Terminal Copper Research Articles

Design of end-on cyanato bridged trinuclear Cu(II) Schiff base complex with salen type Schiff base ligand: synthesis, structural investigation and DFT study

One ONNO-donor tetradentate Schiff base ligand LH2 was derived from the condensation of salicylaldehyde and 1,3-diaminopropane and reacted with Cu(NO3)2·6H2O and NaNCO to yield one trinuclear complex with molecular formula [Cu3L2(µ1,1-NCO)2]. The synthesized complex was characterized by IR, UV–vis spectroscopy, and electrochemical analysis. Single-crystal X-ray diffraction study explores that the two terminal copper atoms adopt square pyramidal geometry, whereas the central copper atom situated at the inversion center is surrounded by four phenoxo oxygens and two end-on cyanato anions to adopt an octahedral geometry. The ONNO-tetradentate Schiff base ligand coordinates with the copper(II) ion via two oxygen atoms of the phenoxo-group and two nitrogen atoms from the imine moiety. A theoretical density functional theory (DFT) calculation was also carried out to supplement the experimental results. All the DFT calculations were done in gas phase.

Characterization and Reactivity Studies of a Terminal Copper–Nitrene Species

AbstractHigh‐valent terminal copper–nitrene species have been postulated as key intermediates in copper‐catalyzed aziridination and amination reactions. The high reactivity of these intermediates has prevented their characterization for decades, thereby making the mechanisms ambiguous. Very recently, the Lewis acid adduct of a copper–nitrene intermediate was trapped at −90 °C and shown to be active in various oxidation reactions. Herein, we describe for the first time the synthesis and spectroscopic characterization of a terminal copper(II)–nitrene radical species that is stable at room temperature in the absence of any Lewis acid. The azide derivative of a triazamacrocyclic ligand that had previously been utilized in the stabilization of aryl–CuIII intermediates was employed as an ancillary ligand in the study. The terminal copper(II)–nitrene radical species is able to transfer a nitrene moiety to phosphines and abstract a hydrogen atom from weak C−H bonds, leading to the formation of oxidized products in modest yields.

Characterization and Reactivity Studies of a Terminal Copper-Nitrene Species.

High-valent terminal copper-nitrene species have been postulated as key intermediates in copper-catalyzed aziridination and amination reactions. The high reactivity of these intermediates has prevented their characterization for decades, thereby making the mechanisms ambiguous. Very recently, the Lewis acid adduct of a copper-nitrene intermediate was trapped at -90 °C and shown to be active in various oxidation reactions. Herein, we describe for the first time the synthesis and spectroscopic characterization of a terminal copper(II)-nitrene radical species that is stable at room temperature in the absence of any Lewis acid. The azide derivative of a triazamacrocyclic ligand that had previously been utilized in the stabilization of aryl-CuIII intermediates was employed as an ancillary ligand in the study. The terminal copper(II)-nitrene radical species is able to transfer a nitrene moiety to phosphines and abstract a hydrogen atom from weak C-H bonds, leading to the formation of oxidized products in modest yields.

A novel trinuclear copper(II) complex containing a symmetric tetradentate N2O2 Schiff base ligand: Synthesis, characterization, crystal structure and its usage as a new precursor for the preparation of CuO particles

A novel linear centrosymmetric trinuclear copper(II) Schiff base complex with the chemical formula [{Cu(μ-L)(H2O)(μ-NO3)}2Cu]·H2O, where L=N,N′-bis(2-hydroxy-4-methoxybenzophenone)-2,2-dimethyl-1,3-propanediamine, was synthesized and characterized by elemental analyses, FT-IR spectroscopy, TG-TA and X-ray crystallography. Single X-ray diffraction analysis revealed four μ-phenoxido- and two μ-NO3− bridges in the complex. The equatorial plane of the three linearly arranged copper(II) atoms is formed by oxygen and nitrogen atoms of two anionic tetradentate Schiff base ligands, each of them coordinated to one of the terminal copper(II) ions. The central copper(II) ion is located in an inversion centre and bonded to four μ-oxygen atoms of the same ligand. Thermogravimetric analysis of the complex revealed its thermal stability and decomposition pattern. Finally, the complex was used for the preparation of CuO particles by solid state thermal decomposition.

