- A comparative study of magnetization dynamics in dinuclear dysprosium complexes featuring bridging chloride or trifluoromethanesulfonate ligands
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We utilized a rigid ligand platform PyCp22- (PyCp22- = [2,6-(CH2C5H3)2C5H3N]2-) to isolate dinuclear Dy3+ complexes [(PyCp2)Dy-(μ-O2SOCF3)]2 (1) and [(PyCp2)Dy-(μ-Cl)]2 (3) as well as the mononuclear complex (PyCp2)Dy(OSO2CF3)(thf) (2). Compounds 1 and 2 are the first examples of organometallic Dy3+ complexes featuring triflate binding. The isolation of compounds 1 and 3 allows us to comparatively evaluate the effects of the bridging anions on the magnetization dynamics of the dinuclear systems. Our investigations show that although the exchange coupling interactions differ for 1 and 3, the dynamic magnetic properties are dominated by relaxation via the first excited state Kramers doublet of the individual Dy sites. Compounds 1 and 3 exhibit barriers to magnetization reversal (Ueff = 49 cm-1) that can be favorably compared to those of the previously reported examples of [Cp2Dy(μ-Cl)]2 (Ueff = 26 cm-1) and [Cp2Dy(thf)(μ-Cl)]2 (Ueff = 34 cm-1).
- Burns, Corey P.,Wilkins, Branford O.,Dickie, Courtney M.,Latendresse, Trevor P.,Vernier, Larry,Vignesh, Kuduva R.,Bhuvanesh, Nattamai S.,Nippe, Michael
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- Synthesis, spectroscopy, and crystal structure of a new stable biscyclopentadienyl uranium(IV) dichloride containing two C5H4-rings interlinked by a metal-coordinated 2,6-bis(methylene)pyridyl unit
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Reaction of the new disodium salt: Na2IVCl2-derivative (Cp = η5-C5H5): μ-(η5-C5H4)2UIVCl2 (1).According to a single-crystal X-ray study, 1 involves a notably strong U-N bond (U-Nav: 2.62(1) Angstroem) along with two nonequivalent Cl ligands (U-Cl: 2.615(3) and 2.636(3) Angstroem).The low-temperature 1H NMR spectrum of the paramagnetic complex is in full accord with the solid state structure 1.Up to room temperature, the dissolved molecules of 1 show no fluxionality on the NMR time scale, although the two CH2 proton resonances appear to undergo coalescence.
- Paolucci, Gino,Fischer, R. Dieter,Benetollo, Franco,Seraglia, Roberta,Bombieri, Gabriella
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- Cobalt complexes of an OSNSO-tetrapodal pentadentate ligand: Synthesis, structures and reactivity
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The novel pentadentate tetrapodal proligand 2,6-bis[(2-hydroxyphenyl)sulfanylmethyl]pyridine (1·H2) and its cobalt(II) complex [Co(1)] (2) were synthesized and characterized by several analytical (EA, ESI-MS) and spectroscopic methods (NMR or EPR, FT-IR), including X-ray crystallography for 1·H2. Cyclic voltammetry studies showed that 2 undergoes a reversible metal-based oxidation (CoII/CoIII). Complex 2 was designed to be applied to organometallic mediated radical polymerization (OMRP), however it exhibited an extremely poor solubility in non-coordinating solvents and several vinyl monomers (styrene, vinyl acetate and tert-butyl acrylate), which hampers its potential as moderator. Complex 2 has a high affinity towards Lewis bases, such as pyridine, leading to the clean formation of the mono-pyridine adduct 2·py, as confirmed by X-ray crystallography. In 2·py, ligand 1 is pentacoordinated to the CoII center, with the two thioether-phenolate (S,O) moieties oriented anti to each other, and the only free coordination site of the octahedron is completed by the additional pyridine, trans to the central pyridine linker of 1. The equilibrium between 2 and 2·py could be studied by 1H NMR. Complex 2 could be cleanly and quantitatively oxidized to its diamagnetic iodo cobalt(III) analog [Co(1)I] (3), by simple reaction with iodine. The latter could then be subjected to a halide abstraction reaction, mediated by K[B(C6F5)], affording the cationic complex [Co(1)][B(C6F5)], 4.
