Advances on the interaction of polypyridyl Cr(III) complexes with transporting proteins and its potential relevance in photodynamic therapy

The present study reports a detailed investigation into the interaction of [Cr(phen)₂(dppz)]³⁺ and [Cr(phen)₃]³⁺ with transferrin, the key protein for the transport of Fe³⁺ in blood plasma; its cycle holds promise as an attractive system for strategies of drug targeting to tumor tissues. This can allow us to understand further the role of both complexes as sensitizers in photodynamic therapy (PDT). Chromium(III) complexes, [Cr(phen)₂(dppz)]³⁺ and [Cr(phen)₃]³⁺, (phen = 1,10-phenanthroline and dppz = dipyridophenazine), where dppz is a planar bidentate ligand with an extended π system, have been found to bind strongly with apotransferrin (apoTf) with an intrinsic binding constant, K_b, of (1.8 ± 0.3) × 10⁵ M^− 1 and (1.1 ± 0.1) × 10⁵ M^− 1 at 299 K, for apoTf-[Cr(phen)₂(dppz)]³⁺ and apoTf-[Cr(phen)₃]³⁺, respectively. The interactions of apoTf with the different Cr(III) complexes were assessed employing UV-visible absorption, fluorescence and circular dichroism spectroscopy. The relative fluorescence intensity of the protein decreased when the increasing concentration of Cr(III) complex was added, suggesting that perturbation around the Trp and Tyr residues took place. The analysis of the thermodynamic parameters ΔG, ΔH, ΔS indicated that the presence of the Cr(III) complex stabilizes the protein with a strong entropic contribution. The binding distances and transfer efficiencies for apoTf-[Cr(phen)₂(dppz)]³⁺ and apoTf-[Cr(phen)₃]³⁺ binding reactions were calculated according to Föster theory of non-radiation energy transfer. All these experimental results suggest that [Cr(phen)₂(dppz)]³⁺ and [Cr(phen)₃]³⁺ bind strongly to apoTf indicating that this protein could act as a carrier of these complexes for further applications in PDT.     

New insights in the DNA-[Cr(phen)2(dppz)] binding and photocleavage properties by the complex with an intercalating ligand

Due to the key role of DNA in cell life and pathological processes, the design of specific chemical nucleases, DNA probes and alkylating agents is an important research area for the development of new therapeutic agents and tools in Biochemistry. Hence, the interaction of small molecules with DNA has attracted in particular a great deal of attention.The aim of this study was to investigate the ability of [Cr(phen)₂(dppz)]³⁺ to associate with DNA and to characterize it as photocleavage reagent for Photodynamic Therapy (PDT).Chromium(III) complex [Cr(phen)₂(dppz)]³⁺, (dppz = dipyridophenazine, phen = 1,10-phenanthroline), where dppz is a planar bidentate ligand with an extended π system, has been found to bind strongly to double strand oligonucleotides (ds-oligo) and plasmid DNA with intrinsic DNA binding constants, K_b, of (3.9 ± 0.3) × 10⁵ M⁻¹ and (1.1 ± 0.1) × 10⁵ M⁻¹, respectively. The binding properties to DNA were investigated by UV-visible (UV-Vis) absorption spectroscopy and electrophoretic studies. UV-Vis absorption data provide clearly that the chromium(III) complex interacts with DNA intercalatively. Competitive binding experiments show that the enhancement in the emission intensity of ethidium bromide (EthBr) in the presence of DNA was quenched by [Cr(phen)₂(dppz)]³⁺, indicating that the Cr(III) complex displaces EthBr from its binding site in plasmid DNA. Moreover, [Cr(phen)₂(dppz)]³⁺, non-covalently bound to DNA, promotes the photocleavage of plasmid DNA under 457 nm irradiation. We also found that the irradiated Cr(III)-plasmid DNA association is able to impair the transforming capacity of bacteria. These results provide evidence confirming the responsible and essential role of the excited state of [Cr(phen)₂(dppz)]³⁺ for damaging the DNA structure. The combination of DNA, [Cr(phen)₂(dppz)]³⁺ and light, is necessary to induce damage. In addition, assays of the photosensitization of transformed bacterial suspensions suggest that Escherichia coli may be photoinactivated by irradiation in the presence of [Cr(phen)₂(dppz)]³⁺. In sum, our results allow us to postulate the [Cr(phen)₂(dppz)]³⁺ complex as a very attractive candidate for DNA photocleavage with potential applications in Photodynamic Therapy (PDT).     

