Synthesis, crystal structure and spectroscopic and electrochemical properties of bridged trisbenzoato copper-zinc heterobinuclear complex of 2,2 `-bipyridine

The synthesis of the heterobinuclear copper-zinc complex CuZn(bz)(3)(bpy)(2)]ClO4 (bz = benzoate) from benzoic acid and bipyridine is described. Single crystal X-ray diffraction studies of the heterobinuclear complex reveals the geometry of the benzoato bridged Cu(II)-Zn(II) centre. The copper or zinc atom is pentacoordinate, with two oxygen atoms from bridging benzoato groups and two nitrogen atoms from one bipyridine forming an approximate plane and a bridging oxygen atom from a monodentate benzoate group. The Cu-Zn distance is 3.345 angstrom. The complex is normal paramagnetic having mu(eff) value equal to 1.75 BM, ruling out the possibility of Cu-Cu interaction in the structural unit. The ESR spectrum of the complex in CH3CN at RT exhibit an isotropic four line spectrum centred at g = 2.142 and hyperfine coupling constants A(av) = 63 x 10(-4) cm(-1), characteristic of a mononuclear square-pyramidal copper(II) complexes. At LNT, the complex shows an isotropic spectrum with g(parallel to) = 2.254 and g(perpendicular to) =2.071 and A(parallel to) = 160 x 10(-4) cm(-1). The Hamiltonian parameters are characteristic of distorted square pyramidal geometry. Cyclic voltammetric studies of the complex have indicated quasi-reversible behaviour in acetonitrile solution. (C) 2014 Elsevier B.V. All rights reserved.

Synthesis and spectroscopy of ruthenium-modified nucleic acids

Redox-active probes are designed and prepared for use in DNA-mediated electron transfer studies. These probes consist of ruthenium(II) complexes bound to nucleosides that possess metal-binding ligands. Low- and high-potential oxidants are synthesized from these modified nucleosides and display reversible one-electron electrochemical behavior. The ruthenium-modified nucleosides exhibit distinct charge-transfer transitions in the visible region that resemble those of appropriate model complexes. Resonance Raman and time-resolved emission spectroscopy are used to characterize the nature of these transitions.

The site-specific incorporation of these redox-active probes into oligonucleotides is explored using post-synthetic modification and solid-phase synthetic methods. The preparation of the metal-binding nucleosides, their incorporation into oligonucleotides, and characterization of the resulting oligonucleotides is described. Because the insertion of these probes into modified oligonucleotides using post-synthetic modification is unsuccessful, solid-phase synthetic methods are explored. These efforts lead to the first report of 3'-metallated oligonucleotides prepared completely by automated solid-phase synthesis. Preliminary efforts to prepare a bis-metallated oligonucleotide by automated synthesis are described.

The electrochemical, absorption, and emissive features of the ruthenium-modified oligonucleotides are unchanged from those of the precursor metallonucleoside. The absence of any change in these properties upon incorporation into oligonucleotides and subsequent hybridization suggests that the incorporated ruthenium(II) complex is a valuable probe for DNA-mediated electron transfer studies.

Transition metal clusters supported by multinucleating ligand frameworks as models of biological active sites

This dissertation describes efforts to model biological active sites with small molecule clusters. The approach used took advantage of a multinucleating ligand to control the structure and nuclearity of the product complexes, allowing the study of many different homo- and heterometallic clusters. Chapter 2 describes the synthesis of the multinucleating hexapyridyl trialkoxy ligand used throughout this thesis and the synthesis of trinuclear first row transition metal complexes supported by this framework, with an emphasis on tricopper systems as models of biological multicopper oxidases. The magnetic susceptibility of these complexes were studied, and a linear relation was found between the Cu-O(alkoxide)-Cu angles and the antiferromagnetic coupling between copper centers. The triiron(II) and trizinc(II) complexes of the ligand were also isolated and structurally characterized.

