Triethylenetetraminehexaacetatoferrato(II)cuprate(II), [FeIICuII-(ttha)]2−: oxidation-induced cross-binuclear metal exchange

Summary The heterobinuclear complex [Fe^IICu^II(ttha)]^2– (1) (ttha^6– = triethylenetetraminehexaacetate), exhibits the same two-nitrogen per metal coordination of the related homobinuclear [Cu _inf2 ^supII (ttha)]^2– complex, but(1) has a signature broad single derivative e.p.r. line atg = 2.11 with a peak-to-peak width of 182 G. Oxidation to the [Fe^IIICu^II(ttha)]^– complex by either O₂ or H₂O₂ initiates a rapid cross-binuclear metal exchange forming homobinuclear [Fe _inf2 ^supIII O(ttha)]^2– and [Cu _inf2 ^sup– (ttha)]^2– products (t _1/2 ca 3.9 s). An isomeric form of [Fe^IIICu^II(ttha)]^–, which has three nitrogen donors bound to Cu^II and only the remaining iminodiacetate fragment bound to Fe^III, rearranges much more slowly (t _1/2 ca 4.8 h).     

Poly[tetraamminecopper(II) bis[tris(μ2‐cyanido‐κ2C,N)dicuprate(I)]]: a unique CuI–CuII mixed‐valence complex containing anionic cuprous cyanide layers and [Cu(NH3)4]2+ cations

The title compound, {[Cu(NH₃)₄][Cu(CN)₃]₂}_n, features a Cu^I–Cu^II mixed‐valence CuCN framework based on {[Cu₂(CN)₃]⁻}_n anionic layers and [Cu(NH₃)₄]²⁺ cations. The asymmetric unit contains two different Cu^I ions and one Cu^II ion which lies on a centre of inversion. Each Cu^I ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the Cu^II ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between Cu^I ions and cyanide bridges produces a honeycomb‐like {[Cu₂(CN)₃]⁻}_n anionic layer containing 18‐membered planar [Cu(CN)]₆ metallocycles. A [Cu(NH₃)₄]²⁺ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu₂(CN)₃]⁻}_n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands.     

catena‐Poly[hexaaquamagnesium(II) [bis(μ3‐5‐nitro‐2‐oxidoisophthalato)dicopper(II)] dihydrate]

In the centrosymmetric dinuclear anions of the title bimetallic complex, {[Mg(H₂O)₆][Cu₂(C₈H₂NO₇)₂]·2H₂O}_n, each Cu^II ion is strongly coordinated by four O atoms in a distorted square‐planar geometry. Two of these O atoms belong to phenolate groups and the other two to carboxylate groups from 5‐nitro‐2‐oxidoisophthalate (L1) trianions, derived from 5‐nitrobenzene‐1,2,3‐tricarboxylic acid (O₂N–H₃L). The phenolate O atoms bridge the two Cu^II ions in the anion. In addition, each Cu^II cation interacts weakly with a symmetry‐related carboxylate O atom of an adjacent L1 ligand, giving a square‐pyramidal coordination geometry. The copper residue forms a ladder‐like linear coordination polymer via L1 ligands. The [Mg(H₂O)₆]²⁺ cations sit on centres of inversion. The polymeric anions, cations and free water molecules are self‐assembled into a three‐dimensional supramolecular network via O—H...O hydrogen bonds.     

A copper(I) coordination polymer incorporation the corrosion inhibitor 1H‐benzotriazole: poly[μ3‐benzotriazolato‐κ3N1:N2:N3‐copper(I)]

The title complex, [Cu(C₆H₄N₃)]_n, was synthesized by the reaction of cupric nitrate, 1H‐benzotriazole (BTAH) and aqueous ammonia under hydrothermal conditions. The asymmetric unit contains three crystallographically independent Cu^I cations and two 1H‐benzotriazolate ligands. Two of the Cu^I cations, one with a linear two‐coordinated geometry and one with a four‐coordinated tetrahedral geometry, are located on sites with crystallographically imposed twofold symmetry. The third Cu^I cation, with a planar three‐coordinated geometry, is on a general position. Two Cu^I cations are doubly bridged by two BTA⁻ ligands to afford a noncentrosymmetric planar [Cu₂(BTA)₂] subunit, and two [Cu₂(BTA)₂] subunits are arranged in an antiparallel manner to form a centrosymmetric [Cu₂(BTA)₂]₂ secondary building unit (SBU). The SBUs are connected in a crosswise manner via the sharing of four‐coordinated Cu^I cations, Cu—N bonding and bridging by two‐coordinate Cu^I cations, resulting in a one‐dimensional chain along the c axis. These one‐dimensional chains are further linked by C—H...π and weak van der Waals interactions to form a three‐dimensional supramolecular architecture.     

