as the carboxylate ones for uranyl extraction.     

Preparation,photophysical, and electrochemical properties of three novel trinuclear Ru(II) polypyridyl complexes based on diazafluorenes

Three tripodal ligands 2,2′,2″-tris[(4,5-diazafluoren-9-ylimino)phenoxyethyl]amine (L¹), 1,3,5-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-2,4,6-trimethylbenzene (L²), 1,1′,1″-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-1″′-(p-tosyloxymethyl)-methane (L³), and corresponding Ru(II) complexes [(bpy)₆L^1–3(Ru^II)₃](PF₆)₆ (Ru-L^1–3) have been prepared. Cyclic voltammetry of the three complexes are consistent with one Ru(II)-centered quasi-reversible oxidation and three ligand-centered reductions. Photophysical behaviors are investigated by UV–Vis absorption and fluorescence spectrometry. The three complexes display metal-to-ligand charge transfer absorption at 445 nm and emission at 578 nm.     

Trinuclear Ru(II) polypyridyl complexes as human telomeric quadruplex DNA stabilizers

Two new trinuclear ruthenium(II) complexes [(bpy)₆Ru₃(tpbip)]⁶⁺ (1) and [(bpy)₆Ru₃(tptaip)]⁶⁺ (2) (bpy = 2,2′-bipyridine, tpbip = 1,3,5-tris(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-benzene, tptaip = 2,4,6-tri(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-1,3,5-triazine) have been synthesized and characterized. The interaction of human telomeric DNA with Ru(II) complexes was explored by means of CD spectroscopy, fluorescence titration, ITC and FRET melting. Results indicated that two complexes not only induce a remarkable conformational change of human telomeric DNA, but also have the ability to stabilize the G-quadruplex.     

The Synthesis and Characterization of Star Shaped Metal Complexes of Triazine Cored Schiff Bases: Their Thermal Decompositions and Magnetic Moment Values

Tripodal ligand III, 2,4,6-tris(4-hydroxybenzimino)-1,3,5-triazine, was synthesized by reacting melamine with 4-hydroxybenzaldehyde. (E)-4-Bromo-2-((2-bromoethylimino)-methyl)phenol VI was obtained by reaction of 5-bromo-2-hydroxybenzaldehyde and 2-bromoethanamine hydrochloride. Melamine cored tripodal Schiff base VII (H₃L) was synthesized by reacting III with VI. Tripodal metal complexes were obtained by reacting H₃L and transition metal salts. The complexes were characterized by elemental analyses, FT-IR, ¹H NMR and LC–MS spectroscopy, thermal analyses and magnetic measurements. Finally, metal ratios of the complexes were determined by atomic absorption spectroscopy. The complexes are square-planar low-spin (S = 1/2) Co(II), diamagnetic square-planar Ni(II), square-planar (S = 1/2) Cu(II) and diamagnetic tetrahedral Zn(II).     

Counteranion-directed assembly of zinc(II) coordination polymers with 1,3,5-tris(1-imidazolyl)benzene

Two novel coordination polymers [Zn₂(tib)(chda)Cl₂] (1) and [Zn(tib)I]I (2) have been prepared by reactions of 1,3,5-tris(1-imidazolyl)benzene (tib) and 1,2-cyclohexanedicarboxylic acid (H₂chda) with corresponding Zn(II) salts, respectively. Complex 1 has a three-dimensional (3D) structure with rare gra (graphite) topology, while 2 is a typical two-dimensional (2D) (4·8²) network. The results revealed that the counteranion plays a subtle and important role in the assembly procedure. Photoluminescent property of the complexes was investigated.     

Synthesis,Spectroscopy, Single-Crystal Structure Analysis and Antibacterial Activity of Two Novel Complexes of Silver(I) with Miconazole Drug

In a previous article, we reported on the higher toxicity of silver(I) complexes of miconazole [Ag(MCZ)₂NO₃ (1)] and [Ag(MCZ)₂ClO₄ (2)] in HepG2 tumor cells compared to the corresponding salts of silver, miconazole and cisplatin. Here, we present the synthesis of two silver(I) complexes of miconazole containing two new counter ions in the form of Ag(MCZ)₂X (MCZ = 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]-1H-imidazole]; X = BF₄⁻ (3), SbF₆⁻ (4)). The novel silver(I) complexes were characterized by elemental analysis, ¹H NMR, ¹³C NMR and infrared (IR) spectroscopy, electrospray ionization (ESI)-MS spectrometry and X-ray-crystallography. In the present study, the antimicrobial activity of all obtained silver(I) complexes of miconazole against six strains of Gram-positive bacteria, five strains of Gram-negative bacteria and yeasts was evaluated. The results were compared with those of a silver sulfadiazine drug, the corresponding silver salts and the free ligand. Silver(I) complexes exhibited significant activity against Gram-positive bacteria, which was much better than that of silver sulfadiazine and silver salts. The highest antimicrobial activity was observed for the complex containing the nitrate counter ion. All Ag(I) complexes of miconazole resulted in much better inhibition of yeast growth than silver sulfadiazine, silver salts and miconazole. Moreover, the synthesized silver(I) complexes showed good or moderate activity against Gram-negative bacteria compared to the free ligand.     