Exploring the interactions of a Tb(III)–quercetin complex with serum albumins (HSA and BSA): spectroscopic and molecular docking studies

Serum albumins (human serum albumin (HSA) and bovine serum albumin (BSA), two main circulatory proteins), are globular and monomeric macromolecules in plasma that transport many drugs and compounds. In the present study, we investigated the interactions of the Tb(III)–quercetin (Tb–QUE) complex with HSA and BSA using common spectroscopic techniques and a molecular docking study. Fluorescence data revealed that the inherent fluorescence emission of HSA and BSA was markedly quenched by the Tb–QUE complex through a static quenching mechanism, confirming stable complex formation (a ground‐state association) between albumins and Tb–QUE. Binding and thermodynamic parameters were obtained from the fluorescence spectra and the related equations at different temperatures under biological conditions. The binding constants (K_b) were calculated to be 0.8547 × 10³ M^?1 for HSA and 0.1363 × 10³ M^?1 for BSA at 298 K. Also, the number of binding sites (n) of the HSA/BSA–Tb–QUE systems was obtained to be approximately 1. Thermodynamic data calculations along with molecular docking results indicated that electrostatic interactions have a main role in the binding process of the Tb–QUE complex with HSA/BSA. Furthermore, molecular docking outputs revealed that the Tb–QUE complex has high affinity to bind to subdomain IIA of HSA and BSA. Binding distances (r) between HSA–Tb–QUE and BSA–Tb–QUE systems were also calculated using the Forster (fluorescence resonance energy transfer) method. It is expected that this study will provide a pathway for designing new compounds with multiple beneficial effects on human health from the phenolic compounds family such as the Tb–QUE complex.     

Spectroscopic Investigation of the Interaction Between Copper (II) 2-oxo-propionic Acid Salicyloyl Hydrazone Complex and Bovine Serum Albumin

The interaction between copper (II) 2-oxo-propionic acid salicyloyl hydrazone (Cu^IIL) and bovine serum albumin (BSA) under physiological conditions was investigated by the methods of fluorescence spectroscopy, UV-Vis absorption, and circular dichroism spectroscopy. Fluorescence data showed that the fluorescence quenching of BSA by Cu^IIL was the result of the formation of the BSA–Cu^IIL complex. The apparent binding constants (K _a) between Cu^IIL and BSA at four different temperatures were obtained according to the modified Stern–Volmer equation. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), for the reaction were calculated to be ?80.79 kJ mol^?1 and ?175.48 J mol^?1 K^?1 according to van’t Hoff equation. The results indicated that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. The binding distance (r) between Cu^IIL and the tryptophan residue of BSA was obtained to be 4.1 nm according to Förster’s nonradioactive energy transfer theory. The conformational investigation showed that the application of Cu^IIL increased the hydrophobicity of amino acid residues and decreased the α-helical content of BSA (from 62.71% to 37.31%), which confirmed some microenvironmental and conformational changes of BSA molecules.     

Synthesis, X-ray crystal structure, DFT- and TDDFT-based spectroscopic property investigations on a mixed-ligand chromium(III) complex, bis[2-(2-hydroxyphenyl)benzimidazolato]-(1,10-phenanthroline)chromium(III) isophthalate

A mixed-ligand Cr(III) complex with 2-(2-hydroxyphenyl)benzimidazole, 1,10-phenanthroline and isophthalic acid, [Cr(pbm)₂(phen)]X_0.5 (1X_0.5) (Hpbm = 2-(2-hydroxyphenyl)benzimidazole; phen = 1,10-phenanthroline; H₂X = isophthalic acid) has been prepared by heating in aqueous solution and characterized, and the geometric structure and spectroscopic properties, investigated experimentally and theoretically by using the density functional theory level (DFT) and the time-dependent density functional theory level (TDDFT). The theoretical-experimental agreement is satisfactory. Further theoretical analyses of electronic structure and molecular orbitals have demonstrated that the low-lying absorption bands in UV-Vis spectrum are mainly π → π∗ ligand-to-ligand charge transfer transition (LLCT) and or π → (d_z²-d_x²-y²-d_yz) ligand-to-metal charge transfer transition (LMCT) in nature.     

