Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α-Synuclein

The interaction between α-synuclein (αSyn) and Cu²⁺ has been suggested to be closely linked to brain copper homeostasis. Disruption of copper levels could induce misfolding and aggregation of αSyn, and thus contribute to the progression of Parkinson's disease (PD). Understanding the molecular mechanism of αSyn-Cu²⁺ interaction is important and controversies in Cu²⁺ coordination geometry with αSyn still exists. Herein, we find that the pathological H50Q mutation has no impact on the kinetics of Cu²⁺ binding to the high-affinity site of wild type αSyn (WT-αSyn), indicating the non-involvement of His50 in high-affinity Cu²⁺ binding to WT-αSyn. In contrast, the physiological N-terminally acetylated αSyn (NAc-αSyn) displays several orders of magnitude weaker Cu²⁺ binding affinity than WT-αSyn. Cu²⁺ coordination mode to NAc-αSyn has also been proposed based on EPR spectrum. In addition, we find that Cu²⁺ coordinated WT-αSyn is reduction-active in the presence of GSH, but essentially inactive towards ascorbate. Our work provides new insights into αSyn-Cu²⁺ interaction, which may help understand the multifaceted normal functions of αSyn as well as pathological consequences of αSyn aggregation.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Poly[[aqua‐μ3‐2,2‐dimethylmalonato‐copper(II)] monohydrate] and poly[aqua‐μ3‐2,2‐dimethylmalonato‐copper(II)]

The coordination mode of the dimethylmalonate ligand in the two title Cu^II complexes, {[Cu(C₅H₃O₄)(H₂O)]·H₂O}_n, (I), and [Cu(C₅H₃O₄)(H₂O)]_n, (II), is the same, with chelated six‐membered, bis‐monodentate and bridging bonding modes. However, the coordination environment of the Cu^II atoms, the connectivity of their metal–organic frameworks and their hydrogen‐bonding interactions are different. Complex (I) has a perfect square‐pyramidal Cu^II environment with the aqua ligand in the apical position, and only one type of square grid consisting of Cu^II atoms linked via carboxylate bridges to three dimethylmalonate ligands, with weak hydrogen‐bond interactions within and between its two‐dimensional layers. Complex (II) has a coordination geometry that is closer to square pyramidal than trigonal bipyramidal for its Cu^II atoms with the aqua ligand now in the basal plane. Its two‐dimensional layer structure comprises two alternating grids, which involve two and four different dimethylmalonate anions, respectively. There are strong hydrogen bonds only within its layers.     

Bis{[μ‐N,N′‐bis­(salicyl­idene)‐1,4‐butane­di­amine‐N,N′,O,O′‐copper(II)]‐μ‐chloro‐chloromercury(II)}

A new tetranuclear Cu^II–Hg^II–Hg^II–Cu^II complex, [Cu₂Hg₂Cl₄(C₁₈H₁₈N₂O₂)₂], has been prepared by means of a copper complex found in the literature. The molecular structure of this complex was determined by X‐ray diffraction and the Cu–Hg–Hg–Cu chain was seen to be non‐linear. The change in magnetic susceptibility with temperature was recorded for this complex and observed to abide by the Curie–Weiss law. The coordination around the Hg^II ions is square pyramidal. The Cu?Hg bridging distance is 3.5269 (7) Å.     

Acrolein and Copper as Competitive Effectors of α-Synuclein

Mounting evidence supports the role of amyloidogenesis, oxidative stress, and metal dyshomeostasis in the development of neurodegenerative disorders. Parkinson's Disease is characterized by α-synuclein (αSyn) accumulation and aggregation in brain regions, also promoted by Cu²⁺. αSyn is modified by reactive carbonyl species, including acrolein (ACR). Notwithstanding these findings, the interplay between ACR, copper, and αSyn has never been investigated. Therefore, we explored more thoroughly the effects of ACR on αSyn using an approach based on LC-MS/MS analysis. We also evaluated the influence of Cu²⁺ on the protein carbonylation and how the ACR modification impacts the Cu²⁺ binding and the production of Reactive Oxygen Species (ROS). Finally, we investigated the effects of ACR and Cu²⁺ ions on the αSyn aggregation by dynamic light scattering and fluorescence assays. Cu²⁺ regioselectively inhibits the modification of His50 by ACR, the carbonylation lowers the affinity of His50 for Cu²⁺ and ACR inhibits αSyn aggregation both in the presence and in the absence of Cu²⁺.     

