Synthesis and spectroscopic characterization of a new family of Ni(4) spin clusters

A new family of tetranuclear Ni complexes [Ni(4)(ROH)(4)L(4)] (H(2)L = salicylidene-2-ethanolamine; R = Me (1) or Et (2)) has been synthesized and studied. Complexes 1 and 2 possess a [Ni(4)O(4)] core comprising a distorted cubane arrangement. Magnetic susceptibility and inelastic neutron scattering studies indicate a combination of ferromagnetic and antiferromagnetic pairwise exchange interactions between the four Ni(II) centers, resulting in an S = 4 spin ground state. Magnetization measurements reveal an easy-axis-type magnetic anisotropy with D approximately -0.93 cm(-)(1) for both complexes. Despite the large magnetic anisotropy, no slow relaxation of the magnetization is observed down to 40 mK. To determine the origin of the low-temperature magnetic behavior, the magnetic anisotropy of complex 1 was probed in detail using inelastic neutron scattering and frequency domain magnetic resonance spectroscopy. The spectroscopic studies confirm the easy-axis-type anisotropy and indicate strong transverse interactions. These lead to rapid quantum tunneling of the magnetization, explaining the unexpected absence of slow magnetization relaxation for complex 1.     

Synthesis and characterization of new thiadiazole derivatives bearing a pyrazole moiety

A series of thidiazole derivatives (4, 7) from pyrazole-3-carboxylic acid chloride (2) and pyrazole-3,4-dicarboxylic acid chloride derivatives (6) were synthesized and characterized. The structures of the new compounds were confirmed byelemental analysis, NMR (¹H and ¹³C) and IR spectra. The molecular and crystal structure of 4-benzoyl-N-[5-(methylthio)-1,3,4-thiadiazol-2-yl]-1,5-di-phenyl-1H-pyrazole-3-carboxamide(4d)was determined by single crystal X-ray diffraction method.     

Synthesis and characterization of a new organo-soluble metal-free and metallophthalocyanines bearing flexible moieties

This paper describes a new symmetric metal-free phthalocyanine and its transition metal complexes which were prepared by a condensation of 1,2-dihydroacenaphthylen-1-ol 1 and 4-nitro phthalonitrile 2 with Co(II), Ni(II), Cu(II), and Zn(II) salts in 2-(dimethylamino)ethanol, respectively. The novel phthalocyanines bearing oxygen donor atoms on peripheral position have been characterized by IR, UV-Vis, ¹H NMR, ¹³C NMR, Mass spectra and elemental analysis. The thermal behaviours of 4-8 were investigated by TG/DTA.     

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands: Synthesis, characterization and ethylene polymerization

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands, bis((3,5-di-tert-butyl-C₆H₂-2-O)R₁CN (2-R₂-C₆H₄))ZrCl₂ {R₁ = Me, R₂ = H (2a); R₁ = Et, R₂ = H (2b); R₁ = Ph, R₂ = H (2c); R₁ = 2-Me-Ph, R₂ = H (2d); R₁ = 2-F-Ph, R₂ = H (2e); R₁ = 2-Cl-Ph, R₂ = H (2f); R₁ = 2-Br-Ph, R₂ = H (2g); R₁ = Ph, R₂ = Me (2h); R₁ = Ph, R₂ = F (2i)}, have been prepared, characterized and tested as catalyst precursors for ethylene polymerization. Crystal structure analysis reveals that complex 2c has a six coordinate center in a distorted octahedral geometry with trans-O, cis-N, cis-Cl arrangement which possesses approximate C₂ symmetry. When activated with methylaluminoxane (MAO), complexes 2a-2i exhibited high ethylene polymerization activities of 10⁶-10⁸ g PE (mol M h)⁻¹. Compared with the bis(phenoxyimine) zirconium analogues bis((3,5-di-tert-butyl-C₆H₂-2-O)CHNC₆H₅)ZrCl₂ (3), the introduction of substituent on the carbon atom of the imine double bond enhanced the catalytic activity and molecular weight of prepared polyethylene. Especially, when the H atom at the carbon atom of the imine double bond was replaced by 2-fluoro-phenyl with strong electronic-withdrawing property, complex 2e displayed the highest catalytic activity, and the polyethylene obtained possessed the highest molecular weight and melt point.     

