Synthesis and structural characterization of two new copper(II) complexes with thiazoline derivative ligands: Influence of the coordination on the phagocytic activity of human neutrophils

Two new copper(II) complexes dichloro[2-(3,4-dichlorophenyl)imine-κN-(2-thiazolin-κN-2-yl)thiazolidine]copper(II) [CuCl₂(TdTn)] (1) and dichloro[2-(3,4-dichlorophenyl)imine-κN-(2-thiazolin-κN-2-yl)tetrahydrothiazine]copper(II) [CuCl₂(TzTn)] (2) were synthesized, then characterized by elemental analysis, UV-Vis-NIR diffuse reflectance, electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility, infrared spectroscopy, and finally their crystal structures determined by X-ray diffractometry. The structural determination of [CuCl₂(TzTn)] (2) was made by conventional single-crystal diffractometry, whereas the procedure followed to resolve the crystal structure of [CuCl₂(TdTn)] (1) by means powder diffractometry using direct-space methods with a ‘Monte-Carlo/parallel tempering’ search algorithm. A final refinement of the crystal structure was performed using the Rietveld method. It was found that the environment around the copper(II) ion for both complexes can be described as having a distorted tetrahedral geometry, with the metallic atom coordinated with two chlorides, one imine nitrogen and one thiazoline nitrogen. The biological activity of the complexes, inorganic salt and their ligands has been evaluated by examining their phagocytic activity on human neutrophils. This activity enhances in the case of the samples treated with [CuCl₂(TdTn)] (1) and [CuCl₂(TzTn)] (2) with respect to the ones to which CuCl₂, TdTn or TzTn was added.     

Monomeric, oligomeric, and polymeric copper(II) complexes of calix[4]arene-derived ligands

Deprotonation of the p-tert-butylcalix[4]arene disubstituted at alternate phenolic positions with picolyl groups 2 was achieved with alkali metal hydrides LiH, NaH, and KH. The dianionic calixarene derivatives were subjected to complete substitution at the phenolic rim with allyl bromide, providing the tetraalkylated derivatives in cone 3a and partial-cone conformations 3b; both compounds were crystallographically characterized. Compound 2, as well as 3a and 3b were tested as ligands towards CuCl₂, affording Cu²⁺ complexes in the first two cases. Polymeric [2·CuCl₂] was obtained from 2 and CuCl₂ in MeOH/CH₂Cl₂ solutions, and consists of chains of the ditopic calixarene acting as an N-donor towards Cu²⁺ ions outside the macrocyclic cavity. Employment of EtOH/CH₂Cl₂ mixtures results in the tricopper complex [(2)₂Cu₃Cl₆(EtOH)₂]. In contrast, reactions of ligand 3a with CuCl₂ afforded monomeric [3a·CuCl₂], while no Cu²⁺ complexes could be obtained when 3b was employed. The presence of intramolecular hydrogen bonds in 2 appears to control the formation of oligomeric or polymeric copper complexes, while the lack of such hydrogen bonds allows the proper alignment of N-donors to coordinate Cu²⁺ directly above the macrocyclic cavity.     

Synthesis, structure, and catalytic activity of chiral Cu(II) and Ag(I) complexes with (S,S)-1,2-diaminocyclohexane-based N4-donor ligands