- Thevenin, Lucas,Daran, Jean-Claude,Poli, Rinaldo,Fliedel, Christophe
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- Metal-ion Selectivity by Macrocyclic Ligands. Part 1. The Interaction of NiII and CuII with Pyridinyl-derived N3O2 Macrocycles; The X-Ray Structures of a Free Macrocycle, its Endomacrocyclic Complexes of NiII and CuII and an Exomacrocyclic Nickel(II) Complex
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The interaction of CuII and NiII with two macrocycles L1 and L2, each containing an N3O2 donor set, has been investigated.Spectrophotometric studies in dimethyl sulphoxide reveal the formation of complexes with 1:1 and 1:2 metal:ligand ratios and conductometric studies in the same solvent indicated that all of the complexes were 1:2 electrolytes.Conductometric titration of the 1:1 copper(II) complexes with chloride in each case indicated the formation of a 1:1 electrolyte, presumably through co-ordination of a chloride ion to the central copper of each complex.Similar titration of the nickel(II) complexes gave evidence for the formation of dinuclear species; each of these was postulated to contain a bridging chloride anion.The stability constants of the complexes together with their enthalpies of co-ordination have been determined in 95percent methanol.Extraction and related transport experiments were carried out and under the conditions employed CuII was favoured over NiII.The X-ray crystal structures of the free macrocycle L1, the 1:1 complexes 1(H2O)>2 and 1(I)>I*MeOH, and the 1:2 complex 12(NO3)>NO3*2MeOH have been determined.The metal in 1(H2O)>2 is six-co-ordinate and lies within the folded macrocyclic cavity.The donor set comprises the five macrocyclic donor atoms and a water molecule.Overall, the co-ordination sphere corresponds to a restricted tetragonal rhombic arrangement.The complex 1(I)>*MeOH also has all donors of the macrocycle co-ordinated with an iodide anion occupying the sixth site to yield a distorted-octahedral geometry.The structure of 12(NO3)>NO3*2MeOH shows that the nickel is again six-co-ordinated, to the aliphatic nitrogen atoms from two macrocycles (each showing exo co-ordination) and a bidentate nitrate anion.
- Bailey, Neil A.,Fenton, David E.,Kitchen, Simon J.,Lilley, Terence H.,Williams, Mark G.,et al.
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- Steric Effect on the Nucleophilic Reactivity of Nickel(III) Peroxo Complexes
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A set of nickel(III) peroxo complexes bearing tetraazamacrocyclic ligands, [NiIII(TBDAP)(O2)]+ (TBDAP = N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) and [NiIII(CHDAP)(O2)]+ (CHDAP = N,N′-dicyclohexyl-2,11-diaza[3.3](2,6)pyridinophane), were prepared by reacting [NiII(TBDAP)(NO3)(H2O)]+ and [NiII(CHDAP)(NO3)]+, respectively, with H2O2 in the presence of triethylamine. The mononuclear nickel(III) peroxo complexes were fully characterized by various physicochemical methods, such as UV-vis, electrospray ionization mass spectrometry, resonance Raman, electron paramagnetic resonance, and X-ray analysis. The spectroscopic and structural characterization clearly shows that the NiO2 cores are almost identical where the peroxo ligand is bound in a side-on fashion. However, the different steric properties of the supporting ligands were confirmed by X-ray crystallography, where the CHDAP ligand gives enough space around the Ni core compared to the TBDAP ligand. The nickel(III) peroxo complexes showed reactivity in the oxidation of aldehydes. In the aldehyde deformylation reaction, the nucleophilic reactivity of the nickel(III) peroxo complexes was highly dependent on the steric properties of the macrocyclic ligands, with a reactivity order of [NiIII(TBDAP)(O2)]+ III(CHDAP)(O2)]+. This result provides fundamental insight into the mechanism of the structure (steric)-reactivity relationship of metal peroxo intermediates. (Figure Presented).
