2D Compound Constructed by Cu3 Units with Mixed Azido and Tetrazole Double Bridges: Synthesis,Structure, and Theoretical Study on Magnetic Properties

The two‐dimensional (2D) layer Cu^II compound [Cu₃(L)₂(N₃)₄] ( 1 ) [L = 2‐amino‐3‐(5‐tetrazole)‐methyate‐N‐pyridine] was synthesized by in‐situ hydrothermal reaction of CuCl₂ · 2H₂O, NaN₃, and 3‐(5‐tetrazole)‐methyate‐N‐pyridine. The central Cu1 and Cu2 atoms are located in five‐coordinate and six‐coordinate arrangements, respectively. Three Cu^II ions are linked by mixed double EO (end‐on)‐azido‐tetrazole bridges to give trinuclear Cu^II clusters, which are further extended by EE (end‐to‐end) azido bridges to form 2D metal‐organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –849 cm^–1) revealed that the double EO‐azido‐tetrazole bridges transmit antiferromagnetic coupling between Cu^II ions.     

Structure and Magnetism of two Polynuclear Complexes Containing both Macrocyclic and Azido Ligands

The two complexes of formula [Cu₂(CuL)₂(μ‐N₃)₄] · 2CH₃OH ( 1 ) and [Cu₂(NiL)₂(μ‐N₃)₄] · 2CH₃OH ( 2 ) (CuL and NiL, H₂L = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclo‐pentadeca‐7,13‐dien), were synthesized and structurally determined. The magnetic susceptibility data of 1 and 2 were analyzed. For complex 1 , magnetic measurements show alternating ferromagnetic and antiferromagnetic exchange couplings J₁ = 23.67 cm^–1, J₂ = –189.11 cm^–1, zJ’ = –0.62 cm^–1. For complex 2 , the doubly bridged asymmetric EO promotes a ferromagnetic interaction between Cu^II and Cu^II ions(J = 40.764 cm^–1).     

Synthesis,Structure, and Magnetic Properties of a Copper(II) Metal‐Organic Framework with Biphenyl‐2,2′,4,4′‐tetracarboxylic Acid

The 2D Cu^II metal‐organic framework [Cu₂(bptc)(H₂O)₄]_n · 4nH₂O ( 1 ) (H₄bptc = biphenyl‐2,2′,4,4′‐tetracarboxylic acid) was hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction and magnetic measurements. In the structure, bptc^4– serves as a twisted Π‐shaped organic building block to connect paddlewheel [Cu₂(COO)₄] dinuclear units and mononuclear units through 2‐/2′‐carboxylate and 4‐/4′‐carboxylate, respectively. According to the magnetic analysis using a dimer‐plus‐monomer model, strong antiferromagnetic coupling is operative within the dinuclear unit (J = –311 cm^–1 based on H = –J S ₁ S ₂), and the compound behaves like a mononuclear molecule at low temperature.     

Four Discrete Transition Metal Complexes Involving Pyridyl‐substituted Nitronyl Nitroxide: Syntheses,Crystal Structures,and Magnetic Properties

Four discrete metal‐radical complexes, [Cu(p‐MePh‐COO)₂(NITpPy)₂] ( 1 ), [Ni(m‐MePhCOO)₂(NITpPy)₂(H₂O)₂] · (CH₃‐OH)₂ ( 2 ), [Mn(p‐MePhCOO)₂(NITpPy)₂(H₂O)₂] ( 3 ), and [Mn(m‐MePhCOO)₂(NITpPy)₂(H₂O)₂] ( 4 ) [NITpPy = 2‐(4‐pyridyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl‐3‐oxide] were synthesized and characterized by elemental analyses, IR spectroscopy, PXRD, single‐crystal X‐ray diffraction, and magnetic susceptibility. For the four complexes, the crystal structural analyses indicate that the two radical ligands coordinated to the metal ions by the nitrogen atoms of the pyridine rings form three spin complexes, where toluates act as co‐ligands. Weak antiferromagnetic interactions [J_Cu–Rad = –6.75 cm^–1 ( 1 ), J_Co–Rad = –4.15 cm^–1 ( 2 ), J_Mn–Rad = –0.22 cm^–1 ( 3 ), and J_Mn–Rad = –3.74 cm^–1 ( 4 )] were observed, spin polarization mechanism and orbital symmetry are used to explain the magnetic coupling in these complexes.     

Assemblies of 1D and 2D Copper(II) Chiral Coordination Polymers by Salicylaldehyde Schiff Bases: Synthesis,Crystal Structures,and Magnetic Properties

Reaction of CuCl₂ · 2H₂O with chiral Schiff bases and sodium dicyanamide led to the formation of two chiral copper(II) coordination polymers, namely [Cu₄(L¹)₂(dca)₄]_n ( 1 ) and [Cu₂(L²)(μ‐Cl)(dca)(H₂O)]_n · nH₂O ( 2 ) {H₂L¹ = (1R, 3S)‐N′,N′′‐bis[salicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, H₂L² = (1R, 3S)‐N′,N′′‐bis[3‐ethoxysalicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, dca = dicyanamide}. Both complexes were structurally characterized by elemental analyses, IR spectroscopy and single‐crystal X‐ray diffraction. Complex 1 exhibits a two‐dimensional polymeric structure formed by single dca bridging tetranuclear Cu₄ units. Complex 2 displays a left‐handed helical chain structure constructed from Cu₂ dimers with single dca bridges. The chirality of 1 and 2 was confirmed by circular dichroism (CD) measurements in solution. Both complexes exhibit strong antiferromagnetic couplings with J = –308(4) cm^–1 for 1 and J = –123(1) cm^–1 for 2 in 2–300 K.     

