Biomimetic oxidation of glutathione by synthetic analogues of the active centres of ‘blue’ copper proteins

The model process of oxidation of reduced glutathione through chelate copper complexes has been studied, the former being structural analogues of the active centers of ‘blue’ copper proteins. Glutathione forms the relatively stable intermediate CuLSG⁺ with copper complexes in acetonitrile. The intramolecular electron transfer S(glutathione)→Cu(II) is the rate-determining step of the substrate oxidation. On the basis of rate constant (k_obs) values as well as activation energy (E³) values, we have concluded that there is a possibility of functional modelling of active centers of type 1 Cu by copper complexes with thioaza ligands.     

Physico-chemical study of first row transition metal ions coordination compounds with N,N′-bis(2-tosylaminobenzylidene)-1,3-diaminopropanol. The crystal structure of bis-azomethine and its cobalt(II) complex

The novel Cu(II), Ni(II), Zn(II), Co(II) coordination compounds with Schiff base ligand - N,N′-bis(2-tosylaminobenzylidene)-1,3-diaminopropanol have been synthesized and studied. The structures of bis-azomethine as well as Co(II) and Zn(II) mononuclear metallochelates have been determined by X-ray analysis. The magnetic properties of all complexes were studied and interpreted in terms of HDVV theory. It was shown that exchange interaction in binuclear copper(II) complexes was affected by tosyl groups.     

Synthetic,structural and molecular mechanics investigation of some mono- and dinuclear copper(I) and copper(II) complexes of macrocyclic and related acyclic ligands

A number of di-Cu(II) complexes of the new tetraimine macrocyclic ligand derived from the Schiff base [2 + 2] condensation of 2,5-diformylfuran with 3-oxa-pentane-1,5-diamine have been prepared by methods which employ the heavier alkaline earth metal ions as templates followed by transmetallation. The complexes have been characterised by spectroscopic and other physical methods. Several of the di-Cu(I) complexes react reversibly with CO in solution and irreversibly with O₂ in a 4:1 Cu:O₂ stoicheiometry. Depending on conditions the oxidation product may be a dinuclear Cu(II) complex of the macrocycle or a mononuclear Cu(II) complex of a new ring-opened ligand. The single crystal X-ray structure of the latter complex has been determined.[CuL](BPh₄)₂ is monoclinic, space group C2/c with a=20.12(1), b=14.48(1), c=22.37(2) Å, β=110.1(1)°, Z=4. 1389 Independent reflections above background were measured on a diffractometer and the structure refined to R=0.108. The cation has imposed C₂ symmetry. The copper atom is bonded to four nitrogen atoms in the ‘outer’ compartment of the ligand with unique CuN distances of 2.050(17) and 1.977(17) Å. The geometry of the copper atom is intermediate between square planar and tetrahedral with an angle of 39.7° between two CuN₂ planes. Molecular mechanics calculations show that this distortion is due to steric effects.     

Synthesis,characterization and antitumor activity of some metal complexes of 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones

Complexes of Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones (XSBH, X = H, 3-NO₂, 3-CH₃O, 5-Cl, 5-Br, 5-CH₃ or 5-NO₂) have been prepared and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature down to liquid nitrogen temperature) and spectral studies. These studies indicate the following structures: monomeric, high-spin, distorted octahedral for Mn(XSBH)₂; monomeric, high-spin, five-coordinate for Fe(XSBH)SO₄·H₂O; dimeric, high-spin phenoxide bridged, five-coordinate for Fe(XSBH)Cl; dimeric, high-spin five-coordinate for Co(XSBH)Cl·2H₂O; dimeric low-spin, five-coordinate for Ni(XSBH)Cl·2H₂O; dimeric, four-coordinate for Zn(XSBH); and a square-planar structure for M(XSBH)Cl·H₂O (M = Cu(II) or Pt(II).Intermolecular antiferromagnetic exchange interactions are present in Fe(III) complexes, where the exchange parameter (J) is ca. −8.0 cm⁻¹ for these complexes. The Fe(III) complexes exhibit asymmetric quadrupole split doublets in their ⁵⁷Fe Mössbauer spectra. The asymmetry is found to be temperature dependent with relatively symmetrical doublets seen at low temperature. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d_x²−y² ground state in square-planar stereo-chemistry. All these metal complexes have been screened for their antitumor activity against the P 388 lymphocytic leukaemia test system in mice and enhanced antitumor activity relative to the free ligand was found but no significant activity at the dosages used.     

