- New Iron(II) Spin-crossover Complexes with Heterocyclic Amine-derived Ligands and STEPS Experiments on Photogenerated Metastable High-spin States
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Cationic complexes of the type NN)3>2+ and NNN)2>2+ have been isolated as Cl-, ClO4-, or BF4- salts, where LNN and LNNN represent bidentate and tridentate nitrogen-donor ligands respectively.The bidentate ligands were 2-(2'pyridyl)benzimidazole (pybzim), 2-(2'-pyridyl)-N-methylbenzimidazole (mpybzim); 2-(2'-pyridyl)benzothiazole (pybzt), 2,2'-dipyridylamine (dpya), and the tridentates di(2-pyridylmethyl)amine (dpyma), 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy), 2,6-bis(N-methylbenzimidazol-2'-yl)pyridine (mbzimpy), and 2,6-bis(benzothiazol-2'-yl)pyridine (bztpy).Except for , all these FeN6 chromophores exhibit strong absorption in the 550 nm region, which is assigned as a metal-to-ligand charge-transfer transition.Between 4 and 320 K, the iron(II) is in the low-spin form in the majority of these compounds; high-spin exceptions are 2 and Cl2.Other complexes show evidence of the onset of a spin transition near 40 deg C, while the salt *CHCl3 is a well defined spin-crossover system.The low-spin complex 2 was excited by irradiation with visible light, and the generation and decay of resulting high-spin form was observed under cryogenic conditions.In solution, 2+ acts as a weak diprotic acid and also exhibits quintet ->/o = -42.7 kJmol-1, ΔSo = -140.9 JK-1mol-1).The complexes are all electrochemically oxidizable to their iron(III) forms in non-aqueous solution, but the dpyma, bztpy, pybtz, and dpya chelates thus formed are unstable.The iron(III) complex -2bzimpy)2>- containing the doubly deprotonated ligand was obtained as its low-spin triethylammonium salt.The high-spin chloro complexes . , Fe(mbzimpy)Cl2, and the mixed-spin iron(II) complex salt were also isolated.
- Addison, Anthony W.,Burman, Sudhir,Wahlgren, Curtis G.,Rajan, Odatt A.,Rowe, Teresa M.,Sinn, Ekkehard
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- Nickel(II) complexes of a 3N ligand as a model for diketone cleaving unusual nickel(II)-dioxygenase enzymes
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Diketone substrate bound nickel(ii) complexes of 2,6-bis(1-methylbenzimidazolyl)pyridine have been synthesized and characterized as relevant active site models for unusual diketone cleaving Ni(ii)-dependent enzymes Ni-ARD and DKDO. The average Ni-Npy/benzim bond distances (2.050-2.107 ?) of model complexes are almost identical to the Ni-NHis bond distances of NiII-ARD (2.02-2.19 ?). The reaction of these adducts with dioxygen exhibited C-C cleavage with the rate of kO2, 5.24-73.71 × 10-3 M-1 s-1. The phenyl substituted adduct regioselectively elicits 52% of benzoic acid as the major product.