Synthesis,structure and electrochemistry of a copper(II) complex with 1,2-di{o-[o-hydroxy(naphthylideneimino)]phenoxy}ethane

The title Schiff base ligand, H₂L, and its complex [CuL] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The electrochemical properties of the single crystal [CuL]·0.5C₂H₄Cl₂ have been investigated by cyclic voltammetry (c.v.). Upon scanning at negative and positive potentials, two reduction and two oxidation waves were observed at E _1/2 ⁰ = –0.47 and –0.77 V and E _1/2 ⁰ = 1.10 and 1.39 V, respectively. Two K _com values for the reduction and oxidation process are 1.2×10⁵ and 8.0×10⁴, respectively, and indicate that the deprotonated ligand, L, has the ability to stabilize the mixed valent states of both Cu^IICu^I and Cu^IICu^III. The crystal structure has been solved by X-ray diffraction, with a final R = 0.0653. Wound around a copper atom, the effectively tetradentate chain ligand, L, coordinates only via its two imino and two phenolate groups at both ends of the chain. The geometry, D _2d symmetry, is best described as trans 'N₂O₂' square-planar with slight tetrahedral distortion. The reason, why the mononuclear [CuL] unit can display two c.v. waves in each process, has been explained on the basis of configuration interchange between mono- and dinuclear units in c.v. electrolyte solution.     

On the Oxidation of Octamethylenetetrathiafulvalene by CuBr2 – Synthesis,Crystal Structure and Magnetic Properties of (OMTTF)2[Cu4Br10]

The reaction of octamethylenetetrathiafulvalene (OMTTF) with excess CuBr₂ in tetrahydrofurane/acetonitrile yields black (OMTTF)₂[Cu₄Br₁₀] ( 1 ). The crystal structure determination shows the presence of OMTTF cations and tetranuclear bromidocuprate anions. The novel anion consists of four edge and corner sharing CuBr₄ tetrahedra, which are connected to a ring. The assignment of the ionic charges and oxidation states for the copper atoms is supported by the magnetic properties. 1 is antiferromagnetic with T_N ≈ 30 K. The magnetic moment reaches 2.54 B.M., which indicates, together with the Curie–Weiss constant of –35 K, a coupling of the paramagnetic spins over the whole temperature region. The ionic charges of the salt‐like compound 1 are therefore (OMTTF²⁺)₂[(Cu⁺)₂(Cu²⁺)₂Br₁₀]^4–. The antiferromagnetism is explained by the coupling of the spins of two Cu²⁺ ions in the anion with an exchange constant of J = –18 cm^–1. The Cu^I and Cu^II atoms are clearly distinguishable in the mixed valent anion. The OMTTF cation is not planar but exhibits an interplanar angle between the two central C₃S₂ ring moieties of 15.3°, which is in accordance to the dicationic oxidation state.     

Metal Complexes with Macrocyclic Ligands. Part XXXIX. Mono- and binuclear copper(II) complexes of a bridging bis[1, 4, 7-triazacyclononane]

The new bis-macrocycle 1, 1′-[(1H-pyrazol-3], 5-diyl)bis(methylene)bis[1, 4, 7-triazacyclononane] ( 1 ) was synthesized and its complexation with Cu²⁺ studied. Potentiometric and spectrophotometric titrations indicate that, in addition to the mononuclear species [Cu(LH₂)]⁴⁺, [Cu(LH)]³⁺, [CuL]²⁺, and [Cu(LH_?1)]⁺, binuclear complexes such as [Cu₂L]⁴⁺, [Cu₂(LH_?1)]³⁺, and [Cu₂(LH_-2)]²⁺ are also formed in solution. The stability constants and spectral properties of these are reported. The binuclear species [Cu₂(LH_?1)]³⁺ specifically reacts with an azide ion to give a ternary complex [Cu₂(LH_?1)(N₃)]²⁺, the stability and structure of which were determined spectrophotometrically and by X-ray diffraction, respectively. The two Cu²⁺ ions are in a square-pyramidal coordination geometry. The axial ligand is one of the N-atoms of the 1, 4, 7-triazacyclononane ring, whereas at the base of the square pyramid, one finds the other two N-atoms of the macrocycle, one N-atom of the pyrazolide and one of the azide, both of which are bridging the two metal centres. In [Cu₂(LH_?1)(N₃)]²⁺, a strong antiferromagnetic coupling is present, thus resulting in a species with a low magnetic moment of 1.36 B.M. at room temperature.     

