The Fe(II) and Co(II) chelation complexes of 2,6-BIS(4-Ethyl-2-Pyridyl)-4-Phenyl-Pyridinl

A study has been made of the spectrophotometric constants of the new modified terpyridine chelation reagent, 2,6-bis(4-ethyl-2-pyridyl)-4-phenyl-pyridine (trivial name “ethyl-terosole”), as its Fe(II) and Co(II) complex cations. This new Iigand is outstanding for use in the trace quantity determination of iron. No advantage as compared to more sensitive ligands previously studied is provided by Co(II) chelation.     

Steric effects on the electronic and molecular structures of nickel(II) and cobalt(II) 2,6-dipyrazol-1-ylpyridine complexes

The complexes [M(L¹R)₂](BF₄)₂ (M=Ni, Co; L¹R=2,6-dipyrazol-1-ylpyridine [L¹H], 2,6-bis-{3-iso-propylpyrazol-1-yl}pyridine [L¹Prⁱ], 2,6-bis-{3-phenylpyrazol-1-yl}pyridine [L¹Ph], 2,6-bis-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine [L¹Mes]) and [M(L²)₂](BF₄)₂ (M=Ni, Co; L²=2-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}-6-{5-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine) have been prepared. Single crystal structure determinations of [M(L¹H)₂](BF₄)₂ (M=Ni, Co) and solvates of [Ni(L¹Mes)₂](BF₄)₂, [Co(L¹Mes)₂](ClO₄)₂ and [Co(L²)₂](BF₄)₂ all show six-coordinate metal centres with local near-D_2d symmetry. The L¹Mes and L² mesityl substituents have only a small effect on the MN{pyrazole} (M=Ni, Co) bond lengths in these compounds. The d–d spectra of the complexes show that L¹Mes is a significantly better donor ligand than L¹H, L¹Prⁱ or L¹Ph, and that L¹Prⁱ is a weaker ligand than might be expected purely on inductive grounds. A combination of UV–Vis/NIR, EPR, NMR and magnetic measurements have demonstrated that all the Co(II) compounds are high-spin in the solid state and in solution at 290 K.     

Structure and catalytic activity of a new iron(II) complex with a tetradentate carboxamide ligand: The effect of the outer-sphere donor on the chemoselectivity of the metal complex catalyst

The interaction between Fe(ClO₄)₂ or Fe(OTf)₂(MeCN)₂ and 2 equiv of the potentially tetradentate ligand bis(2-pyridyl)methyl-2-pyridinecarboxamide (Py₂CHNHCOPy, tpcaH) yields the iron(II) complex [Fe^II(tpcaH)₂]X₂ (X = ClO₄, OTf), in which, according to X-ray crystallography data, tpcaH is facially coordinated to the iron atom as a tridentate ligand through the carbonyl group and two pyridyl donors of the bis(2-pyridyl)methylcarboxamide moiety and the third pyridyl group is uninvolved in coordination. The oxidation of saturated and unsaturated hydrocarbons with hydrogen peroxide involving this complex has been investigated. The presence of the uncoordinated nitrogen donor in the outer coordination sphere of the complex exerts a crucial effect on it catalytic properties.     

Synthesis of 4′-(4‴-benzo-15-crown-5)-methyloxy-2,2′:6′,2″-terpyridine (L) and the crystal structure of its complexes with cobalt(II) and zinc(II): [ML2](ClO4)2 · 3H2O