Chapter 3 describes the synthesis of a series of heterometallic tetranuclear manganese dioxido complexes with various incorporated apical redox-inactive metal cations (M = Na⁺, Ca²⁺, Sr²⁺, Zn²⁺, Y³⁺). Chapter 4 presents the synthesis of heterometallic trimanganese(IV) tetraoxido complexes structurally related to the CaMn₃ subsite of the oxygen-evolving complex (OEC) of Photosystem II. The reduction potentials of these complexes were studied, and it was found that each isostructural series displays a linear correlation between the reduction potentials and the Lewis acidities of the incorporated redox-inactive metals. The slopes of the plotted lines for both the dioxido and tetraoxido clusters are the same, suggesting a more general relationship between the electrochemical potentials of heterometallic manganese oxido clusters and their “spectator” cations. Additionally, these studies suggest that Ca²⁺ plays a role in modulating the redox potential of the OEC for water oxidation.

Chapter 5 presents studies of the effects of the redox-inactive metals on the reactivities of the heterometallic manganese complexes discussed in Chapters 3 and 4. Oxygen atom transfer from the clusters to phosphines is studied; although the reactivity is kinetically controlled in the tetraoxido clusters, the dioxido clusters with more Lewis acidic metal ions (Y³⁺ vs. Ca²⁺) appear to be more reactive. Investigations of hydrogen atom transfer and electron transfer rates are also discussed.

Appendix A describes the synthesis, and metallation reactions of a new dinucleating bis(N-heterocyclic carbene)ligand framework. Dicopper(I) and dicobalt(II) complexes of this ligand were prepared and structurally characterized. A dinickel(I) dichloride complex was synthesized, reduced, and found to activate carbon dioxide. Appendix B describes preliminary efforts to desymmetrize the manganese oxido clusters via functionalization of the basal multinucleating ligand used in the preceding sections of this dissertation. Finally, Appendix C presents some partially characterized side products and unexpected structures that were isolated throughout the course of these studies.

Structure-, stereochemistry-, and metal-regulated DNA binding/cleaving molecules

In the cell, the binding of proteins to specific sequences of double helical DNA is essential for controlling the processes of protein synthesis (at the level of DNA transcription) and cell proliferation (at the level of DNA replication). In the laboratory, the sequence-specific DNA binding/cleaving properties of restriction endonuclease enzymes (secreted by microorganisms to protect them from foreign DNA molecules) have helped to fuel a revolution in molecular biology. The strength and specificity of a protein:DNA interaction depend upon structural features inherent to the protein and DNA sequences, but it is now appreciated that these features (and therefore protein:DNA complexation) may be altered (regulated) by other protein:DNA complexes, or by environmental factors such as temperature or the presence of specific organic molecules or inorganic ions. It is also now appreciated that molecules much smaller than proteins (including antibiotics of molecular weight less than 2000 and oligonucleotides) can bind to double-helical DNA in sequence-specific fashion. Elucidation of structural motifs and microscopic interactions responsible for the specific molecular recognition of DNA leads to greater understanding of natural processes and provides a basis for the design of novel sequence-specific DNA binding molecules. This thesis describes the synthesis and DNA binding/cleaving characteristics of molecules designed to probe structural, stereochemical, and environmental factors that regulate sequence-specific DNA recognition.

Chapter One introduces the DNA minor groove binding antibiotics Netropsin and Distamycin A, which are di- and tri(N-methylpyrrolecarboxamide) peptides, respectively. The method of DNA affinity cleaving, which has been employed to determine DNA binding properties of designed synthetic molecules is described. The design and synthesis of a series of Netropsin dimers linked in tail-to-tail fashion (by oxalic, malonic, succinic, or fumaric acid), or in head-to-tail fashion (by glycine, β-alanine, and γ-aminobutanoic acid (Gaba)) are presented. These Bis(Netropsin)s were appended with the iron-chelating functionality EDTA in order to make use of the technique of DNA affinity cleaving. Bis(Netropsin)-EDTA compounds are analogs of penta(N-methylpyrrolecarboxamide)-EDTA (P5E), which may be considered a head-to-tail Netropsin dimer linked by Nmethylpyrrolecarboxamide. Low- and high-resolution analysis of pBR322 DNA affinity cleaving by the iron complexes of these molecules indicated that small changes in the length and nature of the linker had significant effects on DNA binding/cleaving efficiency (a measure of DNA binding affinity). DNA binding/cleaving efficiency was found to decrease with changes in the linker in the order β-alanine > succinamide > fumaramide > N-methylpyrrolecarboxamide > malonamide >glycine, γ-aminobutanamide > oxalamide. In general, the Bis(Netropsin)-EDTA:Fe compounds retained the specificity for seven contiguous A:T base pairs characteristic of P5E:Fe binding. However, Bis(Netropsin)Oxalamide- EDTA:Fe exhibited decreased specificity for A:T base pairs, and Bis(Netropsin)-Gaba-EDT A:Fe exhibited some DNA binding sites of less than seven base pairs. Bis(Netropsin)s linked with diacids have C₂-symmmetrical DNA binding subunits and exhibited little DNA binding orientation preference. Bis(Netropsin)s linked with amino acids lack C₂-symmetrical DNA binding subunits and exhibited higher orientation preferences. A model for the high DNA binding orientation preferences observed with head-to-tail DNA minor groove binding molecules is presented.