Condensation of (S,S)-1,2-cyclohexanediamine with 2 equiv. of 2-pyridine carboxaldehyde in toluene in the presence of molecular sieves at 70 °C gives N,N′-bis(pyridin-2-ylmethylene)-(S,S)-1,2-cyclohexanediamine (S,S-1) in 95% yield. Reduction of 1 with an excess of NaBH₄ in MeOH at 50 °C gives N,N′-bis(pyridin-2-ylmethyl)-(S,S)-1,2-cyclohexanediamine (S,S-2) in 90% yield. Reaction of 1 or 2 with 1 equiv. of CuCl₂ · 2H₂O in methanol gives complexes [N-(pyridin-2-ylmethylene)-(S,S)-1,2-cyclohexanediamine]CuCl₂ (3) and [Cu(S,S-2)(H₂O)]Cl₂ · H₂O (4), respectively, in good yields. Complex 4 can further react with 1 equiv. of CuCl₂ · 2H₂O in methanol to give [Cu(S,S-2)][CuCl₄] (5) in 75% yield. The rigidity of the ligand coupled with the steric effect of the free anion plays an important role in the formation of the helicates. Treatment of ligand S,S-1 with AgNO₃ induces a polymer helicate {[Ag(S,S-1)][NO₃]}_n (6), while reaction of ligand 2 with AgPF₆ or AgNO₃ in methanol affords a mononuclear single helicate [Ag(S,S-2)][PF₆] (7) or a dinuclear double helicate [Ag₂(S,S-2)₂][NO₃]₂ · 2CH₃OH (8) in good yields, respectively. All compounds have been characterized by various spectroscopic data and elemental analyses. Compounds 1, 3-5, 7 and 8 have been further subjected to single-crystal X-ray diffraction analyses. The Cu(II) complexes do not show catalytic activity for allylation reaction, in contrast to Ag(I) complexes, but they do show catalytic activity for Henry reaction (nitroaldol reaction) that Ag(I) complexes do not.     

Towards absolute asymmetric synthesis. Synthesis and crystal structure of stereochemically labile MCl2 (M = Co, Ni, Cu, Zn) complexes with diamine ligands

In search for new conglomerates, seven stereochemically labile complexes between MCl₂ (M = Co, Cu, Ni, Zn) and bidentate ligands, the commercially available N,N,N′-trimethylethane-1,2-diamine (trimeda) and the somewhat bulkier N-isopropyl-N,N′,N′-trimethylethane-1,2-diamine (itmeda), have been synthesized and characterized using single crystal X-ray diffraction. The trimeda and itmeda ligands exhibit chirogenic nitrogen centers and may form chiral metal complexes that are candidates for total spontaneous resolution. Copper(II) chloride forms the dimeric meso complexes [{CuCl₂(trimeda)}₂] (1) and [{CuCl₂(itmeda)}₂] (2), while [CoCl₂(trimeda)₂] (3) and [NiCl₂(trimeda)₂] (4) exhibit six-coordinate but chiral (R,R)- and (S,S)-complexes. Three examples of the chiral target complex, comprising four-coordinate stereochemically labile monomers, was successfully prepared, viz. [NiCl₂(itmeda)] (5), [ZnCl₂(itmeda)] (6), and [CoCl₂(itmeda)] (7).In all seven complexes, the λ-conformation of the five-membered trimeda-metal chelate ring corresponds to the (S)-configuration at nitrogen, and vice versa. Supramolecular interactions in 3 and 4 form hydrogen-bonded heterochiral ribbons. However, crystals of 5-7 display homochiral interactions resulting in polar phases. Weak CH-Cl interactions in 5 and 6 form homochiral layers. In 7, interactions form homochiral helices along the a-axis.     

Crystal structure and properties of the copper(II) complex of sodium monensin A

The preparation and structural characterization of a new copper(II) complex of the polyether ionophorous antibiotic sodium monensin A (MonNa) are described. Sodium monensin A binds Cu(II) to produce a heterometallic complex of composition [Cu(MonNa)₂Cl₂]·H₂O, 1. The crystallographic data of 1 show that the complex crystallizes in monoclinic space group C2 with Cu(II) ion adopting a distorted square-planar geometry. Copper(II) coordinates two anionic sodium monensin ligands and two chloride anions producing a neutral compound. The sodium ion remains in the inner cavity of the ligand retaining its sixfold coordination with oxygen atoms. Replacement of crystallization water by acetonitrile is observed in the crystal structure of the complex 1. Copper(I) salt of the methyl ester of MonNa, 2, was identified by X-ray crystallography as a side product of the reaction of MonNa with Cu(II). Compound 2, [Me-MonNa][H-MonNa][CuCl₂]Cl, crystallizes in monoclinic space group C2 with the same coordination pattern of the sodium cation but contains a chlorocuprate(I) counter [CuCl₂]⁻, which is linear and not coordinated by sodium monensin A. The antibacterial and antioxidant properties as two independent activities of 1 were studied. Compound 1 is effective against aerobic Gram(+)-microorganisms Bacillus subtilis, Bacillus mycoides and Sarcina lutea. Complex 1 shows SOD-like activity comparable with that of the copper(II) ion.     