Aerobic alcohol ammoxidation catalyzed by copper(I)/amino acid: a scalable protocol to nitriles

A facile, practical and scalable catalyst system for alcohols ammoxidation into nitriles is developed using amino acid as ligand, oxygen as terminal oxidant and copper iodide(CuI) as catalyst. The catalyst system shows excellent functional groups compatibility for a wide range of testing substrates, even the substrates bearing oxidation-sensitive groups such as MeS—, alkenyl and —NH2 can also work well. In addition, the protocol is readily scaled up to more than 20 g and the product can be obtained just through filtration or distillation without conventional column chromatography.

Copper(II) binding properties of hepcidin.

Hepcidin is a peptide hormone that regulates the homeostasis of iron metabolism. The N-terminal domain of hepcidin is conserved amongst a range of species and is capable of binding CuII and NiII through the amino terminal copper–nickel binding motif (ATCUN). It has been suggested that the binding of copper to hepcidin may have biological relevance. In this study we have investigated the binding of CuII with model peptides containing the ATCUN motif, fluorescently labelled hepcidin and hepcidin using MALDI-TOF mass spectrometry. As with albumin, it was found that tetrapeptide models of hepcidin possessed a higher affinity for CuII than that of native hepcidin. The log K1 value of hepcidin for CuII was determined as 7.7. CuII binds to albumin more tightly than hepcidin (log K1 = 12) and in view of the serum concentration difference of albumin and hepcidin, the bulk of kinetically labile CuII present in blood will be bound to albumin. It is estimated that the concentration of CuII-hepcidin will be less than one femtomolar in normal serum and thus the binding of copper to hepcidin is unlikely to play a role in iron homeostasis. As with albumin, small tri and tetra peptides are poor models for the metal binding properties of hepcidin.Electronic supplementary materialThe online version of this article (doi:10.1007/s00775-016-1342-2) contains supplementary material, which is available to authorized users.

Hybrid peptide ATCUN-sh-Buforin: Influence of the ATCUN charge and stereochemistry on antimicrobial activity.

The emergence of antibiotic resistant strains of bacteria has resulted in the need to develop more potent antimicrobials that target microorganisms in a novel manner. Antimicrobial Peptides (AMPs) show great potential for drug development because of their broad activity and unique mechanism of action. Several AMPs contain an Amino Terminal Copper and Nickel (ATCUN) binding motif; however, its function has not yet been determined. We have previously demonstrated that the activity of a truncated version of Buforin II (sh-Buforin, RAGLQFPVGRVHRLLRK-NH2) increases by the addition of an ATCUN motif. We now focus our current studies on understanding the effect of: 1) a positively charged ATCUN sequence, and 2) l-to-d amino acid substitution on the hybrid peptides. We identified that the addition of a positively charged ATCUN motif increases the affinity of the ATCUN-AMP for DNA but does not always result in an enhanced antimicrobial activity over a neutral ATCUN motif. The all-d peptides exhibited up to a 32-fold increase in antimicrobial activity compared to the all-l peptides. The larger activity of the all-d peptides is the result of a larger DNA cleavage activity and higher stability towards proteolysis. Cytotoxicity assays determined that, at their MIC, these peptides caused less than 8% hemolysis and, at 128μM, no toxicity to HeLa and HEK293 cell lines. These results indicate that the ATCUN-AMP hybrids are an attractive alternative for treating infectious diseases and provide key insights into the role of the ATCUN motif in naturally-occurring AMPs.

CopC protein from Pseudomonas fluorescens SBW25 features a conserved novel high-affinity Cu(II) binding site.

