A rare case of solution and solid state inter-conversion of two copper(II) dimers and a copper(II) chain

Three Cu(II)-azido complexes of formula [Cu₂L₂(N₃)₂] (1), [Cu₂L₂(N₃)₂]·H₂O (2) and [CuL(N₃)]_n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N₃ azido bridges (J = −2.59(4) and −0.10(1) cm−¹, respectively). The single 1,1-N₃ bridge in compound 3 mediates a negligible exchange interaction.     

Reactivity of Cu2(lonazolac)4, a lipophilic copper acetate derivative

An acetate-like copper complex of lonazolac (3-(p-chlorophenyl)-1-phenyl-pyrazole-4-acetate) was prepared and characterized. The copper of Cu₂-(lonazolac)₄ was spin-coupled and remained EPR-silent. Water and organic solvents did not affect this magnetic interaction. Superoxide dismutase activity of the Cu complex in micromolar concentrations was detectable in the presence of up to 900 μg per ml of serum albumin or whole serum protein. At 700 μM albumin concentration, a ternary complex between Cu₂(lonazolac)₄ and the protein was formed. The original acetate-copper coordination changed to a biuret-type copper bonding as seen from EPR and electron absorption spectrometry. Lonazolac did not induce a detectable conformational change of the protein near or at the copper binding site. Equilibrium dialysis and optical titration experiments revealed that essentially all copper of the Cu₂-(lonazolac)₄ complex was bound in the specific binding site of serum albumin. The copper complex proved to be an effective inhibitor of lipid peroxidation.     

Solvothermal synthesis, crystal structure and magnetic property of a new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N3)2]2 (2,2′-dpa = 2,2′-dipicolylamine)

A new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N₃)₂]₂1 (2,2′-dpa = 2,2′-dipicolylamine) has been synthesized solvothermally. X-ray crystallography analysis reveals that it consists of two crystallographically independent dimeric manganese moieties; each manganese(II) atom is coordinated by one 2,2′-dipicolylamine, one terminal azido ligand, and double end-on bridging azido ligands, exhibiting a slightly distorted octahedral sphere. There are extensive short contacts among dimeric manganese moieties, which extend the structure into an interesting three-dimensional supramolecular array. Magnetic determination of 1 indicates that dominant ferromagnetic interaction and weak antiferromagnetic interaction, which are ascribed to the end-on azido bridges and the short contacts, respectively, co-exist in this complex.     

Preparation and structural characterization of di-μ-azido-bis[azido(2-aminopyridine)aquo]dicopper(II), [Cu(2-ampy)(N3)2(H2O)]2

Di-μ-azido-bis[azido(2-aminopyridine)aquo]dicopper(II), [Cu(2-ampy)(N₃)₂(H₂O)]₂, was synthesized and characterized by X-ray crystallography. The crystals are triclinic, space group P$\text{1}$, with a = 7.142(1), b = 7.812(1), c = 9.727(1) Å, a = 96.52(1), β = 95.52(1), γ = 113.47(1)°, and Z = 1. The structure was refined to R_F = 0.030 for 1960 observed MoKα diffractometer data. The dimeric molecule, which possesses a crystallographic inversion center, contains both terminal and μ(1)-bridging azido groups. Each copper(II) atom is further coordinated by a 2-aminopyridine ligand (via its ring N atom) and a water molecule to give a distorted square pyramid, with the metal atom raised by 0.17 Å above the N₄ basal plane [CuN (ring) = 2.001(2), CuN (azide) = 1.962(3)–2.018(2) Å] towards the apical aquo ligand [CuO = 2.371(2) Å]. Each water molecule forms an intramolecular O?HN (amine) acceptor hydrogen bond, and is linked by two OH?N (terminal azide) intermolecular donor hydrogen bonds to adjacent dimeric complexes to yield a layer structure parallel to (001). Infrared and electronic spectral data are presented and discussed.     