Imidazo[1,2-a]pyridine-substituted coumarin as a selective ratiometric sensor for Cu2+ ion

A novel fluorescent chemosensor, (E)-7-(diethylamino)-3-((2-phenylimidazo[1,2-a]pyridin-3-ylimino)methyl)-2H-chromen-2-one 1a, has been synthesised and characterised. This chemosensor displayed an extreme selective fluorescence emission only with Cu²⁺ ion over all other metal ions examined. The Job’s plot experiment analysis suggested the binding ratio of the chemosensor 1a with Cu²⁺ was 1:1 metal-to-ligand ratio. The association constant for Cu²⁺ towards receptor 1a obtained from Benesi–Hildebrand plot was found to be 4.859 × 10³ M^?1 with a detection limit 4.6 × 10^?8 M. Fluorescence enhancement caused by Cu²⁺ binding with chemosensor 1a attributed to combinational effect of intramolecular charge transfer and chelation-enhanced fluorescence occurred at pH 8.0.     

Synthesis and metal complexation studies of [2n]thiacalix[m]arene[m]pyrazine

Novel [2_n]thiacalixarenepyrazine and [2_n]thiacalixarenetriazine systems were synthesised by one-pot S_NAr reactions. A screening of the metal-complexing ability of [2₆]hexathiacalix[3]arene[3]pyrazine revealed its affinity for Cu^I, Cu^II and Ag^I metal salts.     

Synthesis,structure and characterization of the trinuclear copper (I) complex [Cu3(μ3-Br)2(dppm)3]Br

The novel trinuclear copper(I) complex [Cu₃(μ₃,-Br)₂(dppm)₃]Br has been obtained by reaction of bis(diphenyl-phosphino)methane (dppm) with cupric bromide. The title complex was characterized by single-crystal X-ray analysis, elemental analysis, molecular weight determination, ³¹P NMR and its conductivity was also measured. The [ Cu₃ (dppm)₃ Br₂ ]⁺ cation consists of a triangular array of copper atoms, with dppm ligands (Ph₂ PCH₂ PPh₂) bridging each edge of the triangle and two triply bridging Br groups bound to the two faces of the Cu₃ unit. Crystallographic data: monoclinic, space group P2₁/c, a = 1.4739(4), b = l.7708(5), c = 2.8395(8) nm, β= 97.16(3)°, V = 7.353nm³, Z = 4, F(000)= 3296, D_calc, = 1.472 g/cm³, μ = 26.478 cm^?1, R=0.06, R_W = 0.08, 4654 reflections observed with I3≥(I).     

Two new 2-D frameworks based on tetra-copper(II)-substituted sandwich-type polyoxotungstate anions and [Cu2(dien)2(OH)]3+ cations

Two new organic–inorganic polyoxometalates [Cu(dien)(H₂O)]₂{[Cu₂(dien)₂(OH)]₂[Cu₄(B-α-XW₉O₃₃)₂]}·4H₂O (X?=?Sb, 1; X?=?As, 2) (dien?=?diethylenetriamine) were hydrothermally synthesized and characterized by elemental analysis, IR spectra, thermogravimetric (TG) analyses, and single-crystal X-ray diffraction. Both compounds are constructed from one four-coordinate [Cu(dien)(H₂O)]²⁺, one {[Cu₂(dien)₂(OH)]₂[Cu₄(B-α-XW₉O₃₃)₂]} building unit, and four water molecules of crystallization. Structural analysis shows that the sandwich-like polyoxotungstate cluster anions [Cu₄(B-α-XW₉O₃₃)₂]^10? are linked by six adjacent dimeric cations [Cu₂(dien)₂(OH)]³⁺ into a 2-D architecture with a (6,3)-connected topology. Magnetic measurements of 1 and 2 exhibit the presence of antiferromagnetic interactions within the tetranuclear-Cu^II cluster.     