Copper homeostasis in the bacterium Pseudomonas fluorescens SBW25 appears to be mediated mainly via chromosomal cue and cop systems. Under elevated copper levels that induce stress, the cue system is activated for expression of a P1B-type ATPase to remove excess copper from the cytosol. Under copper-limiting conditions, the cop system is activated to express two copper uptake proteins, Pf-CopCD, to import this essential nutrient. Pf-CopC is a periplasmic copper chaperone that may donate copper to the inner membrane transporter Pf-CopD for active copper importation. A database search revealed that Pf-CopC belongs to a new family of CopC proteins (designated Type B in this work) that differs significantly from the known CopC proteins of Type A that possess two separated binding sites specific for Cu(I) and Cu(II). This article reports the isolation and characterization of Pf-CopC and demonstrates that it lacks a Cu(I) binding site and possesses a novel Cu(II) site that binds Cu(II) with 100 times stronger affinity than do the Type A proteins. Presumably, this is a requirement for a copper uptake role under copper-limiting conditions. The Cu(II) site incorporates a highly conserved amino terminal copper and nickel (ATCUN) binding motif, NH2-Xxx-Xxx-His, but the anticipated ATCUN binding mode is prevented by a thermodynamically more favorable binding mode comprising His1 as a key bidentate ligand and His3 and His85 as co-ligands. However, upon His1 mutation, the ATCUN binding mode is adopted. This work demonstrates how a copper chaperone may fine tune its copper binding site to meet new challenges to its function.

Copper-binding tripeptide motif increases potency of the antimicrobial peptide Anoplin via Reactive Oxygen Species generation

Antimicrobial peptides (AMPs) are broad spectrum antimicrobial agents that act through diverse mechanisms, this characteristic makes them suitable starting points for development of novel classes of antibiotics. We have previously reported the increase in activity of AMPs upon addition of the Amino Terminal Copper and Nickel (ATCUN) Binding Unit. Herein we synthesized the membrane active peptide, Anoplin and two ATCUN-Anoplin derivatives and show that the increase in activity is indeed due to the ROS formation by the CuII-ATCUN complex. We found that the ATCUN-Anoplin peptides were up to four times more potent compared to Anoplin alone against standard test bacteria. We studied membrane disruption, and cellular localization and found that addition of the ATCUN motif did not lead to a difference in these properties. When helical content was calculated, we observed that ATCUN-Anoplin had a lower helical composition. We found that ATCUN-Anoplin are able to oxidatively damage lipids in the bacterial membrane and that their activity trails the rate at which ROS is formed by the CuII-ATCUN complexes alone. This study shows that addition of a metal binding tripeptide motif is a simple strategy to increase potency of AMPs by conferring a secondary action.

Isolation of Bridging and Terminal Coinage Metal–Nitrene Complexes

Transition metal complexes featuring a metal-nitrogen multiple bond have been widely studied due to their implication in dinitrogen fixation and catalytic nitrogen-carbon bond formation. Terminal copper- and silver-nitrene complexes have long been proposed to be the key intermediates in aziridination and amination reactions using azides as the nitrogen source. However, due to their high reactivity, these species have eluded isolation and spectroscopic characterization even at low temperatures. In this paper we report that a stable phosphinonitrene reacts with coinage metal trifluoromethanesulfonates, affording bridging and terminal copper- and silver-nitrene complexes, which are characterized by NMR spectroscopy and single crystal X-ray diffraction analysis.

