Novel cobalt(Ⅱ) complexes of amino acids-Schiff bases catalyzed aerobic oxidation of various alcohols to ketones and aldehyde

Two cobalt（Ⅱ） complexes 1 and 2 of Schiff bases derived from amino acids were synthesized and used for oxidation of benzyl alcohol with molecular oxygen at different conditions of pH,solvent,temperature and complex/alcohol molar ratio to optimize reaction conditions and to evaluate the catalytic efficiency of new cobalt Schiff base complexes.Under obtained optimum conditions,various alcohols were oxidized to corresponding aldehydes and ketones.

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes

Two cobalt（Ⅱ） complexes of the Schiff base with morpholino or aza-crown ether pendants, CoL^1 and CoL^2, as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester （PNPP）. The analysis of specific absorption spectra of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Co（Ⅱ） complexes, have been formed in reaction processes of the PNPP catalytic hydrolysis. The mechanism of PNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis, has been established based on the mechanism proposed. The acid effect of buffer solution, structural effect of the complexes, and effect of temperature on the rate of PNPP hydrolysis catalyzed by the complexes have been also discussed.

Hydrothermal Syntheses and Crystal Structures of Cobalt(Ⅱ) Complexes Constructed by Dipyrido[3,2-a:2',3'-c]phenazine and Different Carboxylate Ligands

Two new metal-organic complexes,{[Co2（bptc）（DPPZ）2（H2O）2]·H2O}n 1 and {[Co2（ccm）2（DPPZ）2]·2H2O}n 2,were obtained by the hydrothermal reactions of Co（NO3）2·6H2O with chelating ligand dipyrido[3,2-a：2＇,3＇-c]phenazine（DPPZ） and the corresponding carboxylic acid,namely,3,3＇,4,4＇-benzophenonetetracarboxylic acid（H4bptc） or 2-carboxycinnamic acid（H2ccm）,respectively.The complexes were structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectra,and thermal gravimetry.1 presents unique chiral chain structures,which are further consolidated into three-dimensional supramolecular frameworks via noncovalent bonds,such as hydrogen bonding and π-π interactions.2 features infinite double-chain structures,which are connected by strong π-π interactions to result in three-dimensional supramolecular architectures.

Simple, Selective, and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel(Ⅱ), Copper (Ⅱ), Cobalt (Ⅱ), and Iron (Ⅲ) with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone（2-PYAINH） was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9,0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1：2 yellow-orange, 1：2 yellow-green, 1：2 yellow and 1：1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer＇s law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L respectively. The apparent molar absorptivity and Sandell＇s sensitivities were 8.4×10^4, 5.2×10^4, 7.1×10^4, and 3.9×10^4 L·mol^-l·cm^-1, respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 μg·cm2, respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.

Syntheses,Crystal Structures,and Magnetic Properties of Cobalt(Ⅱ) Complexes with 1,1-Cyclohexanediacetic Acid

Two new Co（Ⅱ） coordination polymers,{[Co_3（Hchda）_2（chda）_2（bpp）_2（H_2O）_2]}_n 1 and {[Co（chda）（bpe）（H_2O）]·3H_2O}_n 2（H_2chda = 1,1-cyclohexanediacetic acid,bpp = 1,3-bis（4-pyridinyl）propane and bpe = 1,2-bis（4-pyridinyl）ethylene）,were hydrothermally synthesized and then characterized by elemental analysis,IR spectroscopy,thermogravimetric analysis（TGA）,and single-crystal X-ray diffraction.Complex 1 possesses an infinite metal-organic layer based on triply bridged linear trinuclear subunits and complex 2 exhibits a square（4,4） grid layer with dangling lateral arms resulting from eight-membered rings above and below the layer.In addition,magnetic properties of complexes 1 and 2 are also given.

Synthesis,Structure,and Magnetic Property of One Novel Entangled Cobalt~Ⅱ-organic Compound

One novel entangled cobalt compound, {[Co3（nbta）2（4,4＇-bpy）2（H2O）2]（H2O）2}n （1, H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, 4,4＇-bpy = 4,4＇-bipyridyl）, was prepared and characterized by X-my diffraction, magnetism, elemental analysis, XPS, TGA and IR spectroscopy. The crystal of 1 crystallizes in monoclinic, space group Pc with a = 13.0717（16）, b = 11.4167（14）, c = 15.9342（19） A, β = 90.5190（10）°, V= 2377.9（5） A3, Z= 2, C48H36Co3N8O20, Mr = 1221.64, Dc = 1.706 g/cm3, F（000） = 1242 and μ（MoKa） = 1.128 mm^-1. The final R = 0.0497 and wR = 0.1461 for 4185 observed reflections with I 〉 20（0 and R = 0.0721 and wR = 0.1619 for all data. X-ray diffraction analyses revealed that Co（l） is linked by the nbta3- ligands to form the ladder shape along the c axis, which is further extended into two-dimensional networks via the joint of Co（2） along the a axis. Moreover, these two dimensional motifs are interconnected by the 4,4＇-bpy bridges to form a complicated 3-D polymeric framework. Magnetic measurements revealed that compound 1 shows strong antiferromagnetic property.