Reaction of PtOH complexes with CO2: synthesis and X-ray structure of (PBz3)4Pt2(Ph)2(η1,η1,μ-CO3)·(toluene)

The reaction of (diphoe)Pt(CH₂CN)(OH) and trans-(PBz₃)₂Pt(Ph)(OH) with CO₂ is reported as producing dimeric, bridged carbonato complexes of the type: P₄Pt₂(R)₂(CO₃). The crystal and molecular structure of (PBz₃)₄Pt₂(Ph)₂(μ-CO₃)·(toluene) is also reported, showing η¹, η¹ bonding. The reaction is recognized to proceed in a stepwise fashion through bicarbonato intermediates.     

Magnetic and catalytic properties of a new copper(II)-Schiff base 2D coordination polymer formed by connected helical chains

A dicyanamide bridged 2D polynuclear complex of copper(II) having molecular formula [Cu₂(L)(μ_1,5-dca)₂]_n (1) has been synthesized using the Schiff base ligand N,N′-bis(salicylidene)-1,3-diaminopentane, (H₂L) and sodium dicyanamide (dca). The complex presents a 2D hexagonal structure formed by 1,5-dca singly bridged helical chains connected through double 1,5-dca bridges. The chelating characteristics of the H₂L Schiff base ligand results in the formation of copper(II) dimer with a double phenoxo bridge presenting a very strong antiferromagnetic coupling in the copper(II) derivative (1) (J = −510 cm⁻¹). The dimeric asymmetric unit of 1 is very similar to the active site of the catechol oxidase and, as expected, also presents catalytic activity for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in presence of O₂, as demonstrated by kinetic studies of this oxidation reaction monitored by absorption spectroscopy resulting in high turnover number (K_cat = 259 h⁻¹).     

Spectroscopic, magnetic, and electrochemical studies of a dimeric N-substituted-sulfanilamide copper(II) complex. X-ray and molecular structure of the Cu2(N-(pyridin-2-yl)biphenyl-4-sulfonamidate)4 complex

A dinuclear copper(II) complex with a N-substituted sulfonamide as ligand has been investigated. The new N-(pyridin-2-yl)biphenyl-4-sulfonamide ligand has been prepared and structurally characterized. The copper(II) complex has been synthesized and its crystal structure, magnetic properties and EPR spectra were studied in detail. The metal centers are bridged by four nonlinear triatomic NCN groups. The coordination geometry of the copper(II) ions in the dinuclear entity is distorted square planar with two N-pyridyl and two N-sulfonamido atoms. Magnetic susceptibility data show a moderate antiferromagnetic coupling, with −2 J = 284 cm⁻¹. The EPR spectrum of the polycrystalline sample of the title compound has been measured at the X-band frequency at different temperatures.     

Mono- and dinuclear Fe(III) complexes with the N2O2 donor 5-chlorosalicylideneimine ligands; synthesis, X-ray structural characterization and magnetic properties

Two novel monomeric [C₁₈H₁₇Cl₃N₂O₂Fe] (1) and dimeric [C₃₈H₃₆N₄O₄Cl₆Fe₂] (2) Fe(III) tetradentate Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. In complex (1) the Schiff base ligand coordinates toward one iron atom in a tetradentate mode and each iron atom is five coordinated with the coordination geometry around iron atom which can be described as a distorted square pyramid. The presence of a short (2.89 Å) non-bonding interatomic Fe···O distances between adjacent monomeric Fe(III) complexes results in the formation of a dimer. Structural analysis of compound (2) shows that the structure is a centrosymmetric dimer in which the six coordinated Fe(III) atoms are linked by μ-phenoxo bridges from one of the phenolic oxygen atoms of each Schiff base ligand to the opposite metal center. The variable-temperature (2-300 K) magnetic susceptibility (χ) data of these two compounds have been investigated. The results show that for both complexes Fe(III) centers are in the high spin configuration (S = 5/2) and indicate antiferromagnetic spin-exchange interaction between Fe(III) ions. The obtained results are briefly discussed using magnetostructural correlations developed for other class of iron(III) complexes.     