A new linear double phenoxide-bridged trinuclear Cu(II) Schiff base complex: Synthesis, crystallographic elucidation, magneto-structural correlation and DFT Study

The tetradentate (ONNO) donor Schiff base ligand LH2, derived from the condensation of salicylaldehyde and 1,3-diaminopropane, has been synthesized and reacted with CuBr2 to yield a trinuclear complex with the molecular formula [Cu3L2Br2]. Single crystal X-ray diffraction study reveals that the two terminal copper atoms adopt a square pyramidal geometry, whereas the central copper atom, situated at the inversion centre, is surrounded by four phenoxide oxygen atoms in a square planar fashion. Variable temperature magnetic susceptibility measurement study shows strong antiferromagnetic intra-trimer interactions between the copper centers with a J value of −302cm−1. EPR study of the complex depicts that, due to the exchange coupling between the copper ions, the EPR spectra were unresolved, having very broad resonances with g=2.133. A theoretical DFT calculation was also carried out to supplement the experimental results.

Synthesis, X-ray crystal structure, and electrochemistry of polynuclear azido-bridged manganese(III) and copper(II) Schiff base complexes

Abstract New azido-bridged [MnIII(salabza)(μ-1,3-N3)]n (1), and [CuII4(salabza)2(μ-1,1-N3)2(N3)2(HOCH3)2],(2) complexes with an unsymmetrical Schiff base ligand, {H2salabza = N,N’-bis(salicylidene)-2-aminobenzylamine}, have been synthesized, characterized by spectroscopic and electrochemical methods, and their crystal structures have been determined by X-ray diffraction. In complex 1, each manganese(III) atom is coordinated with N2O2 donor atoms from salabza and two adjacent Mn(III) centers are linked by an end-to-end (EE) azide bridge to form a helical polymeric chain with octahedral geometry around the Mn(III) centers. Complex 2 is a centrosymmetric tetranuclear compound containing two types of Cu(II) centers with square pyramidal geometry. Each terminal copper atom is surrounded by N2O2 atoms of a salabza ligand, and the oxygen atom of the methanol molecule. Each central copper(II) ion is coordinated with two phenoxo oxygen atoms from one salabza, one terminal azido, and two end-on (EO) bridging azido ligands. The central copper(II) ions are linked to each other by the two end-on (EO) azido groups.

Propeller-like heterotrinuclear CuII–LnIII–CuII compounds – Physicochemical properties

The new heterotrinuclear compounds [Cu2Ln(L)2(NO3)(H2O)2](NO3)2·3H2O (where Ln=Sm (1), Eu (2) and L=C19H18N2O4Br2 is the deprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine,) have been synthesized and characterized by FTIR, TG-FTIR, TG/DSC and single crystal X-ray analyses. The complexes of 1 and 2 are isostructural. In the trinuclear compounds two terminal copper(II) ions are coordinated by imino and phenolate oxygen atoms, whereas the central lanthanide(III) ion is bound to the phenolate and methoxy oxygen atoms of the Schiff base ligands. The first change in mass estimated from TG curve corresponds to the loss of water molecules. The decomposition of the Schiff base ligand starts above 200°C. The final decomposition solid products are CuO and Ln2CuO4. The TG-FTIR results show that the main gaseous products in whole decomposition process of complexes are water (H2O), carbon dioxide (CO2), carbon monoxide (CO), nitric oxides (NOx) and bromomethane (CH3Br).

A three-dimensional coordination polymer based on linear trinuclear copper(ii) clusters featuring a ferromagnetic exchange interaction

A new triazine-based dicarboxylic acid, 2,4-bis(4-aminobenzoic acid)-6-(dimethylamino)-1,3,5-triazine (H2L), has been designed and prepared, which has been used for the support of a new coordination polymer constructed from trinuclear copper(II) clusters. The compound was structurally authenticated by single-crystal X-ray diffraction revealing that the compound possesses a three-dimensional (4,8)-connected alb network constructed from trinuclear copper(II) clusters with the general formula [Cu3(L)2(μ2-OH)2] (1). Additionally, compound 1 contains left- and right-handed helical chains along the b axis, which are interlinked by the trinuclear copper(II) clusters. In the basic trinuclear copper(II) cluster, the central copper ion is located on an inversion center with strictly planar four-coordinate coordination geometry, while the coordination spheres of the terminal copper ions are square pyramidal. The three copper atoms are in an exactly linear arrangement, and adjacent coppers are connected by a hydroxo bridge and a bidentate syn–syn carboxylate group. Variable-temperature magnetic susceptibility measurements reveal a ferromagnetic coupling between adjacent copper(II) ions with J = 42.39 cm−1, which is confirmed by the EPR spectrum.