- Kim, Jalee,Shin, Bongki,Kim, Hyunjeong,Lee, Junhyung,Kang, Joongoo,Yanagisawa, Sachiko,Ogura, Takashi,Masuda, Hideki,Ozawa, Tomohiro,Cho, Jaeheung
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- Dual-functional gadolinium-based copper(II) probe for selective magnetic resonance imaging and fluorescence sensing
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A unique gadolinium complex, Nap-DO3A-Gd, comprising a naphthylamine luminescent moiety, a di-2-picolylamine (DPA) binding chelator, and a 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) moiety has been designed and synthesized as a dual-functional probe for selective magnetic resonance imaging and fluorescent sensing of copper(II) in living cells. Nap-DO3A-Gd exhibited a turn-on manner of relaxivity changes and a fluorescent quenching toward Cu2+. Through the introduction of naphthalamide into the Gd3+ contrast agent platform to restrict the coordination ability of the DPA chelator and with Gd3+ coordinating to the DPA moiety to turn away the interferences of other metal cations from Cu 2+ detection, the probe featured selective relaxivity changes toward Cu2+ over other metal ions and brought unique Cu2+- specific luminescent responses. The probe was water-soluble with the luminescent detection limit established at 6 ppb and was successfully used for luminescence imaging detection of copper(II) in living cells. The results demonstrated the efficiency and advantage of our approach in the development of a dual-modality image.
- Zhang, Xiaolin,Jing, Xu,Liu, Tao,Han, Gang,Li, Huaqiang,Duan, Chunying
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- A New Oxygen Containing Pyclen-Type Ligand as a Manganese(II) Binder for MRI and 52Mn PET Applications: Equilibrium, Kinetic, Relaxometric, Structural and Radiochemical Studies
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A new pyclen-3,9-diacetate derivative ligand (H23,9-OPC2A) was synthesized possessing an etheric O-atom opposite to the pyridine ring, to improve the dissociation kinetics of its Mn(II) complex (pyclen = 3,6,9,15-tetraazabicyclo(9.3.1)pentadeca
- Csupász, Tibor,Fekete, Anikó,Hollóczki, Oldamur,Kálmán, Ferenc Krisztián,Szücs, Dániel,Szikra, Dezs?,Tóth, éva,Tóth, Imre,Tircsó, Gyula
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supporting information
(2022/01/31)
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- A selective and sensitive near-infrared fluorescent probe for real-time detection of Cu(i)
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The disruption of copper homeostasis (Cu+/Cu2+) may cause neurodegenerative disorders. Thus, the need for understanding the role of Cu+ in physiological and pathological processes prompted the development of improved methods of Cu+ analysis. Herein, a new near-infrared (NIR) fluorescent turn-on probe (NPCu) for the detection of Cu+ was developed based on a Cu+-mediated benzylic ether bond cleavage mechanism. The probe showed high selectivity and sensitivity toward Cu+, and was successfully applied for bioimaging of Cu+ in living cells. This journal is
- Liu, Yiqing,Kang, Ting,He, Qian,Hu, Yuefu,Zuo, Zeping,Cao, Zhihua,Ke, Bowen,Zhang, Weiyi,Qi, Qingrong
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p. 14824 - 14828
(2021/05/17)
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- Fast and Efficient Nickel(II)-catalysed Transfer Hydrogenation of Quinolines with Ammonia Borane
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Herein we report the first Ni(II)-catalysed transfer hydrogenation of quinolines using ammonia borane (AB) as hydrogen (H2) source. An in situ generated Ni(II)-bis(pyrazolyl)pyridine pre-catalyst could hydrogenate quinoline and its derivatives in excellent yields of up to 90% at 25 °C in 30 minutes. Spectroscopic studies revealed that a Ni(II)-hydride is responsible for the transfer hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline via a 1,4-dihydroquinoline intermediate. (Figure presented.).
- Vermaak, Vincent,Vosloo, Hermanus C. M.,Swarts, Andrew J.
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supporting information
p. 5788 - 5793
(2020/12/01)
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- Novel cuprous ion near-infrared probe, and preparation method and application thereof
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The invention discloses a near-infrared fluorescent probe which is provided with a novel receptor structure (N3O), and has a specific response to cuprous ions in an aqueous solution system, and the problems of poor selectivity and low sensitivity of the c
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Paragraph 0053; 0054
(2019/10/17)
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- VANADIUM INSULIN-MIMETICS, METHODS OF PREPARATION, AND METHODS FOR TREATMENT OF DIABETES
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Disclosed are vanadyl complexes of Formula 1, Formula 2, and Formula 3, wherein Ri, R2, and R are defined as in the description. The pharmaceutical compositions containing these complexes and uses of the complexes for treatment of Diabetes Mellitus, such as Diabetes Mellitus Type 2, are also disclosed.