Ring-opening Polymerization of L-Lactide by an Anionic Cobalt（Ⅱ） Aryloxide

The reaction of anhydrous CoCl2 with NaOAr （ArO=2,4,6-tri-tert-butylphenoxo） in THF at room temperature in 1 ： 3 molar ratio afforded anionic cobalt aryloxide [Na（THF）6][Co（OAr）3] （1）. The definite structure of this com- plex was characterized by X-ray single crystal diffraction. It was found that this anionic aryloxo cobalt（Ⅱ） complex could effectively initiate the ring-opening polymerization of L-lactide both in solution and in bulk, leading to high molecular weight poly（L-lactide）.

Synthesis and Crystal Structure of a Cobalt(Ⅱ) Complex with 2-(4'-Chlorine-benzoyl)-benzoic Acid and 1,10-Phenanthroline

A new metal-organic complex Co2（cbba）4（phen）2（μ2-OH2）（H2cbba=2-（4＇-chlorine-benzoyl）benzoic acid,phen=1,10-phenanthroline） 1 has been hydrothermally synthesized and struc-turally characterized by single-crystal X-ray diffraction,elemental analyses,TG and IR spectroscopy.The compound crystallizes in triclinic,space group P1 with a=10.7659（7）,b=17.1856（11）,c=19.2022（13）,α=83.8120（10）,β=84.9930（10）,γ=87.2070（10）°,V=3515.8（4）3,C80H50Cl4Co2N4O13,Mr=1534.90,Dc=1.450 g/cm3,μ（MoKα）=0.693 mm-1,F（000）=1568,Z=2,the final R=0.0490 and wR=0.1092 for 8216 observed reflections（Ⅰ 〉2σ（Ⅰ））.In the crystal structure,the cobalt atom is six-coordinated with three carboxylate oxygen atoms from three different cbba ligands,one oxygen atom from coordinated water molecule and two nitrogen atoms from phen ligand,showing a distorted octahedral geometry.Furthermore,it exhibits a 3D supramolecular network through π-π and hydrogen bonding interactions.

Hydrothermal Synthesis and Crystal Structure of a New One-dimensional Cobalt(Ⅱ) Complex with 2-Pyridinecarboxyic Acid and 4,4′-Bipyridine Ligands

A new metal-organic coordination polymer [Co（2-pya）2（4,4＇-bipy）]2n-[（4,4＇- bipy）0.5· H2O]2n （2-pya = 2-pyridinecarboxylic acid, 4,4＇-bipy = 4,4＇-bipyridine） 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. The complex crystallizes in tetragonal, space group I41/a with a = b = 22.719（2）, c = 10.710（2）/k, V = 5527.8（14） A3, C54H46N10Co2O10, Mr= 1112.87, Dc = 1.337 g/cm3,μ（MoKa） = 0.665 mm-1, F（000） = 2296, Z = 4, the final R = 0.0633 and wR = 0.1096 for 1261 observed reflections （I 〉 2σ（I））. It exhibits a one-dimensional chain-like structure constructed by mixed ligands of 2-pyridinedicarboxylic acid and 4,4＇-bipyridine.

Dioxygen affinities and catalytic oxidation performance of cobalt(Ⅱ) hydroxamates with benzo-15-crown-5 pendants

The oxygenation constants （Ko2） of cobalt（Ⅱ） hydroxamates （CoL^1 2-CoL^3 2） with benzo-15-crown-5 （B15C5） pendants were measured over the range of -5 to ＋20 ℃, and the values of thermodynamic parameters （ΔH^0 and ΔS^0） were calculated based on these （Ko2） values, Meanwhile, these crowned complexes were employed to the oxidation for p-xylene to p-toluic acid with air at 110Δ under normal atmospheric pressure. The effects of B15C5 pendant and the length of chain bonded to B15C5 in these complexes on the O2-binding capabilities and oxidation for p-xylene were investigated with the comparison of crown-free analogues CoL^4 2.

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes Containing Benzoaza-15-crown-5

Three novel Schiff base cobalt（Ⅱ） complexes containing benzoaza-15-crown-5, CoL^1, CoL^2 and CoL^3 were synthesized and characterized, and these complexes were used in catalytic hydrolysis of carboxylic ester （PNPP, p-nitrophenyl picolinate） as mimic hydrolytic metalloenzyme. The analysis of specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with cobalt（Ⅱ） complexes. The CoL^3 bearing the electron withdrawing group shows better catalytic activity due to its stabilization effect on active species MLS^-. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameter of PNPP catalytic hydrolysis has been calculated and the activation energy for the catalytic hydrolysis is 43.69, 39.76 and 35.44 kJ·mol^-1, respectively.