Differences in Nuclearity, Molecular Shapes, and Coordination Modes of Azide in the Complexes of Cd(II) and Hg(II) with a “Metalloligand” [CuL] (H2L =N,N′-Bis(salicylidene)-1,3-propanediamine): Characterization in Solid and in Solutions, and Theoretical Calculations

Two new heterometallic copper(II)-mercury(II) complexes [(CuL)Hg(N3)2]n (1) and [(CuL)2Hg(N3)2] (2) and one copper(II)-cadmium(II) complex [(CuL)2Cd(N3)2] (3) have been synthesized using "metalloligand" [CuL] (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complex 1 is a one-dimensional (1D) helical coordination polymer constructed by the joining of the dinuclear [(CuL)Hg(N3)2] units through a single μ-l,l azido bridge. In the dinuclear unit the Hg(II) is bonded with two phenoxido oxygen atoms of "metalloligand" [CuL] and two nitrogen atoms of azido ligands. Complex 2 is a linear trinuclear entity, in which two terminal "metalloligands" [CuL] are coordinated to central Hg(II) through double phenoxido bridges. The azido ligands link the central mercury atom with the terminal copper atoms via μ-l,3 bridges. In contrast, the trinuclear complex 3 is bent. Here, in addition to two double phenoxido bridges, central Cd(II) is bonded to two mutually cis nitrogen atoms of two terminal azido ligands. The variation in the coordination modes of the azido ligand seems to be responsible for the different molecular shapes of 2 and 3. Interestingly, bond distances between the Hg atoms and the central nitrogen atom of the azido ligands are 2.790(4) and 2.816(5) Å in 1 and 2.823(4) Å in 2. These bond distances are significantly less than the sum of van der Waals radii of mercury (2.04 Å) and nitrogen (1.55 Å) and considerably longer than the sum of their covalent radii (2.03 Å). However the distances are similar to reported Hg-N bond distances of some Hg(II) complexes. Therefore, we have performed a theoretical density functional theory study to know whether there is any interaction between the central nitrogen atom of the azido ligand and the mercury atoms. We have used the Bader's "atoms-in-molecules", energetic and orbital analyses to conclude that such interaction does not exist. The probable reason for different molecular shapes observed in trinuclear complexes of 2 and 3 also has been studied and explained by theoretical calculations and using the CSD. Electronic spectra, EPR spectra and ESI mass spectra show that all three complexes lose their solid state identity in solution.

Hydrophobic-exterior layer structures and magnetic properties of trinuclear copper complexes with chiral amino alcoholate ligands