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Paragraph 95; 96; 97
(2019/01/05)
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- PROCESSES FOR MAKING TRIAZOLO[4,5D] PYRAMIDINE DERIVATIVES AND INTERMEDIATES THEREOF
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Provided herein are, inter alia, methods for making triazolo[4,5]pyramidine derivatives and intermediates thereof that are useful for treating diseases.
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Paragraph 0323
(2018/10/25)
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- Photocatalytic CO2 Reduction by Trigonal-Bipyramidal Cobalt(II) Polypyridyl Complexes: The Nature of Cobalt(I) and Cobalt(0) Complexes upon Their Reactions with CO2, CO, or Proton
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The cobalt complexes CoIIL1(PF6)2 (1; L1 = 2,6-bis[2-(2,2′-bipyridin-6′-yl)ethyl]pyridine) and CoIIL2(PF6)2 (2; L2 = 2,6-bis[2-(4-methoxy-2,2′-bipyridin-6′-yl)ethyl]pyridine) were synthesized and used for photocatalytic CO2 reduction in acetonitrile. X-ray structures of complexes 1 and 2 reveal distorted trigonal-bipyramidal geometries with all nitrogen atoms of the ligand coordinated to the Co(II) center, in contrast to the common six-coordinate cobalt complexes with pentadentate polypyridine ligands, where a monodentate solvent completes the coordination sphere. Under electrochemical conditions, the catalytic current for CO2 reduction was observed near the Co(I/0) redox couple for both complexes 1 and 2 at E1/2 = -1.77 and -1.85 V versus Ag/AgNO3 (or -1.86 and -1.94 V vs Fc+/0), respectively. Under photochemical conditions with 2 as the catalyst, [Ru(bpy)3]2+ as a photosensitizer, tri-p-tolylamine (TTA) as a reversible quencher, and triethylamine (TEA) as a sacrificial electron donor, CO and H2 were produced under visible-light irradiation, despite the endergonic reduction of Co(I) to Co(0) by the photogenerated [Ru(bpy)3]+. However, bulk electrolysis in a wet CH3CN solution resulted in the generation of formate as the major product, indicating the facile production of Co(0) and [Co-H]n+ (n = 1 and 0) under electrochemical conditions. The one-electron-reduced complex 2 reacts with CO to produce [Co0L2(CO)] with νCO = 1894 cm-1 together with [CoIIL2]2+ through a disproportionation reaction in acetonitrile, based on the spectroscopic and electrochemical data. Electrochemistry and time-resolved UV-vis spectroscopy indicate a slow CO binding rate with the [CoIL2]+ species, consistent with density functional theory calculations with CoL1 complexes, which predict a large structural change from trigonal-bipyramidal to distorted tetragonal geometry. The reduction of CO2 is much slower than the photochemical formation of [Ru(bpy)3]+ because of the large structural changes, spin flipping in the cobalt catalytic intermediates, and an uphill reaction for the reduction to Co(0) by the photoproduced [Ru(bpy)3]+.
- Shimoda, Tomoe,Morishima, Takeshi,Kodama, Koichi,Hirose, Takuji,Polyansky, Dmitry E.,Manbeck, Gerald F.,Muckerman, James T.,Fujita, Etsuko
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supporting information
p. 5486 - 5498
(2018/05/17)
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- Rigid Mn(II) chelate as efficient MRI contrast agent for vascular imaging
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The aza-semi-crown pentadentate ligand rigidified by pyridine and piperidine rings was designed and synthesized. It can react with Mn(II) in water to form complex with improved longitudinal relaxivity, leading to efficient signal intensity enhancement of vascular vessels under a clinical magnetic resonance imaging scanner.
- Su, Hongying,Wu, Changqiang,Zhu, Jiang,Miao, Tianxin,Wang, Dan,Xia, Chunchao,Zhao, Xuna,Gong, Qiyong,Song, Bin,Ai, Hua
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supporting information
p. 14480 - 14483
(2013/01/16)
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- Stereospecific polymerization of 1,3-butadiene catalyzed by cobalt complexes bearing N-containing diphosphine PNP ligands
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A series of cobalt complexes bearing N-containing diphosphine PNP ligands has been synthesized and characterized. The nature of the ligand structure affects the binding of the ligand to the cobalt center and determines the coordination geometry of the cobalt complexes. All the complexes have been employed to catalyze the polymerization of 1,3-butadiene, in combination with methylaluminoxane (MAO) or ethylaluminum sesquichloride (EASC) as the cocatalyst. Both the nature of the ligand and the type of cocatalyst had a remarkable influence on the polymerization activity, microstructure and molecular weight of the resulting polymers. The [Co]/MAO catalytic systems resulted in relatively lower conversions of butadiene and cis-1,4 contents in the polymers than the corresponding [Co]/EASC catalytic systems. Upon activation with EASC, the polymerization behaviors of the catalytic systems were also affected by the reaction parameters.