- Ramasubramanian, Ramamoorthy,Anandababu, Karunanithi,Kumar, Mukesh,Mayilmurugan, Ramasamy
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- N3-Ligated nickel(ii) diketonate complexes: synthesis, characterization and evaluation of O2reactivity
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Interest in O2-dependent aliphatic carbon-carbon (C-C) bond cleavage reactions of first row divalent metal diketonate complexes stems from the desire to further understand the reaction pathways of enzymes such as DKE1 and to extract information to develop applications in organic synthesis. A recent report of O2-dependent aliphatic C-C bond cleavage at ambient temperature in Ni(ii) diketonate complexes supported by a tridentate nitrogen donor ligand [(MBBP)Ni(PhC(O)CHC(O)Ph)]Cl (7-Cl; MBBP = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine) in the presence of NEt3spurred our interest in further examining the chemistry of such complexes. A series of new TERPY-ligated Ni(ii) diketonate complexes of the general formula [(TERPY)Ni(R2-1,3-diketonate)]ClO4(1: R = CH3;2: R = C(CH3)3;3: R = Ph) was preparedunder airand characterized using single crystal X-ray crystallography, elemental analysis,1H NMR, ESI-MS, FTIR, and UV-vis. Analysis of the reaction mixtures in which these complexes were generated using1H NMR and ESI-MS revealed the presence of both the desired diketonate complex and the bis-TERPY derivative [(TERPY)2Ni](ClO4)2(4). Through selective crystallization1-3were isolated in analytically pure form. Analysis of reaction mixtures leading to the formation of the MBBP analogs [(MBBP)Ni(R2-1,3-diketonate)]X (X = ClO4:5: R = CH3;6: R = C(CH3)3;7-ClO4: R = Ph; X = Cl:7-Cl: R = Ph) using1H NMR and ESI-MS revealed the presence of [(MBBP)2Ni](ClO4)2(8). Analysis of aerobic acetonitrile solutions of analytically pure1-3,5and6containing NEt3and in some cases H2O using1H NMR and UV-vis revealed evidence for the formation of additional bis-ligand complexes (4and8) but suggested no oxidative diketonate cleavage reactivity. Analysis of the organic products generated from3,7-ClO4and7-Clrevealed unaltered dibenzoylmethane. Our results therefore indicate that N3-ligated Ni(ii) complexes of unsubstituted diketonate ligands do not exhibit O2-dependent aliphatic C-C bond clevage at room temperature, including in the presence of NEt3and/or H2O.
- Berreau, Lisa M.,Elsberg, Josiah G. D.,Fuller, Amy L.,Peterson, Austin
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- Thermodynamic Programming of Erbium(III) Coordination Complexes for Dual Visible/Near-Infrared Luminescence
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Intrigued by the unexpected room-temperature dual visible/near-infrared (NIR) luminescence observed for fast-relaxing erbium complexes embedded in triple-stranded helicates, in this contribution, we explore a series of six tridentate N-donor receptors L4–L9 with variable aromaticities and alkyl substituents to extricate the stereoelectronic features responsible for such scarce optical signatures. Detailed solid-state (X-ray diffraction, differential scanning calorimetry, optical spectroscopy) and solution (speciations and thermodynamic stabilities, spectrophotometry, NMR and optical spectroscopy) studies of mononuclear unsaturated [Er(Lk)2]3+ and saturated triple-helical [Er(Lk)3]3+ model complexes reveal that the stereoelectronic changes induced by the organic ligands affect inter- and intramolecular interactions to such an extent that 1) melting temperatures in solids, 2) the affinity for trivalent erbium in solution, and 3) optical properties in luminescent complexes can be rationally varied and controlled. With this toolkit in hand, mononuclear erbium complexes with low stabilities displaying only NIR emission can be transformed into molecular-based dual Er-centered visible/NIR emitters operating at room temperature in both solid and solution states.
- Golesorkhi, Bahman,Guénée, Laure,Nozary, Homayoun,Fürstenberg, Alexandre,Suffren, Yan,Eliseeva, Svetlana V.,Petoud, Stéphane,Hauser, Andreas,Piguet, Claude
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- Solution aggregation of platinum(ii) triimine methyl complexes
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The NMR chemical shifts of [Pt(tpy)(CH3)](PF6) (1) and [Pt(mbzimpy)(CH3)](PF6) (2), where tpy = 2,2′;6′2′′-terpyridine and mbzimpy = 2,6-bis(N-methylbenzimidazol-2-yl)pyridine, in room-temperature DMSO-d6 displayed concentration dependence as a result of formation of dimers. Quantification of these dimers, expressed by equilibrium constant (K), shows a greater tendency of 2 to aggregate in solution. Structural conformations of these dimers were confirmed by 2D 1H-1H NOESY; the results explicitly suggest a head-to-tail stacking arrangement of molecules in dimers. This journal is
- Connick, William B.,Shingade, Vikas M.
