Syntheses,Spectral, Thermal and Electrochemical Studies of 3-Carboxylacetonehydroxamic Acid and its Iron(Ii), Cobalt(Ii), Nickel(Ii), Copper(Ii) and Zinc(Ii) Complexes

3-Carboxylacetonehydroxamic acid (CAHA) and its iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV-Vis and IR spectra and magnetic susceptibility. The pK _a1 and pK _a2 values of the ligand in aqueous solution were found to be 6.5 ± 0.1 and 8.6 ± 0.1, which correspond to dissociation of carboxyl and hydroxamic protons, respectively. The dianion CAH acts as a tetradentate ligand through the hydroxamate and carboxylate groups and coordinates to the divalent metal ions, forming coordination polymers with a metal-to-ligand ratio of 1 : 1 in the solid state. FTIR spectra and thermal decomposition of the ligand and its metal complexes were recorded and briefly discussed. The electrochemical behavior of the complexes was investigated by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, the iron(II) and copper(II) cations form stable complex species with a metal-to-ligand ratio of 1 : 2 in solution. The iron(II), cobalt(II) and nickel(II) complexes show two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo quasi-reversible and reversible electrode reactions, respectively. The stability constants of the complexes were determined by square wave voltammetry.     

Synthesis and characterization of a new Schiff base derived from 2,3-diaminopyridine and 5-methoxysalicylaldehyde and its Ni(II), Cu(II) and Zn(II) complexes. Electrochemical and electrocatalytical studies

We describe the synthesis and characterization of a new tetradentate Schiff base ligand obtained from 2,3-diaminopyridine and 5-methoxysalicylaldehyde. This ligand (H₂L) reacted with nickel(II), copper(II), and zinc(II) acetates to give complexes. The ligand and its metal complexes were characterized using analytical, spectral data (UV–vis, IR, and mass spectroscopy), and cyclic voltammetry (CV). The crystal structure of the copper complex was elucidated by X-ray diffraction studies. The electrochemical behavior of these compounds, using CV, revealed that metal centers were distinguished by their intrinsic redox systems, e.g. Ni(II)/Ni(I), Cu(II)/Cu(I), and Zn(II)/Zn(I). Moreover, the electrocatalytic reactions of Ni(II) and Cu(II) complexes catalyze the oxidation of methanol and benzylic alcohol.     

Synthesis,characterization, thermal,and redox properties of a vic-dioxime and its metal complexes

A new vic-dioxime ligand containing benzophenone hydrazone units, N′-(benzophenone hydrazone)glyoxime [LH₂] has been prepared from benzophenone hydrazone and anti-chloroglyoxime in absolute ethanol. Mononuclear nickel(II), cobalt(II), copper(II), zinc(II), and cadmium(II) complexes were also synthesized. Ligand and complexes were characterized by elemental analyses, FT-IR, ¹H NMR, and ¹³C NMR spectroscopy, magnetic moments, and DTA/TG techniques. On the basis of the magnetic and spectral evidences a square-planar geometry for Ni(II) and Cu(II) complexes, tetrahedral for Cd(II) and Zn(II) complexes, and octahedral for Co(II) complex were proposed. Redox behaviors of ligand and its complexes were also investigated by cyclic voltammetry at the glassy carbon electrode.     

New metal complexes derived from S-benzyldithiocarbazate (SBDTC) and chromone-3-carboxaldehyde: synthesis,characterization, antimicrobial,antitumor activity and DFT calculations

Novel monobasic tridentate ONS donor ligand (HL) was synthesized from the condensation reaction of chromone-3-carboxaldehyde with S-benzyldithiocarbazate (SBDTC). Reaction of the ligand with the metal ions copper(II), nickel(II), cobalt(II), oxidovanadium(IV), cerium(III), manganese(II), zinc(II), and cadmium(II) afforded dimeric complexes with the general formula [ML(Y)_m(H₂O)_x]₂·(Y)_m·nH₂O·zCH₃OH, Y?=?NO₃ or Cl, m?=?0–2, x?=?0–2, n?=?0–2, and z?=?0–1 for all complexes except oxidovanadium(IV) complex which has the formula [VOL(H₂O)]₂(SO₄). Structures of the ligand and its metal complexes were established through elemental, spectroscopic data (FT-IR, UV-Vis, and mass), thermal analyses, as well as conductivity and magnetic susceptibility measurements. The geometrical structures of the metal complexes are octahedral and square planar. The ligand and its complexes were subjected to in vitro bioassays against the gram-negative and gram-positive bacteria and the fungus strain with good results for some of these compounds. The antitumor activity of the ligand and its copper(II) and oxidovanadium(IV) complexes were investigated against HepG2 cell line. The molecular parameters of the ligand and its metal complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program, and computed data were correlated with the experimental results. The HOMO→LUMO electron transition potentially occurs from S-benzyldithiocarbazate to chromone moieties with 4.048?eV. The Mn(II) complex has the highest value of energy barrier, while Cu(II) complex has the lowest value among the complexes. All synthesized complexes have energy gap lower than free ligand and therefore these complexes are more reactive than the free ligand.     