Synthesis,Structure and Polymorphism of a Novel Two-dimensional Cobalt(Ⅱ)Coordination Polymer Constructed from Citrazinate Ligand

The polymeric Co（Ⅱ） complex[Co（Hdhpc）（py）]n（1）（py = pyridine,H3dhpc =2,6-dihydroxypyridine-4-carboxyl acid） was prepared and characterized.X-ray diffraction data revealed that the compound crystallizes in dimorphic 1α and 1β forms at room and low temperature,respectively.The former crystallizes in the orthorhombic crystal system,space group Pbcm with a =7.209（1）,b = 14.834（3）,c = 15.376（3） A°,V= 1644.3（5）A°3,Z = 4,C（16）H（13）CoN3O4,Mr = 370.22,Dc= 1.496 g/cm^3,F（000） = 756,μ = 1.068 mm^-1,R = 0.0633 and wR = 0.1192.While 1β is attributed to the monoclinic space group C2/c with a = 32.102（4）,b = 7.022,c = 14.945（2）A°,β = 109.052（5）°,V= 3184.4（6） A°3,Z= 8,Dc= 1.544 g/cm^3,F（000） = 1512,μ = 1.103 mm^-1,R = 0.0428 and wR =0.0797.The conformation changes of pyridines between Co-citrazinate planes leading to a reversible single-crystal to single-crystal transformation.The variable temperature magnetic data indicate a weak ferrimagnetism.

Synthesis and Crystal Structure of Cobalt(Ⅱ) and Copper(Ⅱ) Complexes Involving L-Aamino Alcohols

Two novel L-amino alcohol coordination cobalt and copper complexes I and Ⅱ were obtained separately from the direct reaction of L-plenylglycinol with Co（Ⅱ） acetate tetrahydrate in anhydrous ethanol and L-leucinol with Cu（Ⅱ） chloride dihydrate in anhydrous methanol. The structures of I and Ⅱ were determined by single-crystal X-ray diffraction and further characterized by elemental analysis and IR. For I： [Co3（C51H66N3O16）]2（OAc）, monoclinic, space group P21, a = 15.022（3）, b = 14.242（3）, c = 28.922（6） A, β = 98.944（4）°, V = 6112（2） A3, Z = 4, Dc = 1.339 g/cm^3, the final R = 0.0860 for 21906 observed reflections with I 〉 2（I）. For Ⅱ： Cu2[C24H58N4O7Cl]Cl, orthorhombic, space group P212121, a = 6.1861（13）, b = 20.838（4）, c = 28.274（6） , V = 3644.6（13） 3, Z = 4, Dc = 1.310 g/cm^3, the final R = 0.0642 for 11106 observed reflections with I 〉 2（I）. The complexes were then used to catalyze the Henry reaction and catalytic activity determined by 1H NMR.

Ionothermal Syntheses and Crystal Structures of Two Cobalt(Ⅱ) Compounds:Co(2,2'-bpy)_2Br_2 and Co(1,10-phen)_2Br_2

Two cobalt（Ⅱ） compounds,Co（2,2-bpy） 2 Br 2 （1,2,2-bpy=2,2-bipyridyl） and Co（1,10-phen） 2 Br 2 （2,1,10-phen=1,10-phenanthroline）,have been prepared under ionothermal reactions using the 1-propyl-3-methylimidazolium bromide ionic liquid solvent.Single-crystal X-ray analyses reveal that 1 crystallizes in a monoclinic space group P2 1 /c,with a=8.5509（13）,b=14.804（2）,c=15.650（2）,β=97.119（2） o,V=1965.8（5） 3,Z=4,C 20 H 16 Br 2 N 4 Co,M r=531.12,D c=1.795 g/cm 3,μ=4.950 mm-1,F（000）=1044,the final R=0.0467 and wR=0.0736 for 2291 observed reflections with I 2σ（Ⅰ）.Complex 2 crystallizes in a monoclinic space group P2 1 /n,with a=10.4237（8）,b=16.8657（12）,c=12.4945（9）b,β=102.110（1） o,V=2147.7（3） 3,Z=4,C 24 H 16 Br 2 N 4 Co,M r=579.16,D c=1.791 g/cm 3,μ=4.540 mm-1,F（000）=1140,the final R=0.0431 and wR=0.1042 for 3470 observed reflections with I 2σ（Ⅰ）.The mononuclear molecules of 1 are linked by the C-H···Br hydrogen bonds and π-π interactions to form a three-dimensional supramolecular framework structure.The C-H···Br hydrogen bonds and π-π interactions link the mononuclear molecules of 2 to give a two-dimensional layer structure.