Structure-specific binding of [Co(phen)2(HPIP)] to a DNA duplex containing sheared G:A mismatch base pairs

The binding of a Co(III) complex to the decanucleotide d(CCGAATGAGG)₂ containing two pairs of G:A mismatches was studied by 2D-NMR, UV absorption, and molecular modeling. NMR investigations indicate that racemic [Co(phen)₂(HPIP)]Cl₃ [HPIP = 2-(2-hydroxyphenyl) imidazo [4,5-f][1,10] phenanthroline] binds the decanucleotide by intercalation: the HPIP ligand selectively inserts between the stacked bases from the minor groove at the terminal regions and from the major groove at the sheared region. Further, molecular modeling revealed that the recognition shows strong enantioselectivity: the Λ-isomer preferentially intercalates into the T₆G₇:A₅A₄ region from the DNA major groove, while Δ-isomer favors the terminal C₁C₂:G₁₀G₉ region and intercalates from the minor groove. Detailed energy analysis suggests that the steric interaction, especially the electrostatic effect, is the primary determinants of the recognition event. Melting experiments indicate that binding stabilizes the DNA duplex and increases the melting temperature by 9.5 °C. The intrinsic binding constant of the complex to the mismatched duplex was determined to be 3.5 × 105 M⁻¹.     

Theoretical studies on DNA-binding, DNA-photocleavage and spectral properties of Co(III) complexes [Co(phen)2(L)] (L = pip, hpip, hnaip)

Theoretical studies on the DNA-binding, DNA-photocleavage and spectral properties of Co(III) polypyridyl complexes [Co(phen)₂(L)]³⁺ (L = pip, hpip, hnaip) have been carried out, using the density functional theory (DFT), Hartree-Fock (HF) and configuration interaction singles (CIS) methods. The optimized geometric structures of these Co(III) complexes in aqueous solution are more close to experimental data than those in vacuo at the B3LYP/LanL2DZ level. Based on the optimized geometric structures in solution, the electronic structures of these Co(III) complexes were analyzed and the trend in the DNA-binding constants (K_b) was reasonably explained. In particular, via the analysis of natural charges of the complexes in ground state and excited state, it is very interesting to find the following: under UV or visible light irradiation, the Co(Ш) polypyridyl complexes undergo an intra-molecular electron transfer from S₀ state to T₁ state, and the positive charges on the main-ligand in the T₁ state are greatly increased, so as to form a radical cation with strong oxidation ability. Meanwhile, the change in geometry of the complexes under light irradiation also helps to the radical cation easily approaching and further oxidating DNA-base-pairs. These results offer the theoretical explanation for the photo-induced oxidation-reduction mechanism which was experimentally proposed on DNA-photocleavage by Co(Ш) polypyridyl complexes. In addition, the electronic absorption spectra of these complexes were calculated and simulated in aqueous solution using the time dependent DFT (TDDFT) method, in satisfying agreement with experimental results, and the properties of experimental absorption bands have been theoretically explained in detail.     

The light switch effect upon the association of [Ru(1,10-phenanthroline)2dipyrido[3,2-a:2',3'-c]phenazine]2+ with single stranded poly(dA) and poly(dT)

Large enhancement in the luminescence intensity of the Delta- and Lambda-Ru(phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) complexes upon their association with single stranded poly(dA) and poly(dT) is reported in this work. As the mixing ratio ([[Ru(phen)(2)DPPZ](2+)]/[DNA base]) increases, the luminescence intensity increase in a sigmoidal manner, indicating that the enhancement involves some cooperativity. At a high mixing ratio, the luminescence properties are affected by the nature of the DNA bases and not by the absolute configuration of the [Ru(phen)(2)DPPZ](2+) complex, indicating that the single stranded poly(dA) and poly(dT) do not recognize the configuration of the metal complex. In the case of the Lambda-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex, the manner of the enhancement is somewhat different from the other Ru(II) complex-polynucelotide combinations: the luminescence intensity reached a maximum at an intermediate mixing ratio of 0.32, and gradually decreased as the mixing ratio increased. In contrast to other complexes at high mixing ratios, an upward bending curve was found in the Stern-Volmer plot, which indicates that the micro-environment of the Lambda-[Ru(phen)(2)DPPZ](2+) is heterogeneous. In the Delta-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex case, formation of this highly luminescent species at an intermediate mixing ratio is far less effective.     