- Chen, Lin,Ai, Pengfei,Gu, Jianming,Jie, Suyun,Li, Bo-Geng
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- Design and synthesis of Sn-porphyrin based molecular gates
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The design, synthesis, and structural characterization, both in solution by 1H NMR and in the solid state by X-ray diffraction on single crystals, of a series of molecular gates based on Sn-porphyrin derivatives are presented. The molecular systemis based on a porphyrin core bearing at the meso positions either phenyl or pyridyl groups as a stator, octahedral Sn(IV) cation located at the center of the porphyrin as a hinge, and different handles connected to the porphyrin through Sn-O axial bonds. The stability of the complexes in the presence of different acids is also reported.
- Guenet, Aurelie,Ernest Graf,Nathalie Kyritsakas,Hosseini, Mir Wais
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scheme or table
p. 1872 - 1883
(2010/05/01)
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- A molecular gate based on a porphyrin and a silver lock
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A Sn(IV) metallaporphyrin bearing a 4-pyridyl group on one meso position and a handle equipped also with a pyridyl unit functions in solution as a molecular gate in the presence of silver cation: the complexation-decomplexation of Ag(i) corresponds to the
- Guenet, Aurelie,Graf, Ernest,Kyritsakas, Nathalie,Allouche, Lionel,Hosseini, Mir Wais
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p. 2935 - 2937
(2008/02/10)
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- Predetermined helical chirality in octahedral complexes with a novel pentadentate C2-symmetrical chiral bis(oxazoline) ligand
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The first example of the pentadentate bis(oxazolines) has been synthesized using a modular approach that readily provides access to this ligand class. This ligand allows the controlled transfer of carbon-centered to octahedral, metal-centered chirality, a
- Seitz, Michael,Kaiser, Anja,Powell, Douglas R.,Borovik, Andrew S.,Reiser, Oliver
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p. 737 - 741
(2007/10/03)
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- Drugs for diabetes
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Use for the diabetes treatment of compounds or salts thereof, having the following general formula (I): A-(B)b0—(C)c0—NO2 wherein A contains the radical of a drug having an antiiflammatory or analgesic activity, B is a bivalen: linking group wherein the precursor must meet the tests described in the application, C is a a bivalent linking group as defined in the invention.
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- Nitroderivatives as drugs for diseases having an inflammatory basis
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Use for the treatment of diseases having an inflammatory basis of compounds or salts thereof, having the following general formula (I): A-Xt-L-(W)p—NO2 wherein A contains the radical of a drug, Xt and W arc bivalent radicals, L, is a covalent bond or oxygen, sulphur, NRtc wherein Rtc is H or a C1-C5 linear or branched alkyl.
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- Nitric oxide-donating non-steroidal anti-inflammatory drugs: The case of nitroderivatives of aspirin
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Nitric oxide (NO) acts as a key signalling mechanism in a number of cells and tissues in the mammalian organism. Modulation of the biosynthesis of NO has emerged to be relevant to the treatment of a variety of human diseases. In the attempt to reduce the serious side effects of non-steroidal anti-inflammatory drugs (NSAIDs), especially in the gastrointestinal tract, a NO-releasing moiety has been linked to conventional NSAIDs. A prototypical example is that of NO-releasing derivatives of aspirin. Thanks to the cytoprotective action of NO such compounds do not produce gastric damage and are emerging as an interesting novel group of drugs for their unique pharmacological properties.