Synthesis of pyridine-based polyaminocarboxylic ligands bearing a thioalkyl anchor

A bicyclic tetraazatriacetic chelating agent containing a thioalkyl pendant group was prepared. Four synthetic routes have been investigated via a Mitsunobu reaction from 2,4-[bishydroxymethyl]-3-hydroxy-pyridine 1. Deprotection of trityl thioether compound 5c led to ligand 6c in 22% overall yield from the starting 3-hydroxypyridine.     

Synthesis and characterization of new galactosylated-based N2O-donors tridentate ligands

The synthesis and characterization of three novel N₂O-donor ligands containing the group 4-[1-β-d-2,3,4,6-tetra-O-acetyl-galactosyl)]benzaldehyde are presented. The insertion of this group was designed to increase the absorption of the prodrug in tumor cells, and is part of an ongoing work in our group with tridentate ligands to develop potential cobalt(III) prodrugs. The synthetic route described here allowed the isolation of pure ligands with yields ranged 81–89%. Finally, compounds were characterized by IR, NMR and HRMS (ESI⁺).     

Synthesis,characterization, and antimicrobial activity of new benzoylthiourea ligands

In this study, new benzoylthiourea derivatives, (E)-N-[(2-benzamidomethyleneamino)ethylcarbamothioyl]benzamide H₃L′, N-(1-(3-benzoylthioureido)propan-2-ylcarbamothioyl)-benzamide H₄L″, (E)-N-[4-(benzamidomethyleneamino)phenylcarbamothioyl]benzamide H₃L‴, were synthesized. Structures of the compounds were identified by spectroscopic techniques. In addition, all synthesized compounds were evaluated for in vitro antibacterial and antifungal activity. Compound H₃L‴ exhibited antibacterial activity.     

Synthesis and characterization of new organocobaloxime derivatives with asymmetric dioxime ligands

New organocobaloxime derivatives of the types [Co(HL)₂(All)X], [CoL₂(All)XB₂F₄] and [CoL₂(All)X(Cu(phen))₂](ClO₄)₂ [H₂L¹ = 4-(4-chlorophenylamino)biphenylglyoxime and H₂L² = 4-(naphthyl-1-amino)biphenylglyoxime; phen = 1,10-phenanthroline; All = Allyl; X = H₂O, py (pyridine), APy (acetylpyridine)] were synthesized and characterized by elemental analysis, molar conductance, FT-IR, ¹H NMR and magnetic susceptibility measurements. Trinuclear complexes {CoL₂(All)X[Cu(phen)]₂}(ClO₄)₂ have planar N-donor heterocyclic base [1,10-phenanthroline (phen)]. The IR spectra indicated that the complexes coordinate through the N atom of the oxime group of each ligand. The magnetic susceptibilities of the complexes indicated that they are diamagnetic (low-spin d ⁶ octahedral) except trinuclear complex which show a subnormal magnetic moment.     

Synthesis and structural characterization of ruthenium(II) complexes bearing phosphine-pyrazolyl based tripod ligands

Phosphine-pyrazolyl based tripod ligands ROCH₂C(CH₂Pz)₂(CH₂PPh₂) (R = H, Me, allyl; Pz = pyrazol-1-yl) were efficiently synthesized and characterized. Reactions of these ligands with [Ru(η⁶-p-cymene)Cl₂]₂ afforded complexes of the type [Ru(η⁶-p-cymene)Cl₂](L) (6-8) in which the ligands exhibit κ¹-P-coordination to the metal center. Complex [Ru(η⁶-p-cymene)Cl₂{Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}] (6) underwent chloride-dissociation in CH₂Cl₂/MeCN to give complex [RuCl(η⁶-p-cymene){κ²(P,N)-Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}][Cl] (9). Complexes 6-9 demonstrated poor to moderate catalytic activity in the transfer hydrogenation of acetophenone. All these complexes were fully characterized by analytical and spectroscopic methods and their molecular structures were determined by X-ray crystallographic study.     

