Linear Pentanuclear Research Articles

New metal complexes with inhibiting and biocide properties

Methanol solutions of various concentrations have been developed based on synthesized N, Nʹ- (pirazin-2-il) pyridine - 2,6-diamine ligand (N5-2pz), its linear pentanuclear of nickel string (II) [Ni5(μ5-dpzpda)4Cl2] (Ni5-N5-2pz) and tetracyclic copper complex (II) [Cu4(Hdpzpda)2(CH3COO)6] (Cu4-N5-2pz). Anticorrosion impact of these solutions on carbon steel Сt20 was studied on the model of produced water saturated with carbon dioxide (CO2) in the medium of hydrogen sulphide with different concentrations (H2S). Biocide properties of developed solutions against corrosion bacteria (sulphate-reducing bacteria, Tionand hydrocarbon oxidizing bacteria) have been studied on the samples of produced water taken from flooded production wells of “Bibiheybat” OGPD as well and good results obtained.

Linear pentanuclear nickel(II) and tetranuclear copper(II) complexes with pyrazine-modulated tripyridyldiamine ligand: Synthesis, structure and properties

By using tripyridyldiamine ligand, N,N’-di(pyrazin-2-yl)pyridine-2,6-diamine (H2dpzpda), linear pentanuclear nickel(II) [Ni5(µ5-dpzpda)4Cl2] (1) and tetranuclear copper(II) [Cu4(Hdpzpda)2(CH3COO)6] (2) complexes were first synthesized and structurally characterized. This pentanickel linear metal chain is helically wrapped by four syn-syn-syn-syn type dpzpda2- ligands. There are two types of NiNi distances existing in the complex. The terminal NiNi distances bonded to the axial ligand are longer (2.3877(8) Å) affected by the axial ligands. The inner NiNi distances are very short and remain constant (2.3071(6) Å). Two terminal Ni(II) ions bonded to the axial ligands are in a square-pyramidal (NiN4Cl) environment and exhibit long NiN bonds (2.097(4) Å), which are consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions display short NiN (1.8915(8)–1.903(4) Å) bond distances, which are consistent with a square planar (NiN4), the diamagnetic arrangement of a low-spin Ni(II) configuration. Temperature-dependent magnetic research revealed an antiferromagnetic interaction between the two terminal atoms through a superexchange pathway along metal cores with a parameter of about −51.0 cm–1. Observation of the first oxidation peak in the cyclic voltammograms of 1 at +1.206 V revealed that this complex is the most resistant to oxidation among all known pentanuclear nickel strings with unmodulated and modulated oligo-α-pyridylamido ligands. The structure of 2 consists of four copper atoms linearly placed with a copper(II) acetate dimer in the centre. In complex 2 ligand H2dpzpda coordinates to the Cu(II) atoms as a tetradentate ligand in an all anti conformation. Copper complex 2 is built to a 1-D supramolecular chain structure through intermolecular hydrogen bond and strong π-π interaction (3.19 Å) between the pyridine and pyrazine rings. From the magnetic susceptibility data, 2 shows strong antiferromagnetic coupling, which was satisfactorily fitted using Hamiltonian H = J1(S1S2 + S3S4) + J2S2S3. The best fitting result were obtained with the parameters J1 = 10.64 cm−1, J2 = −175.36 cm−1, g = 2.11.

An azide-bridged copper(II) complex: poly[piperazine-1,4-dium [tetra-μ₃-azido-κ¹²N¹:N¹:N¹-hexa-μ₂-azido-κ¹²N¹:N¹-di-μ₂-azido-κ⁴N¹:N³-pentacopper(II)] tetrahydrate

A new Cu(II)-azide complex, {(C4H12N2)[Cu5(N3)12]·4H2O}n, has been synthesized by the reaction of piperazine, Cu(OAc)2·2H2O (OAc is acetate) and NaN3. In the structure, μ2-1,1- and μ3-1,1,1-azide anions bridge five Cu(II) cations to form a linear pentanuclear cluster unit, which is further linked by μ2-1,1- and μ2-1,3-azide anions to form a two-dimensional condensed [Cu5(N3)12]n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three-dimensional supramolecular network.

