Hyperbranch‐polyethyleniminated functional polymers. I. Synthesis,characterization of novel ABA type of dumbbell‐like polyethyleniminated polyoxypropylenediamines,and their complexing properties with copper(II) ions in aqueous solution

Novel ABA‐type dumbbell‐like water‐soluble copolymers [D230(EI)₄, D400(EI)₄, and D400(EI)₈] were synthesized by introducing ethylenimine (EI) groups into both sides of polyoxypropylenediamines via a simple in situ ethylamination of polyoxypropylenediamine with 2‐chloroethylamine hydrochloride. The structures of the resultant polymers were identified by Fourier transform infrared spectroscopy and ¹H NMR. The percentages of primary, secondary, and tertiary amine present were determined by the potentiometric titration method after treatments with the appropriate chemicals of salicylaldehyde and acetic anhydride. The surface tension and solubilizing behavior of pyrene in the presence of these polymers in aqueous medium were also investigated, and the efficiency to reduce the surface tension and solubilizing behavior of pyrene depends on the attachments of EI to polymer backbone. The chelating properties of these polymers were examined quantitatively by ultraviolet–visible (UV–vis) spectroscopy in the presence of Cu²⁺ ions in aqueous solution, and continuous variation analysis revealed that the most stable complex is formed at the normality ratio of [N]/[Cu²⁺] = 3.0. UV–vis spectroscopy and transmission electron microscopy were used to evaluate the dumbbell‐like water‐soluble copolymer, D400(EI)₈, as a stabilizer for preparing colloidal noble metal nanoparticles (Au and Pt) in aqueous solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1360–1370, 2003     

Potentiometric and spectrophotometric titration of Cu2+ complexes with N-isopropyl-2-methyl-1,2-propanediamine

The complexation of Cu²⁺ by N-isopropyl-2-methyl-1,2-propanediamine (L) has been studied by potentiometric and spectrophotometric titration. The dominant complexes formed in this system are [CuL]²⁺, [CuL₂]²⁺, [Cu₂L₂(OH)₂]²⁺, and [CuL(OH)₂]. The data were thoroughly tested for different models with [CuL(OH)]⁺, [CuL(OH)]⁺, [Cu(OH)]⁺, and [Cu₂(OH)₂]²⁺ as additional species. The importance of steric factors is indicated by the d-d* spectra: for [CuL₂]²⁺, (λ_max = 499 nm) the absorption maximum is shifted by 50 nm to high energies relative to [Cu(en)₂]²⁺, (λ_max = 549 nm), whereas the opposite is true for the 1:1 complexes ([CuL]²⁺ : λ_max = 712 nm,s [Cu(en)]²⁺ : λ_max = 660 nm).     

123 Phases in CeLa2Cu2MgO8 samples

A tetragonal 123 phase with the composition close to CeLa₂ { Cu ₂ ²⁺ } [Mg²⁺]O₈ (the braces indicate the Cu(2) positions; the brackets indicate the Cu(1) positions) with the parameters a = b = 0.3909(3) nm, c = 1.6591(8) nm was prepared at 860°C under an oxygen atmosphere with an elevated oxygen pressure. When the lanthanum-for-barium substitution was incomplete, the resulting 123 phase had the composition close to CeLa_1.7Ba_0.3{ Cu _1.7 ²⁺ } [Mg]O₈ with the unit cell parameters a = b = 0.3868(3) nm, c = 1.6578(8) nm that contains Cu³⁺ in the Cu(2) positions. The partial substitution of barium for lanthanum (the melting point of barium oxide is almost 500°C lower that of the lanthanum oxide) appreciably facilitated the synthesis: the 123 phase in this sample was more than 90%. The existence of Cu³⁺ in the Cu(2) positions enhanced the electrical conductivity of the sample.     