Transition metal halide salts of N-methylmorpholine: Synthesis, crystal structures and magnetic properties of N-methylmorpholinium salts of copper(II), cobalt(II) and manganese(II)

A family of complexes of N-methylmorpholinium metal halides has been synthesized and analyzed using X-ray crystallography and temperature dependant magnetic susceptibility. The compounds produced include (nmmH)₂[CuCl₄] (1), (nmmH)₂[CoCl₄] (2), (nmmH)₂[MnCl₄] (3), (nmmH)₂[CuBr₄] (4), (nmmH)₂[CoBr₄] (5), and (nmmH)₂[MnBr₄] (6) [nmmH = N-methylmorpholinium]. The compounds are all isomorphous and exhibit weak one dimensional antiferromagnetic interactions, with a contribution from single-ion anisotropy in the case of the cobalt complexes.     

Cu(II) complexes with square pyramidal (N2S)CuCl2 chromophore: Jahn-Teller distortion and subsequent effect on spectral and structural properties

One monomeric neutral Cu(II) complex [(pmtpm)CuCl₂] (1) is reported by Lindoy and Livingstone [8]. Two new complexes namely, μ-Cl bridged binuclear Cu(II) complex [{(pmtpm)Cu(Cl)}₂ μ-Cl](ClO₄) (2) and a bis μ-Cl bridged binuclear Cu(II) complex [{(pmtpm)Cu}₂(μ-Cl)₂](ClO₄)₂ (3) derived from a tridentate Schiff base ligand, 2-pyridyl-N-(2′-methylthiophenyl)methyleneimine (pmtpm) were synthesized and characterized by various spectroscopic methods and by X-ray crystallography. (N₂S)CuCl₂ chromophore(s) of distorted square pyramidal coordination geometries around Cu(II) ion(s) have been observed for all the complexes 1-3. The equatorial sites of the square plane comprise two N and a thioether S donor atoms of the pmtpm ligand as well as one Cl⁻ ion (terminal in 1 and 2, and bridging in 3) while the remaining axial site is occupied by a terminal Cl⁻ ion (for 1) or a bridging Cl⁻ ion (for 2 and 3). The equatorial Cu-Cl distances are much shorter [1: 2.2511(4) Å, 2: 2.2307(12) Å, 3: 2.2513(12) Å] than the axial Cu-Cl distances [1: 2.4394(4) Å, 2: 2.5597(9) Å, 3: 2.7037(12) Å]. The correlation of an axial Cu-Cl bond elongation with a lower g_|| value in the solid state EPR spectrum and a blue shifted ligand field transition in the solid and solution phase absorption spectrum has been observed.     

Copper(II) chloride/1-methylbenzotriazole chemistry: influence of various synthetic parameters on the product identity, structural and magnetic characterization, and quantum-chemical studies