Synthesis,characterization, fluorescence and redox features of new <Emphasis Type="Italic">vic</Emphasis>-dioxime ligand bearing pyrene and its metal complexes

A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH₂), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses, IR, UVVIS and ¹H and ¹³C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH₂) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base, as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN₄ coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively.     

Synthesis,spectral, and biological studies of transition metal chelates of N-[1-(3-aminopropyl)imidazole]salicylaldimine

Tridentate chelate complexes M[LX?·?2H₂O], where M?=?Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been synthesized from the Schiff base L?=?N-[1-(3-aminopropyl)imidazole]salicylaldimine and X?=?Cl. Microanalytical data, UV-Vis, magnetic susceptibility, IR, ¹H-NMR, mass, and EPR techniques were used to confirm the structures. Electronic absorption spectra and magnetic susceptibility measurements suggest square-planar geometry for copper complex and octahedral for other metal complexes. EPR spectra of copper(II) complex recorded at 300?K confirm the distorted square-planar geometry of the copper(II) complex. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species and one fungus. The electrochemical behavior of the copper complex was studied by cyclic voltammetry.     

Mononuclear,homo- and hetero-binuclear complexes of 1-(5-(1-(2-aminophenylimino)ethyl)-2,4-dihydroxyphenyl)ethanone: synthesis,magnetic, spectral,antimicrobial, antioxidant,and antitumor studies

A new Schiff base, H₂L, was prepared by condensation of 4,6-diacetylresorcinol with o-phenylenediamine in molar ratio 1?:?1. The ligand reacted with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), oxovanadium(IV), and dioxouranium(VI) ions in the absence and presence of LiOH to yield mononuclear and homobinuclear complexes. The mononuclear dioxouranium(VI) complex [(HL)-(UO₂)(OAc)(H₂O)]·5H₂O was used to synthesize heterobinuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, ¹H-, and ¹³C-NMR, electronic, ESR and mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal analysis. In the absence of LiOH, mononuclear complexes (1, 4, and 9) were obtained; in the presence of LiOH, binuclear complexes (3, 5, 7, and 10) as well as mononuclear complexes (2, 6, and 8) were obtained. In the mononuclear complexes, the coordinating sites are the phenolic oxygen, azomethine nitrogen, and amino nitrogen. In addition to these coordinating sites, the free carbonyl and phenolic OH are involved in coordination in binuclear complexes. The metal complexes exhibited octahedral, tetrahedral, and square planar geometries while the uranium is seven-coordinate. The antimicrobial and antioxidant activities of the ligand and its complexes were investigated. The ligand and the metal complexes showed antitumor activity against Ehrlich Acites Carcinoma.     

Synthesis,Structure, and Properties of Novel Enamine Containing Coumarin and Phosphonium Fragments

Condensation of 4-hydroxy-3-formylcoumarin with 4-aminobenzyl(triphenyl)phosphonium bromide has led to the formation of a phosphonium salt existing in DMSO solution as a mixture of two enamine forms, Z and E, according to NMR spectroscopy and quantum-chemical simulations data. Basing on the obtained salt, the ML₂ metal chelates of zinc(II), copper(II), and nickel(II) have been synthesized. Luminescence properties of the ligand and its complex with zinc have been studied.

     

A novel vic-dioxime ligand and its Ni(II), Cu(II) and Co(II) complexes containing calix[4]pyrrole moiety: synthesis, characterization and redox properties

A new calix[4]pyrrole functionalized vic-dioxime, 3-(4-methyl-9,9,14,14,19,19-hexaethylcalix[4]pyrrole)benzoaminoglyoxime (LH₂) was synthesized from anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at room temperature. The mononuclear complexes {nickel(II), copper(II) and cobalt(II)} of this vic-dioxime ligand were prepared and their structures were confirmed by elemental analysis, IR and UV–Vis spectrophotometry, magnetic susceptibility; the MS, ¹H and ¹³C NMR spectra of the LH₂ ligand and its Ni(II) complex were also recorded. The experimental results indicated that the ligand:metal ratio was 2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is with most vic-dioximes. Electrochemical properties of the ligand, and its complexes were investigated in DMSO solution by cyclic voltammetry at 200?mV?s^?1 scan rate.     