Electrical and Spectroscopic Properties of TTF and TSF Salts with Tetrahalogenozinc(II) and -cadmium(II) Anions

Several tetrathiafulvalene (TTF) and tetraselenafulvalene (TSF) salts of tetrahalogenozinc(II) and -cadmium(II) anions D_x [MX₄] (D = TTF or TSF; M = Zn and Cd; X = Cl, Br, and I; x = 2.0-6.6) have been prepared by the reaction of [TTF]₃[BF₄]₂ or [TSF]₃[BF₄]₂ with [NEt₄]₂[MX₄] in acetonitrile and by the electrolysis of TTF or TSF in acetonitrile containing [NEt₄]₂[MBr₄]. Electrical resistivities of these salts measured for compressed pellets fall in the range 1 × (10¹–10⁷) Ω cm at 25 °C; the value decreases with increasing bulkiness of the anions: [MCl₄]^2– > [MBr₄]²⁻ > [MI₄]²⁻. Stackings and electronic states of TTF and TSF molecules are discussed on the basis of electronic reflectance, ESR, IR, and Raman spectra.     

Pyryliumverbindungen. XXVII. Spezifisch deuterierte Carbo- und Heterocyclen via 2,4,6-Triaryl-[3,5-2H2]pyryliumsalze

Pyrylium Compounds. XXVIII. Specifically Deuterated Carbo- and heterocycles via 2,4,6-Triaryl[3,5-²H₂]pyrylium Salts On heating with catalytic amounts of bases(e.g. triethyl amine) in deuterated alcohols such as methan[²H]ol or ethan[²H]ol pseudobases of 2, 4, 6-triarylpyrylium salts 1 undergo fast¹H/²H isotopic exchange reaction affording 1, 3, 5-triaryl[2, 4, 4-²H₃]pent-2-ene-1,5-diones which with [²H] perchloric acid give highly deuterated 2, 4, 6-triaryl-[3, 5-²H] pyrylium perchlorates 8 . These salts are obtainable also directly from 1 through a one-pot procedure by ring opening of the latter with deuterium oxide under the above-mentioned¹H/²H isotopic exchange conditions followed by recyclization of the formed 1, 3, 5-triaryl[2, 4, 4-²H₃]pent-2-ene-1, 5-diones with [²H]ClO₄. Ring transformations of 2, 4, 6-triphenyl[3, 5-²H²]pyrylium perchlorate (8a) to 2, 4, 6-triphenyl[3, 5-²H₂]nitrobenzene (9) 2, 4, 6-triphenyl[3, 5-²H₂]pyridine (10) , 1, 2, 4, 6-tetraphenyl[3, 5-²H₂]pyrydinium perchlorate (11) , 2, 4, 6-triphencyl[3, 5-²H₂]thiopyrylium perchlorate (12) , 2-benzoyl-3, 5-diphenyl[4-²H]furan (13) , and 3, 5, 7-triphenyl-[4, 4, 6-²H₃]4H-1, 2-diazepin (14) demonstrate the usability of pyrylium salts of type 8 as starting materials for syntheses of specifically deuterated carbo- and hetrocycles.     

Wechselwirkungen in Kristallen. 98. Mitt. Protonierte Hexamethylmelamin-Salze mit verschiedenen Anionen: Monomeres Tetraphenylborat,dimeres Trifluoracetat und polymeres Chlorid-Dihydrat

Interaction in Crystals. 98. Protonated Hexamethylmelamin Salts with Different Anions: Monomeric Tetraphenylborate, Dimeric Trifluoracetate and Polymeric Chloride-Dihydrate Hexamethylmelamin (2,4,6-tris(dimethylamino)-1,3,5-triazine), on monoprotonation at one of the triazine nitrogens keeps its close to planar skeleton. Its salts with different anions reflect biochemically interesting hydrogen-bridge networks: Crystallization of the hydrochloride from isopropanol solution containing Li^⊕ [B^⊖(C₆H₅)₄], yields “naked” molecular cations, packed in herringbone fashion in between the lattice-dominating bulky, phenyl-shielded and non-protonable tetraphenylborate anions. From trifluoroacetic acid, crystals with sandwich-like subunits connected by hydrogen-bridged anions [F₃CCOO^⊖…︁HOOCCF₃] are obtained. The hydrochloride salt, prepared by adding aqueous HCl to a diethylether solution, crystallizes in stacks of triazinium cation dimers with an intermolecular bridge N^⊕-H…︁Cl^⊖…︁H^⊕N in between chloride-bydrate strands (…︁Cl^⊖…︁HOH…︁O(H)H…︁Cl^⊖…︁). Together, the structures of the three different hexamethyl-melaminium salts further illustrate the influence of anions on the crystallization of protonated nitrogen heterocycles and complement that of counter cation cation solvation in molecular anion salts.     