Chapter Two describes the design, synthesis, and DNA binding properties of a series of chiral molecules: Bis(Netropsin)-EDTA compounds with linkers derived from (R,R)-, (S,S)-, and (RS,SR)-tartaric acids, (R,R)-, (S,S)-, and (RS,SR)-tartaric acid acetonides, (R)- and (S)-malic acids, N ,N-dimethylaminoaspartic acid, and (R)- and (S)-alanine, as well as three constitutional isomers in which an N-methylpyrrolecarboxamide (P1) subunit and a tri(N-methylpyrrolecarboxamide)-EDTA (P3-EDTA) subunit were linked by succinic acid, (R ,R)-, and (S ,S)-tartaric acids. DNA binding/cleaving efficiencies among this series of molecules and the Bis(Netropsin)s described in Chapter One were found to decrease with changes in the linker in the order β-alanine > succinamide > P1-succinamide-P3 > fumaramide > (S)-malicamide > N-methylpyrrolecarboxamide > (R)-malicamide > malonamide > N ,N-dimethylaminoaspanamide > glycine = Gaba = (S,S)-tartaramide = P1-(S,S)-tanaramide-P3 > oxalamide > (RS,SR)-tartaramide = P1- (R,R)-tanaramide-P3 > (R,R)-tartaramide (no sequence-specific DNA binding was detected for Bis(Netropsin)s linked by (R)- or (S)-alanine or by tartaric acid acetonides). The chiral molecules retained DNA binding specificity for seven contiguous A:T base pairs. From the DNA affinity cleaving data it could be determined that: 1) Addition of one or two substituents to the linker of Bis(Netropsin)-Succinamide resulted in stepwise decreases in DNA binding affinity; 2) molecules with single hydroxyl substituents bound DNA more strongly than molecules with single dimethylamino substituents; 3) hydroxyl-substituted molecules of (S) configuration bound more strongly to DNA than molecules of (R) configuration. This stereochemical regulation of DNA binding is proposed to arise from the inherent right-handed twist of (S)-enantiomeric Bis(Netropsin)s versus the inherent lefthanded twist of (R)-enantiomeric Bis(Netropsin)s, which makes the (S)-enantiomers more complementary to the right-handed twist of B form DNA.