Study of copper(II) and nickel(II) ternary complexes involving tertiary amines and phenyl or hydroxylphenyl substituted amino acids

Formation constants of ternary complexes MAL, where M = Cu(II) or Ni(II). A = 2.2′bipyridyl. 1, 10-phenanthroline, and L = 3.4-dihydroxyphenylalanine (dopa), tyrosine, or phenylalanine have been determined by using the computer program SCOGS. It is observed that dopa coordinates with Cu(II)-A and Ni(II)-A through the aminocarboxylate and only over the pH range 3–8, though the ligand coordinates with free Cu(II) ion from the amino carboxylate end in the lower pH range (pH 2–4) and from the catechol end at the higher pH range (pH > 5). The visible spectrum of Cu-A-dopa is similar to that of Cu-A-phenylalanine or Cu-A-tyrosine over the entire pH range, confirming amino carboxylate coordination. Δ log K (K_MAL - log_KML) is found to be positive in all the six Cu(II) complexes. whereas it is negative in Ni(II) complexes. Release in the ternary complexes of the repulsion between the Cu(II) dπ electron and electrons delocalized over the phenyl ring has been proposed as a probable reason for the positive Δ log K.     

Stability studies in relation to IR data of some schiff base complexes of transition metals and their biological and pharmacological studies

Schiff bases derived from salicylaldehyde and 2-substituted anilines and their Cu(II), Ni(II) and Co(II) complexes have been synthesized and characterized by their elemental analysis, TGA, IR and electronic spectral studies, molar conductance and magnetic susceptibility measurements. The mode of bonding between Cu(II), Ni(II) and Co(Il) and Schiff bases has been studied by IR spectrophotometry. The shift in the band positions of the groups involved in coordination has been utilized to estimate the metal- nitrogen bond lengths. The results obtained are in good agreement with the values of metal-nitrogen modes and ligand-field splitting energy (10 Dq). The antimicrobial activities of the synthesized ligands and their metal complexes have been determined on Gram-positive (Staphylococcus aureus), Gram- negative (Escherichia coli) bacteria and on fungi like Aspergillus niger, Aspergillus nidulense and Candida albicans. The antimicrobial activity of the organic ligands increased several folds on chelation as compared to the ligand molecule alone. However, their anti-inflammatory activity showed a different pattern; the activity of some ligands was more than their respective metal chelates. It is interesting to note that only cobalt complexes exhibited anti-inflammatory activity.     

Chiral bimetallic complexes from chiral salen metal complexes and mercury (II) halides and acetates: the anionic groups interact with Cu(II) in apical position

A series of chiral bimetallic complexes have been prepared containing both Cu(II) and Hg(II) metal centers. The complexes possess chiral salen ligands which host Cu(II) in the center of the cis-N₂O₂ chromophore and Hg(II) via two oxygen atoms of the chromophore. Halogen and acetate groups from mercury salts interact with the Cu(II) center. The X-ray crystallographic data of 11 reveals a short distance of Cl?Cu (3.22-3.26 Å). EPR study also discloses a strong interaction, in particular, of acetate group with Cu.     

Isostructural M(RL)2(hfac)2 complexes with RL = 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine

5-(4-(N-tert-Butyl-N-aminoxylphenyl))pyrimidine (RL, 4PPN) forms crystallographically isostructural and isomorphic pseudo-octahedral M(RL)₂(hfac)₂ complexes with M(hfac)₂, M = Zn, Cu, Ni, Co, and Mn. Multiple close contacts occur between sites of significant spin density of the organic radical units. Magnetic behavior of the Zn, Cu, Ni, Co complexes appears to involve multiple exchange pathways, with multiple close crystallographic contacts between sites that EPR (of 4PPN) indicates to have observable spin density. Powder EPR spectra at room temperature and low temperature are reported for each complex. Near room temperature, the magnetic moments of the complexes are roughly equal to those expected by a sum of non-interacting moments (two radicals plus ion). As temperature decreases, AFM exchange interactions become evident in all of the complexes. The closest fits to the magnetic data were found for a 1-D Heisenberg AFM chain model in the Zn(II) complex (J/k = (?)7 K), and for three-spin RL—M—RL exchange in the other complexes (J/k = (?)26 K, (?)3 K, (?)6 K, for Cu(II), Ni(II), and Co(II) complexes, respectively).     