Spectral properties and bio-activity of copper(II) clofibriates, part III: crystal structure of Cu(clofibriate)2(2-pyridylmethanol)2, Cu(clofibriate)2(4-pyridylmethanol)2(H2O) dihydrate, and Cu2(clofibriate)4(N,N-diethylnicotinamide)2

New copper(II) clofibriates (clof, {2-(4-chlorophenoxy)-2-methylpropionic or 2-(4-chlorophenoxy)isobutyric acid}) of composition Cu(clof)₂L₂ (where L=2-pyridylmethanol (2-pymeth) (1), N-methylnicotinamide (Menia) (4), N,N-diethylnicotinamide (Et₂nia) (5), isonicotinamide (isonia) (7) or methyl-3-pyridylcarbamate (mpc) (8)), [Cu(clof)₂(4-pymeth)₂(H₂O)] · 2H₂O (4-pymeth=4-pyridylmethanol) (2 · 2H₂O) and Cu(clof)₂L (where L=4-pymeth (3) or Et₂nia (6)) have been prepared and spectroscopically characterized. All the Cu(clof)₂L₂ compounds seem to possess distorted octahedral copper(II) stereochemistry with differing tetragonal distortions. An X-ray analysis of 1 was carried out and it featured a tetragonal-bipyramidal geometry around the copper(II) atom. X-ray analysis of 2 · 2H₂O featured a square-pyramidal geometry around copper(II) atom. Both the Cu(clof)₂L compounds seem to consist of a binuclear unit of tetracarboxylate type bridging. An X-ray analysis of 6 revealed typical binuclear paddle-wheel type structure, consisting of two copper(II) atoms in square-pyramidal geometry bridged by four carboxylate anions in the xy-plane. All complexes under study were characterized by EPR and electronic spectroscopy. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi.     

Spectral and structural studies of a new oxalato-bridged dinuclear copper(II) complex having two 3-(thiophen-2-yl)-1,10-phenanthroline ligands in a trans configuration

In this paper, spectral and structural characterizations of a new dinuclear copper(II) complex (1), formulated as [Cu₂(3-(thiophen-2-yl)-1,10-phenanthroline)₂(μ-oxalate)(DMF)₂](ClO₄)₂ (DMF = N,N′-dimethylformamide), have been described. Two five-coordinate copper(II) centers are bridged by a four-dentate oxalate dianion forming a planar molecular geometry with the Cu-Cu separation of 5.117(4) Å. The two ligands in 1 adopt a trans configuration to each other and two monodentate DMF molecules are positioned at each side of the molecular plane. In addition, typical π-π stacking interactions are found between adjacent phenanthroline and thiophene rings forming a layered packing structure. A compressed pyramidal configurational alteration is observed for each copper(II) center when the temperature is decreased from 291(2) to 100(2) K.     

Magneto-structural correlations and DFT calculations in two rare tetranuclear copper(II)-clusters with doubly phenoxo and end-on azido bridges: Syntheses, structural variations and EPR studies

By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear Cu^II complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H₂L = (OH)C₆H₄(CH₃)CN(CH₂)₃NC(CH₃)C₆H₄(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV-Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu₄(μ-L)₂(μ_1,1-N₃)₂(N₃)₂] (1) and the red [Cu₄(μ-L)₂(μ_1,1-N₃)₂(N₃)₂(H₂O)₂] (2) crystals show that the coordination environment of the two μ-phenoxo and μ_1,1-azido bridged isomorphous tetranuclear Cu^II complexes are slightly different. Thus, both complexes are formed by very similar building units, although with a significant variation in the bridging Cu-O(phenoxo)-Cu and Cu-N(azido)-Cu bond angles. The consequences of these structural variations on the magnetic properties have been investigated from both the experimental and theoretical points of view by variable temperature magnetic measurements and DFT calculations.     

Spectroscopic and magnetic properties of a novel pyrazine-bridged copper(II) chain: [Cu(terpy)(pyz.)](ClO4)2

The [Cu(Terpy)(pyz.)](ClO₄)₂ complex (were Terpy = 2,2′:6′,2′'-terpyridine and pyz. = pyrazine) was synthesized and characterized by means of spectral and magnetic properties. UV-visible and EPR spectra indicate a square pyramidal coordination for the copper(II) ion. Magnetic susceptibility measurements, reported in the temperature range 2–125 K, are analyzed in terms of regular and alternating Heisenberg-chain models giving 2J = ?4.4 K, g = 2.19 (regular chain) and 2J = ?5.6 K, 2J′ = ?1.7 K, g = 2.15 (alternating chain). The better agreement obtained with the alternating-chain model allows us to propose a dimerized zig-zag chain structure with the pyz. ligand bridging the copper(II) ions.     