Structural Diversity of Infinite 3d–4f Heterometallic Cluster Compounds Driven by Various Lanthanide Radii

The syntheses, structures, and characterization of six Ln³⁺–Cu²⁺–glycine (Hgly) coordination polymers are described in this paper. They represent three types of structures. Type I (Ln=La ( 1 ), Pr ( 2 ), and Sm ( 3 )) is a 1D catenarian polymer comprising [Ln₂] nodes bridged by four cis‐Cu(gly)₂ linkers. Type II (Ln=Eu ( 4 ) and Dy ( 5 )) is a 2D open framework with a 4⁴‐net, composed of novel [Ln₆Cu₂₂] cluster nodes linked by trans‐Cu(gly)₂ linkers. Furthermore, the inner structures of the [Ln₆Cu₂₂] nodes, and the connection mode between the nodes and linkers are slightly different for 4 and 5 . Type III (Ln=Er ( 6 )) is a 3D open framework with a novel 3⁶?4¹⁸?5³?6 topology, made up of [Er₆Cu₂₄] cluster nodes and trans‐Cu(gly)₂ linkers. The rich variety of the resulting structures owes itself mainly to the interselection between the dynamic control of metalloligands and cationic components. A transition from frequency dependence to frequency independence is observed in the field‐induced magnetization lag for 1 – 3 . The frequency dependence at low temperatures may come from the antiferromagnetic Cu? Cu interaction through the [Ln₂] nodes, whereas the frequency independence may be due to the disappearance of the antiferromagnetic Cu? Cu interaction at high temperatures.     

Halido-bridged Copper(II) Complexes with 1-tert-Butyl-1H-tetrazole: Crystal Structure and Magnetic Properties

Complex [Cu(tbt)Cl₂]_n (tbt = 1-tert-butyl-1H-tetrazole) was prepared by reaction of tbt with copper(II) chloride in solution. According to single-crystal X-ray analysis, this complex presents 1D coordination polymer, formed at the expense of double chlorido bridges between neighboring pentacoordinate copper(II) cations. 1-tert-Butyl-1H-tetrazole acts as monodentate ligand coordinated by Cu^II cations via the heteroring N⁴ atoms. The temperature-dependent magnetic susceptibility measurements of novel complex [Cu(tbt)Cl₂]_n as well as described previously 1D coordination polymer [Cu(tbt)₂Cl₂]_n, and linear trinuclear complex [Cu₃(tbt)₆Br₆], were carried out. Magnetic studies revealed that the copper(II) ions were weakly ferromagnetically coupled in polymeric copper(II) chloride complexes, whereas complex [Cu₃(tbt)₆Br₆] showed antiferromagnetic coupling.     

Structure and Magnetic Properties of a 2D Paddle‐wheel Dinuclear[Cu2] Cluster‐based Polymer with 1,1‐Cyclohexanediacetate Ligand

One new two‐dimensional (2D) Cu^II polymer [Cu(CHDA)(H₂O)]_n ( 1 ) was synthesized solvothermally based on 1,1‐cyclohexanediacetic acid (H₂CHDA) ligand. Single‐crystal X‐ray diffraction analysis reveals that 1 has a 2D framework structure consisting of paddle‐wheel dinuclear [Cu₂] cluster unit and CHDA^2– connector, which bears a 4‐connected sql network with Schläfli symbol of (4⁴.6²). Magnetic studies indicate the presence of strong antiferromagnetic coupling (J = –302 cm^–1) between the two Cu^II ions in the paddle‐wheel dicopper(II) entity.     

Komplexe mit makrocyclischen Liganden,II. Zweischrittmechanismus bei der Komplexbildung von Cu2+ mit meso-5,7,7,12,14,14-Hexamethyl-1,4,8,11-tetraazacyclotetradecan

The complex formation between Cu^II and the title compound (tet a) is studied by spectrophotometry and pH-stat techniques. Between pH 4 and 5,5 the reaction proceeds in two steps, the first giving a blue intermediate, Cu(teta)²⁺ (blue), exhibiting a broad absorption band at 620 nm. Titration with NaOH and the absorption spectrum suggest that, in the intermediate, Cu^II is coordinated to only two amino groups of the ligand. Both steps are slow compared to other complex formation reactions of Cu^II. The rate of the first step, in which Cu(tet a)²⁺ (blue) is formed, is given by v₁ = k₁ · [Cu²⁺] [(tet a) H]/[H⁺] with k₁ = 2,7 · 10^?6 s^?1 at 40° and I = 0,1. In the second step the last two nitrogens of the quadridentate ligand are bound to Cu^II, giving the mauve end product. The rate of this step is given by v₂ = k₂ · [Cu(tet a)OH⁺ (blue)] [OH^?] with k₂ = 1,2 · 10³ M^?1 s^?1 at 50° and I = 0,5.     