Model complexes of the active site of galactose oxidase. Effects of the metal ion binding sites

Model compounds of the active site of galactose oxidase have been developed by using new cofactor model ligands, L1H (2-methylthio-4-tert-butyl-6-[{bis(pyridin-2-ylmethyl)amino}methyl]phenol) and L2H (2-methylthio-4-tert-butyl-6-[{bis(6-methylpyridin-2-ylmethyl)amino}methyl]phenol). Treatment of the ligands with copper(II) and zinc(II) perchlorate in the presence of triethylamine followed by anion exchange reaction with NaPF₆ or NaBPh₄ provided the corresponding copper(II) and zinc(II) complexes, the crystal structures of which have been determined by X-ray crystallographic analysis. All the copper(II) and zinc(II) complexes have been isolated as a dimeric form in which the phenolate oxygen of each ligand acts as the bridging ligand to form a rhombic M₂(OAr)₂ core (M=Cu or Zn). The dimeric complexes can be converted into the corresponding monomer complexes by the treatment with exogenous ligand such as acetate ion. The redox potential and the spectroscopic features of the monomer complexes have also been examined. Furthermore, the copper(II)- and zinc(II)-complexes of the phenoxyl radical species of the ligands have been generated in situ by the oxidation of the phenolate complexes with (NH₄)₂[Ce^IV(NO₃)₆] (CAN) in CH₃CN, and their spectroscopic features have been explored. The structures and physicochemical properties of the phenolate and phenoxyl radical complexes of L1 and L2 have been compared to those of the previously reported copper(II) and zinc(II) complexes of L3 (2-methylthio-4-tert-butyl-6-[{bis(2-pyridin-2-ylethyl)amino}methyl]phenol) in order to get insights into the interaction between the metal ions and the organic cofactor moiety.     

The lability of copper ions sorbed on humic acid

Abstract

Interaction between copper (II) ions and humic acids can yield at least three different types of complex. The soluble forms promote migration of the metal ion in environmental systems and the labile content can be more ‘biologically active’. In our study, the distribution of copper between ‘fixed’, ‘non-labile’ and ‘labile’ complex forms at different pH values has been evaluated by equilibrating Cu-loaded humic acid with ion exchange resins of different types (and counter ion forms). Metal loadings of 35 to 225 μmol g^?1 were obtained by equilibrating 10 or 50 mg of purified acid with Cu (II) solutions (10^?4 M, pH 2 to 4.5). After removal of the aqueous phase, the Cu-loaded particles were re-suspended in water and a porous cage containing excess resin exchanger was added to each sample vial. After overnight mixing, the cage was retrieved and phases separated. Analysis of the aqueous phase determined the non-labile soluble copper released at the equilibrium pH; the ‘labile’ fraction value was found by back-extracting the washed resins into 0.05 M EDTA (pH 7). At pH <6, about one fifth of the sorbed Cu was labile and about 5% was released as a soluble non-labile complex. The majority of the Cu remained firmly fixed to the solid phase. Above pH 6, the substrate dissolved and the percentage present as a non-labile species increased from 5 to 75% as the pH changed from 5 to 8.5. Around pH 7, the labile content peaked at around 40%, but this fraction value dropped to ?10% at pH 8.5 (due in part to metal hydroxide formation). The type of synthetic exchanger used controlled the system pH, and the associated functional groups (sulfonate, carboxylate or chelating) had some influence on the distribution patterns observed. The distribution was also influenced by the amount of Cu (II) sorbed on the substrate.     

Copper(II)-N2S2 complexes of the imines of 1-phenyl-3-formyl-2(1H)-pyridinethione

Several copper(II) complexes of the imines formed by condensation of 1-phenyl-3-formyl-2(1H)-pyridinethione and a primary amine (pyt-R) or a diamine (pyt₂-R′) have been synthesized and characterized. The complexes have a CuN₂S₂ core and the sulfur donors exhibit thiolate character. The complexes of type [Cu(pyt₂-R′)] [ClO₄]₂ display optical and ESR spectral behavior that indicates a progressive distortion of the metal coordination geometry from square- planar toward flattened tetrahedral as the carbon chain length of the R′ bridge is varied from two to four atoms. The spectral properties of the complexes of type [Cu(pyt-R)₂] [ClO₄]₂ are more similar to one another and indicate significant distortion of Cu(II) from the planar arrangement.     