A new structural type for a binuclear chloride-bridged copper(II) complex. Structural and magnetic characterization of di-μ-chloro-chloropentakis(benzimidazole) dicopper(II) monochloride tetrahydrate, [Cu2Cl3(C7H6N2)5]Cl·4H2O

The synthesis, crystal structure determination and magnetic properties of a new five-coordinated unsymmetrical copper(II) dinuclear complex [Cu₂Cl₃(C₇H₆N₂)₅]Cl·4H₂O are reported. The crystals are orthorhombic, space group Pnma with 4 formula units in a cell of dimensions: a = 19.506(3), b = 17.384(4), C = 11.940(2) Å. The structure was solved by direct methods. Least-squares refinement using 2138 independent reflections with I3σ(I) has led to a final value of the conventional R factor (on F) of 0.047 and R_w of 0.049. The complex cation consists of pairs of deformed trigonal-bipyramidal copper(II) centers which share an edge by two equatorial chloride ions. The equatorial coordination sites of the Cu(1) atom are occupied by three chloride ligands, while of the Cu(2) atom by two chloride and one benzimidazole ligands. The axial sites are occupied by the nitrogen atoms from four benzimidazole ligands. The Cu atoms and equatorial ligands are located on the symmetry plane. The Cu---Cu non-bonding distance in the complex is 3.386(1) Å; the two shorter bridging Cu(1)---Cl(1) and Cu(2)---Cl(1) distances are 2.402(2) and 2.424(2) Å; the two longer Cu(1)---Cl(2) and Cu(2)---Cl(2) are 2.620(2) and 2.551(2) Å. The Cu(1)---Cl(1)---Cu(2) and Cu(1)---Cl(2)---Cu(2) angles are 89.1(1) and 81.8(1)°. The structure is the first example of a bibridged binuclear complex with two non-equivalent Cu---Cl---Cu bridges. Comparison to other binuclear bis(μ-halide)-bridged copper complexes of similar structure has been made. Magnetic susceptibility measurements indicate ferromagnetic coupling of the copper(II) centers, the intramolecular exchange parameter, 2J, being 5.6 cm⁻¹ and the intermolecular one J′ = −0.6 cm⁻¹. The investigation of the electronic structure of the complex and the orbital interpretation of the magnetic coupling based on extended Hückel molecular orbital calculations are also presented.     

[Mn2(Fpymo)4(H2O)4]: Synthesis, structure, magnetism and thermally induced solid-to-solid polymerisation reactions

The reaction of an aqueous solution of Mn(ClO₄)₂ · 6H₂O with 5-fluoro-2-hydroxypyrimidine (HFpymo) and NaOH in 1:2:1 ratio affords a species analysing as Mn(Fpymo)₂(H₂O)₂ (1) in 70% yield. Single crystal X-ray analysis reveals that 1 consists of [Mn₂(μ-Fpymo-N¹,O²)₂(Fpymo-O²)₂(H₂O)₄] dinuclear units, in which each Mn(II) ion shows a slightly distorted trigonal bipyramidal stereochemistry. Thermal treatment of 1 above 150 °C gives an anhydrous, amorphous material analysing as Mn(Fpymo)₂ (2a). Further heating of this compound above 250 °C results in the formation of the microcrystalline Mn(Fpymo)₂ species (2b). The thermal dependence of the magnetic susceptibility χ has been studied for species 1 and 2b in the 2-300 K temperature range at 100, 300 and 5000 Oe field strengths. The fitting of the χ values of 1 to the Curie-Weiss equation gives values of C = 2.450(2) and θ = 1.0(2) K, which is indicative of an almost negligible magnetic interaction between the Mn(II) centres. At variance, 2b shows a significant antiferromagnetic behaviour, with a decrease of the μ_eff values upon cooling. The fitting of the χ values of 2b to the Curie-Weiss equation gives the respective C and θ values of 4.26(1) and −14.8(3) K, which agrees with an efficient coupling of the magnetic Mn(II) centres, possibly through bridges of the Fpymo-N¹,N³ kind, within a polymeric network. The N₂ and CO₂ gas adsorption measurements at 77 K and 293 K, respectively, show that the 2b phase is not microporous, which is reflected in its low BET surface (19 m² g⁻¹) and its BJH pore size distribution.     