- Chiroli, Valerio,Benedini, Francesca,Ongini, Ennio,Del Soldato, Piero
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p. 441 - 446
(2007/10/03)
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- Toward protein-cleaving catalytic drugs: Artificial protease selective for myoglobin
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A protein-cleaving catalyst highly selective for a disease-related protein can be used as a catalytic drug. As the first protein-cleaving catalyst selective for a protein substrate, a catalyst for myoglobin (Mb) was designed by attaching the Cu(II) or Co(
- Jeon, Joong Won,Son, Sang Jun,Yoo, Chang Eun,Hong, In Seok,Suh, Junghun
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p. 2901 - 2910
(2007/10/03)
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- Nitroxyderivatives having antinflammatory, analgesic and antithrombotic activity
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Organic or inorganic salts of compounds of general formula: A—X1—N(O)zfor use as medicaments having anti-inflammatory, analgesic and antithrombotic activity, wherein A is R(COXu)twherein t is 0 or 1; u is 0 or 1
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- Dinuclear and trinuclear Zn(II) calix[4]arene complexes as models for hydrolytic metallo-enzymes. Synthesis and catalytic activity in phosphate diester transesterification
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Calix[4]arenes modified with two or three Zn(II)-2,6- bis(aminomethyl)pyridyl groups, 3-[Zn]2 and 5-[Zn]3, respectively, were investigated as models for dinuclear and trinuclear metallo-enzymes that catalyze the cleavage of phosphate
- Molenveld, Peter,Stikvoort, Wendy M. G.,Kooijman, Huub,Spek, Anthony L.,Engbersen, Johan F. J.,Reinhoudt, David N.
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p. 3896 - 3906
(2007/10/03)
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- Bicyclopol yazamacrocyclophosphonic acid complexes for use as contrast agents
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Bicyclopolyazamacrocyclophosphonic acid compounds are disclosed which may form inert complexes with Gd, Mn or Fe ions. The overall charge of the complex can be varied to alter the in vivo biolocalization. Such complexes can be covalently attached to an antibody, antibody fragment or other biologically active molecule to form conjugates. The complexes and conjugates are useful as contrast agents for diagnostic purposes.
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- Polyazamacrocyclofluoromonoalkylphosphonic acids, and their complexes, for use as contrast agents
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Polyazamacrocyclofluoromonoalkylphosphonic acid compounds are disclosed which form inert complexes with Gd, Mn, Fe or La ions. The complexes are useful as contrast agents for diagnostic purposes.
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- Chiral tridentate C2 diphosphine ligands for enantioselective catalysis
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We describe the synthesis of four ligands of a family of tridentate diphosphine ligands possessing C2 symmetric chirality for use in transition metal complex asymmetric catalysis.
- Sablong, Rafael,Newton, Claire,Dierkes, Peter,Osborn, John A.
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p. 4933 - 4936
(2007/10/03)
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- Bicyclopolyazamacrocyclocarboxylic acid complexes for use as contrast agents
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Complexes of bicyclopolyazamacrocyclocarboxylic acid with Gd, Mn or Fe ions are disclosed. The complexes can be covalently attached to a biologically active molecule, e.g. an antibody or antibody fragment, to form conjugates. The complexes and conjugates are useful as contrast agents for diagnostic purposes.
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- Bicyclopolyazamacrocyclophosphonic acid complexes for use as radiopharmaceuticals
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Complexes of bicyclopolyazamacrocyclophosphonic acid compounds with a metal ion, e.g. 153 Sm, 177 Lu, 159 Gd, 149 Pm, 140 La, 175 Yb, 166 Ho, 90 Y, 47 Sc, 186 Re, 188 Re, 142 Pr, 99m Tc, 67 Ga, 68 Ga, 105 Rh, 97 Ru, 111 In, 113m In or 115m In ion, are disclosed. The complexes can be covalently attached to a biologically active molecule, e.g. an antibody or antibody fragment, to form conjugates. The complexes and conjugates are useful as radiopharmaceutical agents for therapy and/or diagnostic purposes.
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- Reactivity of Heterocyclic Nitrogen Donors in Systems containing the Tetrachloroaurate(III) Anion
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A series of gold(III) complexes of the type has been prepared and characterized (L = oxazole, benzoxazole, thiazole, their benzo and methyl-substituted derivatives, or 2-methylbenzoselenazole).The five-membered N.O-, N,S- and N,Se-heterocyclic bases are all bound to Au(III) through nitrogen.The kinetics of the displacement of L by chloride to give (1-) has been studied in methanol-water (95:5. v/v) at 25.0 deg C and I = 0.20 mol dm-3 (LiClO4).The equilibrium constants for the reversible processes have also been determined.The reactions of the corresponding pyridine, 4-chloro-, 4-cyano- and 2,6-bis(chloromethyl)-pyridine complexes have also been reexamined under the same conditions.The equlibrium constants, K2, depend upon the basicity of the nitrogen in the ligands and points for all ligands, irrespective of ring size and composition, lie roughly on the same log K2 versus pKa curve.There is no significant systematic steric effect on the equilibrium constants of the sort found for the more basic methyl pyridines.The complexes of the five-membered heterocyclic ligands are approximately ten times less reactive than those of the six-membered N-heterocycles of comparable basicity and exhibit steric retardation from ortho-methyl substituents.The nucleophilicities of these ligands have been calculated and five-membered N,O- and N,S-heterocycles are considerably less reactive than six-membered N-heterocycles of similar basicity.