Electron spin resonance study of the copper(II) complexes of human and dog serum albumins and some peptide analogs

Electron spin resonance spectra of the first Cu(II) complexes of human serum albumin, dog serum albumin, l-aspartyl-l-histidine N-methylamide and glycyl-glycyl-l-histidine N-methylamide have been studied using isotopically pure ⁶⁵Cu in its chloride form. At 77° K, the esr spectra of Cu(II) complex of human serum albumin exhibited only one form of esr signal between pH 6.5 and 11. No intermediate forms were detected. The presence of an equally spaced nine-line superhyperfine structure with spacing ～15 G indicated considerable covalent bonding between Cu(II) and four nitrogen atoms derived from the protein. The esr spectrum form of Cu(II) bound to human serum albumin detected at neutral pH would be consistent with the participation of four nitrogens from the α-NH₂ group, two peptide groups, and the imidazole group of a histidine residue. In contrast, the esr spectra of Cu(II)-dog serum albumin complex showed a transition from a low pH form to a high pH form as the pH was increased to 9.5. These spectral changes were found to be reversible upon lowering the pH. Ligand superhyperfine splittings in the low pH form of the esr signal of Cu(II)-dog albumin were not resolved. The distinct pH dependence of the esr signals observed in human and dog serum albumin complexes could be correlated to their respective optical spectra changes as a function of pH. At room temperature and in the pH range between 6 and 11, the esr spectra of Cu(II) complexes of l-aspartyl-l-alanyl-l-histidine N-methylamide and glycyl-glycyl-l-histidine N-methylamide exhibited a well-resolved nine-line superhyperfine structure indicating metal coordination with four equivalent nitrogen atoms of peptide.     

Radical production by hydrogen peroxide/bicarbonate and copper uptake in mammalian cells: modulation by Cu(II) complexes

The presence of the bicarbonate/carbon dioxide pair is known to accelerate the transition metal ion-catalysed oxidation of various biotargets. It has been shown that stable Cu(II) complexes formed with imine ligands that allow redox cycling between Cu(I) and Cu(II) display diverse apoptotic effects on cell cultures. It is also reported that Cu(II)-tetraglycine can form a stable Cu(III) complex. In the present study, radical generation from H₂O₂ and H₂O₂/HCO₃⁻ in the presence of these two different classes of Cu(II) complexes was evaluated by monitoring the oxidation of dihydrorhodamine 123 and NADH and by the quantitative determination of thiobarbituric acid reactive substances (TBARs method). Cu(II)-imine complexes produced low levels of reactive species whereas Cu(II)-Gly-derived complexes, as well as the free Cu(II) ion, produced oxygen-derived radicals in significantly larger amounts. The effects of these two classes of complexes on mammalian tumour cell viability were equally distinct, in that Cu(II)-imine complexes caused apoptosis, entered in cell and remained almost unaffected in high levels whilst, at the same concentrations, Cu(II)-Gly peptide complexes and Cu(II) sulphate stimulated cell proliferation, with the cell managing copper efficiently. Taken together, these results highlight the different biological effects of Cu(II) complexes, some of which have been recently studied as anti-tumour drugs and radical system generators, and also update the effects of reactive oxygen species generation on cell cycle control.     

Effects of arbuscular mycorrhizal inoculation on the growth,zinc distribution and photosynthesis of two citrus cultivars grown in low-zinc soil

Key message

‘Newhall’ and ‘Ponkan’ citrus cultivars grafted on trifoliate orange with mycorrhization by Glomus intraradices displayed different responses to low-Zn, and the optimal growth of ‘Newhall’ was more fungal inoculation dependent.