123 Phases in Ce-La-Nd-2Cu-Mg-O and Ce-2Nd-2Cu-Mg-O samples

We show that the substitution of lanthanum by neodymium, whose oxide melts at a temperature 500°C lower than La₂O₃, appreciably facilitates the synthesis of 123 phases with their Cu(1) positions fully or selectively substituted by magnesium. 123 phases with unit cells doubled in plane ab (phases “336”) and with compositions close to Ce₂(La_1.4Nd₂Ba_0.6){ Cu _3.4 ²⁺ Cu _0.6 ³⁺ } [Mg₂]O₁₆ (a = b = 0.5498(5) nm, c = 1.6425(8) nm), and Ce₂(La_1.7Nd₂K_0.3){ Cu _3.4 ²⁺ Cu _0.6 ³⁺ } [Mg₂]O₁₆ (a = b = 0.5498(5) nm, c = 1.6488(8) nm), and Ce₂(Nd_3.4Ba_0.6){ Cu _3.4 ²⁺ Cu _0.6 ³⁺ } [Mg₂]O₁₆ (a = b = 0.5474(5) nm, c = 1.6425 nm), where the parentheses indicate the Ba positions, the braces indicate the Cu(2) positions, and the brackets indicate the Cu(1) positions, were synthesized using modified nitrate technology at 810°C in flowing oxygen. The existence of Cu³⁺ in the Cu(2) positions endows the phases with electrical conductivity. The conductivity versus temperature curves show the semiconductor trend. The samples do not experience superconducting transitions up to 60 K.     

In situ assembly of a host–guest linked,mixed valence copper(II)–copper(I) coordination polymer [Cu(1,2-en)2(μ3-I)2Cu2(μ2-I)2]n via partial reduction of copper(II) under ambient conditions

A 2-D coordination polymer, [Cu(1,2-en)₂(μ₃-I)₂Cu₂(μ₂-I)₂]_n (1), was formed at room temperature by in situ insertion of [Cu(1,2-en)₂]²⁺ guests into 1-D chains of a [Cu₂I₄]^2? host [1,2-en?=?1,2-diaminoethane]. The structure of the complex was confirmed by single-crystal X-ray diffraction study. The shortest copper(I)–copper(I) distance within the complex is 2.89?Å.     

Crystal Structure and Characterization of Two Layered Copper(II) Coordination Polymers with Anions of 3‐Phosphonopropionic Acid and (RS)‐2‐Phosphonobutyric Acid

Blue single crystals of Cu[μ₃‐O₃P(CH₂)₂COOH] · 2H₂O ( 1 ) and Cu[(RS)‐μ₃‐O₃PCH(C₂H₅)COOH] · 3H₂O ( 2 ) were prepared in aqueous solutions (pH = 2.5–3.5). 1 crystallizes in space group Pbca (no. 61) with a = 812.5(2), b = 919.00(9), and c = 2102.3(2) pm. Cu²⁺ is fivefold coordinated by three oxygen atoms stemming from [O₃P(CH₂)₂COOH]^2– anions and two water molecules. The Cu–O bond lengths range from 194.0(3) to 231.8(4) pm. The connection between the [O₃P(CH₂)₂COOH]^2– anions and the Cu²⁺ cations yields a polymeric structure with layers parallel to (001). The layers are linked by hydrogen bonds. 2 crystallizes in space group Pbca (no. 61) with a = 1007.17(14), b = 961.2(3), c = 2180.9(4) pm. The copper cations are surrounded by five oxygen atoms in a square pyramidal fashion with Cu–O bonds between 193.6(4) and 236.9(4) pm. The coordination between [O₃PCH(C₂H₅)COOH]^2– and Cu²⁺ results in infinite puckered layers parallel to (001). The layers are not connected by any hydrogen bonds. Each layer contains both R and S isomers of the [O₃PCH(C₂H₅)COOH]^2– dianion. Water molecules not bound to Cu²⁺ are intercalated between the layers. UV/Vis spectra suggest three d–d transition bands at 743, 892, 1016 nm for 1 and four bands at 741, 838, 957, and 1151 nm for 2 , respectively. Magnetic measurements suggest a weak antiferromagnetic coupling between Cu²⁺ due to a super‐superexchange interaction. Thermoanalytical investigations in air show that the compounds are stable up to 95 °C ( 1 ) and 65 °C ( 2 ), respectively.     