- Canovese, Luciano,Cattalini, Lucio,Tomaselli, Michele,Tobe, Martin L.
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p. 307 - 314
(2007/10/02)
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- Sulphoxide Substituted Pyridines as Phase-transfer Catalysts for Nucleophilic Displacements and Alkylations
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2-Methylsulphinyl-, 2-methylsulphinylmethyl-, 2,6-bis(methylsulphinyl)-, 2,6-bis(methylsulphinylmethyl)-pyridines, bis(2-pyridylmethyl)sulphoxide, and 2-methylsulphinylpyridine N-oxide have been prepared.These sulphoxides served as good phase-transfer catalysts which accelerate SN2 type displacements of octyl bromide with various nucleophiles (thiolate, cyanide, thiocyanate, and phenoxide) in solid-liquid two-phase systems.Alkylations of phenylacetonitrile and benzyl methyl ketone with alkyl halides were also carried out in liquid-liquid two-phase systems in the presence of the above sulphoxides to afford the corresponding monoalkylated products in high yields.Pyridine derivatives bearing polysulphinyl groups were found to be even more effective catalysts for these two-phase alkylations.Neither 2-methylthio- nor 2-methylsulphonyl-pyridine catalysed SN2 type displacement reactions effectively.
- Furukawa, Naomichi,Ogawa, Satoshi,Kawai, Tsutomu,Oae, Shigeru
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p. 1833 - 1838
(2007/10/02)
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- Macrocyclic Dioxo Pentaamines: Novel Ligands for 1:1 Ni(II)-O2 Adduct Formation
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Substituted and unsubstituted macrocyclic dioxo pentaamines, 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione, form stable 1:1 square-pyramidal complexes with Ni(II) and Cu(II), which possess two deprotonated amide donors in equatorial positions.The high-spin Ni(II) complexes show a very low Ni(II,III) redox potential of +0.24 V vs.SCE and are easily oxidized chemically or electrochemically to Ni(III) complexes.Moreover, the Ni(II) complexes react with molecular oxygen to form 1:1 Ni(II)-O2 adducts in aqueous solution, as established by a combination of polarographic, spectrophotometric, and manometric methods.Comparative studies with relevant pentadentate macrocyclic polyamine complexes revealed that the two deprotonated amide groups and the fifth amine donor incorporated in the 16-membered macrocyclic frame are essential for the formation of the Ni(II)-O2 adducts.The oxygen uptake reaction is first order in and in -2L>0 in aqueous solutions, and the second-order rate constant is 1.7*102 s-1 M-1 at 35 deg C.The attack of O2 at the sixth coordinate site is competitively inhibited by imidazole.The O2 complexation constant KO2 is determined to be 1.9*104 M-1 at 35 deg C by potentiometric titration.Novel features of the Ni(II)-O2 adducts are discussed.
- Kimura, Eiichi,Machida, Ryosuke,Kodama, Mutsuo
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p. 5497 - 5505
(2007/10/02)
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- SEQUENCE OF REPLACEMENT OF HYDROGEN IN 2,6-DIMETHYLPYRIDINE BY LITHIUM OR HALOGEN
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It is shown that, according to the results of chromatographic mass spectrometry, the reaction of 2,6-dimethylpyridine with phenyllithium leads only to the monolithium derivative.The chlorination and bromination of 2,6-dimethylpyridine with various reagents were studied systematically.A method for the conversion of 2,6-bis(chloromethyl)pyridine to 2,6-bis(hydroxymethyl)pyridine is given.
- Karpman, Ya.S.,Azimov, V.A.,Anisimova, O.S.,Yakhontov, L.N.
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