Synthesis of an end-capped sexithiophene bearing fused tetrathiafulvalene (TTF) units

[structure: see text] We report the synthesis of a novel end-capped sexithiophene derivative bearing two pendent, fused tetrathiafulvalene (TTF) units linked to the main chain through 1,4-dithiin heterocycles. Cyclic voltammetry and absorption spectroscopy are used to investigate the electronic properties of this hybrid electroactive material. The oligomer has a band gap of 2.1 eV, and the material can be oxidized through the sexithiophene and TTF units simultaneously.     

Synthesis and characterization of hexacoordinate cobalt(III) complexes bearing three C,O-bidentate ligands

Hexacoordinated Co(III) complexes bearing three C,O-bidentate ligands (9a and 9b) were prepared from 1-bromo-2-(p-tolyloxymethyl)benzene (8a) and 1-bromo-2,6-bis(p-tolyloxymethyl)benzene (8b), respectively. Both complexes were stable in air at room temperature. X-ray analyses revealed that the structures of both complexes were essentially the same. According to variable temperature ¹H NMR study, it was found that the two oxygen ligands on the same aromatic ring of 9b interchanged with each other.     

Synthesis and characterization of a new soluble metal-free and metallophthalocyanines bearing biphenyl-4-yl methoxy groups

The synthesis and characterization of peripherally tetra-biphenyl-4-yl-methoxy substituted metal-free (4), Ni(II) (5), Cu(II) (6), Zn(II) (7), Co(II) (8) and Pb(II) (9) phthalocyanine derivatives are reported. These new phthalocyanine derivatives show the enhanced solubility in organic solvents and they have been characterized by a combination of IR, ¹H NMR, ¹³C NMR, UV–vis, mass spectral data, elemental analysis and thermal analysis methods (TG/DTA). The photophysical (fluorescence quantum yield and lifetime) and photochemical (singlet oxygen generation and photodegradation quantum yield) properties of tetra-biphenyl-4-yl-methoxy substituted zinc (II) phthalocyanine derivative (7) are also investigated. The fluorescence of this phthalocyanine derivative (7) is effectively quenched by addition of 1,4-benzoquinone (BQ).     

Synthesis of a family of heterocyclic ligands derived from bisphenols: new flexible bridging ligands for use in metallosupramolecular chemistry

The preparations are described of 35 new bridging ligands from five bisphenols through coupling each with seven different heterocyclic units. X-ray crystal structures of five representative examples revealed different conformations in the solid state with the terminal nitrogen donors being separated by distances ranging from 8 to 23 Å.     

Synthesis of soluble bis-terpyridine ligands bearing ethynylene-phenylene spacers

Soluble and rigid terpyridine-based ditopic ligands bearing one to five phenylene/ethynylene modules have been synthesized by way of a stepwise procedure. Each module is attached to the terpyridine unit via an ethynylene fragment and functionalized at the 4-position with an additional ethynylene connector and in the 2,5-positions with two flexible dodecyloxy chains. The synthetic protocol is based on sequential Pd(0)-catalyzed cross-coupling reactions between a terpyridine subunit grafted with the necessary diethynyl/phenyl or ethynylphenyl/bromide appendage. For ditopic ligands displaying an even number of phenyl/ethynylene modules, the final step involves a single cross-coupling reaction between 4'-ethynylene-2,2':6',6' '-terpyridine and the appropriate bromo derivative. In the case of the ligands having an odd number of phenylene/ethynylene fragments, a double cross-coupling reaction between an extended dibromopolyphenylene intermediate and 4'-ethynylene-2,2':6',6' '-terpyridine or 1-(4'-ethynylene-2,2':6',2' '-terpyridine)-4-ethynylene-2,5-didodecyloxy-benzene is required. For ligands I-V, optimal preparative conditions were found with [Pd(0)(PPh(3))(4)] (6 mol %) in n-propylamine at 70 degrees C. Oxidative dimerization of the 1-(4'-ethynylene-2,2':6',2' '-terpyridine)-4-ethynylene-2,5-didodecyloxybenzene derivative in the presence of cupric salts and oxygen gives the corresponding homoditopic ligand II(2)() bearing a central diphenyldiacetylene spacer. Spectroscopic data for the new oligomers are discussed in terms of the extent of pi-electron conjugation. Upon increasing the number of phenylene/ethynylene modules, there is a progressive lowering in energy of absorption and fluorescence transitions.     