Synthesis, structure, magnetism, and electrochemical properties of a linear pentanuclear Ni5 compound derived from an oligo-α-pyridylamino ligand: Ni5(μ-dmpdda)4(NCS)2

The synthesis, crystal structures, electrochemical, and magnetic properties of a linear pentanuclear Ni5 compound derived from an oligo-α-pyridylamino ligand, [Ni5(μ-dmpdda)4(NCS)2] [dmpdda-H2 = N,N′-di(4-methylpyridin-2-yl)pyridine-2,6-diamine], are reported. Ni5(μ-dmpdda)4(NCS)2 involve a Ni5 linear chain unit with all of the Ni–Ni–Ni angles being nearly 180°, terminated by two axial ligands. The pentanuclear linear metal chain is helically wrapped by four syn–syn–syn–syn type dmpdda2− ligands. There are two types of Ni–Ni distances in this complex. Terminal Ni–Ni distances bonded with the axial ligand are longer (2.377 Å); the inner Ni–Ni distances are short at 2.2968 Å. Terminal Ni(II) ions bonded with the axial ligands are square-pyramidal (NiN4NCS) with long Ni–N bonds (2.092 Å), consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions have short Ni–N (1.901–1.925 Å) bond distances, consistent with a square planar (NiN4), diamagnetic arrangement of a low-spin Ni(II) configuration. This compound exhibits magnetic behavior similar to [Ni5(μ-tpda)4(NCS)2], indicating an antiferromagnetic interaction of two terminal high-spin Ni(II) ions.

Two novel Zn(II) coordination polymers based on trigonal ligand: 4′-(4-pyridyl)-3,2′:6′,3″-terpyridine

Abstract Two novel Zn(II) coordination polymers, [Zn5(pytpy)8(fum)4(H2O)4(OH)2]n · n(CH3OH) · 2n(H2O) (1) and [Zn3(pytpy)4 (btc)2]n · 2n(H2O) (2) (pytpy = 4′-(4-pyridyl)-3,2′:6′,3″-terpyridine, H2fum = fumaric acid, H3btc = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized and structurally characterized. Complex 1 is a 2D layer structure, which is constructed from linear pentanuclear Zn(II) subunits interconnected via bidentate-bridging pytpy ligands and tridentate-bridging fum2− anions. Complex 2 is a 3D network structure, μ2-pytpy ligands link the layers based on the heart-like hexanuclear subunits to form the 3D network. Both complexes show strong fluorescence emission upon excitation at 310 nm in solid state. Additionally, these two complexes possess great thermal stabilities, especially for 2, the framework is stable up to 350 °C.

Synthesis, Structure, Magnetism and Electrochemical Properties of Linear Pentanuclear Complex: Ni5(µ‐dmpzda)4(NCS)2

Abstract The synthesis, crystal structure, electrochemical and magnetic properties of a type of pyridine‐modulated linear pentanuclear complex, [Ni5(µ‐dmpzda)4(NCS)2] [dmpzda‐H2=N,N′‐di(4‐methyl pyridin‐2‐yl)pyrazine‐2,6‐diamine], were studied. The complex involves a Ni5 linear chain unit with all of the Ni‐Ni‐Ni being nearly 180°, terminated by the two axial ligands. This pentanuclear linear metal chain is helically wrapped by four syn‐syn‐syn‐syn type dmpzda ligands. There are two types of Ni–Ni distances existing in the complex. The terminal Ni–Ni distances bonded with the axial ligand are longer (2.3821 Å) affected by the axial ligands. The inner Ni–Ni distances are very short and remain constant (2.2959 Å). Two terminal Ni(II) ions bonded with the axial ligands are in a square‐pyramidal (NiN4NCS) environment and exhibit long Ni–N bonds (2.103 Å), which are consistent with a high‐spin Ni(II) configuration. The inner three Ni(II) ions display short Ni–N (1.886–1.906 Å) bond distances, which are consistent with a squareplanar (NiN4), diamagnetic arrangement of a low‐spin Ni(II) configuration. This compound exhibits similar [Ni5(µ‐tpda)4(NCS)2] magnetic behavior, indicating an antiferromagnetic interaction of two terminal high‐spin Ni(II) ions in these complexes.