Chapter Three describes the design and synthesis of molecules for the study of metalloregulated DNA binding phenomena. Among a series of Bis(Netropsin)-EDTA compounds linked by homologous tethers bearing four, five, or six oxygen atoms, the Bis(Netropsin) linked by a pentaether tether exhibited strongly enhanced DNA binding/cleaving in the presence of strontium or barium cations. The observed metallospecificity was consistent with the known affinities of metal cations for the cyclic hexaether 18-crown-6 in water. High-resolution DNA affinity cleaving analysis indicated that DNA binding by this molecule in the presence of strontium or barium was not only stronger but of different sequence-specificity than the (weak) binding observed in the absence of metal cations. The metalloregulated binding sites were consistent with A:T binding by the Netropsin subunits and G:C binding by a strontium or barium:pentaether complex. A model for the observed positive metalloregulation and novel sequence-specificity is presented. The effects of 44 different cations on DNA affinity cleaving by P5E:Fe were examined. A series of Bis(Netropsin)-EDTA compounds linked by tethers bearing two, three, four, or five amino groups was also synthesized. These molecules exhibited strong and specific binding to A:T rich regions of DNA. It was found that the iron complexes of these molecules bound and cleaved DNA most efficiently at pH 6.0-6.5, while P5E:Fe bound and cleaved most efficiently at pH 7.5-8.0. Incubating the Bis(Netropsin) Polyamine-EDTA:Fe molecules with K₂PdCl₄ abolished their DNA binding/cleaving activity. It is proposed that the observed negative metalloregulation arises from kinetically inert Bis(Netropsin) Polyamine:Pd(II) complexes or aggregates, which are sterically unsuitable for DNA complexation. Finally, attempts to produce a synthetic metalloregulated DNA binding protein are described. For this study, five derivatives of a synthetic 52 amino acid residue DNA binding/cleaving protein were produced. The synthetic mutant proteins carried a novel pentaether ionophoric amino acid residue at different positions within the primary sequence. The proteins did not exhibit significant DNA binding/cleaving activity, but they served to illustrate the potential for introducing novel amino acid residues within DNA binding protein sequences, and for the development of the tricyclohexyl ester of EDTA as a superior reagent for the introduction of EDT A into synthetic proteins.

Chapter Four describes the discovery and characterization of a new DNA binding/cleaving agent, [SalenMn(III)]OAc. This metal complex produces single- and double-strand cleavage of DNA, with specificity for A:T rich regions, in the presence of oxygen atom donors such as iodosyl benzene, hydrogen peroxide, or peracids. Maximal cleavage by [SalenMn(III)]OAc was produced at pH 6-7. A comparison of DNA singleand double-strand cleavage by [SalenMn(III)]⁺ and other small molecules (Methidiumpropyl-EDTA:Fe, Distamycin-EDTA:Fe, Neocarzinostatin, Bleomycin:Fe) is presented. It was found that DNA cleavage by [SalenMn(III)]⁺ did not require the presence of dioxygen, and that base treatment of DNA subsequent to cleavage by [SalenMn(III)]⁺ afforded greater cleavage and alterations in the cleavage patterns. Analysis of DNA products formed upon DNA cleavage by [SalenMn(III)] indicated that cleavage was due to oxidation of the sugar-phosphate backbone of DNA. Several mechanisms consistent with the observed products and reaction requirements are discussed.

Chapter Five describes progress on some additional studies. In one study, the DNA binding/cleaving specificities of Distamycin-EDTA derivatives bearing pyrrole N-isopropyl substituents were found to be the same as those of derivatives bearing pyrrole N-methyl substituents. In a second study, the design of and synthetic progress towards a series of nucleopeptide activators of transcription are presented. Five synthetic plasmids designed to test for activation of in vitro run-off transcription by DNA triple helix-forming oligonucleotides or nucleopeptides are described.

Chapter Six contains the experimental documentation of the thesis work.

A multifunctional iridium carbazolyl orange phosphor for high performance two-element WOLED exploiting exciton-managed fluorescence/phosphorescence

By attaching a bulky, inductively electron-with drawing trifluoromethyl (CF3) group on the pyridyl ring of the rigid 2-[3(N-phenylcarbazolyl)]pyridine cyclometalated ligand, we successfully synthesized a new heteroleptic orange-emitting phosphorescent iridium(III) complex [Ir(L-1)(2)(acac)] 1 (HL1=5-trifluoromethyl-2-[3-(N-phenylcarbazolyl)]pyridine, Hacac = acetylacetone) in good yield.

Multifunctional metallophosphors with anti-triplet–triplet annihilation properties for solution-processable electroluminescent devices

With the goal to provide organometallic triplet emitters with good hole-injection/hole-transporting properties, highly amorphous character for simple solution-processed organic light-emitting diodes, and negligible triplet-triplet (T-T) annihilation, a series of new phosphorescent cyclometalated Ir-III and Pt-II complexes with triphenylamine-anchored fluorenylpyridine dendritic ligands were synthesized and characterized. The photophysical, thermal, electrochemical and electroluminescent properties of these molecules are reported.