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- Copper(II)-benzimidazole complexes as efficient fluorescent probes for l-cysteine in water
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Copper(ii) complexes [Cu(L1)(H2O)2](SO3CF3)21 and [Cu(L2)(H2O)2](SO3CF3)22 based on 2,6-bis(benzimidazolyl)pyridine were synthesized and are reported herein as highly selective "turn-on" optical probes for l-cysteine. The Cu(ii)/Cu(i) redox potential of probe 1 (0.14 V vs. NHE) was lower than that of 2 (0.233 V vs. NHE) in water. The molecular structure of 2 adopted a square pyramidal geometry (τ = 0.2545), with the Cu-Npy bond (1.958 ?) of its middle pyridine unit being shorter than the other two Cu-Nbenzim bonds (Cu-N, 1.995, 2.000 ?). The axial Cu-O2 bond distance (2.247 ?) was slightly longer than the equatorial Cu-O1 bond distance (1.953 ?). The square-based geometry was further supported by the A∥ value of 156 × 10-4 cm-1 in EPR at 70 K. The d-d and ligand-based transitions appeared at 662 and 314-356 nm for 1 and 651 and 313-360 nm for 2, respectively, in HEPES buffer at pH 7.34. These probes showed selective and efficient "turn-on" fluorescence behaviour towards Cys over other natural amino acids with a binding constant for 1 of 5.4 × 104 and 1.30 × 104 M-1 for 2 and a limit of detection of 2.9 × 10-8 M and 3.32 × 10-8 M, respectively, for 1 and 2 at pH 7.34. The quantum yield for the detection of Cys by 1 (14.7%) was much lower than by 2 (23%). The fluorescence intensity of 1 and 2 were also slightly enhanced by histidine, but at a relatively lower level than that exhibited by Cys.
- Maheshwaran, Duraiyarasu,Priyanga, Selvarasu,Mayilmurugan, Ramasamy
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- Tuning of redox potentials by introducing a cyclometalated bond to bis-tridentate ruthenium(II) complexes bearing bis(N -methylbenzimidazolyl) benzene or -pyridine ligands
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A series of asymmetrical bis-tridentate cyclometalated complexes including [Ru(Mebib)(Mebip)]+, [Ru(Mebip)(dpb)]+, [Ru(Mebip)(Medpb)]+, and [Ru(Mebib)(tpy)]+ and two bis-tridentate noncyclometalated complexes [Ru(Mebip)2]2+ and [Ru(Mebip)(tpy)]2+ were prepared and characterized, where Mebib is bis(N-methylbenzimidazolyl)benzene, Mebip is bis(N-methylbenzimidazolyl) pyridine, dpb is 1,3-di-2-pyridylbenzene, Medpb is 4,6-dimethyl-1,3-di-2- pyridylbenzene, and tpy is 2,2′:6′,2″-terpyridine. The solid-state structure of [Ru(Mebip)(Medpb)]+ is studied by X-ray crystallographic analysis. The electrochemical and spectroscopic properties of these ruthenium complexes were studied and compared with those of known complexes [Ru(tpy)(dpb)]+ and [Ru(tpy)2]2+. The change of the supporting ligands and coordination environment allows progressive modulation of the metal-associated redox potentials (Ru II/III) from +0.26 to +1.32 V vs Ag/AgCl. The introduction of a ruthenium cyclometalated bond in these complexes results in a significant negative potential shift. The RuII/III potentials of these complexes were analyzed on the basis of Lever's electrochemical parameters (E L). Density functional theory (DFT) and time-dependent DFT calculations were carried out to elucidate the electronic structures and spectroscopic spectra of complexes with Mebib or Mebip ligands.
- Yang, Wen-Wen,Zhong, Yu-Wu,Yoshikawa, Shinpei,Shao, Jiang-Yang,Masaoka, Shigeyuki,Sakai, Ken,Yao, Jiannian,Haga, Masa-Aki
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- 2,6-Bis(benzimidazol-2-yl)pyridine as a potent transmembrane anion transporter
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2,6-Bis(benzimidazol-2-yl)pyridine was shown to exhibit potent anionophoric activity via a process of both Cl-/NO3- antiport and H+/Cl- symport. This is in sharp contrast to the finding that its corresponding N-methylated analog exhibited negligible activity and reveals the importance of the imidazolyl-NH fragments in the anion-transport process.