A new mixed-valence hexanuclear cobalt complex, [Co4Co2(dea)2(Hdea)4)(piv)4](ClO4)2·H2O: Synthesis, crystal structure and magnetic properties

A new Co^II/Co^III hexanuclear complex, [Co₄^IICo₂^III(dea)₂(Hdea)₄)(piv)₄](ClO₄)₂·H₂O 1, has been obtained by reacting cobalt(II) perchlorate, diethanolamine, and pivalic acid (H₂dea = diethanolamine and piv = pivalato anion). The cobalt ions are held together by four μ₃ and four μ₂ alkoxo bridges as well as by four syn-syn carboxylato groups. The hexanuclear motif contains four Co(II) and two Co(III) ions. The {Co^II₄Co^III₂(μ₂-O)₄(μ₃-O)₄} core can be described as a four face-sharing monovacant and bivacant distorted heterocubane units. The cobalt(III) ions are hexacoordinated. Two of the cobalt(II) are hexacoordinated, while the two others are pentacoordinated with a bipyramidal stereochemistry. The magnetic properties of 1 have been investigated in the temperature range 1.9-300 K. Compound 1 exhibits an overall antiferromagnetic behaviour with a ground singlet spin state.     

Structure and magnetism of two new linear trinuclear copper(II) clusters obtained from the tetradentate N2O2 ligand bis(2-hydroxybenzyl)-1,3-diaminopropane

Reaction of bis(2-hydroxybenzyl)-1,3-diaminopropane (H₂bhbd) with copper(II) perchlorate and copper(II) chloride in methanol, respectively, leads to linear trinuclear clusters, namely [Cu₃(bhbd)₂(CH₃OH)₂(ClO₄)₂] (1) and [Cu₃(bhbd)₂Cl₂](CH₃OH)₄ (2). These coordination compounds were characterized by X-ray crystallography, UV-Vis, IR and EPR spectroscopy, and magnetic susceptibility measurements. Both complexes have a linear trinuclear array of copper ions bridged by means of phenolato O atoms and separated by a distance of 2.985(4) Å (1) and 2.937(4) Å (2). Strong antiferromagnetic interactions between these adjacent Cu^II ions govern the magnetochemistry of 1 (J = −303(1) cm⁻¹) and 2 (J = −482(3) cm⁻¹) resulting in S = 1/2 ground states fully populated below 150 K. A correlation between the interaction parameter J and the angles within the trinuclear clusters is proposed.     

Unexpected assembly of a novel triply bridged diiron(II) core by a bidentate Schiff base ligand

The unusual dinucleating properties of a simple bidentate Schiff base (LH, 1) in the presence of weakly coordinating methanol solvent lead to the self-assembly of (2) (b and t refer to bridging and terminally bound ligands, respectively). Complex 2 is the first diiron(II) species in which the two metal centers are triply bridged by single atoms in an asymmetric fashion, involving both μ-O^Ph and μ-OH^Me bridges. This binding mode produces an Fe?Fe distance of 3.139(1) Å. Dinucleation appears to be driven by a combination of ligand deficiency and solvent-mediated chemistry reminiscent of host-guest interactions. The presence of a μ-MeOH ligand is unprecedented in iron chemistry. Parallel-mode EPR spectra of complex 2 recorded at 4 K show an intense negative signal at g_∥≈16, suggesting the dimeric form exists in solution.     