The relationship between the structures of periphery ligands and the DNA binding mode of [Ru(II)(1,10-phenanthroline)(L1L2)dipyrido[3,2-a:2',3'-c]phenazine](n+) (L1=Cl or pyridine and L2=pyridine, n=1,2)

The binding modes of the [Ru(II)(1,10-phenanthroline)(L₁L₂) dipyrido[3,2-a:2′,3′-c]phenazine]²⁺ {[Ru(phen)(py) Cl dppz]⁺ (L₁ = Cl, L₂ = pyridine) and ([Ru(phen)(py)₂dppz]²⁺ (L₁ = L₂ = pyridine)} to native DNA is compared to that of the [Ru(II)(1,10-phenanthroline)₂dipyrido[3,2-a:2′,3′-c]phenazine]²⁺ complex ([Ru(phen)₂dppz]²⁺) by various spectroscopic and hydrodynamic methods including electric absorption, linear dichroism (LD), fluorescence spectroscopy, and viscometric titration. All measured properties, including red-shift and hypochromism in the dppz absorption band, nearly perpendicular molecular plane of the dppz ligand with respect to the local DNA helix axis, prohibition of the ethidium binding, the light switch effect and binding stoichiometry, increase in the viscosity upon binding to DNA, increase in the melting temperature are in agreement with classical intercalation of dppz ligand of the [Ru(phen)₂dppz]²⁺ complex, in which both phenanthroline ligand anchored to the DNA phosphate groups by electrostatic interaction. [Ru(phen)(py)₂ dppz]²⁺ and [Ru(phen)(py) Cl dppz]⁺ complexes had one of the phenanthroline ligand replaced by either two pyridine ligands or one pyridine plus a chlorine ion. They exhibited similar protection from water molecules, interaction with DNA bases, and occupying site that is common with ethidium. The dppz ligand of these two Ru(II) complex were greatly tilted relative to the DNA helix axis, suggesting that the dppz ligand resides inside the DNA and is not perpendicular relative to the DNA helix axis. These observation suggest that anchoring the [Ru(phen)₂dppz]²⁺complex by both phenanthroline is essential for the dppz ligand to be classically intercalated between DNA base-pairs.     

Triboluminescence and crystal structure of the centrosymmetric complex [Tb(NO3)2(Acac)(Phen)2]·H2O

The atomic structure of crystals of the complex [Tb(NO₃)₂(Acac)(Phen)₂]·H₂O, (AA – acetylacetonate anion, Phen – 1,10‐phenanthroline) characterized by an intensive luminescence and triboluminescence has been determined by means of an X‐ray structural analysis method. Centrosymmetric crystals have a monoclinic syngony: a = 11.2298(1), b = 9.6492(1), c = 13.2745(1) Å, β = 101.290(1), space group P2/n, Z = 2, ρ_calc = 1.790 g/cm³. The crystal structure is represented by individual С₂₉Н₂₅N₆O₉Tb complexes linked through van der Waals interactions with clearly expressed cleavage planes. The Tb(III) atom coordination polyhedron reflects the state of a distorted square antiprism. The structural aspects of the suggested model of formation of the triboluminescent properties were considered and the role of the cleavage planes discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis, characterization and the thermodynamic study of intermediate sitting-atop (i-SAT) complexes of free base meso-tetraarylporphyrins with InCl3

The reaction of free base para-substituted meso-tetraarylporphyrins (H₂T(p-X)PP, X = H, OMe, Me, and Cl) with indium(III) chloride in CHCl₃ and mild conditions produced intermediate sitting-atop (i-SAT) complexes, [InCl₂(H₂T(p-X)PP)]InCl₄, as sole products. In the proposed structures of these complexes, four pyrrole rings are tilted alternatively up and down the porphyrin plane. This distortion makes suitable orientation of lone pairs of two pyrrolenine nitrogens for electron donation to an indium center of cation. The 1:2 (porphyrin:indium) formation constant of resulting i-SAT complexes were calculated by the computer fitting of the complexes absorbance versus mole ratio data based on appropriate equations. Thermodynamic parameters, ΔG⁰, ΔH⁰, and ΔS⁰, have been determined and the influence of electron donation of the para-substituted aryl groups in the free base porphyrins on the stability of the complexes is discussed.     