Abstract

The effects of arbuscular mycorrhizal (AM) fungus, Glomus intraradices, on plant growth, zinc (Zn) concentration and distribution, and photosynthesis were investigated in ‘Newhall’ navel orange (Citrus Sinensis) and ‘Ponkan’ tangerine (Citrus reticulata) grafted on the rootstock trifoliate orange (Poncirus trifoliata) exposed to low-Zn soil. Under the Zn-poor condition, the two cultivars showed similar decreases in growth, levels of leaf chlorophyll, gas exchange parameters, root soluble sugar, and Zn levels in various plant parts; however, the Zn percentage in the roots of ‘Ponkan’ was increased while in ‘Newhall’ it remained stable, indicating ‘Newhall’ may have a higher Zn translocation efficiency from the roots to the scion’s shoots. AM inoculation improved growth, Zn concentrations and photosynthesis in the two cultivars. AM-infected seedlings had lower minimal fluorescence values but higher maximal fluorescence values than non-infected seedlings. In addition, they were more efficient in terms of photosystem II’s (PS II’s) maximal and potential photochemistry. The greater changes appeared in ‘Newhall’, implying AM symbioses could alleviate the negative effects of low-Zn on the PS II reaction center. In addition, AM-infected ‘Newhall’ and ‘Ponkan’ seedlings had higher Zn percentages in the leaves but lower Zn ratios in the roots than non-AM-infected seedlings, especially in the former cultivar. These results indicate that G. intraradices has the potential to enhance the growth and Zn distribution in ‘Newhall’ grafted on trifoliate orange seedlings grown in low-Zn soil in a greenhouse.     

Bis-bidentate bridging ligands containing two N,O-chelating pyrazolyl-phenolate units; double helical complexes with Co(II), Cu(II) and Zn(II)

Two ligands have been prepared in which N,O-bidentate chelating pyrazolyl-phenolate units, based on 3-(2-hydroxyphenyl)pyrazole, are connected via methylene linkages to aromatic (1,4-phenylene or 3,3′-biphenylene) spacers. In each case the two N,O-donor units are too far apart to chelate to a single metal ion. Complexes of both ligands with Co(II), Cu(II) and Zn(II) were prepared and structurally characterised; in all cases the complexes are dinuclear double helicates M₂L₂, with each four-coordinate metal ion bound by a chelating unit from each of the two ligands in the complex. For Co(II) and Zn(II) the two M(NO) planes at each metal are close to perpendicular, indicative of a geometry which may be described as approximately distorted tetrahedral; for the Cu(II) complexes the angle between the two Cu(NO) planes is less, indicative of a distortion towards a more planar coordination geometry.     

Olefin aziridination by copper(II) complexes: Effect of redox potential on catalytic activity

A series of new copper(II) complexes of four sterically hindering linear tridentate 3N ligands N′-ethyl-N′-(pyrid-2-ylmethyl)-N,N-dimethylethylenediamine (L1), N′-benzyl-N′-(pyrid-2-ylmethyl)-N,N-dimethylethylenediamine (L2), N′-benzyl-N′-(6-methylpyrid-2-yl-methyl)-N,N-dimethylethylenediamine (L3) and N′-benzyl-N′-(quinol-2-ylmethyl)-N,N-dimethylethylenediamine (L4) have been isolated and examined as catalysts for olefin aziridination. The complexes [Cu(L1)Cl₂]·CH₃OH 1, [Cu(L2)Cl₂]·CH₃OH 2, [Cu(L3)Cl₂]·0.5 H₂O 3 and [Cu(L4)Cl₂] 4 have been structurally characterized by X-ray crystallography. In all of them copper(II) adopts a slightly distorted square pyramidal geometry as inferred from the values of trigonality index (τ) for them (τ: 1, 0.02; 2, 0.01; 3, 0.07; 4, 0.01). Electronic and EPR spectral studies reveal that the complexes retain square-based geometry in solution also. The complexes undergo quasireversible Cu(II)/Cu(I) redox behavior (E_1/2, −0.272 − −0.454 V) in acetonitrile solution. The ability of the complexes to mediate nitrene transfer from PhINTs and chloramine-T trihydrate to olefins to form N-tosylaziridines has been studied. The complexes 3 and 4 catalyze the aziridination of styrene very slowly yielding above 80% of the desired product. They also catalyze the aziridination of the less reactive olefins like cyclooctene and n-hexene but with lower yields (30-50%). In contrast to these two complexes, 1 and 2 fail to catalyze the aziridination of olefins in the presence of both the nitrene sources. All these observations have been rationalized based on the Cu(II)/Cu(I) redox potentials of the catalysts.     