Synthesis of copper(II) complexes with 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (L). Molecular and crystal structures of L and [Cu2L2Cl4]·2MeCN

A series of copper(II) complexes, i.e. Cu₂LCl₄, CuLCl₂·H₂O and [Cu₂L₂Cl₄]·2MeCN (8), based on a new potentially polytopic ligand, 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (3b, L), have been synthesized. The crystal structures of L and [Cu₂L₂Cl₄]·2MeCN were studied by X-ray single crystal analysis. The dinuclear compound [Cu₂L₂Cl₄]·2MeCN represents the first example of structurally characterized metal complexes with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. Both copper atoms have distorted tetragonal-pyramidal 3N + 2Cl environment. Surprisingly, in contrast to the complexes based on 3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-amine (pyridinyl analog of L), the compound [Cu₂L₂Cl₄]·2MeCN adopts a dinuclear trans-(N′,N¹,N²)₂ double bridging binding mode which is due to tridentate coordination of two L molecules linking two copper atoms through N¹,N²-triazole and N′-pyrimidine atoms. It seems to be reasonable that it is methyl groups in pyrimidinyl moiety that obstruct the expected dinuclear (N′,N¹,N²,N″)₂ double bridging coordination being one of the most common for 4-substituted 3,5-di(pyridin-2-yl)-4H-1,2,4-triazoles and 3,5-di(pyridin-2-yl)-1,2,4-triazolates. Due to π-π stacking interactions, molecules of Cu₂L₂Cl₄ in the structure of [Cu₂L₂Cl₄]·2MeCN form 1D chains.     

Angular trinuclear copper(II) complexes of N4O-donor ligand: Syntheses, crystal structures and magnetic properties

Two trinuclear copper(II) complexes of a Schiff-base type N₄O-donor ligand (LH) derived from 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione and 1,3-diaminopropan-2-ol are reported. Complex [Cu₃L₂(ClO₄)₄] (1) has an angular C₂-symmetric trinuclear core as revealed from single-crystal X-ray diffraction studies. The terminal coppers are in square-pyramidal geometry with an N₃O₂ coordination environment while the central one is in octahedral geometry with an N₂O₄ donor environment. Complex [Cu₃L₂(ClO₄)(N₃)(H₂O)](ClO₄)₂ · H₂O (2) has an unsymmetrical trinuclear core with an intramolecular hydrogen bonding interaction between the water and azide anion coordinated to Cu(1) and Cu(3) center, respectively. All the copper centers in 2 are in square-pyramidal geometry. The average Cu?Cu distance between closest metal ions in both the complexes is 3.897 Å. The coordination environment of coppers in 1 approximately mimics that of multicopper oxidases in the oxidized form and the environment in 2 mimics that of the azide derivative of ascorbate oxidase. Both 1 and 2 exhibit doublet spin ground state due to strong antiferromagnetic coupling operating through the alkoxo-bridged oxygen atoms between the copper centers.     

Spectroscopic and magnetic properties of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand with perchlorate transition metal salts. Crystal structure of [Cu(4-pmOpe)2(ClO4)2]

The perchlorate M(II) (M = Cu, Ni, Co) complexes with the diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand of the composition [M(4-pmOpe)₂ (H₂O)₂](ClO₄)₂ (M = Ni, Co) and [Cu(4-pmOpe)₂(ClO₄)₂] were prepared and studied. The ligand contains two donor atoms, i.e. pyridine nitrogen and phosphoryl oxygen atoms. In particular, the crystal structure of [Cu(4-pmOpe)₂(ClO₄)₂] was determined by the X-ray method. Its structure consists of a one-dimensional polymeric chain in which copper(II) ions are N,O-bridged by two 4-pmOpe organic ligands in a trans arrangement. Two perchlorate ions occupy the fifth and the sixth coordination sites. The Cu?Cu distance is 9.180 Å. The crystal packing is determined by the weak intermolecular C-H?O hydrogen contacts. The coordination compounds were identified and characterized by elemental analysis, spectroscopic and magnetic studies. Spectroscopic and magnetic results of the copper(II) compound are presented in the light of the crystal structure. The magnetic data indicate very weak intra- and interchain magnetic exchange interactions (J^’ = −0.43 and zJ^’ = 0.29 cm⁻¹, respectively). The spectroscopic and magnetic properties of the Co(II) and Ni(II) complexes indicate octahedral and polymeric structure of both compounds in which 4-pmOpe ligand also acts as N,O-bridge between metal ions.