Anti-cancer study and whey protein complexation of new lanthanum(III) complex with the aim of achieving bioactive anticancer metal-based drugs

In this study, a new lanthanum (III)-amino acid complex utilizing cysteine has been synthesized and characterized. The anticancer activities of the prepared La(III) complex against MCF-7 cell lines were studied. Results of MTT assay showed that at all three incubation times, the cytotoxic effect of prepared La(III) complex on MCF-7 breast cancer cell lines displays a time- and dose-dependent inhibitory effects. The interactions of the La(III) complex with two whey proteins (bovine serum albumin, BSA, and Bovine β-lactoglobulin, βLG) have been explored by using spectroscopic and molecular dicking methods. The obtained results indicated that La(III) complex strongly quenched the fluorescence of two carrier proteins in static quenching mode and also, BSA hah stronger binding affinity toward studied complex than βLG whit binding constant values of K_{BSA-La?Complex}?～?0.11?×?10⁴ M^?1 and K_{βLG-La?Complex}?～?0.63?×?10³ M^?1 at 300 K. The thermodynamic parameters revealed the contribution of hydrogen bond and Vander Waals interactions in both systems. The distances of the La(III) complex whit whey proteins were calculated using Förster energy transfer theory and proved existence of the energy transfer between two proteins and prepared La(III) complex with a high probability. FT-IR and UV–Vis absorption measurements indicated that the binding of the La(III) to BSA and βLG may induce conformational and micro-environmental changes of the proteins. The docking results indicate that the La(III) complex bind to residues located in the site II of BSA and second site of βLG.

Communicated by Ramaswamy H. Sarma     

A solution thermodynamic study of the Cu(II) and Zn(II) complexes of EBTA: X-ray crystal structure of the dimeric complex [Cu2(EBTA)(H2O)3]2

The copper(II) complex of the acyclic EBTA ligand (H₄EBTA = 1,2-bis(2-aminoethoxy)benzene-N,N,N′,N′-tetraacetic acid) has been prepared and characterized by X-ray analysis. The two copper ions of the dinuclear unit present the same distorted octahedral coordination polyhedra. The EBTA ligand is shared between two copper coordination centres, with the formation of centrosymmetric dimers, which are linked in a supramolecular tridimensional structure via additional interactions through the coordinated waters molecules with adjacent carboxylic oxygen atoms. The stability and protonation constants of EBTA with Cu(II) and Zn(II) ions indicate a higher stability of these complexes with respect to the corresponding complexes with the more flexible EGTA ligand (H₄EGTA = ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid). On the other hand, the lower stability of [Gd(EBTA)]⁻ than [Gd(EGTA)]⁻ results in a decreased overall selectivity (lower K_sel) of EBTA towards Gd(III) and suggests that this complex may undergoes transmetallation reactions under physiological conditions.     

Synthesis and characterization of [Co(NO2)2(acac)(IMH2py)] with one-electron-reduced imino nitroxide radical associated with unusual displacement of acetylacetonate in the starting complex trans-Na[Co(NO2)2(acac)2]

A reaction of trans-Na[Co(NO₂)₂(acac)₂] with IM2py(2(2^′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl) in methanol afforded trans-[Co(NO₂)₂(acac)(IMH2py)](IMH2py=1-hydroxyl-2(2^′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole); one-electron reduction of the N-O radical moiety in IM2py and displacement of one of the two acac ligands with retention of two nitrito ligands in the starting complex during the reaction. This new complex was characterized by UV-Vis, ¹H NMR spectra and X-ray analysis.     