Bis(2,2 '-bipyridine)(5,6-epoxy-5,6-dihydro-[1,10] phenanthroline)ruthenium: Synthesis and electrochemical and electrochemiluminescence characterization

In this work, an electrochemiluminescence (ECL) reagent bis(2,2'-bipyridine)(5,6-epoxy-5,6-dihydro-[1,10]phenanthroline)ruthenium complex (Ru-1) was synthesized, and its electrochemical and ECL properties were characterized. The synthesis of Ru-1 was confirmed by IR spectra, element analysis, and H-1 NMR spectra. For further study, its UV-vis absorption and fluorescence emission spectra were investigated. Ru-1 also exhibited quasi-reversible Ru-II/Ru-III redox waves in acetonitrile solution. The aqueous ECL behaviors of Ru-1 were also studied in the absence and in the presence of tripropylamine.

Novel Re(I) dendrimers: synthesis, characterization and theoretical studies

Four novel diimine rhenium(I) carbonyl complexes with the formula [Re(CO)(3)(L) Br], where L = 2-(4-(9H-carbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (P1), 2-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl) phenyl)-1H-imidazo-[4,5-f][1,10] phenanthroline (P2), 2-(4-(6-(9H-carbazol-9-yl)-9H-3,9'-bicarbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (D1), and 2-(4-(3', 6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-9H-3,9'-bicarbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (D2), have been successfully synthesized and fully characterized by (HNMR)-H-1, IR, and UV-Vis, etc. The luminescence quantum yields (LQYs) of the parent Re(I) complexes P1 and P2 are 0.13 and 0.16, respectively, which are much higher than the previously reported Re(I) dendrimers. The HOMOs and the LUMOs of P1 and P2 are calculated to be mainly composed of [d(Re) + pi(CO + Br)] and pi*(L) orbital, respectively.

Synthesis, photophysical properties, and theoretical studies on pyrrole-containing bromo Re(I) complex

Two bromo rhenium(I) carbonyl complexes with the formula of [Re(CO)(3)(L)Br], where L = 1,10-phenanthroline (Phen-Re) and 5-(1H-pyrrol-1-yl)-1,10-phenanthroline (Pyph-Re), were successfully synthesized with the aim to analyze the effect of the pyrrole (Py) moiety on the photophysical properties of Pyph-Re. It was found that the triplet metal-to-ligand charge-transfer d pi (Re) --> pi*(N-N) emission of Phen-Re and Pyph-Re centered at ca. 527 nm with the luminescence quantum yield (LQY) of 0.015 and ca. 578 nm with the LQY of 0.011, respectively. At the same time, the geometrical structures of the ground state and the absorption spectral properties of Phen-Re and Pyph-Re were also calculated with the 6-31G* basis set employed on C, H, N, O, and Br atoms, and LANL2DZ adopted on Re atom.

Selective oxidation of cyclohexane with hydrogen peroxide in the presence of copper pyrophosphate

Liquid phase oxidation of cyclohexane was carried out under mild reaction condition over copper pyrophosphate catalyst in CH3CN using hydrogen peroxide as an oxidant at the temperature between 25 and 80 degrees C. The copper pyrophosphate catalyst was characterized by means of XRD, FT-IR and water contact angle measurement. It was found that appropriate surface hydrophobicity is the key factor for the excellent performance of the catalyst. In addition, a significant improvement for the cyclohexane conversion in the presence of organic acid was observed.

Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis

By incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C-2']picolinate (Flrpic) for blue emission and bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1 H-benzoimidazol-N,C-3) iridium(acetylacetonate) ((fbi)(2)Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5 lm W-1, corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8 cd A(-1). Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density-voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of Flrpic and (fbi)(2)Ir(acac) are, respectively, host-guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses.