Synthesis,Characterization, Crystal Structure,and Biological Activities of Transition Metal Complexes with 1‐Phenyl‐3‐methyl‐5‐hydroxypyrazole‐4‐methylene‐8′‐quinolineimine

The Schiff base ligand, 1‐phenyl‐3‐methyl‐5‐hydroxypyrazole‐4‐methylene‐8′‐quinolineimine, and its Cu^II, Zn^II, and Ni^II complexes were synthesized and characterized. The crystal structure of the Zn^II complex was determined by single‐crystal X‐ray diffraction, indicating that the metal ions and Schiff base ligand can form mononuclear six‐coordination complexes with 1:1 metal‐to‐ligand stoichiometry at the metal ions as centers. The binding mechanism and affinity of the ligand and its metal complexes to calf thymus DNA (CT DNA) were investigated by UV/Vis spectroscopy, fluorescence titration spectroscopy, EB displacement experiments, and viscosity measurements, indicating that the free ligand and its metal complexes can bind to DNA via an intercalation mode with the binding constants at the order of magnitude of 105–106 M ^–1, and the metal complexes can bind to DNA more strongly than the free ligand alone. In addition, antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for hydroxyl radical in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as mannitol. The ligand and its metal complexes were subjected to cytotoxic tests, and experimental results indicated that the metal complexes show significant cytotoxic activity against lung cancer A 549 cells.     

Binding of Cu+ and Cu2+ with peptides: Peptides = oxytocin,Arg8‐vasopressin,bradykinin, angiotensin‐I,substance‐P,somatostatin, and neurotensin

The intrinsic binding ability of 7 natural peptides (oxytocin, arg⁸‐vasopressin, bradykinin, angiotensin‐I, substance‐P, somatostatin, and neurotensin) with copper in 2 different oxidation states (Cu^I/II) derived from different Cu^+/2+ precursor sources have been investigated for their charge‐dependent binding characteristics. The peptide‐Cu^I/II complexes, [M − (n‐1)H + nCu^I] and [M − (2n‐1)H + nCu^II], are prepared/generated by the reaction of peptides with CuI solution/Cu‐target and CuSO₄ solution and are analyzed by using matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry. The MALDI mass spectra of both [M − (n‐1)H + nCu^I] and [M − (2n‐1)H + nCu^II] complexes show no mass shift due to the loss of ─H atoms in the main chain ─NH of these peptides by Cu⁺ and Cu²⁺ deprotonation. The measured m/z value indicates the reduction of Cu^I/II oxidation state into Cu⁰ during MALDI processes. The number and relative abundance of Cu⁺ bound to the peptides are greater compared with the Cu²⁺ bound peptides. Oxytocin, arg⁸‐vasopressin, bradykinin, substance‐P, and somatostatin show the binding of 5Cu⁺, and angiotensin‐I and neurotensin show the binding of 7Cu⁺ from both CuI and Cu targets, while bradykinin shows the binding of 2Cu²⁺, oxytocin, arg⁸‐vasopressin, angiotensin‐I, and substance‐P; somatostatin shows the binding of 3Cu²⁺; and neurotensin shows 4Cu²⁺ binding. The binding of more Cu⁺ with these small peptides signifies that the bonding characteristics of both Cu⁺ and Cu²⁺ are different. The amino acid residues responsible for the binding of both Cu⁺ and Cu²⁺ in these peptides have been identified based on the density functional theory computed binding energy values of Cu⁺ and the fragment transformation method predicted binding preference of Cu²⁺ for individual amino acids.     