- Peng, Chen-Chen,Li, Zhi,Deng, Li-Qun,Ke, Zhuo-Feng,Chen, Wen-Hua
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- Luminescent Pt(2,6-bis(: N -methylbenzimidazol-2-yl)pyridine)X+: A comparison with the spectroscopic and electrochemical properties of Pt(tpy)X+(X = Cl, CCPh, Ph, or CH3)
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A series of platinum(ii) pincer complexes of the formula Pt(mbzimpy)X+, 1(a-d), (mbzimpy = 2,6-bis(N-methylbenzimidazol-2-yl)pyridine; X = Cl; (a), CCPh; (b), Ph; (c), or CH3; (d), CCPh = phenylacetylide, and Ph = Phenyl) have been synthesized and characterized. Electronic absorption and emission, as well as electrochemical properties of these compounds, have been investigated. Pt(tpy)X+ analogs (tpy = 2,2′;6′2′′-terpyridine), 2(a-d), have also been investigated and compared. Electrochemistry shows that 1 and 2 analogs undergo two chemically reversible one-electron reduction processes that are shifted cathodically along the a b c d series. Notably, these reductions occur at slightly higher negative potentials in the case of 1. The absorption spectra of 1 and 2 in acetonitrile exhibit ligand-centered (1LC) transitions (? ≈ 104 M-1 cm-1) in the UV region and metal-to-ligand-charge transfer (1MLCT) transitions (? ≈ 103 M-1 cm-1) in the visible region. The corresponding visible bands of 1b and 2b have been assigned to 1(LLCT/MLCT) mixed state (LLCT: ligand-to-ligand-charge transfer). The preceding 1LC and 1MLCT transitions of 1 occur at lower energies than that of 2. These 1LC transitions have distinctly been blue-shifted along a c d in 2, but occur at nearly identical energies in 1. Conversely, 1MLCT transitions are red-shifted along a c d in both the analogs. The 77 K glassy solutions of 1 and 2 exhibit an intense vibronically-structured emission band at λmax(0-0) in the 470-560 nm range. This band is red-shifted along b a ≤ c d in 1 and along a ≤ d ≈ c ? b in 2. The main character of these emissions is assigned to 3LLCT emissive state in 1b and 2b, whereas to 3LC in the rest of the compounds. Relative stabilization of these spin-forbidden emissive states is discussed by invoking configuration mixing with the higher-lying 3MLCT state.
- Connick, William B.,Grove, Levi J.,Shingade, Vikas M.
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supporting information
p. 9651 - 9661
(2020/07/30)
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- Rhodium-catalyzed selective C - H functionalization of NNN tridentate chelating compounds via a rollover pathway
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Reported herein is the first example of the Rh(NHC)-catalyzed selective bis C-H alkylation of NNN tridentate chelating compounds in reaction with alkenes. The observed excellent site-selectivity can readily be explained by the postulated rollover pathway in the C-H bond activation step. The reaction is highly facile affording bis-alkylated tridentate products in high yields over a broad range of versatile heteroarene substrates and alkene reactants including ethylene gas, thus enabling its applications to be feasible in coordination and synthetic chemistry.
- Hong, Seung Youn,Kwak, Jaesung,Chang, Sukbok
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supporting information
p. 3159 - 3162
(2016/02/23)
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- Ruthenium or osmium complexes and their uses as catalysts for water oxidation
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The present invention provides ruthenium or osmium complexes and their uses as a catalyst for catalytic water oxidation. Another aspect of the invention provides an electrode and photo-electrochemical cells for electrolysis of water molecules.