Synthesis,spectroscopic and voltammetric studies of mixed-ligand copper(II) complexes of amino acids

Two Cu^II complexes of the type [Cu(L¹)(L²)] (where L¹ = tryptophanate or phenylalaninate; L² = cysteine thiolate) have been prepared and characterised, and their spectrophotometric and voltammetric behaviour has been investigated. The results obtained by means of FT-IR, e.s.r., u.v.–vis. spectroscopy and by voltammetry revealed the existence of two different [Cu(L¹)(L²)] complexes. A significance decrease in the g _|| value and, concomitantly, an increase in the d–d transition energy was observed when a mixed-ligand complex is present. The observed anisotropic g-values indicate the presence of Cu^II in a tetragonally distorted octahedral geometry. Formation of a mixed-ligand copper complex can be considered as a type of synergism in the presence of cysteine. The redox state Cu^II or Cu^I of copper in the Cu(L²) complex depends on the analysing conditions, i.e., cysteine forms a Cu^II complex under aerobic conditions and a Cu^I complex in anaerobic media. Tryptophan or phenylalanine is bound to Cu^II ions in the Cu(L¹) complexes.     

Synthesis of a new salt containing polyoxometallate anion and M?Cu?S cluster cation [MS4Cu4(γ-MePy)8][M6O19] (M = Mo,W). Crystal structure of [WS4Cu4(γ-MePy)8] [W6O19]

Reactions of (NH₄)₂MS₄, AgBr and CuBr in γ-methylpyridine produced one new compound, [MS₄Cu₄(γ-MePy)8][M₆O₁₉] (1, M = W; 2 , M = Mo), of which 1 was characterized by single crystal X-ray analysis. The crystal data: orthorhombic, Pbcn, a = 15.434(4), b = 16.732(2), c = 28.657(7) Å, V = 7400.8(8) ų, Z = 4 , R = 0.072 for 3121 independent data. The compound is the first example which contains both polyoxotungstate anion and heteropolynuclear cluster cation. In the structure of the cation four edges of the tetrahedral WS^2?₄ core are coordinated by four copper atoms, giving a WS₄Cu₄ aggregate of approximate D_2h symmetry. The differences between the reaction of Cu⁺ with MS^2?₄ and that of Ag+ with MS^2?₄ in pyridine and its derivatives are discussed.     

Fluorescent chemosensors based on a new type of lower rim-dansylated and bridge-substituted calix[4]arenes

The synthesis, structural and chemosensing properties of several lower rim-dansylated calix[4]arenes bearing different methylene bridge substituents are described. Compared to bridge-unsubstituted pendants neither the conformational nor the fluorescence characteristics of the calixarene core are perceptibly influenced by the bridge substituent. X-ray structure as well as NMR measurements indicates the lower rim-propoxylated and-dansylated calixarenes to adopt the cone conformation capable of the complexation of Cu²⁺ ions at micromolar level. Fluorescent measurements point to selective 1:2 calixarene: Cu²⁺ complex formation with sensing parameters being of a suitable level to make the use as a potentially immobilisable chemosensor for the detection of Cu²⁺ ions promising.     

Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity

The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of Cu^II or Na^I/Ni^II under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [Cu^II(μ‐CH₃COO)₂(κO‐DAPTA=O)]₂ ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]₂(BPh₄)₂ ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear Cu^II complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence Cu^II/Cu^I complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand.     

Halide Abstraction from Organic Solvents in Reactions of a Copper(I) Alkoxide: Synthesis and Crystal Structures of [Cu5(dppm)(dppm−)2(OtBu)Cl2] and [Cu3(dppm)3Br2][CuBr2]

The synthesis and structures of the two Cu^I halide complexes [Cu₅(dppm)(dppm^?)₂(O^tBu)Cl₂] and [Cu₃(dppm)₃Br₂][CuBr₂] (dppm = Ph₂PCH₂PPh₂, dppm^? = [Ph₂PCHPPh₂]^?) are reported. The compounds were obtained by treating reaction mixtures of [CuO^tBu] and dppm with dichloromethane or dibromomethane.     

Hydrothermal syntheses and crystal structures of two CuI coordination polymers: [CuI(TATP)(CN)] n and [CuI(bpy)(SCN)] n (TATP = 1,4,8,9-tetranitrogen-trisphene, bpy = 2,2′-bipyridine)

Two new Cu^I coordination polymers, [Cu^I(TATP) (CN)] _n (1) and [Cu^I(bpy)(SCN)] _n (2) (TATP = 1,4,8,9-tetranitrogen-trisphene, bpy = 2,2′-bipyiridine), have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, and X-ray crystallography. In 1 and 2, the metal centers are linked by bridging CN⁻/SCN⁻ to form one-dimensional chains in the crystals and are stabilized by interchain π–π stacking interaction.     