New multinuclear europium(III) complexes as phosphors applied in fabrication of near UV-based light-emitting diodes

Two new multinuclear europium(III) complexes, [Eu(AFTFBD)₃]₂(1,4-bmb) and [Eu(AFTFBD)₃]₃(tmb) were designed and synthesized, where HAFTFBD was 2-acetylfluorene-4,4,4-trifluorobutane-1,3-dione, 1,4-bmb was 1,4-bis[2-(2′-pyridyl)benzimidazolyl]benzene and tmb was 1,3,5-tris[2-(2′-pyridyl)benzimidazolyl]benzene. The complexes were characterized by IR, UV–visible, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The complexes emit the characteristic red luminescence of Eu³⁺ ion due to the ⁵D₀–⁷F_J (J = 0–4) transitions under 395 nm-light excitation. Bright red light-emitting diodes were fabricated by coating the selected complex (Eu(AFTFBD)₃)₃(tmb) onto ～395 nm-emitting InGaN chips, and the LEDs show appropriate CIE chromaticity coordinates in red area. All these results suggest that the Eu(III) complexes are promising candidates as red component for application in fabrication of near UV-based white light-emitting diodes.     

Coagulation of polymer–Cu2+ complexes in polymer films and its application for producing semiconducting CuI surface layers

In poly(vinyl alcohol) and polyacrylamide films containing the corresponding polymer–Cu²⁺ complexes, the reason why the films may gain surface electrical semiconductivity as high as 10^?3 Ω^?1 when treated with acetone solution of iodine was investigated. Optical and scanning electron microscope observations indicated that the coagulated polymer–Cu²⁺ complexes favor the appearance of the high conductivity and that the state of coagulation depends on the anions of the copper salts used as well as two parameters, F₁ ≡ [Cu²⁺]/[MU] and F₂ ≡ [OH^?]/[Cu²⁺], where [MU] is the molar concentration of monomeric units of the polymer and [OH^?] is that of hydroxide ions added. The effectiveness of the anions in causing coagulation decreases in the order of SO₄^2? > Cl^? > NO₃^? ≈ Br^?. The whitish substance that appears on the film surface after the iodine treatment gives x-ray Debye–Scherrer rings characteristic of γ-CuI. The γ-CuI surface layer adheres to the film rather firmly, at least in polyacrylamide, and is responsible for the conductivity. By controlling the state of coagulation of the complexes and hence the formation of the γ-CuI surface layer, we have produced films with anisotropic surface electrical semiconductivity, i.e., σ_∥ ≈ 10^?4 Ω^?1 and σ_∥/σ_⊥ = 1 ? 10³. Optical and ESR spectra are also obtained to understand the mechanism of γ-CuI formation and to clarify the optical properties of the films.     

New lipophilic cyclo- and poly-phosphazenes containing surfactant substituents

The reaction of the sodium salt of the commercially available surfactant Igepal CA 210^™ with hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1) and poly(dichlorophosphazene), [—P(Cl₂)=N—]_n (Publisher's note: for graphical representation please see printed journal or the Acrobat PDF version on this website.) affords lipophilic cyclo- and poly-phosphazenes SSCP (2) and SSPP (4), respectively. These materials, containing a short chain oligo etheroxy side group while being completely insoluble in water, are soluble in a wide range of solvents ranging from hexane to chloroform. The polymer, SSPP (4) forms polymer–metal salt complexes with lithium salts. DC conductivity measurements by a complex impedance method have been carried out. The maximum conductivity observed for SSPP–LiClO₄ (O: Li ratio, 6:1) is 1·0×10^-6Scm^-1 at 348K. © 1998 SCI.     

Zirconium tetra-n-butylate modified with different organic acids: Hydrolysis and polymerization of the products

In this work, (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu ⁿ )₄, with MAc and different organic acids, (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu ⁿ )₄ was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1:2 [Zr(OBu ⁿ )₄:MAc] by FT-IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acid-butyric acid (PrCOOH)] was made for a combination ratio of 1:1:1 [MAc:RCOOH:Zr(OBu ⁿ )₄; R: Me, Et, Pr] and the products were characterized by¹H-NMR, FT-IR, and UV spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer coulometric titration and thermal analysis, respectively. Methyl ethyl ketone(MEK) and chloroform were chosen as solvents.     