Solution-processible multi-component cyclometalated iridium phosphors for high-efficiency orange-emitting OLEDs and their potential use as white light sources

The synthesis and photophysical studies of several multifunctional phosphorescent iridium(III) cyclometalated complexes consisting of the hole-transporting carbazole and fluorene-based 2-phenylpyridine moieties are reported. All of them are isolated as thermally and morphological stable amorphous solids. Extension of the pi-conjugation through incorporation of electron- pushing carbazole units to the fluorene fragment leads to bathochromic shifts in the emission profile, increases the highest oc- cupied molecular orbital levels and improves the charge balance in the resulting complexes because of the propensity of the carbazole unit to facilitate hole transport. These iridium-based triplet emitters give a strong orange phosphorescence light at room temperature with relatively short lifetimes in the solution phase. The photo- and electroluminescence properties of these phosphorescent carbazolylfluorene-functionalized metalated complexes have been studied in terms of the coordinating position of carbazole to the fluorene unit. Organic light-emitting diodes (OLEDs) using these complexes as the solution-processed emissive layers have been fabricated which show very high efficiencies even without the need for the typical hole-transporting layer.I These orange-emitting devices can produce a maximum current efficiency of similar to 30 cd A(-1) corresponding to an external quantum efficiency of similar to 10 % ph/el (photons per electron) and a power efficiency of similar to 14 Im W-1.

Synthesis, crystal structure, and magnetic properties of {[Cu(oxbe)]Mn(H2O)[Cu(oxbe)(DMF)]}(n)center dot nDMF center dot nH(2)O: From dissymmetrical mononuclear entities to a 3D heterometallic supramolecular coordination polymer

Self-assembly of the building block [Cu(oxbe)](-) with Mn(II) led to a novel coordination polymer {[Cu(oxbe)]Mn(H2O)(Cu(oxbe)(DMF)]}(n).nDMF.nH(2)O, where H(3)oxbe is a new dissymmetrical ligand N-benzoato-N'-(2-aminoethyl)-oxamido and DMF = dimethylformamide. The crystal forms in the triclinic system, space group P(1)over-bar, with a = 9.260(4) angstorm, b = 12.833(5) angstrom, c = 15.274(6) angstrom , alpha = 76.18(3)degrees, beta = 82.7(3)degrees, gamma = 82.31(3)degrees, and Z = 2. The crystal structure of the title complex reveals that the two-dimensional bimetallic layers are constructed of (CuMnII)-Mn-II-Cu-II chains linked together by carboxylate bridge and hydrogen bonds help to produce a novel three-dimensional channel-like structure. The magnetic susceptibility measurements (5-300 K) were analyzed by means of the Hamiltonian (H)over-cap = -2J(S)over-cap (Mn)((S)over-cap(Cu1) + (S)over-cap(Cu2)), leading to J = -17.4 cm(-1).

From dissymmetrical mononuclear entities to centrosymmetrical heterotrinuclear complex with 2D supramolecular structure: synthesis, characterization, crystal structure, and magnetic properties

A new centrosymmetrical heterotrinuclear complex, {[Cu(oxbe)](2)Co(H2O)(2)}.2DMF.DMA with 2D supramolecular structure, has been obtained by the self-assembly of a dissymmetrical building block [Cu(oxbe)](-) with bivalent metal ion Co2+, where H(3)oxbe is dissymmetrical ligand N-benzoato-N'-(2-aminoethyl)oxamido, DMF = dimethylformamide, DMA = dimethylamine. Its structure was determined by single crystal X-ray analysis. The molecular structure is centrosymmetrical with the cobalt atom lying on an inversion center. Through the hydrogen bonds and d-pi stacking interactions, a 2D supramolecular structure is formed. This study exemplifies a new method for the assembly of supramolecular structure using a dissymmetrical brick. Magnetic susceptibility measurements (5-300 K) indicate that the central cobalt and terminal copper metal ions are antiferromagnetically coupled with J = -23.1 cm(-1).

Ethylene polymerization by self-immobilized neutral nickel catalysts bearing allyl groups

[Ni(Ph)(PPh3)(N,O)] complexes containing phenyliminophenolato ligands (N,O) (1: N,O = A; 2: N,O = B; 3: N,O = Q 4: N,O = D; 5: N,O = E) have been synthesized and characterized. The molecular structure of 4 was determined by single-crystal X-ray analysis. Complexes 2-5 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization without the use of co-catalysts. The high ethylene polymerization activities of ca. 10(5) g.PE mol(-1) Ni.h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene could be accomplished by changing the ligand structures and reaction conditions. The self-immobilization of catalysts brings about a dramatic increase in the catalytic activities of ethylene polymerization.