Dipyridylamide Donor Disposition and Isophthalate Substituent Steric Effect on the Dimensionality and Topology of Divalent Copper Coordination Polymers

Divalent copper coordination polymers containing an isophthalate ligand and a dipyridylamide ligand show different dimensionalities and topologies depending on pyridyl nitrogen donor disposition and the steric bulk of the substituent on the dicarboxylate aromatic ring. According to single‐crystal X‐ray diffraction, [Cu(ip)(3‐pna)]_n ( 1 , ip = isophthalate, 3‐pna = 3‐pyridylnicotinamide) shows a (4, 4) layered grid structure based on {Cu₂(OCO)₂} dimeric units. {[Cu(ip)(3‐pina)]·H₂O}_n ( 2 , 3‐pina = 3‐pyridylisonicotinamide) exhibits similar dimeric units, but in contrast to 1 these are connected into a non‐interpenetrated 3D 6⁵8 cds network. Both [Cu(mip)(3‐pina)]_n ( 3 , mip = 5‐methylisophthalate) and [Cu(meoip)(3‐pina)]_n ( 4 , mip = 5‐methoxyisophthalate) display dimer‐based 4¹²6³ pcu networks in contrast to 2 . Use of 5‐hydroxyisophthalate (H₂hip) as a precursor afforded a mixture of {[Cu₂(hip)₂(3‐pina)₄]·9.5H₂O}_n ( 5 ) and [Cu(hip)(3‐pina)]_n ( 6 ). Compound 5 shows a 2D interdigitated structure with [Cu(hip)]_n coordination polymer layers featuring {Cu₂(OCO)₂} dimeric units and pendant 3‐pina ligands, while 6 also showed a dimer‐based 4¹²6³ pcu network. Use of the very sterically bulky 5‐tert‐butylisophthalate (tbip) ligand afforded the 1D chain coordination polymer {[Cu(tbip)(3‐pina)₂(H₂O)]·H₂O}_n ( 7 ), which contains isolated copper ions in contrast to 1 – 6 , and has a curious “butterfly“ resemblance. Very weak antiferromagnetic coupling is seen within the {Cu₂(OCO)₂} dimeric units in 1 . Thermal decomposition behavior is also discussed.     

Controllable Synthesis of Covellite Nanoparticles via Thermal Decomposition Method

In this study, covellite (CuS) nanoparticles were synthesized through a facile and low temperature thermal decomposition method using [Cu(sal)₂]- oleylamine complex, (sal = salicylaldehydeato, prepared in situ from [Cu(sal)₂] and oleylamine as the precursors), and sulfur as the Cu²⁺ source and S source, respectively. Scanning electron microscope, transmission electron microscope, electron diffraction and ultraviolet–visible absorption (UV–Vis) spectra were used for the characterization of the products. The effect of reaction parameters, such as the copper:sulfur molar ratio, the reaction temperature and the reaction time on the shape, size and phase of CuS nanostructures, was investigated. The results showed that the, covellite (hexagonal structure of CuS) with an average size between 20 and 45 nm could be obtained with the Cu:S molar ratio of 1: 3 at 105 °C for 60 min. With increasing the reaction temperature from 105 to 200 °C, non-stoichiometric Cu_1.65S with the average size of 25–50 nm was obtained due to the different existing state of the released Cu²⁺ ions from the copper-oleylamine complex.     

Synthesis,Crystal Structure,and Characterization of Two Novel One‐ and Two‐Dimensionally Polymeric Copper(II) Phosphonoacetates