C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion

C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion has been established performing the reaction of 1,2-bis(2-pyridylmethylthio)ethane(BPT¹), 1,3-bis(2-pyridyl-methylthio)propane(BPT²) and 3,4-bis(2-pyridylmethylthio)-5-methyltoluene (BPT³) with Bu₄N[ReOCl₄] in dry alcoholoic medium. In case of BPT¹ and BPT², new 2-(2-pyridylmethylthio)ethane-1-thiol (L¹H) and 3-(2-pyridylmethylthio)propane-1-thiol (L²H) ligand, respectively were formed in situ through cleavage of one C–S(thioether) bond, resulting in the neutral oxorhenium(V) complexes of formulation [ReO(L¹)Cl₂] (1a) and [ReO(L²)Cl₂] (1b); where as in case of BPT³, binary oxorhenium(V) complex of 3,4-dimercapto-toluene ligand (L³H₂), formulated as Bu₄N[ReO(L³)₂] (1c) through cleavage of two C–S(thioether) bonds. The presence of picolinic acid, as by-product in the filtrates of the C–S bond cleavage reactions in dry alcohol, was detected by treatment of copper(II) salts and GC–MS techniques. But in hydrated alcoholic medium no C–S bond cleavage induced by ReO(V) ion occurred in any of the BPT systems rather the conversion of ReO(V) into perrhenate salt was observed; this reaction mixture, in turn on reaction with copper(II) nitrate trihydrate salt, produce [Cu(BPT)Cl]ReO₄ (2) type complexes. The solid-state structures of complexes 1a and 2a were established by X-ray crystallography.     

Tetrathiafulvalene. XIX. Synthese und Eigenschaften elektronenleitender Poly-Dithiolenkomplexe mit Ethylentetrathiolat und Tetrathiafulvalentetrathiolat als Brückenliganden

Tetrathiafulvalenes. XIX. Synthesis and Properties of Electron Conducting Poly-Dithiolene Complexes with Ethylene Tetrathiolat and Tetrathiafulvalene Tetrathiolat as Bridge Ligands [1,3]-Dithiolo[4,5-d]-1,3-dithiol-2,5-dione 7 and 5-(5-oxo[1,3]-dithiolo[4,5–d]1,3-dithiole-2-ylidene)[1,3]-dithiolo[4,5–d]1,3–dithiol-2-one 8 were synthesised from 1,3-dithiole-2-thione-4,5-dithiolat. The ligands react with salts of iron, cobalt, nickel, palladium, platinum and copper to give the polymer complexes 22a–g and 23a–e , respectively. Irradiation of 7 in the presence of iron penta-, dicobalt octa- or nickel tetracarbonyl gives the corresponding dithiolene complexes 21a–c . The amorphous insoluble polymer complexes from types 21, 22 , and 23 have been characterised by i.r.-spectroscopy, susceptibility and conductivity measurements. The nickel complexes have the highest electrical conductivity (σ_RT ∼ 10⁻¹Ω⁻¹cm⁻¹, pellets) with a very low activation energy (0,045 eV, 100–300 K) A high electron delocalization in the direction of the polymer chain and an easy charge transfer from chain to chain is supposed.     

Ethylene polymerization by alkylidene‐bridged asymmetric dinuclear titanocene/MAO systems

Two asymmetric alkylidene‐bridged dinuclear titanocenium complexes (CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂)_nC₅H₄), 1 (n = 3) and 2 (n = 4) have been prepared by treating two equivalents of CpTiCl₃ with the corresponding dilithium salts of the ligands C₉H₇(CH₂)_nC₅H₅ (n = 3, 4). Additionally, Ti(η⁵:η⁵‐n‐BuC₅H₄C₅H₅)Cl₂ (3) and Ti(η⁵:η⁵‐n‐BuC₉H₆C₅H₅)Cl₂ (4) were synthesized as corresponding mononuclear complexes. All complexes were characterized by ¹H, ¹³C NMR, and IR spectroscopy. Homogenous ethylene polymerization catalyzation using those complexes has been conducted in the presence of methylaluminoxane (MAO). The influences of reaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results showed that the catalytic activities of both dinuclear titanocenes were higher than those of the corresponding mononuclear titanocenes. Although the two dinuclear complexes were different in only one [CH₂] unit, the catalytic activity of 2 was about 50% higher than that of 1; however, the molecular weight of polyethylene (PE) obtained by 2 was lower than that obtained from 1. The molecular weight distribution of PE produced by these dinuclear complexes reached 6.9 and 7.3, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3317–3323, 2006