The trinuclear secondary building unit (SBU) {Cu3(μ-L)4X2} constructed from chelating and alcoholate-O-bridging chiral amino alcoholate (amino alkoxido, μ-L) and terminal halide ligands (X) gives rise to two-dimensional (2D) homochiral supramolecular polymers through the bridging action of the halide ligand. Compounds 2D-[Cu3(μ-L)4(μ3-X)2] {X = Br (1 to 4), X = Cl (5, 6); L = amino-ethanolate (1, 5), (R)-2-amino-propan-1-olate (2), (R)-2-amino-butan-1-olate (ab) (3, 6), (R)-2-amino-2-phenyl-ethanolate (4)} were synthesized from 2-amino alcohol, LH with CuBr2 or CuCl2, respectively, in the presence of triethylamine (TEA). The crystal packing of isomorphous 2D-[Cu3(μ-L)4(μ3-X)2] shows a separation of the hydrophobic alkyl from the hydrophilic amino-/alcoholate-/Cu–Br-region. Charge-assisted Cu(2+)⋯(−)Br- and hydrogen-bonding interactions in the hydrophilic region are the driving force of “hydrophobic exterior layer” formation with a hydrophilic interior exposing the hydrophobic alkyl groups to the exterior. Stacking of the layers through weak van-der-Waals interactions between the alkyl groups correlates with formation of thin crystal plates along the stacking direction. A lower ligand concentration yields both dinuclear and mononuclear SBUs in one-dimensional (1D-) homochiral coordination polymers 1D-[{Cu2(μ-ab)2Br2}2{(μ3-Br)Cu(abH)2Br}{(μ3-Br)Cu(abH)(CH3OH)Br}] (7) and 1D-[{Cu2(μ-ab)2Cl2}2{(μ3-Cl)Cu(abH)(CH3CH2OH)Cl}2] (8). In {[Cu(rac-abH)(rac-ab)H2O]ClO4}2 (9) two SBUs combine through charge assisted H-bonds to a dimeric unit. Temperature dependent magnetic susceptibility measurements of 1 and 3 show ferromagnetic coupling but no magnetic ordering. However, at temperatures lower than 3 K an onset of long-range magnetic ordering can be observed. AC magnetic measurements in the range of 1.9 K to 5 K at different frequencies show that the long range magnetic ordering is achieved at lower temperatures than that. Correlation of magnetic coupling with the Cu–O–Cu angle is in agreement with the structural parameters of 1 and 3. Very good agreement between experimental and DFT calculated J,j coupling constants shows that the interaction between the terminal copper(II) ions in these linear trinuclear SBUs is operative and it cannot be neglected.

Tetrakis(2,2′-bipyridine)-1κ4N,N′;4κ4N,N′-{μ4-N,N′-bis[3-(2-oxidoethylamino)propyl]oxamidato(4−)-1:2:3:4κO:κ3N,N′,O′:κ3O′′,N′′,N′′′:κO′′′}tetracopper(II) tetrakis(perchlorate)

The title complex, [Cu(4)(C(12)H(22)N(4)O(4))(C(10)H(8)N(2))(4)](ClO(4))(4), has a novel tetranuclear copper(II) cation with the oxamidate and ethanolate groups of a trans tetraanion of N,N'-bis[3-(hydroxyethylamino)propyl]oxamide (H(4)heap) as bridges. The Cu...Cu separation through the oxamide group is 5.1592 (15) A, while those through the two ethanolate bridges are 3.3845 (13) and 3.3392 (13) A. The two central copper(II) ions are in square-planar N(2)O(2) environments, while the two terminal copper(II) ions have distorted N(4)O square-pyramidal geometries. The heap(4-) ligand, with an iminoalcohol form, has both an oxamide and two ethanolate bridges. Two of the four perchlorate anions are disordered and have long contacts with the square-planar Cu(II) ions. The three-dimensional structure features arene-perchlorate C-H...O hydrogen bonds and pi-pi stacking.

Di- and trinuclear olato-bridged copper(II) compounds of 3,7-bis(3-olatopropyl)-1,3,5,7-tetraazabicyclo[3,3,1]nonane (protan 2−); the structures of [{Cu(μ-protan)} 2Cu](ClO 4) 2·H 2O and [{Cu(μ-protan)}Cu(OH) 2](ClO 4) 2·0.5(EtOH)