Tc(NX)Y3(Me2PhP)2 complexes (X = O or S; Y = Cl or Br). Preparation,characterization and EPR studies

The d⁵-‘low-spin’ Tc(II) complexes tribromonitrosyl-bis(dimethylphenylphosphine)technetium(II) and tribromo-thionitrosyl-bis(dimethylphenylphosphine)technetium(II) were prepared by ligand exchange starting from the analogous chloro compounds. The complexes were characterized chemically and IR, UVVis and EPR spectroscopically.In the room temperature EPR spectra a well-resolved ⁹⁹Tc hyperfine splitting is observed inidicating a ground state of the unpaired electron which is well separated from the other orbit states. The general features of the spectra at low temperatures are characteristic for an axially symmetric spin Hamiltonian. Analysis of the ⁹⁹Tc and ³¹P hfs (hfs = hyperfine splittings) shows a marked covalency of the Tcligand bonds. A comparison is given between the chloro and bromo, as well as between the nitrosyl and thionitrosyl complexes.     

Optical properties of Cu(II) complexes with heparin and related glycosaminoglycans.

Absorption and circular dichroism measurements have been carried out to obtain information regarding the stability and the nature of complexes between Cu(II) and heparin, and between Cu(II) and related glycosaminoglycans. In the presence of Cu(II), all glycosaminoglycans, except keratan sulfate, show a characteristic absorption band near 237 nm, which we assign to charge-transfer bands involving ligands to metal ion. From the absorbance values, the formation constants of Cu(II)-heparin and Cu(II)-(itN)-desulfated heparin have been determined to be approximately 1 × 10⁴ and 2 × 10² mol^?1, respectively. The large difference in the stability constant values is attributed to the difference in the charge density of the polymers, and to involvement of more than one ligand in the case of heparin. The CD characteristics of the Cu(II)-heparin complex suggest that both carboxyl and sulfamino groups are involved as ligands. The appearance of extrinsic CD bands in heparin, heparan sulfate, dermatan sulfate, and N-desulfated heparin at pH > 5 is ascribed to asymmetry of chelate rings. Absence of CD change in chondroitin sulfate and N-desulfated heparin (pH < 5) in the presence of Cu(II) suggests that only the carboxyl group is involved in those complexes. The differences either in iduronic acid conformation (C-1 vs. 1-C) or in intersaccharide linkages between dermatan sulfate and heparin (or heparan sulfate) are revealed in the difference CD spectra between the complexes and the polymers. The change in the intrinsic Cotton effect on complex formation is accounted for as a change in spatial orientation of the ligand groups rather than as a major conformational change of the polymers.     

Metal—phenoxyalkanoic acid interactions. Part 14. The crystal and molecular structures of diaquabis(4-fluorophenoxyacetato)copper(II) bis(4-fluorophenoxyacetic acid)dihydrate and tetra-μ-(4-fluorophenoxyacetato-0,0′)-bis[(2-aminopyrimidine)copper(II)]

The crystal structures of two copper(II) complexes of 4-fluorophenoxyacetic acid (4-FPAH) have been determined by X-ray diffraction. [Cu(4-FPA)₂(H₂O)₂]·2(4-FPAH)·2H₂O (1) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 14.808(2), b = 9.832(2), c = 6.847(2) Å, α = 87.77(2), β = 98.41(2), γ = 112.33(2)° and was refined to a residual of 0.038 for 1697 ‘observed’ reflections. The coordination sphere in this complex is tetragonally distorted octahedral comprising two waters [CuO, 1.940(3) Å], two unidentate carboxylate oxygens [CuO, 1.942(2) Å] and two ether oxygens [CuO, 2.471(2) Å]. Two adducted [4-FPAH] acid molecules are linked to the un-coordinated oxygens of the acid ligands by hydrogen bonds [2.547(4) Å]. [Cu₂(4-FPA)₄(2-aminopyrimidine)₂] (2) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 12.688(2), b = 11.422(2), c = 7.951(1) Å, α = 78.74(1), β = 107.51(1), γ = 75.78(1)°, and was refined to a residual of 0.042 for 2683 ‘observed’ reflections. (2) is a centrosymmetric tetracarboxylate bridged dimer with four similar CuO (equatorial) distances [1.967–1.987 Å; 1.977(3) Å mean] and the axial position occupied by the hetero nitrogen of the 2-aminopyrimidine ligand [CuN, 2.176(3) Å]. The Cu---Cu separation is 2.710(1) Å. Crystal data are also presented which confirm the isostructurality of complex (2) with [Cu₂(phenoxyacetate)₄(2-aminopyrimidine)₂], the Co^II, Mg^II and Mn^II4-fluorophenoxyacetate complexes with their phenoxyacetic and 4-chlorophenoxyacetic acid analogues, and of Cd^II4-fluorophenoxyacetate with Cd^II and Zn^II phenoxyacetates.