The synthesis of 4′-(4?-benzo-15-crown-5)-methyloxy-2,2′:6′,2″-terpyridine (L) and is complexes with cobalt(II) and zinc(II) [CoL₂](ClO₄)₂ · 3H₂O (I) and [ZnL₂](ClO₄)₂ · 3H₂O (II) was described. For L and its complexes, the parameters of electronic absorption spectra in acetonitrile were determined and ¹H NMR signals were assigned. The structures of I and II were determined by X-ray crystallography. Compounds I and II are isostructural and consist of complex cations [ML₂]²⁺ (M = Co, Zn), ClO ₄ ^? anions, and crystal water molecules. The M atoms are located in special positions on twofold axes. The M atoms are surrounded by six N atoms of the terpyridine moieties of two organic molecular ligands. The M-N distance for the N(2) atoms of the central rings of the terpyridine moieties in both structures is shorter than for the side rings. The coordination polyhedra of the M atoms can be described as severely distorted octahedra. The major distortion of the octahedra is that the N…N distances in a terpyridine moiety are considerably shorter than those between the atoms of different moieties. The maximal deviation of the terpyridine atoms from the mean-square planes through these atoms is observed for the C(2) atom: 0.103(3) and 0.106(4) Å in I and II, respectively. The Co(1) and Zn(1) atoms are at a distance of, respectively, 0.1682(14) and 0.1415(17) Å from the corresponding planes.     

Spectroscopic, thermal and structural studies of a new mercury(II) complex of 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine (pyterpy) ligand, [Hg (hpyterpy)(SCN)2]2(MeSO4)2

A new mercury(II) complex [Hg(Hpyterpy)(SCN)₂]₂(MeSO₄)₂ was prepared from the reaction of 4′-(4-pyridyl)-2,2′:6′,2″- terpyridine (pyterpy), as a polypyridyl ligand, with mercury(II) thiocyanate. The compound was characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy and its structure was determined by X-ray single-crystal diffraction. The thermal stability of compound was studied by thermogravimetric (TG) and differential thermal analyses (DTA).     

Synthesis,characterization and biological activities of homo-binuclear Cu(II) and Zn(II) complexes derived from 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde derivatives

Few novel binuclear Schiff base metal complexes [M₂LCl₃], where M = Cu(II) and Zn(II); L= 2,6-bis-({2-[(3-hydroxy-4-nitrobenzylidene)amino]ethylimino}methyl)-4-methylphenol (BHEM), 2,6-bis-({2-[(3,4-dimethoxybenzylidene)amino]ethylimino} methyl)-4-methylphenol (BDEM) and 2,6-bis-({2-[(2,3,5-trichlorobenzylidene)amino]ethylimino}methyl)-4-methylphenol (BTEM), have been synthesized and characterized by analytical and spectral data. The data suggest that BHEM/BDEM/BTEM ligands afford square-pyramidal/distorted square-pyramidal geometry on metalation with Zn(II)/Cu(II). The binding behaviour of these complexes with DNA has been investigated using electronic absorption spectroscopy as well as viscosity and voltammetric measurements; the results show that they interact with DNA through intercalating way. From the DNA cleavage study of these complexes, investigated by gel electrophoresis, we found that they efficiently cleave supercoiled pUC19 DNA in the presence of a reducing agent (3-mercaptopropionic acid) and on irradiation with UV light of 360 nm wavelength. The mechanism reveals that singlet oxygen (¹O₂) plays a significant role in the photo cleavage. The superoxide dismutase (SOD) mimetic activity of the synthesized complexes demonstrates that most of the complexes have promising SOD-mimetic activity. The antimicrobial study indicates that the complexes inhibit the growth of bacteria and fungi more than the free ligands.     

Synthesis,structures and magnetic properties of two 2D → 3D entangled Cobalt(II) coordination polymers

Two Co(II) coordination polymers, namely Co(HBTC)(4-bpdb)·H₂O (1) and Co(HBTC)(3-bpdb)·H₂O (2) (H₃BTC = 1,3,5-benzenetricarboxylic acid, 4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene, 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3- butadiene), have been hydrothermally synthesized and characterized both structurally and magnetically. Compound 1 exhibits a (2D → 3D) polythreaded architecture. It is assembled from HBTC^2? ligands to form a 2D puckered (4,4) layer plus 4-bpdb ligands which are orientated above and below each layer. The structure of compound 2 consists of a 2D (3,5) wavelike sheet constructed from HBTC^2? anions and 3-bpdb spacers. The uncoordinated carboxyl groups of the HBTC^2? ligands protrude from both sides of the wavelike sheet to form a 2D → 3D interdigitated motif. The magnetic properties of both compounds are also investigated, indicating antiferromagnetic interactions between the adjacent metal centers.     