Synthese,Struktur und EPR‐Untersuchungen von binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))‐Komplexen des CuII,NiII, ZnII,CdII und PdII

Synthesis, Structure and EPR Investigations of binuclear Bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato)) Complexes of Cu^II, Ni^II, Zn^II, Cd^II and Pd^II The synthesis of binuclear Cu^II‐, Ni^II‐, Zn^II‐, Cd^II‐ and Pd^II‐complexes of the quadridentate ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and the crystal structures of the Cu^II‐ and Ni^II‐complexes are reported. The Cu^II‐complex crystallizes in two polymorphic modifications: triclinic, (Z = 1) and monoclinic, P2₁/c (Z = 2). The Ni^II‐complex was found to be isostructural with the triclinic modification of the copper complex. The also prepared Pd^II‐, Zn^II‐ and Cd^II‐complexes could not be characterized by X‐ray analysis. However, EPR studies of diamagnetically diluted Cu^II/Pd^II‐ and Cu^II/Zn^II‐powders show axially‐symmetric g and A ^Cu tensors suggesting a nearly planar co‐ordination within the binuclear host complexes. Diamagnetically diluted Cu^II/Cd^II powder samples could not be prepared. In the EPR spectra of the pure binuclear Cu^II‐complex exchange‐coupled Cu^II‐Cu^II pairs were observed. According to the large Cu^II‐Cu^II distance of about 7,50Å a small fine structure parameter D = 26·10^?4 cm^?1 is observed; T‐dependent EPR measurements down to 5 K reveal small antiferromagnetic interactions for the Cu^II‐Cu^II dimer. Besides of the dimer in the EPR spectra the signals of a mononuclear Cu^II species are observed whose concentration is T‐dependent. This observation can be explained assuming an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions.     

Synthese,Strukturen und X‐/Q‐Band‐EPR‐Untersuchungen von N,N‐Diethyl‐N′‐3,5‐di(trifluormethyl)benzoylthioureato‐Komplexen des CuII,NiII und PdII sowie EPR‐spektroskopische Charakterisierung eines CuII‐CuII‐Dimers

The synthesis and the structures of (i) the ligand N,N‐Diethyl‐N′‐3,5‐di(trifluoromethyl)benzoylthiourea HEt₂dtfmbtu and (ii) the Ni^II and Pd^II complexes of HEt₂dtfmbtu are reported. The ligand coordinates bidendate forming bis chelates. The Ni^II and the Pd^II complexes are isostructural. The also prepared Cu^II complex could not be characterized by X‐ray analysis. However, the preparation of diamagnetically diluted powders Cu/Ni(Et₂dtfmbtu)₂ and Cu/Pd(Et₂dtfmbtu)₂ suitable for EPR studies was successful. The EPR spectra of the Cu/Ni and Cu/Pd systems show noticeable differences for the symmetry of the CuS₂O₂ unit in both complexes: the Cu/Pd system is characterized by axially‐symmetric g< and A ^cu tensors; for the Cu/Ni system g and A ^Cu have rhombic symmetry. EPR studies on frozen solutions of the Cu^II complex show the presence of a Cu^II‐Cu^II dimer which is the first observed for Cu^II acylthioureato complexes up to now. The parameters of the fine structure tensor were used for the estimation of the Cu^II‐Cu^II distance.     

Palladium‐Catalyzed Alkoxycarbonylation of Terminal Alkenes To Produce α,β‐Unsaturated Esters: The Key Role of Acetonitrile as a Ligand

A mild protocol has been developed for the Pd^II‐catalyzed alkoxycarbonylation of terminal olefins to produce α,β‐unsaturated esters with a wide range of substrates. Key features are the use of MeCN as solvent (and/or ligand) to control the reactivity of the intermediate Pd complexes and the combination of CO with O₂, which facilitates the Cu^II‐mediated reoxidation of the Pd⁰ complex to Pd^II and prevents double carbonylation.     

Synthesis,Crystal Structure,Thermal Stability,Magnetic Property,and Biological Activity of a New Copper(II) Complex Based on 1,2,4‐Benzenetricarboxylic Acid and 2,2′‐Bipyridine

Based on an asymmetric 1,2,4‐benzenetricarboxylic acid (H₃btc) and 2,2′‐bipyridine (bpy), a new Cu^II complex, Cu₂(H₂btc)₄(bpy)₂ · 8H₂O ( 1 ), was synthesized and structurally characterized by single‐crystal X‐ray diffraction, hirshfeld surface (HS) analysis, IR spectroscopy, powder X‐ray analysis, thermal gravimetry analysis (TGA), magnetic susceptibility, EPR measurement, and UV/Vis spectrometry. Complex 1 shows a dinuclear copper structure. The Cu^II of each dinuclear moiety are in a slightly distorted square‐pyramidal environments. Magnetic susceptibility of 1 shows a ferromagnetic coupling between both metal atoms. The interaction of 1 with bovine serum albumin (BSA) is investigated using UV/Vis, fluorescence spectroscopic methods. The Cu^II complex shows strong binding propensity in albumin binding study.     

Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity

The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of Cu^II or Na^I/Ni^II under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [Cu^II(μ‐CH₃COO)₂(κO‐DAPTA=O)]₂ ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]₂(BPh₄)₂ ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear Cu^II complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence Cu^II/Cu^I complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand.     

Synthese,Strukturen, NMR‐ und EPR‐Untersuchungen der binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato))‐Komplexe des NiII und CuII

Synthesis, Structures, NMR and EPR Investigations of Binuclear Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato)) Complexes of Ni^II and Cu^II The synthesis of binuclear Cu^II and Ni^II complexes of the quadridentate ligand N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenourea) and their crystal structures are reported. The complexes crystallize monoclinic, P2₁/c (Z = 2). In the EPR spectra of the binuclear Cu^II complex exchange‐coupled Cu^II‐Cu^II pairs were observed. In addition the signals of a mononuclear Cu^II species are observed what will be explained with the assumption of an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions. Detailed ¹³C and ⁷⁷Se NMR investigations on the ligand and the Ni^II complex allow an exact assignment of all signals of the heteroatoms.     

A Stable Organic π‐Radical of a Zinc(II)–Copper(I)–Zinc(II) Complex of Decaphyrin

A Zn^II‐Cu^I‐Zn^II heterotrimetal complex of decaphyrin was synthesized by stepwise metalations: metalation of a [46]decaphyrin with Zn^II ions to produce a 46π decaphyrin bis(Zn^II) complex and its subsequent metalation with Cu^II ion. In the second metalation step, it has been shown that Cu^II ion is reduced to a Cu^I ion in the complex and a dianionic bis(Zn^II) containing [46]decaphyrin ligand is oxidized to the corresponding monoanionic [45]decaphyrin ligand, indicating a non‐innocent nature of the decaphyrin ligand. Despite the radical nature, the heterotrimetal complex is fairly stable under ambient conditions and exhibits almost no intermolecular magnetic interaction, owing to extensive delocalization of an unpaired electron in the large π‐conjugated circuit of decaphyrin moiety.     

Key Intermediate Species Reveal the Copper(II)‐Exchange Pathway in Biorelevant ATCUN/NTS Complexes

The amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards Cu^II ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped‐flow and microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate Cu^II complexes formed by glycyl–glycyl–histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two‐nitrogen coordination, t_1/2≈100 ms at pH 6.0 and the ability to maintain the Cu^II/Cu^I redox pair is the best candidate for the long‐sought reactive species in extracellular copper transport.     

Visible‐Light‐Accelerated Copper(II)‐Catalyzed Regio‐ and Chemoselective Oxo‐Azidation of Vinyl Arenes

The visible‐light‐accelerated oxo‐azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap)₂]Cl or [Cu(dap)Cl₂] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. Cu^II is proposed as the catalytically active species, which upon coordinating azide will undergo light‐accelerated homolysis to form Cu^I and azide radicals. This activation principle (Cu^II‐X→Cu^I+X^.) opens up new avenues for copper‐based photocatalysis.     

Effects of Divalent Metal Ions on the Chaperone Activity and Structure of Rat Lens H18G Mutant αB‐Crystallin