Synthesis and characterization of a new ethynyl-bridged C60 derivative bearing a diketopyrrolopyrrole moiety

A new soluble C₆₀ derivative bearing a diketopyrrolopyrrole (DPP) moiety has been synthesized by ethynylation reaction. Characterization by UV-visible spectrophotometry and cyclic voltammetry has been performed in order to study the influence of the DPP moiety on electronic and optical properties of the fullerene. Moreover, DFT calculations have been conducted on the derivative and its precursor in order to correlate the orbital geometry with experimental data.     

Synthesis,structure and catalytic properties of new half-titanocene complexes bearing substituted cyclopentadienyl and aryloxide ligands

New cyclopentadienyltitanium aryloxide complexes, 1-phenyl-2,3,4,5-Me4CpTi(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂ (1) and [4,4′-biphenyl-(2,3,4,5-Me₄Cp)₂][Ti(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂]₂ (2), have been prepared by treatment of cyclopentadienyltitanium trichloride complexes [PhMe₄CpTiCl₃ and 4,4′-biphenyl-(Me₄CpTiCl₃)₂] with 1 or 2 equiv of lithium salt of 2,6-di-isopropyl-4-butylphenol. Complexes 1 and 2 have been characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. The molecular structure of 1 has been determined by single-crystal X-ray diffraction. Upon activation with ⁱBu₃Al and Ph₃CB(C₆F₅)₄, 1 and 2 both exhibit good catalytic activity for ethylene polymerization, producing polyethylene with moderate molecular weight and melting point.     

Synthesis and characterization of functionalized ferrocenylsilanes bearing a bulky substituent

Several types of overcrowded ferrocenylsilanes, Tbt(Fc)SiX₂(Tbt=2, 4, 6-tris[bis(trimethylsilyl)methyl]phenyl, Fc=ferrocenyl, X = H, OH, and Br) were synthesized and characterized. In addition, DFT calculations for ferrocenylsilanediol systems indicated the existence of the intramolecular hydrogen bonding between the Fe atom and H–O moiety in Tbt(Fc)Si(OH)₂. Dedicated to Professor Mitsuo Kira on the occasion of his 2005 Wacker Awardy     

Synthesis and characterization of new organotin(IV) complexes with polyfunctional ligands

New mono-, di- and tri-organotin(IV) derivatives containing the neutral bis(2-pyridylthio)methane ligand, [(pyS)₂CH₂] and tris(2-pyridylthio)methane ligand, [(pyS)₃CH] have been synthesized from reaction with SnR_nCl_4−n (R = Me, ⁿBu, Ph and Cy, n = 1-3) acceptors. Mono-nuclear adducts of the type {[(pyS)₂CH₂]R_nSnCl_4−n} and {[(pyS)₃CH]R_nSnCl_4−n} have been obtained and characterized by elemental analyses, FT-IR, ESI-MS, multinuclear (¹H and ¹¹⁹Sn) NMR spectral data. The ¹H and ¹¹⁹Sn NMR and ESI-MS data suggest for the triorganotin(IV) derivatives a complete dissociation of the compounds in solution. The mono- and di-organotin(IV) derivatives show a greater stability in solution, and their spectroscopic data are in accordance with the existence of six-coordinated RSnCl₃N₂ or R₂SnCl₂N₂ species.     