Ionothermal synthesis and crystal structure of a new organic–inorganic hybrid compound: catena‐poly[bis(1‐ethyl‐3‐methylimidazolium) [hepta‐μ‐bromido‐pentacuprate(I)]]

A new organic–inorganic hybrid compound, catena‐poly[bis(1‐ethyl‐3‐methylimidazolium) [μ₅‐bromido‐tri‐μ₃‐bromido‐tri‐μ₂‐bromido‐pentacuprate(I)]], {(C₆H₁₁N₂)₂[Cu₅Br₇]}_n, has been obtained under ionothermal conditions from a reaction mixture containing Ba(OH)₂·8H₂O, Cu(OH)₂·2H₂O, As₂O₅, 1‐ethyl‐3‐methylimidazolium bromide and distilled water. The crystal structure consists of complex [Cu₅Br₇]²⁻ anions arranged in sinusoidal {[Cu₅Br₇]²⁻}_n chains running along the a axis, which are surrounded by 1‐ethyl‐3‐methylimidazolium cations. Three of the five unique Br atoms and one of the three Cu^I atoms occupy special positions with half‐occupancy (a mirror plane perpendicular to the b axis, site symmetry m). The Cu^I ions are in a distorted tetrahedral coordination environment, with four Br atoms at distances ranging from 2.3667 (10) to 2.6197 (13) Å, and an outlier at 3.0283 (12) Å, exceptionally elongated and with a small contribution to the bond‐valence sum of only 6.7%. Short C—H...Br contacts build up a three‐dimensional network. The Cu...Cu distances within the chain range from 2.8390 (12) to 3.0805 (17) Å, indicating the existence of weak Cu^I...Cu^I cuprophilic interactions.     

Template-directed synthesis of macrocyclic copper(II) complexes of diazacyclam, 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane

Template reaction of copper(II) nitrate with N-(2-aminoethyl)-1,3-diaminopropane and formaldehyde yields a macrocyclic copper(II) complex of 1,3,6,10,12,15-hexaazatricyclo[13.3.1.1^6,10]eicosane (L), [CuL(NO₃)₂] (1). Replacement of nitrate with perchlorate gives [CuL(ClO₄)₂] (2). These complexes have been characterized by FT-IR and Raman spectroscopies, electronic absorption, cyclic voltammetry, and X-ray crystallography. The crystal structure of 1 shows that copper has distorted octahedral geometry with two secondary and two tertiary amines of the macrocycle and two oxygen atoms from nitrate coordinating the axial positions. The copper in 2 has the same geometry with axial positions occupied by one oxygen atom of perchlorate. Copper lies on the plane of four coordinated nitrogen atoms and there is no rms deviation from this plane. Cyclic voltammetry of 1 and 2 gives two one-electron waves corresponding to Cu^II/Cu^III (?0.75,??0.72) and Cu^II/Cu^I (0.48, 0.24) processes. For understanding of geometry parameters in diazacyclam-based copper(II) complexes, a survey on complexes from CSD structures is presented. In this study the macrocycle hole size was estimated by ionic radii of metal ions located inside of it.     

Synthesis and characterization of mononuclear copper(II) and dinuclear cadmium(II) complexes with di-(2-picolyl)sulfide

The reaction of CuCl₂ · 2H₂O and CdCl₂ with di-(2-picolyl)sulfide (dps) leads to the formation of mononuclear copper(II) and binuclear cadmium(II) complexes, [Cu(dps)Cl₂] · H₂O (1) and [(dps)(Cl)Cd^II(μ-Cl)₂Cd^II(Cl)(dps)] (2). The copper atom in (1) is coordinated to one sulfur and two nitrogen atoms from the dps ligand and two chlorides in a distorted square-pyramidal environment. Complex (2) has two distorted octahedra sharing the basal edge that contain the bridging chloro ligands, each of which resides at a center of inversion. Cyclic voltammetric data show that (1) undergoes two reversible one-electron waves corresponding to Cu^II/Cu^III and Cu^II/Cu^I processes. However, cyclic voltammetry of (2) gives two irreversible reduced waves.