Transition metal complexes of the tripodal ligand 4-(2′-pyridylmethyl)-4-azaheptane-1,7-diamine. Crystal structures of [CuLCl]ClO4 and [NiL(MeCN)2](ClO4)2

The tripodal ligand 4-(2′-pyridylmthyl)-4-azaheptane-1,7-diamine has been prepared by reaction of 2-aminemethyl pyridine with acrylonitrile, followed by the reduction of the nitrile groups. Copper(II), nickel(II), zinc(II), cobalt(III) and chromium(III) complexes of the ligand have been prepared and characterized and the crystal structures of the complexes [CuLCl]ClO₄ and [NiL(MeCN)₂](ClO₄)₂ determined. The copper complex is five coordinate with approximate square pyramidal stereochemistry with the apical position occupied by a primary amine donor. The nickel complex is octahedral with the pyridine nitrogen donor lying trans to an acetonitrile ligand.     

Bis -(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C₁₅H₂₆N₅P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for copper and cobalt complexes. The EPR spectra of copper complex in acetonitrile at 300 K and 77 K were recorded. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by well-diffusion method. The zone of inhibition values were measured at 37°C for a period of 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. Catalytic study indicates the copper complex has efficient catalytic activity in oxidation of amitriptyline.     

New Copper（Ⅱ） and Nickel（Ⅱ） Complexes of 4-Morpholinoacetophenone Thiosemicarbazone： Structural, Electrochemical and Antimicrobial Studies

4-Morpholinoacetophenone thiosemicarbazone, MAPT, and its nickel（Ⅱ） and copper（Ⅱ） complexes have been prepared and characterized by elemental analysis, magnetic susceptibility, spectral methods （FT-IR, ^1H NMR） and cyclic voltammetry. Electrochemical behaviors of the complexes have been studied by cyclic voltammetry in DMF media showing metal centered reduction processes for both of them. The redox properties, nature of the electrode processes and the stability of the complexes were discussed. [Cu（MAPT）2]Cl2 complex shows Cu（Ⅱ）/Cu（Ⅰ） couple and quasi-reversible wave associated with the Cu（Ⅲ）/Cu（Ⅱ） process. The reduction/oxidation potential values depend on the structures of complexes. Also, the antimicrobial activities of these complexes were determined against S. aureus, E. coli and B. subtilis.     

Bifunctional Cyclam‐Based Ligands with Phosphorus Acid Pendant Moieties for Radiocopper Separation: Thermodynamic and Kinetic Studies

Two macrocyclic ligands based on cyclam with trans‐disposed N‐methyl and N‐(4‐aminobenzyl) substituents as well as two methylphosphinic (H₂ L1 ) or methylphosphonic (H₄ L2 ) acid pendant arms were synthesised and investigated in solution. The ligands form stable complexes with transition metal ions. Both ligands show high thermodynamic selectivity for divalent copper over nickel(II) and zinc(II)—K(CuL) is larger than K(Ni/ZnL) by about seven orders of magnitude. Complexation is significantly faster for the phosphonate ligand H₄ L2 , probably due to the stronger coordination ability of the more basic phosphonate groups, which efficiently bind the metal ion in an “out‐of‐cage” complex and thus accelerate its “in‐cage” binding. The rate of Cu^II complexation by the phosphinate ligand H₂ L1 is comparable to that of cyclam itself and its derivatives with non‐coordinating substituents. Acid‐assisted decomplexation of the copper(II) complexes is relatively fast (τ_1/2=44 and 42 s in 1 M aq. HClO₄ at 25 °C for H₂ L1 and H₄ L2 , respectively). This combination of properties is convenient for selective copper removal/purification. Thus, the title ligands were employed in the preparation of ion‐selective resins for radiocopper(II) separation. Glycidyl methacrylate copolymer beads were modified with the ligands through a diazotisation reaction. The separation ability of the modified polymers was tested with cold copper(II) and non‐carrier‐added ⁶⁴Cu in the presence of a large excess of both nickel(II) and zinc(II). The experiments exhibited high overall separation efficiency leading to 60–70 % recovery of radiocopper with high selectivity over the other metal ions, which were originally present in 900‐fold molar excess. The results showed that chelating resins with properly tuned selectivity of their complexing moieties can be employed for radiocopper separation.     