Transition metal complexes bearing 2,6-bis(imino)pyridyl: Synthesis,structure, ethylene polymerization/ oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyridine}Cl₂ [M=Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6)] have been synthesized. At 25°C, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(II), Co(II) catalysts can reach 4.02 ×10⁶ g/mol-Fehatm for ethylene polymerization and 3.98×10⁵ g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.

     

Cycloheptyl‐fused NNO‐ligands as electronically modifiable supports for M(II) (M = Co,Fe) chloride precatalysts; probing performance in ethylene oligo‐/polymerization

The N,N,O‐cobalt(II), [2,3‐{C₄H₈C(NAr)}:5,6‐{C₄H₈C(O)}C₅HN]CoCl₂ (Ar = 2,6‐(CHPh₂)₂‐4‐MeC₆H₂ Co1 , 2,6‐(CHPh₂)₂‐4‐EtC₆H₂ Co2 , 2,6‐(CHPh₂)₂‐4‐ClC₆H₂ Co3 , 2,6‐(CHPh₂)₂‐4‐FC₆H₂ Co4 ) and N,N,O‐iron(II) complexes, [2,3‐{C₄H₈C(NAr)}:5,6‐{C₄H₈C(O)}C₅HN]FeCl₂ (Ar = 2,6‐(CHPh₂)₂‐4‐MeC₆H₂ Fe1 , 2,6‐(CHPh₂)₂‐4‐EtC₆H₂ Fe2 , 2,6‐(CHPh₂)₂‐4‐ClC₆H₂ Fe3 , 2,6‐(CHPh₂)₂‐4‐FC₆H₂ Fe4 ), each containing one sterically enhanced but electronically modifiable N‐2,6‐dibenzhydryl‐4‐R²‐phenyl group, have been prepared by a one‐pot template approach using α,α′‐dioxo‐2,3:5,6‐bis(pentamethylene)pyridine, the corresponding aniline along with the respective cobalt or iron salt in acetic acid. Distorted square pyramidal geometries are a feature of the molecular structures of Co1 – Co4 . Upon activation with MAO or MMAO, Co1 – Co4 show good activities (up to 2.2 × 10⁵ g mol^?1(Co) h^?1) affording short chain oligomers (C₄–C₃₀) with good α‐olefin selectivity. By contrast, Fe1 – Fe4 , in the presence of MMAO, displayed moderate activities (up 10.9 × 10⁴ g(PE) mol^?1(Fe) h^?1) for ethylene polymerization forming low‐molecular‐weight linear polymers (up to 13.0 kg mol^?1) incorporating saturated n‐propyl and i‐butyl chain ends. For both cobalt and iron, the precatalysts incorporating the more electron withdrawing 4‐R²‐substituents [Cl ( Co3 / Fe3 ), F ( Co4 / Fe4 )] deliver the best catalytic activities, while with cobalt, these types of substituents additionally broaden the oligomeric distribution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3980–3989     

Synthesis and X-ray crystal structures of N,N,N′,N′-tetraalkylpyridine-2,6-dithiocarboxamides (S-dapt) complexes of cobalt(II) and nickel(II)

Reactions of anhydrous CoX₂ (X?=?Br^?, SCN^?) and Ni(ClO₄)₂ with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br₂] (1), [Co(S-dppt)(SCN)₂] (2), and [Ni(S-dept)₂]·(ClO₄)₂·H₂O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1?:?1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other hand, prefers an octahedral geometry with 1?:?2 metal–ligand ratio. The coordination behavior of S-dapt has been compared to the analogous oxo(O-daap) ligands. Lesser propensity of S atom to get involved in H-bonding interactions ensures an S-N-S type of tridentate coordination by S-dapt.     

Transition metal complexes bearing 2,6-bis(imino)pyridyl: Synthesis,structure, ethylene polymerization/ oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyridine}Cl₂ [M=Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6)] have been synthesized. At 25°C, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(II), Co(II) catalysts can reach 4.02 ×10⁶ g/mol-Fehatm for ethylene polymerization and 3.98×10⁵ g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.     