Synthesis and characterization of new water stable antimony(III) complex with pyrimidine-2-thione and in vitro biological study

A novel water stable, antimony(III) complex with the heterocyclic thioamide; 2-mercapto-pyrimidine (pmtH), of formula [Sb(pmt)₃] · 0.5(CH₃OH), has been synthesized and characterized by elemental analysis, ¹H, ¹³C NMR and FT-IR spectroscopic techniques. Crystal structure of the molecule has been determined by X-ray diffraction at ambient conditions. The compound [C₁₂H₉N₆S₃Sb · 0.5(CH₃OH)] is monoclinic, space group P2₁/c, a = 7.0646(7), b = 16.3767(14), c = 14.7265(13) Å, β = 92.016(7)°, Z = 4. In complex, three sulfur and three nitrogen atoms from thione ligands form a distorted pendagonal pyramidal geometry around antimony(III). The toxicity of the compound against tumor pleiomorphic cells, which has been isolated from a leiomyosarcoma tumor in the Wistar rat (chemical carcinogenesis using BaP) was studied in vitro. The results show that the compound did not destroy or prevent multiplication in vitro in leiomyosarcoma cells in low doses. The influence of the compound in the platelet aggregation, which correlates with the above tumor cells enhanced metastatic potential, has also been studied. The anti-metastatic capability study shows that the compound inhibited cancer cell induced aggregation up to the value of 10% in all mM concentrations tested.     

Comparative studies on the interactions of baicalein and Al(III)–baicalein complex with human serum albumin

A new potential drug aluminum(III)–baicalein complex (ALBC) was synthesized and characterized. The binding mechanisms of baicalein (BC) and ALBC to human serum albumin (HSA) under simulative physiological conditions were investigated, in order to understand the pharmacokinetics of BC and ALBC. Fluorescence spectroscopy results suggested that the binding level of BC is higher than that of ALBC. Results of UV–vis, synchronous fluorescence, 3D fluorescence, circular dichroism and Fourier transform infrared spectroscopic analyses consistently demonstrated that the conformation of HSA was altered when bound to BC or ALBC. The distance between HSA as a donor and BC (or ALBC) as an acceptor was determined via fluorescence resonance energy transfer. The results of competitive experiments and molecular docking studies indicated that BC was located in site I (subdomain IIA) on HSA and that ALBC was bound to HSA mainly within site II (subdomain IIIA). Copyright © 2015 John Wiley & Sons, Ltd.     

NMR study of the interaction of plastocyanin with chromium(III) analogues of inorganic electron transfer reagents

High resolution nuclear magnetic resonance spectroscopy has been used to examine the interaction of plastocyanins from French bean (Phaseolus vulgaris) and cucumber (Cucumis sativus) with three complexes—potassium hexacyanochromate(III), hexamminechromium(III) nitrate and tris(1,10-phenanthroline)-chromium(III) perchlorate—which are analogues of inorganic electron transfer reagents. The results indicate a high degree of specificity in the binding of these complexes and two binding sites on the protein are identified. One binding site is situated close to the copper atom and is clearly suited to outer sphere electron transfer through one of the histidine ligands. The other binding site is more distant from the copper atom and this mechanism cannot be operative. Electron transfer via hydrophobic channels or electron tunneling are possible mechanisms of electron transfer.     

X-ray and Fe Mössbauer study on a Fe(III) complex of 2-acetyl-1,3-indandione

Single-crystal X-ray structure of an iron(III) complex of 2-acetyl-1,3-indandione is resolved which reveals that a racemic mixture, composed of Δ-fac and Λ-fac stereoisomers, is formed. Both species have octahedral geometry, but slightly distinguishable. Detailed Mössbauer data indicate a high-spin electronic structure of the Fe(III) centres Fe1 and Fe2 with spin-spin magnetic relaxation process. Two different approaches for computer processing of the experimental Mössbauer spectra are considered.     

A novel tetranuclear lanthanide(III)-copper(II) complex of the macrocyclic oxamide [PrCu3] (macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione): synthesis, structure and magnetism

A novel tetranuclear lanthanide(III)-copper(II) complex of macrocyclic oxamide, [Pr(CuL)₃(H₂O)₂](SCN)₃ · 1.5H₂O (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) (1), has been synthesized, structurally characterized and preliminary investigated by magnetic studies. The structure of the title complex consists of a cationic PrCu₃ core, noncoordinated monovalent SCN⁻ anions and H₂O molecules; the packing diagram shows open channels formed through intermolecular weak interactions. The temperature-dependent magnetic susceptibilities were analyzed by an approximate treatment being enlightened by Matsumoto et al. leading to J = −1.62 × 10⁻² cm⁻¹, Δ = 3.12 cm⁻¹, g_Cu = 2.13, respectively.