Blue single crystals of Cu[μ₂‐OOC(CH₂)PO₃H] · 2H₂O ( 1 ) and Cu_1.5[μ₃‐OOC(CH₂)PO₃] · 5H₂O ( 2 ) were prepared in aqueous solution. In compound 1 [space group C2/c (no. 15) with a = 1623.3(2), b = 624.0(1), c = 1495.5(2) pm, β = 122.45(1)°], Cu is coordinated by three oxygen atoms stemming from the hydrogenphosphonoacetate dianion and three water molecules to form a distorted octahedron. The Cu–O bonds range from 190.4(3) to 278.5(3) pm. The connection between the Cu²⁺ cations and the hydrogenphosphonoacetate dianions leads to a two‐dimensional structure with layers parallel to (101). The layers are linked by hydrogen bonds. In compound 2 [space group P1 (no. 2) with a = 608.2(1), b = 800.1(1), c = 1083.6(1) pm, α = 94.98(1)°, β = 105.71(1)°, γ = 109.84(1)°], two crystallographically independent Cu²⁺ cations are coordinated in a square pyramidal and an octahedral fashion, respectively. The Cu–O bonds range from 192.9(2) to 237.2(2) pm. The coordination of the phosphonoacetate trianion to Cu(1) results in infinite polyanionic chains parallel to [100] with a composition of {Cu(H₂O)[OOC(CH₂)PO₃]}_n^n–. Hydrated Cu(2) cations are accommodated between the chains as counterions. 1 and 2 show structural features of cation exchangers. Magnetic measurements reveal a paramagnetic Curie‐Weiss behavior. Compound 2 shows antiferromagnetic coupling between Cu²⁺ ions due to a super‐superexchange coupling. The UV/Vis spectra of 1 suggest three d–d transition bands at 763 nm (²B₁ → ²E), 878 nm (²B₁ → ²B₂), and 1061 nm (²B₁ → ²A₁). Thermoanalytical investigations in air show that compound 1 is stable up to 165 °C, whereas decomposition of 2 begins at 63 °C.     

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.     

Low-temperature activation of nitrogen oxide on Cu-ZSM-5 catalysts

The adsorption and activation of NO molecules on Cu-ZSM-5 catalysts with different Cu/Al and Si/Al ratios (from 0.05 to 1.4 and from 17 to 45, respectively) subjected to different pretreatment was studied by ultraviolet-visible diffuse reflectance (UV-Vis DR). It was found that the amount of chemisorbed NO and the catalyst activity in NO decomposition increased with an increase in the Cu/Al ratio to 0.35–0.40. The intensity of absorption bands at 18400 and 25600 cm⁻¹ in the UV-Vis DR spectra increased symbatically. It was hypothesized that the adsorption of NO occurs at Cu⁺ ions localized in chain copper oxide structures with the formation of mono- and dinitrosyl Cu(I) complexes, and this process is accompanied by the Cu²⁺...Cu⁺ intervalence transfer band in the region of 18400 cm⁻¹. The low-temperature activation of NO occurs through the conversion of the dinitrosyl Cu(I) complex into the π-radical anion (N₂O₂)⁻ stabilized at the Cu²⁺ ion of the chain structure, [Cu²⁺-cis-(N₂O₂)⁻], by electron transfer from the Cu⁺ ion to the cis dimer (NO)₂. This complex corresponds to the L → M charge transfer band in the region of 25600 cm⁻¹. The subsequent destruction of the complex [Cu²⁺-cis-(N₂O₂)⁻] at temperatures of 150–300°C leads to the release of N₂O and the formation of the complex [Cu²⁺O⁻], which further participates in the formation of the nitrite-nitrate complexes [Cu²⁺(NO₂)⁻], [Cu²⁺(NO)(NO₂)⁻], and [Cu²⁺(NO₃)⁻] and NO decomposition products.     

Microstructure of metallic copper nanoparticles/metallic disc interface in metal–metal bonding using them

This paper describes a metal–metal bonding technique using metallic Cu nanoparticles prepared in aqueous solution. A colloid solution of metallic Cu particles with a size of 54 ± 15 nm was prepared by reducing Cu²⁺ (0.01 M (CH₃COO)₂Cu) with hydrazine (0.6 M) in the presence of stabilizers (5 × 10^?4 M citric acid and 5 × 10^?3 M cetyltrimethylammonium bromide) in water at room temperature in air. Discs made of metallic materials (Cu, Ni/Cu, or Ag/Ni/Cu) were successfully bonded under annealing at 400 °C and pressurizing at 1.2 MPa for 5 min in H₂ gas with help of the metallic Cu particle powder. Shear strength required for separating the bonded discs was 27.9 ± 3.9 for Cu discs, 28.1 ± 4.1 for Ni/Cu discs, and 13.8 ± 2.6 MPa for Ag/Ni/Cu discs. Epitaxial crystal growth promotes on the discs with a good matching for the lattice constants between metallic nanoparticles and metallic disc surfaces, which leads to strong bonding. Copyright © 2013 John Wiley & Sons, Ltd.     