αB‐crystalin, a small heat shock protein and a component of α‐crystalin, is a molecular chaperone playing an important role in preventing the formation of cataracts. It has been reported that His18 is an important site for Cu²⁺ to bind with to form a stable metal complex and thus to enhance this chaperone‐like activity of human αB‐crystalin. In this work, we used site‐directed mutagenesis to clone and express H18G rat lens αB‐crystalin in order to investigate the role of His18 in chaperoning activity. We found that 1 mM of Cu²⁺, or Zn²⁺, rather than Mg²⁺, significantly enhanced the chaperone‐like activity of wild type αB‐crystalin. Whereas, it is Zn²⁺ and Mg²⁺, not Cu²⁺, that significantly reduced this activity of H18G αB‐crystalin. In the absence of cation, H18G showed better activity compared to the wild type αB‐crystalin. ANS fluorescence measurement showed there was no linear relationship between chaperone‐like activity and surface hydrophobicity, indicating that surface hydrophobicity is not a prerequisite for chaperone‐like activity. An HPLC size‐exclusion chromatography study showed that in the presence of metal ions, wild type αB‐crystalin tended to aggregate via dissociation and re‐association into a high molecular aggregate with a molecular weight higher than 1400 kDa and then precipitated, suggesting that the presence of metal ions is a factor leading to the formation of cataracts. Both the near and far UV‐CD spectra suggested that the wild type αB‐crystalin reflected more β‐sheet structural characteristics; whereas the H18G reflected more random coil characteristics. The H18G induced structural alterations as to develop more random coil characteristics and more micro‐environmental changes around the tryptophan residues. This work suggested that His18 may not be a crucial binding site for Cu²⁺, but rather that it may be an important binding site for Zn²⁺ in terms of chaperone‐like activity and the process of metal induced self‐aggregation is prerequisite for chaperone‐like activity to occur.     

Evidence of CuI/CuII Redox Process by X‐ray Absorption and EPR Spectroscopy: Direct Synthesis of Dihydrofurans from β‐Ketocarbonyl Derivatives and Olefins

The Cu^I/Cu^II and Cu^I/Cu^III catalytic cycles have been subject to intense debate in the field of copper‐catalyzed oxidative coupling reactions. A mechanistic study on the Cu^I/Cu^II redox process, by X‐ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopies, has elucidated the reduction mechanism of Cu^II to Cu^I by 1,3‐diketone and detailed investigation revealed that the halide ion is important for the reduction process. The oxidative nature of the thereby‐formed Cu^I has also been studied by XAS and EPR spectroscopy. This mechanistic information is applicable to the copper‐catalyzed oxidative cyclization of β‐ketocarbonyl derivatives to dihydrofurans. This protocol provides an ideal route to highly substituted dihydrofuran rings from easily available 1,3‐dicarbonyls and olefins.     

5,20‐Bis(ethoxycarbonyl)‐Substituted Antiaromatic [28]Hexaphyrin and Its Bis‐NiII and Bis‐CuII Complexes

5,20‐Bis(ethoxycarbonyl)‐[28]hexaphyrin was synthesized by acid catalyzed cross‐condensation of meso‐diaryl‐substituted tripyrrane and ethyl 2‐oxoacetate followed by subsequent oxidation. This hexaphyrin was found to be a stable 28π‐antiaromatic compound with a dumbbell‐like conformation. Upon oxidization with PbO₂, this [28]hexaphyrin was converted into an aromatic [26]hexaphyrin with a rectangular shape bearing two ester groups at the edge side. The [28]hexaphyrin can incorporate two Ni^II or Cu^II metals by using the ester carbonyl groups and three pyrrolic nitrogen atoms to give bis‐Ni^II and bis‐Cu^II complexes with essentially the same dumbbell‐like structure. The antiaromatic properties of the [28]hexaphyrin and its metal complexes have been well characterized.     

A mixed‐valence chair‐like tetranuclear copper(I,II) cluster with three linking modes of the 3,5‐bis(2‐pyridyl)‐1,2,4‐triazole ligand

In the tetranuclear copper complex tetrakis[μ‐3,5‐bis(2‐pyridyl)‐1,2,4‐triazolido]bis[3,5‐bis(2‐pyridyl)‐1,2,4‐triazolido]dicopper(I)dicopper(II) dihydrate, [Cu^I₂Cu^II₂(C₁₂H₈N₅)₆]·2H₂O, the asymmetric unit is composed of one Cu^I center, one Cu^II center, three anionic 3,5‐bis(2‐pyridyl)‐1,2,4‐triazole (2‐BPT) ligands and one solvent water molecule. The Cu^I and Cu^II centers exhibit [Cu^IN₄] tetrahedral and [Cu^IIN₆] octahedral coordination environments, respectively. The three independent 2‐BPT ligands adopt different chelating modes, which link the copper centers to generate a chair‐like tetranuclear metallomacrocycle with metal–metal distances of about 4.4 × 6.2 Å disposed about a crystallographic inversion center. Furthermore, strong π–π stacking interactions and O—H...N hydrogen‐bonding systems link the tetracopper clusters into a two‐dimensional supramolecular network.