A pyrazine-bridged linear pentanuclear copper(II) complex and related tri- and dinuclear complexes showing various coordination structures and magnetic couplings

Sterically bulky pyrazines have been successfully utilized for the preparation of discrete oligo-nuclear TBP (trigonal bipyramidal), SqP (square pyramidal), and Oh (octahedral) copper(II) complexes. We have synthesized a unique linear pentanuclear complex [{Cu(hfac) 2} 5(μ-2-butyl-3-methylpyrazine) 4]. The two terminal copper(II) ions have a SqP structure while the three inner ions have an Oh one. The solvent molecule was incorporated in the clearance of the lattice. From another reaction under harsh conditions, we separated [{Cu(hfac) 2} 3(μ-2-butyl-3-methylpyrazine) 2], which can be regarded as the central moiety of the pentanuclear one. We also prepared a dinuclear complex [{Cu(hfac) 2} 2(μ-tetramethylpyrazine)], in which the pyrazine nitrogen atoms were located at TBP equatorial positions. Single-crystal EPR measurements supported its compressed TBP structure. The exchange coupling was antiferromagnetic with J TBP–TBP/ k B = −3.6 K. The linear trinuclear [{Cu(hfac) 2} 3(μ-2,3,5-trimethylpyrazine) 2], having two TBP Cu ions with an intervening Oh Cu ion, showed very weak antiferromagnetic coupling. DFT calculations on these compounds indicated that the σ-type orbital overlap between the Cu and N atoms is essential for superexchange interactions.

Coligand Modulated Six-, Eight-, and Ten-Connected Zn/Cd-1,2,4-Triazolate Frameworks Based on Mono-, Bi-, Tri-, Penta-, and Heptanuclear Cluster Units

Using nonsubstituted 1,2,4-triazole and the second bridging ligands as coligands, a series of three-dimensional metal–organic frameworks based on different secondary building units (SBUs), namely, Zn2(trz)3(SCN) (1), Zn2(trz)2(ox) (2), Cd3(trz)2(suc)Cl2(3), [Cd5(trz)6(OAc)2Cl2(H2O)2]·2H2O (4), and [Zn7(trz)6(1,2,4,5-BTC)2(H2O)6]·8H2O (5) (trz = 1,2,4-triazole, ox = oxalate, suc = succinic acid, 1,2,4,5-BTC = 1,2,4,5-benzenetetracarboxylate), have been synthesized and structurally characterized with the aid of single-crystal X-ray diffraction. The SBUs in 1–5 vary from mononuclear, binuclear, linear trinuclear, linear pentanuclear to heptanuclear d10-1,2,4-triazolate polynuclear clusters. Compound 1 presents a complicated 3,6-connected topology based on three nonequivalent nodes. Compound 2 adopts a 6-connected 3D network of distorted α-Po topology that is built from dizinc units. The structure of 3 consists of two intersecting (4,4) grids which generate a novel self-penetrating 4,8-connected net with (456...

Tri- and pentanuclear tungsten-(mu-S)-M clusters (M = W, Cu, Ag).

The thiotungstate [Et4N]2[OW(WS4)2], [Et4N]2.1, containing the linear [[S2W(VI)(mu-S)2]2W(IV)=O] core, was prepared from [Et4N]2[WS4] in the presence of the sulfide scavenger Cd2+. Addition of 1,2-bis(o-diphenylphosphinophenyl)ethane (diphosphine) and Cu+ or Ag+ to solutions of 1 in MeCN/DMF led to coordination of the (diphosphine)Cu/Ag fragments to the terminal sulfido ligands of 1, yielding novel linear pentanuclear, heterometallic clusters [mu-[OW(IV)(DMF)(W(VI)S4)2][M(diphosphine)]2], 2 (M = Cu) and 3 (M = Ag). Along with 2, the trinuclear cluster [[mu-(W(VI)S4)[Cu(diphosphine)(2)]], 4, was also obtained. The molecular and crystal structures of [Et4N]2.1, 2.MeCN, 3.MeCN, and 4.2MeCN.CH2Cl2 have been determined.

Unsymmetrical linear pentanuclear nickel string complexes: [Ni(5)(tpda)(4)(H(2)O)(BF(4))](BF(4))(2) and [Ni(5)(tpda)(4)(SO(3)CF(3))(2)](SO(3)CF(3)).

The one-electron oxidized linear pentanuclear nickel complexes [Ni(5)(tpda)(4)(H(2)O)(BF(4))](BF(4))(2) (1) and [Ni(5)(tpda)(4)(SO(3)CF(3))(2)](SO(3)CF(3)) (2) have been synthesized by reacting the neutral compound [Ni(5)(tpda)(4)Cl(2)] with the corresponding silver salts. These compounds have been characterized by various spectroscopic techniques. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 15.3022(1) A, b = 31.0705(3) A, c = 15.8109(2) A, beta = 92.2425(4) degrees, V = 7511.49(13) A(3), Z = 4, and compound 2 crystallizes in the monoclinic space group C2/c with a = 42.1894(7) A, b = 17.0770(3) A, c = 21.2117(4) A, beta = 102.5688(8) degrees, V = 14916.1(5) A(3), Z = 8. X-ray structural studies reveal an unsymmetrical Ni(5) unit for both compounds 1 and 2. Compounds 1 and 2 show stronger Ni-Ni interactions as compared to those of the neutral compounds.