A systematic investigation of the CuCl₂/Mebta (Mebta = 1-methylbenzotriazole) reaction system is described, involving the determination of the influence of the Cu^II:Mebta ratio, the nature of solvent and the presence of counterions on the identity of the reaction products. As a consequence, complexes [Cu₂Cl₄(Mebta)₄] (1), [CuCl₂(Mebta)₂] (2), {[Cu₂Cl₄(Mebta)₂]}_n (3), [Cu₄OCl₆(Mebta)₄] · 0.25H₂O (4 · 0.25H₂O) and [Cu₂Cl₂(Mebta)₆](ClO₄)₂ (5) have been isolated and structurally characterized by single-crystal X-ray studies. Mebta behaves as a monodentate ligand binding through N(3). 1 is a dinuclear complex, the structure of 2 consists of discrete monomeric units, and that of 3 is composed of linear, well-separated polymeric chains of Cu^II atoms. The molecules of 4 · 0.25H₂O have a central μ₄-oxide ion surrounded tetrahedrally by four Cu^II atoms. In the cations of 5 the two Cu^II centres are asymmetrically bridged by two chloro ligands, with three Mebta molecules completing five coordination at each metal. Complexes were characterized by spectroscopic (IR, far-IR, solution UV/Vis) and thermal decomposition (TG, DTG, and DTA) techniques. Variable-temperature magnetic susceptibility data for 1, 3 and 5 showed intramolecular (1, 5) and intrachain (3) ferromagnetic exchange interactions. Estimates of the Jparameters, experimentally derived, were in close agreement with a new magneto-structural criterion developed by us, holding for bis(μ-chloro) copper(II) dimers. A comparison between the CuCl₂/Mebta and CuBr₂/Mebta systems is also presented.     

Synthesis and properties of (2-pyridyl)alkylamine- and (2-pyridyl)alkylamine–amide-coordinated copper(II) complexes: Structures and non-covalent interactions

Reaction of the ligand N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine (mpppa) with equimolar amounts of [Cu(H₂O)₆][ClO₄]₂ or CuCl₂ · 2H₂O in MeCN afforded mononuclear copper(II) complexes [Cu(mpppa)][ClO₄]₂ (1) and [Cu(mpppa)Cl₂] (2). Crystal structure analysis reveals CuN₃O (two pyridyl, an aliphatic amine, and an amide oxygen) coordination in 1 and CuN₃Cl₂ (two pyridyl, an aliphatic amine, and two chlorides) coordination in 2. Crystal packing diagram of 1 reveals that one of the perchlorate counteranions provides weak coordination to copper(II) centers and in turn the copper(II) centers assume pseudo-six-coordination, generating 1D chain. Notably, one of the copper(II)-coordinated chloride ions in 2 participates in an intramolecular N–H?Cl interaction. Intermolecular C–H?Cl interactions in the solid state generate helical structure. Spectroscopic (IR, UV–Vis, and EPR) and redox properties of the two complexes have been investigated and compared.     

Elevation of [3H]cimetidine binding by CuCl2 in brain membranes of rats

Influences of dithiothreitol (DTT), p-chloromercuriphenyl sulfonate (PCMPS) and ascorbate on CuCl₂-induced elevation of [³H]cimetidine binding were investigated in brain membranes of rats. CuCl₂ (10–500 μM) elevated specific [³H]cimetidine binding in a concentration-dependent manner. There were two types of [³H]cimetidine binding in the presence of 50 μM CuCl₂: high affinity binding with K_d = 1.97 nM and low affinity with K_d = 21.6 nM. PCMPS (10 and 100 μM) reduced the binding in both media with and without CuCl₂. DTT (1–30 μM) or ascorbate (0.1 and 1.0 mM) markedly elevated the binding in the presence of CuCl₂ but showed no effect and ascorbate rather inhibited the binding in the absence of CuCl₂. DTT (0.1 mM) diminished the binding in the presence and absence of CuCl₂. CuCl₂ (50 μM) significantly (P < 0.01) increased the IC₅₀ of histamine for [³H]cimetidine binding and the effect was greater than that from 100 μM GTP. It is suggested that sulfhydryl groups sensitive to PCMPS could interact with Cu²⁺ and thus be involved in an elevation of cimetidine binding. Cu²⁺ seems to regulate affinity of agonist binding for cimetidine binding sites presumably by acting on cimetidine binding sites and/or GTP binding regulatory proteins.     