A compound with a linear trinuclear copper(II) cation, [Cu 3(μ-protan) 2](ClO 4) 2·H 2O (protanH 2 = 3,7-bis(3-hydroxypropyl)-1,3,5,7-tetraazabicyclo[3,3,1]-nonane) is formed by reaction of copper(II) perchlorate, 3-aminopropanol, ammonia and methanal. The cation is approximately centrosymmetrical with Cu⋯Cu = 2.9870(5) and 2.9485(5) Å. The terminal copper(II) ions are coordinated by nitrogen atoms 3 and 7 of the tetraazabicycle (Cu–N mean = 2.021(5) Å) and the two oxygen atoms of the 3,7-bis(3-olatopropyl) substituents (Cu–O mean = 1.911(3) Å), which also act as bridging groups to the central copper(II) ion (Cu–O mean = 1.926(4) Å). The cation is both helically twisted (dihedral angle N3⋯N7⋯N3′⋯N7′ = 20(1)°) and bent (angle Cu⋯Cu⋯Cu = 171(1)°). The copper(II) ions have tetrahedrally twisted square planar primary coordination, with perchlorate ion oxygen atoms weakly coordinated axially to the two terminal copper(II) ions, on opposite sides of the “plane” of the molecule, while the central copper(II) ion is weakly coordinated axially by a water molecule, with all axial Cu–O distances ca. 2.9 Å. One N·CH 2·CH 2·CH 2·O chelate ring for each protan 2− ligand shows conformational disorder and the perchlorate ions show rotational disorder. Partial hydrolysis of the protan 2− compound gave a compound [{Cu(μ-protan)}Cu(OH) 2](ClO 4) 2·0.5(EtOH) which has a dinuclear cation, with one copper(II) ion in square-planar coordination by tetradentate protan 2− and the other in square-planar coordination by the two bridging oxygen atoms of the protan 2− ligand and by two hydroxide ions, with Cu⋯Cu = 3.045(1) Å. With differing mole ratios of the same reactants compounds of the dinuclear cation [{Cu(μ-pta)} 2] 2+ (ptaH = 3(3-hydroxypropyl)-1,3,5,7-tetraazabicyclo[3,3,1]nonane) are formed.

Thermal decomposition of linear tetranuclear copper(II) complexes including μ-azido bridges

In the first instance, mononuclear Cu(II) complexes are prepared with bis-N,N′(salicylidene)-1.3-propanediamine and derivatives. After that, these mononuclear complexes are combined with μ-bridges, by the help of azide ions, to obtain the tetranuclear complexes. Prepared complexes are characterised using IR spectroscopy, elemental analysis, and X-Ray techniques. In addition, the complexes are further analysed via TG and DSC. Molecular models of two of the nine prepared complexes are determined using X-Ray diffraction methods. The two terminal copper ions are observed to be in square pyramide coordination sphere between two oxygens of the organic ligand, two iminic nitrogens and an oxygen of the solvent while the other two cupper ions are observed to be in square pyramide coordination sphere between the fenolic oxygens of the organic ligand and the nitrogen donors of the three azide ions. It is found that the fenolic oxygens form μ-bridge and two azide ions are monodentate coordinated. In the TG analyses, the complexes are observed to decompose in a highly exothermic manner at about 200 °C. This thermal reaction is partially similar to that of explosive molecules and the data from DSC proved that the liberated heat is at explosive material levels.

Synthesis and structure of photoluminescent di- and trinuclear copper(I) complexes assembled from alkane-bridged bis-imidazole

[Cu 2Br 2L 1(PPh 3) 4] 2 · 2CH 2Cl 2 · 3H 2O ( 1) (L 1 = bis( N-imidazolyl)butane) and [Cu 3I 2(PPh 3) 6(L 2) 2] · 2DMSO · Br · H 2O ( 2) (L 2 = bis( N-imidazolyl)methane) have been synthesized and characterized by X-ray diffraction analysis and elemental analysis. Compound 1 is a tetracoordinated dinuclear complex, it consists of two Cu(PPh 3) 2 units bridged by a bis( N-imidazolyl)butane ligand. While compound 2 is a trinuclear copper(I) complex, in the compound copper atoms are located in two kinds of coordination spheres, for the two terminal copper(I) atoms, they are surrounded by two P, one N, and one iodine atoms to complete their tetrahedron geometry. While the middle copper(I) atom is surrounded by two P and two nitrogen atoms, the bromide anion exists as free counter anion. The photoluminescent studies show that the two complexes display intense blue emissions.