Linear pentacobalt complexes: synthesis, structures, and physical properties of neutral and one-electron oxidation compounds

A series of linear pentanuclear cobalt complexes, including both neutral and one-electron oxidized forms, have been synthesized. The one-electron oxidation products were prepared either by reaction with silver salts or by bulk electrolysis. In all of these complexes, the pentacobalt chain adopts a symmetrical arrangement and is helically wrapped by four tpda [the dianion of N,N′-bis(α-pyridyl)-2,6-diaminopyridine] ligands. Two sets of Co–Co bond distances are observed, in which the average internal (inner) bond is about 0.06 A shorter than the external (outer) one. After one-electron oxidation, the average Co–Co and Co–N bond distances are not significantly different from those of the neutral analogues, whereas the Co–X (X = axial ligand) bond lengths exhibit a slight decrease in length. All of these complexes show two reversible redox couples at about +0.35 and +0.85 V (vs. Ag/AgCl). The first oxidation is a metal-centered reaction and the product has been structurally characterized. The second oxidation product is stable on the time scale of spectroelectrochemistry, but undergoes reduction to form the corresponding one-electron oxidation product under the crystallization conditions. The NMR results are consistent with the paramagnetism of both the neutral and oxidized complexes. The magnetic measurements indicate that the neutral and one-electron oxidized molecules have spin states of S = 1/2 and 1, respectively.

Dinuclear CuII and NiII complexes of 3-formylsalicylic acid oxime: cis/trans topology and extension of a cis-CuII2 complex to a pentanuclear CuIICuIIMnIICuIICuII complex

3-Formylsalicylic acid oxime (H3L) formed the following dinuclear CuII and NiII complexes: [Cu2(HL)2]·0.5H2O (1), Na[Cu2(HL)(L)]·3H2O (2) and [Ni2(HL)2]·2.5H2O (3). The structures of Na[Cu2(HL)(L)(H2O)] (2′) and [Ni2(HL)2(H2O)4]·8H2O (3′) have been determined by X-ray crystallography. Complex 2 has a cis arrangement of the two ligands providing dissimilar {CuN2O2} and {CuO4} chromophores sharing the two phenolic oxygen atoms. The N2O2 cavity has a hydrogen-bonded N–O⋯H⋯O–N linkage as the lateral chain, and the Cu in this site has a square-pyramidal geometry with a water molecule at the axial site. The Cu in the O4 cavity has a planar geometry. Complex 3 has a trans configuration with respect to its two ligands and each Ni has a six-coordinate geometry with two water molecules at the axial sites. Complex 1 has a trans configuration based on its having a chemical formula and IR spectrum similar to 3. The following interconversion among dinuclear Cu complexes has been established by pH adjustment: trans-[Cu2(HL)2] (1) ⇌ cis-[Cu2(HL)(L)]− (2) ⇌ trans-[Cu2(L)2]2− (water molecules are omitted). On the other hand, 3 showed the following interconversion: trans-[Ni2(HL)2] (3) ⇌ trans-[Ni2(L)2]2−. The cis Cu2 complex 2 was reacted with MnII to afford [Mn{Cu2(HL)(L)}2(H2O)4]·H2O·2DMF (4) that has a linear pentanuclear CuIICuIIMnIICuIICuII structure formed by the coordination of two molecules of 2 to a MnII through a carboxylate group.

Linear Five-Centred Chromium Multiple Bonds Bridged by Four tpda2 Ligands [tpda2 = tripyridyldiamido dianion] – Synthesis and Structural Studies

The linear pentanuclear chromium complexes [CrII5(μ5-tpda)4Cl2] (1), [CrII5(μ5-tpda)4(NCS)2] (2), [CrIIICrII4(μ5-tpda)4F2](BF4) (3), and [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4), with four all-syn tri(α-pyridyl)diamido dianion (tpda2–) ligands, have been prepared and structurally characterized. Compounds 1 and 2 possess a delocalized Cr(II)–Cr(II)–Cr(II)–Cr(II)–Cr(II) five-centred metal–metal bond of order 1.5. In both 1 and 2 two values for CrII–CrII bond lengths are found both; the outer ones connected with axial ligands are 2.284(1) and 2.285(2) Å, and the inner ones are 2.2405(8) and 2.246(1) Å, for 1 and 2, respectively. When compound 1 reacts with 2 equiv. of AgBF4 or Ag(OTf), a oxidation reaction takes place and one of the terminal chromium(II) ions is oxidized to produce [CrIIICrII4(μ5-tpda)4F2]BF4 (3) or [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4). Two short Cr–Cr distances [1.969(2) and 2.138(2) Å for 3, 1.846(1) and 1.922(1) Å for 4] are found, with the presence of two quadruple bonds among four adjacent CrII ions. The fifth CrIII ion, which is separated from the neighboring CrII ion by 2.487(2) Å for 3 and 2.610(1) Å for 4, is simply a square pyramidal unit with no metal–metal bonding interaction.