Facile anaerobic oxidative dehydrogenation promoted by bases: The case of copper-2,4-dihydro-1H-benzo[d][1,3]oxazine complexes

Two new 2,4-dihydro-1H-benzo[d][1,3]oxazines (L₁ and L₂) were prepared by condensation of 2-quinolinecarboxaldehyde and 2-amino-benzyl alcohols and tested as N,N’-bidentate ligands toward CuCl₂. Treatment of the resulting copper(II) derivatives with Et₃N promoted an oxidative dehydrogenation yielding the corresponding copper(I) [Cu(L-ox)Cl] complexes, 2, (L-ox = 4H-benzo[d][1,3]oxazine). The [Cu(L₂-ox)Cl] species, 2b, was characterized by single crystal X-ray diffraction, showing a trigonal geometry at the metal center and reacted with PPh₃ and CO, affording [Cu(L₂-ox)(PPh₃)Cl], 4b, and [Cu(L₂-ox)(CO)Cl], 6b, respectively. The latter species, stable in the solid state, was structurally characterized by diffraction methods and showed tetrahedral coordination of the Cu(I) ion.     

Transition metal complexes of 2-amino-3,5-dihalopyridines: Synthesis, structures and magnetic properties of Cu(3,5-diCAP)2X2 and Cu(3,5-diBAP)2X2

A family of bis(2-amino-3,5-dihalopyridine)dihalocopper(II) compounds has been synthesized, including (3,5-diCAP)₂CuCl₂ (1), (3,5-diCAP)₂CuBr₂ (2), (3,5-diBAP)₂CuCl₂ (3), and (3,5-diBAP)₂CuBr₂ (4) [3,5-diCAP = 2-amino-3,5-dichloropyridine; 3,5-diBAP = 2-amino-3,5-dibromopyridine]. These complexes have been analyzed through single crystal X-ray diffraction and temperature dependant magnetic susceptibility. The compounds are all isostructural, forming bi-bridged chains with long Cu-X?Cu bridges in the crystal lattice. The two copper chloride compounds (1 and 3) exhibit weak antiferromagnetic interactions along these chains.     

Synthesis, crystal structure, spectroscopic and magnetic properties of copper(II) complexes with 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine (PyTT)

The copper(II) complexes [Cu(PyTT)₂(H₂O)](NO₃)₂ (A) and [CuCl₂(μ-PyTT)₂CuCl(H₂O)]Cl · 3H₂O (B) were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, UV-Vis-NIR diffuse reflectance and magnetic susceptibility measurements. In the mononuclear compound A the copper ion is in a distorted square pyramidal geometry, with the equatorial plane formed by two thiazoline nitrogen atoms, one imino nitrogen atom and one water molecule, whereas the axial site is occupied by one imino nitrogen atom. The compound B is dinuclear and both Cu(II) centres present environments that can be described as slightly distorted square pyramidal geometries. The observed molar magnetic susceptibility for A (μ=2.13 BM) allows to exclude metal-metal interactions, supporting a monomeric structural formulation for this compound. In compound B, magnetic susceptibility measurements in the temperature range 6.2-288 K show an intradimer antiferromagnetic interaction (J=−11.8 cm⁻¹).     

Effects of CuCl2 on the hydrolysis of cyclic GMP and cyclic AMP by the activator-dependent cyclic nucleotide phosphodiesterase from bovine heart

CuCl₂ non-comepetitively inhibited the hydrolysis of cyclic GMP and cyclic AMP by the activator-dependent phosphodiesterase from bovine heart in the presence of 5 mM Mg²⁺, 10 μM Ca²⁺ and phosphodiesterase activator with K_i values of approximately 2 μM for both substrates. CuCl₂ inhibition was also non-competitive with Mg²⁺, Ca²⁺ and phosphodiesterase activator. Dialysis demonstrated that CuCl₂ inhibition in reversible. Treatment of the enzyme with p-hydroxymercuribenzoate resulted in the loss of enzyme activity, suggesting the presence of sulfhydryl groups essential for enzyme activity. The inhibitory activity of CuCl₂ was not additive with that p-hydroxymercuribenzoate, therefore CuCl₂ may inhibit enzyme activity by binding to one or more essential sulfhydryl groups. CuCl₂ also inhibited the hydrolysis of cyclic AMP by the cyclic AMP-specific phosphodiesterase from bovine heart with an I₅₀ value of 18 μM. Several effects of Cu²⁺ are discussed which have been noted in other studies and might be due, in part, to changes in cyclic nucleotide levels following alterations in phosphodiesterase activity.     