Synthesis and structural characterization of new multiferrocenyl diyne ligands and their cobalt carbonyl complexes

New multiferrocenyl diyne ligands FcC(CH₃)₂Fc′–C≡C–C≡C–Fc [L ₁ ; Fc?=?C₅H₅FeC₅H₄; Fc′?=?C₅H₅Fe(1,3-disubstituted)C₅H₃], FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc (L ₂ ) and their complexes [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc][Co₂(CO)₆] _n [n?=?1, (1); n?=?2, (2)], [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc][Co₂(CO)₆] _n [n?=?1, (3); n?=?2, (4)] have been synthesized by the coupling reaction of terminal ferrocenylacetylene and the reaction of ligands L₁ and L₂ with Co₂(CO)₈. The composition and molecular structure of the ligands L₁ , L₂ and their cobalt complexes were characterized by element analysis, IR, ¹H(¹³C)NMR and MS. The electrochemical properties of compounds L₁ , L₂ , 1, 2, 3, 4 were studied by cyclic voltammetry(CV). The results of the electrochemical research reveal that all three ferrocenyl groups in L₁ become redox active centers, but there are only two (not four) ferrocenyl redox active centers in L₂ .     

Synthesis and characterization of a new family of square-planar nickel(II) carbonyl derivatives

The reaction of [NBu(4)](2)[Ni(C(6)F(5))(4)] (1) with solutions of dry HCl(g) in Et(2)O results in the protonolysis of two Nibond;C(6)F(5) bonds giving [NBu(4)](2)[[Ni(C(6)F(5))(2)](2)(mu-Cl)(2)] (2 a) together with the stoichiometrically required amount of C(6)F(5)H. Compound 2 a reacts with AgClO(4) in THF to give cis-[Ni(C(6)F(5))(2)(thf)(2)] (3). Reacting 3 with phosphonium halides, [PPh(3)Me]X, gives dinuclear compounds [PPh(3)Me](2)[[Ni(C(6)F(5))(2)](2)(mu-X)(2)] (X=Br (2 b) or I (2 c)). Solutions of compounds 2 in CH(2)Cl(2) at 0 degrees C do not react with excess CNtBu, but do react with CO (1 atm) to split the bridges and form a series of terminal Ni(II) carbonyl derivatives with general formula Qcis-[Ni(C(6)F(5))(2)X(CO)] (4). The nu(CO) stretching frequencies of 4 in CH(2)Cl(2) solution decrease in the order Cl (2090 cm(-1))>Br (2084 cm(-1))>I (2073 cm(-1)). Compounds 4 revert to the parent dinuclear species 2 on increasing the temperature or under reduced CO pressure. [NBu(4)]cis-[Ni(C(6)F(5))(2)Cl(CO)] (4 a) reacts with AgC(6)F(5) to give [NBu(4)][Ni(C(6)F(5))(3)(CO)] (5, nu(CO)(CH(2)Cl(2))=2070 cm(-1)). Compound 5 is also quantitatively formed ((19)F NMR spectroscopy) by 1:1 reaction of 1 with HCl(Et(2)O) in CO atmosphere. Complex 3 reacts with CO at -78 degrees C to give cis-[Ni(C(6)F(5))(2)(CO)(2)] (6, nu(CO)(CH(2)Cl(2))=2156, 2130 cm(-1)), which easily decomposes by reductive elimination of C(6)F(5)bond;C(6)F(5). Compounds 3 and 6 both react with CNtBu to give trans-[Ni(C(6)F(5))(2)(CNtBu)(2)] (7). The solid-state structures of compounds 3, 4 b, 6, and 7 have been established by X-ray diffraction methods. Complexes 4-6 are rare examples of square-planar Ni(II) carbonyl derivatives.