Linear Five-Centred Chromium Multiple Bonds Bridged by Four tpda2– Ligands [tpda2– = tripyridyldiamido dianion] – Synthesis and Structural Studies

The linear pentanuclear chromium complexes [CrII5(μ5-tpda)4Cl2] (1), [CrII5(μ5-tpda)4(NCS)2] (2), [CrIIICrII4(μ5-tpda)4F2](BF4) (3), and [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4), with four all-syn tri(α-pyridyl)diamido dianion (tpda2–) ligands, have been prepared and structurally characterized. Compounds 1 and 2 possess a delocalized Cr(II)–Cr(II)–Cr(II)–Cr(II)–Cr(II) five-centred metal–metal bond of order 1.5. In both 1 and 2 two values for CrII–CrII bond lengths are found both; the outer ones connected with axial ligands are 2.284(1) and 2.285(2) A, and the inner ones are 2.2405(8) and 2.246(1) A, for 1 and 2, respectively. When compound 1 reacts with 2 equiv. of AgBF4 or Ag(OTf), a oxidation reaction takes place and one of the terminal chromium(II) ions is oxidized to produce [CrIIICrII4(μ5-tpda)4F2]BF4 (3) or [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4). Two short Cr–Cr distances [1.969(2) and 2.138(2) A for 3, 1.846(1) and 1.922(1) A for 4] are found, with the presence of two quadruple bonds among four adjacent CrII ions. The fifth CrIII ion, which is separated from the neighboring CrII ion by 2.487(2) A for 3 and 2.610(1) A for 4, is simply a square pyramidal unit with no metal–metal bonding interaction.

Synthesis, Crystal Structures, and Magnetic Properties of a Series of Linear Pentanickel(II) Complexes: [Ni(5)(&mgr;(5)-tpda)(4)X(2)] (X = Cl(-), CN(-), N(3)(-), NCS(-)) and [Ni(5)(&mgr;(5)-tpda)(4)(CH(3)CN)(2)]- (PF(6))(2) (tpda(2-) = the Tripyridyldiamido Dianion).

The synthesis, crystal structures, and magnetic properties of linear pentanuclear complexes, [Ni(5)(&mgr;(5)-tpda)(4)X(2)](n)()(+) [tpdaH(2) = tripyridyldiamine, with different axial ligands X = Cl(-) (1), CN(-) (2), N(3)(-) (3), and NCS(-) (4) (n = 0) and CH(3)CN (5) (n = 2)], are reported. All of the [Ni(5)(tpda)(4)](2+) moieties are isostructral and involve a Ni(5) linear chain unit with all of the angleNi-Ni-Ni being nearly 180 degrees, terminated by the two axial ligands. The pentanuclear linear metal chain is helically wrapped by four syn-syn-syn-syn type tpda(2-) ligands. There are two types of Ni-Ni distances existing in these complexes. The terminal Ni-Ni distances bonded with the axial ligand are longer (2.35-2.40 Å) and affected by various axial ligands. The inner Ni-Ni distances are very short and remain constant ( approximately 2.30 Å). The relationship between terminal Ni-Ni distances and properties of the axial ligands on 1-5 will be discussed. Two terminal Ni(II) ions bonded with the axial ligands are in a square-pyramidal (NiN(4)X) environment and exhibit long Ni-N bonds ( approximately 2.10 Å) which are consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions display short Ni-N ( approximately 1.90 Å) bond distances which are consistent with a square-planar (NiN(4)), diamagnetic arrangement of a low-spin Ni(II) configuration. All compounds exhibit similar magnetic behavior, indicating an antiferromagnetic interaction of two terminal high-spin Ni(II) ions in these complexes. The XANES (X-ray absorption near-edge absorption spectroscopy) spectra also confirm the existence of the high-spin and low-spin Ni(II) ions in these complexes.