Synthesis, Crystal Structure, and Fluorescent and Thermal Stability Properties of Two New Cobalt(Ⅱ) Complexes with 2,2’-Bipy as Ligand

Two new cobalt（Ⅱ）complexes[Co2（2,2?-bipy）2（dpa）2（H2O）5]·4H2O（1）and Co（2,2?-bipy）3（SO4）]·7.5H2O（2）have been synthesized with diaphonic acid（H2dpa）and 2,2?-bipyridine（2,2?-bipy）as ligands.In 1,two neighboring cobalt（Ⅱ）ions are linked together by one bridging diaphonic acid group,forming an asymmetric dinuclear structure.1 crystallizes in triclinic,space group ■ with a=9.825（6）,b=13.007（8）,c=19.586（1）?,α=80.773（1）o,β=77.065（1）o,γ=85.902（1）o,Mr=431.4,V=2406.5（3）?3,Dc=1.48 g/cm3,Z=2,μ（MoKα）=0.767 mm-1,F（000）=1112,the final R=0.0379 and wR=0.0862.The central cobalt（Ⅱ）ions in 1 and 2 are coordinated with six atoms,forming distorted octahedral coordination geometry.The fluorescence and thermal stability properties of 1 and 2 are also reported.

Infrared Spectroscopic and Theoretical Studies on Cobalt(Ⅱ) Complex of Maleinitriledithiolate and 4, 4′-Dimethyl-2, 2′-bipyridine

The complete experimental IR spectra and vibrational analysis of the title complex Co(mnt)(dmbpy) were reported in this paper. The results show that the complex molecule has a planar geometry belonging to point group C 2v and ground electronic state with spin quartet. A new method for analyzing vibrational spectra of complicated molecule is established. The essential of this method is to point out main fixed points and pivotal vibrational units in assignment for each fundamental band. Two new symbols η (heaving along the specified direction) and M (midpoint of a bond or unit) were defined for describing the vibrational modes accurately.

Model of In Situ Composite of Cobalt(Ⅱ)-Phthalocyanine and Carbonyl Iron for Organic/Inorganic Nanocomposites

Cobalt-phthalocyanine/iron nanocomposite particles have been obtained using method of composite in situ, with the mixture of carbonyl iron and solution of cobalt ( Ⅱ ) - phthalocyanine (Co-Pc) ultrasonic dispersing in N,N-dimethyl-formamide (DMF). Structure characterization of their inner and surface have relation with method of carbonyl iron joined in the mixture, contents of carbonyl iron and Co-Pc in the mixture of Co-Pc ultrasonic dispersing in DMF. With a method of composite in situ controlling reasonable experiment condition, it can be obtained that cobalt-phthalocyanine/iron nanocomposite particles has completely been covered with Co-Pc, they had structure of Chinese gooseberry in inner and mere made up of almost regular spherical shape and the average diameter is 1. 4 μm.

Study on Cobalt(Ⅱ)Ionprobe for Cysteine Determination

A spectrophotometric method for the determination of cysteine was developed basing on the reaction of cysteine with cobalt (Ⅱ) in NH 4Cl NH 4OH. The molar absorptivity is 7.98×10 3 L·mol -1 ·cm -1 at 284 nm. Beer′s law is obeyed for cysteine in the range of 0～2.0×10 -4 mol·L -1 . The method was applied to the assay of cysteine in urine.

Electrochemical Study of Phosphine Cobalt(Ⅱ) Complex with 2-mercaptobenzothiazole

Cyclic voltammetry is used to study the electrochemical behavior of CoCl 2, Co(dppe) 2Cl 2 and Co(mbt S,N) 2(dppe) [Hmbt=2 mercaptobenzothiazole; dppe=1,2 (diphenylphosphino)] in DMF or MeCN solution with 0.1 mol·L -1 Bu n 4NBF 4 as electrolyte on the Pt electrode. The results indicate that the reduction potential, transfer coefficient and diffusion coefficient of Co(Ⅱ), Co(dppe)(Ⅱ) and Co(mbt S,N) 2(dppe) in DMF and MeCN depend on the solvent coordinated species, the volume and structure of ion. This is the characterization of the synergistic coordination effect.

CHARACTERIZATION OF COBALT(Ⅱ)-PHTHALOCYANINE-METAL IRON COMPOSITES FOR MAGNETORHEOLOGICAL FLUIDS

Magnetorheological suspension based on 20 (v/V) % CoPc-iron composite particles dispersed in sili-cone oil have been obtained, which exhibited dynamic shear stress up to 2000Pa upon application of external magnetic field at 1300 Oe. The response is faster than 0. 15 -with superior reversibility of changes in viscosity induced by external magnetic field at above 12. 5℃. Further, it was found that the MR fluid is in possession of long-term stability a-gainst sedimentation.