Synthesis and β-glucuronidase inhibitory activity of 2-arylquinazolin-4(3H)-ones

2-Arylquinazolin-4(3H)-ones 1–25 were synthesized by reacting anthranilamide with various benzaldehydes using CuCl₂·2H₂O as a catalyst in ethanol under reflux. Synthetic 2-arylquinazolin-4(3H)-ones 1–25 were evaluated for their β-glucuronidase inhibitory potential. A trend of inhibition IC₅₀ against the enzyme in the range of 0.6–198.2 μM, was observed and compared with the standard d-saccharic acid 1,4-lactone (IC₅₀ = 45.75 ± 2.16 μM). Compounds 13, 19, 4, 12, 14, 22, 23, 25, 15, 8, 17, 11, 21, 1, 3, 18, 9, 2, and 24 with the IC₅₀ values within the range of 0.6–44.0 μM, indicated that the compounds have superior activity than the standard. The compounds showed no cytotoxic effects against PC-3 cells. A structure–activity relationship is established.     

[{Cu(pz)(Opo)}2(μ-Cl)2]: A new dinuclear copper(II) complex with a chloride bridge and mixed blocking ligands

A new copper(II) complex with chloride bridges and mixed blocking ligands, [{Cu(pz^Ph)(Opo)}₂(μ-Cl)₂] (1), whereby pz^Ph = 3-phenyl-pyrazolyl, and OpoH = 2-hydroxypyridine-N-oxide, has been obtained by degrading tris(pyrazolyl)borate in the presence of hydrated CuCl₂ salt and the ligand Opo⁻. The molecular structure of 1 was solved by X-ray diffraction. The two Cu(II) atoms of the dinuclear complex have a pyramidal arrangement in which the two pyramids share one base-to-apex edge with parallel basal planes. Magnetic susceptibility measurements revealed ferromagnetic coupling between the Cu atoms, with J = +8.72 cm⁻¹. X-band EPR spectra of CH₂Cl₂ solutions of 1 were recorded at different temperatures.     

Four new copper(II) complexes with di-substituted s-triazine-based ligands

In this paper, two di-substituted triazine-based ligands, 6-chloro-N,N,N′N′-tetrakis-pyridin-2-ylmethyl-[1,3,5]triazine-2,4-diamine (L1), and 6-chloro-N,N′-bis-pyridin-2-ylmethyl-N,N′-bis-thiophen-2-ylmethyl-[1,3,5]triazine-2,4-diamine (L2), have been prepared. Reaction of CuCl₂·2H₂O and Cu(NO₃)₂·3H₂O with L1 and L2 results in the formation of [Cu₂Cl₄(L1)]·3MeOH (compound 1), [Cu₄(NO₃)₈(L1)₂]·2.07CH₂Cl₂·0.93MeOH (compound 2), [Cu₂Cl₄(L2)₂] (compound 3) and [Cu(NO₃)₂(L2)]·CH₂Cl₂ (compound 4), respectively, which have been fully characterized and determined by single-crystal X-ray crystallography, FT-IR, elemental analysis, thermogravimetric measurement and magnetic susceptibility. The dinuclear compound 1 shows strong π-π interactions between the neighboring pyridine rings. The nitrate-π (1,3,5-triazine ring) interaction with the distance of 2.755 Å in compound 2, is the closest contact reported so far. Compounds 3 and 4 are mononuclear copper(II) compounds, in which none of thiophene rings coordinates with copper(II) ion. In addition, the different orientations of two thiophene rings in compounds 3 and 4 lead to the π-π and CH₂Cl₂-π (thiophene ring) interactions in compound 4, but not in compound 3.     