Dimetallic functionalities in liposome bilayers

A dicopper(II) complex can be covalently linked to palmitate/palmitoyl-oleoyl-phosphatidylcholine (PA/POPC) liposomes using the following one-pot strategy: preformed [Cu₂(bpbp)(PA)](ClO₄)₂ (bpbp^?  = 2,6-bis((N,N′-bis(2-picolyl)amino)methyl)-4-tertbutylphenolato) was incorporated into POPC liposomes with a loading of up to 10 mol%. Despite its shape and charge, the decoration of PA/POPC liposomes with {Cu₂(bpbp)}³⁺ did not disrupt the liposome structure; however, the mean liposome diameter increased from about 130 nm (0 mol% dicopper complex) to about 150 nm (10 mol% dicopper complex). Single-crystal X-ray structures furnish ‘snapshots’ of the pH-dependent solution state derivatives of {Cu₂(bpbp)}³⁺, and model the structure of the [Cu₂(bpbp)(PA)]²⁺ head group at the surface of the liposomes. An impressive plasticity in the intramolecular non-bonded Cu….Cu distance for these ions, ranging from 3 to 4 Å, in [Cu₂(bpbp)OH]²⁺, [Cu₂(bpbp)(OAc)(H₂O)]²⁺ and [Cu₂(bpbp)(H₂O)₂]³⁺ allows for their utility as labile reagents in water. Remarkably, the flexible dicopper site is selective for a single carboxylate ligand, so that [Cu₂(bpbp)(PA)]²⁺ is favoured even in the presence of other chemically similar oxoanions, such as CO₃^2 ? , HCO₃^? , NO₃^? , ClO₄^? , ReO₄^?  and CF₃SO₃^? .     

Assembly of an interpenetrating three-dimensional mixed-valence Cu/Cu coordination polymer

A novel cyano-bridged three-dimensional mixed-valence Cu(II)/Cu(I) compound [Cu₂(oxpn)][Cu(CN)₂]₂ (oxpn²⁻ = dianion of N,N^′-bis(3-aminopropyl)oxamide) has been synthesized and structurally characterized. Single crystals of 1 formed by diffusion of Cu₂(oxpn)Cl₂ and K₃[Cr(CN)₅(NO)] in H₂O for two months. The structure of the title compound consists of threefold interpenetrating 3D frameworks. In each 3D network, oxamidato-bridged dimeric [Cu₂(oxpn)]²⁺ units connect 1D polymeric [Cu(CN)₂]⁻ anions giving rise to a 3D structure. Room temperature magnetic measurement shows the presence of strong magnetic coupling between the Cu(II) ions. Electronic paramagnetic resonance spectrum measurements show the transitions due to the excited triplet state.     

An unexpected dinuclear Cu(II) complex with a bis(Salamo) chelating ligand: synthesis,crystal structure,and photophysical properties

An unexpected dinuclear Cu(II) complex, [Cu₂(L²)₂], has been synthesized via complexation of Cu(II) acetate monohydrate with a bis(Salamo) ligand H₂L¹. Catalysis of Cu(II) ions results in unexpected cleavage of two N–O bonds in H₂L¹, giving a dialkoxo-bridged dinuclear Cu(II) complex. Each Cu(II) complex possesses a Cu–O–Cu–O four-membered ring instead of the usual bis(Salamo) [Cu₂L¹] complex with H₂L¹. The H₂L¹ molecule is stabilized by intramolecular O1–H1?N1 hydrogen bonds and π?π stacking interactions linking adjacent molecules into a 1-D infinite zigzag chain. In the structure of the Cu(II) complex, intermolecular hydrogen bonds have stabilized the Cu(II) complex to form a self-assembling infinite 1-D linear chain. Furthermore, the H₂L¹ ligand shows intense photoluminescence with two emissions at ca. 370 and 464 nm upon excitation at 310 nm. The Cu(II) complex shows photoluminescence with maximum emission at ca. 423 nm upon excitation at 370 nm.