Electro-oxidation and electro-reduction of some iron (II), cobalt(II) and nickel(II) polypyridyl complexes in acetonitrile

Cyclic voltammetry and controlled potential coulometry studies of 2,2′-bipyridyl, 4,4′-dimethyl-2,2′-bipyridyl and 2,2′, 2″-terpyridyl complexes of Fe(II), Co(II) and Ni(II) in acetonitrile are described. E_1/2 values for M(III)/M(II) and M(II)/M)I) couples are compared and crystal field effects discussed. A series of M(I) and M(III) polypyridyl complexes have been prepared by controlled potential electrolysis; these include a number of 3+ and 1+ oxidation state complexes of nickel which have not previously been isolated — [Ni(bipy)₃]-(ClO₄)₃, [Ni(dimbipy)₃](ClO₄)₃, [Ni(terpy)₂](ClO₄)₃ and [Ni(bipy)₂]ClO₄.     

Cd(II) Complexes of 2,2':6',2'‐Terpyridine Substituted at 4'‐Position with Thienyl Groups: Synthesis,Structures, Luminescence,and Photocatalytic Activities

Four new complexes, namely Cd(II)(4'‐(2‐(5‐R‐thienyl))‐terpyridine)₂(ClO₄)₂ (R = hydrogen ( 1 ), bromo ( 2 ), methyl ( 3 ), and methoxy ( 4 )), were synthesized and characterized by high‐resolution mass spectrometry, infrared (IR) spectroscopy, and elemental analysis. Complexes 2 and 4 were further characterized by single‐crystal X‐ray diffraction analysis, which showed that the Cd(II) ions in complexes 2 and 4 are both six‐coordinated with the N₆ coordination sphere, displaying distorted octahedral geometries. The luminescence of complexes 1 – 4 was studied. Moreover, the photocatalytic properties of complexes 1 – 4 were investigated and compared with those of their parent complex Cd(II)(terpyridine)₂(ClO₄)₂.     

Crystal structure and thermal properties of novel Co(II) complexes with 2,6-pyridine-dicarboxylate containing infinite one-dimensional chain: [CoL1(H2O)4][Co(pydc)2]·2H2O and [Co(H2O)6]×[Co(pydc)2]L2·H2O (L1 = 1,3-bis(4-pyridyl)propane, L2 = 3-amino-1H-1,2,4-triazole, pydc = 2,6-pyridine-dicarboxylic acid)

The two title compounds were prepared from the ligand pydc with cobalt(II) acetate in the presence of L¹ and L² (L¹ = 1,3-bis(4-pyridyl)propane, L² = 3-amino-1H-1,2,4-triazole, pydc = 2,6-pyridinedicarboxylic acid). The complexes were characterized by elemental analysis, IR spectrum and single crystal X-ray diffraction. Single crystal analysis shows that in two complexes coordination number around Co atom is six with distorted octahedral geometry, and both two complexes consist of ion pairs containing cationic [Co(H₂O) _n ]²⁺ and anionic [Co(pydc)₂]^2- units.     

Synthesis,vibrational spectra,and structure of 4′-(4″-benzo-15-crown-5)oxy-2,2′:6′,2″-terpyridine (L) and its transition metal complexes. Extraction and ion-selective properties of L

Complexes of Co(II), Ni(II), Zn(II), and Cu(II) perchlorates and hexafluorophosphates with 4′-(4″-benzo-15-crown-5)oxy-2,2′:6′,2″-terpyridine (L) [M(L)₂](ClO₄)₂ · 3H₂O and [M(L)₂](PF₆)₂ · 2H₂O were synthesized. The spectral criteria of ligand coordination through the terpyridine nitrogen atoms were established. An assumption concerning the benzo-15-crown-5 conformation in the ligand molecule in the synthesized complexes was made. The extraction and ion-selective properties of L were studied.     