Phosphoryl Complexes of Some Metal(II) Trifluoromethanesulfonates

Cobalt(II), nickel(II), copper(II), and zinc(II) trifluoromethanesulfonates form complexes with the phosphoryl ligands hexamethylphosphoric triamide, nonamethyl imidodiphosphoric tetramide, trimorpholinophosphine oxide, tributylphosphine oxide, and triphenylphosphine oxide. The compounds have been prepared by a substitution reaction using trialkyl orthoformates as dehydrating agents and were investigated with the aid of infrared and ligand-field spectroscopy. In all compounds the ligands coordinate via the phosphoryl oxygen atoms. In some complexes the trifluoromethanesulfonate anions are (semi-)coordinated to the metal ions. The coordination around the metal ions was found to be tetrahedral, square pyramidal, or octahedral depending on the particular combination of metal ion and ligand. In its coordination behaviour the CF₃SO₃^? ion resembles the perrhenate ion.     

Synthesis and properties of transition and lanthanide complexes with benzyl monohydrazone-3-hydrazine- 4-benzyl-6-phenyl pyridazine ligand (BHP)

Synthesis and characterization of benzyl-monohydrazone-3-hydrazino-4-benzyl-6-phenyl pyridazine (BHP) and its complexes with copper(II), nickel(II), cobalt(II), zinc(II), manganese(II), cadmium(II), thorium(IV), dioxyuranium(VI), samarium(III) and erbium(III) are presented. The protonation equilibrium of BHP ion and complex formation equilibrium with the metal ions have been studied by potentiometry in 75% (v/v) dioxane-water and 0.10M KNO₃ at different temperatures (10, 20, 30 and 40°C). A series of mononuclear complexes [ML _n ]^{(1? z )+} (L^? =?BHP and n =?1 ??z) were found in solution and their formation constants, enthalpies and entropies were determined.

The solid metal complexes and corresponding thermal products were elucidated by elemental analysis, conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy. The use of BHP as analytical reagents for the determination of copper(II), nickel(II) and cobalt(II) as well as extracting agents for these metal ions are discussed.     

Synthesis,spectroscopic characterization,electrochemical behaviour and thermal decomposition studies of some transition metal complexes with an azo derivative

Complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a novel heterocyclic azo derivative, formed by coupling diazotized 2-amino-3-carbethoxy-4,5-dimethylthiophene with acetylacetone were synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, UV–vis, IR, ¹H NMR and EPR spectral data. Spectral studies revealed that the ligand existed in an internally hydrogen bonded azo-enol form rather than the keto-hydrazone form and coordinated to the metal ion in a tridentate fashion. Analytical data revealed that all the complexes exhibited 1:1 metal–ligand ratio. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry was proposed for each complex. The nickel(II) complex has undergone facile transesterification reaction when refluxed in methanol for a long period. The ligand and the copper(II) complex were subjected to X-ray diffraction study. The electrochemical behaviour of copper(II) complex was investigated by cyclic voltammetry. The thermal behaviour of the same complex was also examined by thermogravimetry.     

Biligand metal chelates of 1,10-phenanthroline and several salicyclic acid derivatives in solution

Summary Mixed ligand complexes of copper(II), zinc(II), nickel(II) and cobalt(II) ions involving 1,10-phenanthroline (phen) as primary and 3,5-dinitrosalicylic acid (dnsa), 5-nitrosalicylic acid (nsa), 5-chlorosalicylic acid (csa) and 3,5-dibromosalicylic acid (dbsa) as secondary ligands in solution have been investigated potentiometrically [25°, µ = 0.1 M [NaClO₄], medium 50% v: v aqueous ethanol]. The stability order of mixed ligand complexes with respect to the metal ions obeys the natural order: cobalt(II) < nickel(II) < copper(II) > zinc(II). The stabilities of the heterometal chelates have been compared with the corresponding homometal chelates of the secondary ligands and have been interpreted in terms of metal-ligand effects and coulombic interactions between various ligand anion species present.     