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(2013/09/12)
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- Nickel(II) dibromide complexes bearing bis(benzimidazolyl)amine and Bis(benzimidazolyl)pyridine ligands for ethylene oligomerizations
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A series of bis(benzimidazolyl)amine and bis(benzimidazolyl)pyridine ligands and their respective nickel(II) dibromide complexes were synthesized and fully characterized. After activation of the nickel complexes with ethylaluminum sesquichloride showed productivity in excess of 106 (g-oligomer)(mol-Ni)-1h-1bar-1 towards ethylene oligomerization, producing butenes as major products. The bis(benzimidazolyl) pyridine nickel complexes showed higher activity and dimerization selectivity than corresponding bis(benzimidazolyl)amine nickel complexes. Graphical Abstract: [InlineMediaObject not available: see fulltext.]
- Lee, Gyeong Mi,Appukuttan, Vinu K.,Suh, Hongsuk,Ha, Chang-Sik,Kim, Il
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experimental part
p. 1608 - 1615
(2012/03/22)
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- Synthesis, crystal structure and DNA-binding properties of a cadmium(II) complex with 2,6-bis(N-methylbenzimidazol-2-yl)pyridine
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A new complex of Cd(II) picrate (pic) based on the ligand 2,6-bis(N-methylbenzimidazol-2-yl)-pyridine (mbbp) has been synthesized and characterized by elemental analysis, electrical conductivity, 1H NMR, IR and UV/Vis spectral measurements. The crystal structure of the Cd(II) complex, [Cd(mbbp)2](pic)2, has been determined by single-crystal X-ray diffraction. The Cd(II) cation is bonded to two mbbp ligands through six nitrogen atoms, resulting in a distorted octahedral geometry.Interaction of the complex with DNA was investigated by spectrophotometric methods and viscosity measurements. The experimental results suggest that the Cd(II) complex binds to DNA in an intercalation mode.
- Wu, Huilu,Huang, Xingcai,Yuan, Jingkun,Kou, Fan,Jia, Fei,Liu, Bin,Bai, Ying
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experimental part
p. 1049 - 1055
(2011/12/14)
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- Stereospecific polymerizations of 1,3-butadiene catalyzed by Co(II) complexes ligated by 2,6-bis(benzimidazolyl)pyridines
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Highly stereoregular polybutadiene polymers with 1,4-cis isomeric content is synthesized using a series of 2,6-bis(benzimidazolyl)pyridine Co(II) on activation with alkylaluminum cocatalysts under moderate reaction conditions.
- Appukuttan, Vinukrishnan,Zhang, Lin,Ha, Ju Young,Chandran, Deepak,Bahuleyan, Bijal Kottukkal,Ha, Chang-Sik,Kim, Il
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scheme or table
p. 84 - 90
(2010/10/01)
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- METAL COMPLEX COMPOUND AND ORGANIC ELECTROLUMINESCENT DEVICE USING SAME
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A metal-complex compound which comprises a tridentate chelate ligand having a specified partial structure. An organic electroluminescence device which comprises at least one organic thin film layer sandwiched between a pair of electrode consisting of an anode and a cathode, wherein the organic thin film layer comprises the metal-complex compound, which emits light by applying an electric voltage between the pair of electrode. The present invention provides an organic EL device which emits blue light with high purity and of short wavelength with an enhanced efficiency of light emission.
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(2010/11/28)
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- Polycyclic pyridines as potassium ion channel modulators
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The present invention provides a genus of polycyclic pyridines that are useful as modulators of potassium ion channels. The modulators of the invention are of use in both therapeutic and diagnostic methods.
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(2008/06/13)
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- Models for Copper-Dioxygen Complexes: the Chemistry of Copper(II) with Some Planar Tridentate Nitrogen Ligands
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The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2), 2,6-bis(benzothiazol-2-yl)pyridine (bzthpy, 3), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4), and 2,2',6',2"-terpyridyl (terpy, 5) is reported.Electronic and EPR spectra are consistent with the complexes 2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper.Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl- and OH- (provided that the ligand has no acidic protons) for all ligands except terpy.The reaction between 2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25 deg C), and also the formation of an imidazolate-bridged dinuclear species.
- Piguet, Claude,Bocquet, Bernard,Mueller, Edgar,Williams, Alan F.
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p. 323 - 337
(2007/10/02)
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