A Flexible Ligand for Multipurpose Complexation

Abstract

The synthesis of the flexible ligand 2,6-bis-{(bis-(2-aminoethyl)amino(methyl}anisole (L) is reported. The basicity behaviour in aqueous solution was studied by potentiometry (25°C, I = 0.15 mol dm^?3, Me₄NCl). L behaves as pentaprotic base (logK₁ = 10.31(2), logK₂ = 9.65(2), logK₃ = 9.16(2), logK₄ = 8.39(2), logK₅ = 2.14(2)). The stability constants for Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were determined by potentiometry and all of these metalions were found to form both mono and binuclear species: logK_ML = 9.39(3) for Co(II); 14.5(1) for Ni(II); 17.57(7) for Cu(II); 10.62(2) for Zn(II) and 9.83(3) for Cd(II). LogK_M2L = 15.19(3) for Co(II); 19.57(5) for Ni(II); 28.44(3) for Cu(II); 16.77(6) for Zn(II) and 14.62(3) for Cd(II). The crystals of [Cu₄L₂(N₃)₆](ClO₄)₂·H₂O are triclinic, space group P-1 a = 13.770(6), b = 14.043(2), c = 16.800(3) Å, α = 105.700(1), β = 102.790(3), γ = 103.660(3)°, Z = 2. L behaves as ditopic ligand and the crystal lattice consists of branched chains of Cu(II) ions.     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

Synthesis,structure and magnetic properties of iron (II), cobalt (II) and nickel (II) complexes of 2,6-bis(pyrazol-3-yl)pyridine and paramagnetic counterions

Iron (II), cobalt (II) and nickel (II) complexes of 2,6-bis(pyrazol-3-yl)pyridine (bpp) with [Cr(C₂O₄)₃]³⁻ have been prepared. They were characterised by single-crystal X-ray diffraction, magnetic susceptibility measurements and thermal gravimetric analyses. All three compounds are isostructural and they are formed by isolated [M^II(bpp)₂]²⁺ and [Cr(C₂O₄)₃]³⁻ complexes and free ClO₄ ⁻. As expected, only the salt [Fe(bpp)₂]₂[Cr(C₂O₄)₃]ClO₄·5H₂O shows a thermal spin transition with transition temperature (T_1/2) around 375 K that is correlated to the loss of water molecules.     

Preparation and spectroscopic characterization of iron(II) and copper(II) complexes of a functionalized crown ether

Condensation between 4′-aminobenzo-15-crown-5- and 4-antipyrinecarboxaldehyde yielded the functionalized crown ether (L = 1,5-dimethyl-4-[(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-15-ylimino)methyl]-2-phenyl-1,2-dihydro-3H-pyrazol-3-one). A 1:1 (Na⁺:L) complex has been prepared. The reaction of Fe(II) and Cu(II) salts with L gave complexes of composition [Fe(L)Cl₂] and [Cu(L)₂Cl₂]. Heteronuclear complexes [Fe(L)Cl₂Na]ClO₄ and [Cu(L)₂Cl₂Na]ClO₄ have also been synthesized from the reactions of [Fe(L)Cl₂] and [Cu(L)₂Cl₂] with NaClO₄. The compounds have been characterized by microanalyses and spectroscopic methods.     

Synthesis,characterization, crystal structure,and DNA binding of two copper(II)–hydrazone complexes

Two new Cu(II)–hydrazone complexes, [Cu(L)(Hbpe)ClO₄]·ClO₄·[Cu(L)Cl] (1) and [Cu(HL)₂]·1.5ClO₄·0.5OH (2) (where HL?=?(E)-N′-(1-(pyridine-2-yl)ethylidene)benzohydrazide and bpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene), have been synthesized and characterized by physicochemical methods. The structures of the complexes have been established by single-crystal X-ray diffraction direct methods, which reveal that the metal ions have distorted square-pyramidal and square-planar geometries in 1, and a distorted octahedral geometry in 2. DNA binding of HL, 1, and 2, performed by UV–vis titration in tris-buffer medium, yielded binding constants, which are 9.5 × 10³, 1.88 × 10⁴, and 4.66 × 10⁴ M^?1, respectively. Viscosity measurements suggest a surface or groove-binding mode of interaction between CT-DNA with HL, 1, and 2.