New copper(II) and zinc(II) complexes based on azo Schiff base ligand: Synthesis,crystal structure,photoisomerization study and antibacterial activity

Newly synthesized mononuclear copper(II) and zinc(II) complexes containing an azo Schiff base ligand (L), prepared by condensation of 2-hydroxy-5-(o-tolyldiazenyl)benzaldehyde and propylamine, were obtained and then characterized using infrared and NMR spectroscopies, mass spectrometry and X-ray diffraction. Ligand L behaves as a bidentate chelate by coordinating through deprotonated phenolic oxygen and azomethine nitrogen. The copper and zinc complexes crystallize in triclinic and orthorhombic systems, respectively, with space groups P⁻1 and Pca2₁. In these complexes, the Cu(II) ion is in a square planar geometry while the Zn(II) ion is in a distorted tetrahedral environment. The photochemical behaviors of ligand L, [Cu(L)₂] and [Zn(L)₂] were investigated. The azo group in L underwent reversible trans–cis isomerization under UV and visible irradiation. This process was inhibited for the complexes. In addition, ligand L and its copper and zinc complexes were assessed for their in vitro antibacterial activities against four pathogenic strains.     

Synthesis,structural characterization and biological evaluation of mononuclear transition metal complexes of zwitterionic dehydroacetic acid N‐aroylhydrazone ligand

Synthesis and characterization of mononuclear transition metal complexes viz., Co(II), Ni(II), Cu(II) and Zn(II) with a newly designed ligand, (E)‐2‐benzamido‐N'‐(1‐(2‐hydroxy‐6‐methyl‐4‐oxo‐4H‐pyran‐3‐yl) ethylidene) benzohydrazide ( H ₂ L ) are reported. Molecular structures of H ₂ L , Ni(II) and Cu(II) complexes were determined by single‐crystal X‐ray diffraction studies. The structures were stabilized by various intra/inter‐molecular H‐bonding, C‐H···π and π···π stacking interactions. H ₂ L exists in zwitterionic form and acts in a monoanionic manner. Ligand/metal ratio was 2:1 for cobalt, nickel and zinc, whereas 1:1 for the copper complex. Co(II), Ni(II) and Zn(II) complexes display distorted octahedral geometry, while the Cu(II) complex shows distorted square pyramidal geometry around the metal ion. Hirshfeld surface analysis and 2D fingerprint plots revealed that H ₂ L and its complexes were supported mainly by H?H, O?H and C?H intermolecular interactions. The synthesized compounds were screened for in vitro anti‐inflammatory activity by gelatin zymography and the activity was comparable with tetracycline. Their cleavage behavior towards calf thymus DNA has been studied using agarose gel electrophoresis method. H ₂ L and Cu(II) complex were selected by National Cancer Institute (NCI) for in vitro single dose testing in the full NCI 60 cell lines panel assay. Finally, molecular docking simulation effectively proves the binding of all the synthesized compounds at cyclooxygenase‐2 (COX‐2) active sites.     

Nickel(II) and copper(II) complexes of aza macrocycles derived from trichloromethane

Syntheses of nickel(II) complexes of the tetraaza macrocycles 2,7-dichloro-1,3,6,8-tetraazacyclodecane (DCCD) and 2,8-dichloro-1,3,7,9-tetraazacyclododecane (DICD) and a copper(II) complex of 2,6,8,12,13,17-hexaazabicyclo[5.5.5]heptadecane (HBCH) are reported in the template condensation of trichloromethane with 1,2-diaminoethane or 1,3-diaminopropane. Formulation of the synthesized products [Ni(DCCD)(H₂O)₂]Cl₂, [Ni(DICD)(H₂O)₂]Cl₂?·?H₂O, and [Cu₃(HBCH)(H₂O)₆]Cl₆, and the metal-free ligand hydrochloride HBCH?·?6HCl has been confirmed by elemental analyses, conductivity measurements, and spectral studies. Potentiometric studies of nickel(II) and copper(II) complexes of HBCH and structurally similar 2,5,8,10,13,16,17,20,23-nonaazabicyclo[7.7.7]tricosane (NACT, earlier derived from trichloromethane and diethylenetriamine) have also been performed in the structural support of HBCH. In 1?:?1, metal?:?HBCH solution, copper(II) is coordinated to four N-donors of two-HN(CH₂)₃NH– groups of the ligand in a non-planar tetraaza cavity. The equilibrium constant value (log?K?=?15.41) for the reaction Cu^2+?+?A???CuA²⁺ (A?=?HBCH) is in favor of the cyclic structure of the ligand. A high value (log?K?=?23.27) for corresponding reaction in the NACT system is due to conformational change in the ligand, where copper(II) organizes the macrocycle to form a nearly planar cavity in which the cation fits well.