Killing of Bacillus subtilis Spores by a Modified Fenton Reagent Containing CuCl2 and Ascorbic Acid

Bacillus subtilis spores were killed by CuCl₂-ascorbic acid, chloride ions were essential for killing of spores, and spores with defective coats were killed more rapidly. CuCl₂-ascorbic acid did not damage spore DNA, and spores killed by this reagent initiated germination. However, spores killed by CuCl₂-ascorbic acid may have damage to their inner membrane.     

Crystal structural, electrochemical and computational studies of two Cu(II) complexes formed by benzotriazole derivatives

Two Cu(II)-containing complexes, [Cu(pbbt)Cl₂]₂ · CH₃OH (1) and [Cu(bbbt)_1.5Cl₂]_n (2) (pbbt = 1,1′-(1,3-propylene)bis-1H-benzotriazole, bbbt = 1,1′-(1,4-butanediyl)bis-1H-benzotriazole), have been synthesized and characterized. Single crystal X-ray diffraction shows that 1 exhibits discrete binuclear structure, in which two Cu(II) ions are bridged together through two Cl⁻ anions and two pbbt ligands. Whereas 2 displays infinitely extended two-dimensional reticulate grid structure with hexagon units in which six Cu(II) ions act as corners and six bbbt ligands serve as sides. The electrochemical studies show that their redox processes in the potential range of 0.1-0.9 V are quasi-reversible and controlled by diffusion. The diffusion coefficients decrease with increase in the molecular weight of the complexes and the size of the molecules. Further investigation exhibits that their electrochemical properties obtained from experiments are consistent with their crystal data and the computed parameters. For example, the observed one-pair well-defined redox waves in the cyclic voltammetry (CV) diagrams correspond to the X-ray diffraction results that all of the Cu(II) ions in the title complexes are equivalent, respectively; the cathodic shifts (as compared with CuCl₂) of the reduction potentials of 1 and 2 are in agreement with the computed results: the LUMO energies of the complexes (−3.789 eV for 1 and −4.330 eV for 2) are higher than that of CuCl₂ (−6.942 eV).     

The efficacy and sterilisation of human decellularised dermal allografts with combinations of cupric ions and hydrogen peroxide

Decellularised tissue allografts have been used in reconstructive surgical applications and transplantation for many years. Some of the current methods of sterilisation have a detrimental effect on the tissue graft structure and function. The anti-microbial activity of cupric ions and hydrogen peroxide (H₂O₂) are well known however their combined application is not currently utilised as a decontamination agent in the tissue banking world sector. The aim of this study was to determine the combined concentrations of copper chloride (CuCl₂) and H₂O₂ that have the optimal bactericidal and sporicidal activity on decellularised (dCELL) human dermis. The first part of this study established the decimal reduction time (D-value) of CuCl₂ (0.1 mg/L and 1 mg/L) together with H₂O₂ (0.01, 0.1, 0.5 and 1%) for Staphylococcus epidermidis, Escherichia coli and Bacillus subtilis spores. The second part of this study identified the most effective CuCl₂ and H₂O₂ concentration that decontaminated dCELL human dermis inoculated with these pathogens. Of all the concentrations tested, 0.1 mg/L CuCl₂ in combination with 1% H₂O₂ had the shortest D-value; S. epidermidis D = 3.15 min, E. coli D = 2.62 min and B. subtilis spores D = 18.05 min. However when adsorbed onto dCELL dermis, S. epidermidis and E. coli were more susceptible to 1 mg/L CuCl₂ together with 0.5% H₂O₂. These studies show promise of CuCl₂–H₂O₂ formulations as potential sterilants for decellularised dermal allografts.