Magnetic Properties of Mixed Ligand NiII2 and NiII4 Complexes Composed of Macrocyclic Hexaamine‐Dithiophenolato and Bridging Tetrazolato Ligands

The magnetic properties of the dinuclear and tetranuclear nickel(II) tetrazolato complexes [Ni₂L(RCN₄)][BPh₄] (R = H ( 4 ), Me ( 5 ), Ph ( 6 )) and [(Ni₂L)₂(1,4‐(CN₄)₂‐C₆H₄)][BPh₄]₂ ( 7 ), where (L)^2– represents a 24‐membered macrocyclic N₆S₂ supporting ligand, are reported. Analysis of temperature‐dependent magnetic susceptibility measurements over the temperature range from 2 to 300 K revealed the presence of weak ferromagnetic exchange interactions between the Ni^II ions in the binuclear [Ni₂L(μ‐L′)]⁺ subunits with magnetic exchange coupling constant values of J₁ = 13.5 cm^–1 for 4 , J₁ = 20.0 cm^–1 for 5 , J₁ = 19.2 cm^–1 for 6 , and J₁ = 15.2 cm^–1 for 7 ( H = –2JS₁S₂). The exchange coupling J₂ across the bistetrazolato bridge in 7 is less than 0.1 cm^–1, which suggests that no significant interdimer coupling occurs in this compound. The synthesis and crystal structure of the new complex 7 ·2MeCN is also reported.     

Hydrogen‐Bond‐Based Magnetic Exchange Between μ‐Diethylnicotinamide(aqua)bis(X‐salicylato)copper(II) Polymeric Chains

Polymeric salicylatocopper(II) complexes of unusual composition [C u(X‐ sal)₂( μ‐denia)(H₂O)]_n [denia = diethylnicotinamide, and X‐sal = 5‐methylsalicylate ( 1 ), 3‐methylsalicylate ( 2 ), 4‐methoxysalicylate ( 3 ), 3,5‐dichlorosalicylate ( 4 ) and 3,5‐dibromosalicylate ( 5 )] were synthesized and characterized. Magnetic measurements were performed in the temperature range 1.8–300 K. The structural unit of all complexes consists of a Cu^II atom, which is monodentately coordinated by the pair of X‐salicylate anions in trans positions. Water and the diethylnicotinamide ligand occupy the other two basal plane positions of the tetragonal pyramid. The axial positions are occupied by a diethylnicotinamide oxygen atom of neighboring structural units, thus forming a spiral polymeric structure parallel to b axis. Magnetic measurements showed that all complexes 1 – 5 exhibit a susceptibility maximum at about 6–8 K. The obtained data fit to Bleaney–Bowers equation gave singlet‐triplet energy gaps 2J = –8.60 cm^–1 for 1 , 2J = –6.57 cm^–1 for 2 , 2J = –8.57 cm^–1 for 3 , 2J = –6.82 cm^–1 for 4 , and 2J = –6.45 cm^–1 for 5 . The supramolecular structure based on hydrogen bonds [described by supramolecular synthons R₂²(10) and R₂²(12)] is the pathway for antiferromagnetic interactions of the magnetically coupled pairs of copper atoms of neighboring chains within the 2D supramolecular layers. The results of the magnetic measurements suggest involvement of the COO groups in the magnetic interaction pathway for all five complexes.     

Crystal Structures,Magnetism, and Dye Degradation Catalytic Properties of Copper 2‐Methoxycarboxybenzoate Coordination Complexes

Copper coordination complexes containing the 2‐methoxycarboxybenzoate (2‐mcob) ligand show different topologies depending on the nature of the dipyridyl coligand. [Cu₂(2‐mcob)₂(ebin)]_n ( 1 ) [ebin = ethanebis(isonicotinamide)] shows a ladder structure based on anti‐syn bridged [Cu(OCO)]_n chain motifs. [Cu₂(2‐mcob)₂(bbin)(H₂O)₂] ( 2 ) [bbin = butanebis(isonicotinamide)] displays a dimeric molecular structure. [Cu₂(2‐mcob)₂(hbin)]_n ( 3 ) [hbin = hexanebis(isonicotinamide)] manifests a ladder structure very similar to that of 1 . {[Cu(2‐mcob)(dpa)] · H₂O}_n ( 4 ) [dpa = bis(4‐pyridyl)amine] shows a chain coordination polymer structure. All four materials showed significant promise as heterogeneous degradation catalysts for Congo Red dye in aqueous suspension under ultraviolet irradiation. Variable temperature magnetic susceptibility experiments for 1 indicated the presence of weak antiferromagnetic exchange (g = 2.059(2), J = –0.84(2) cm^–1). Thermal degradation behavior is also discussed.     

Syntheses,Structures, and Properties of Two New Tri‐spin Lanthanide‐Nitronyl Nitroxide (LnIII = GdIII and HoIII) Complexes

Abstract. Two radical–Ln^III–radical complexes, [Ln(hfac)₃(NITPh‐Ph)₂] [Ln = Gd ( 1 ) and Ho ( 2 ), hfac = hexafluoroacetylacetonate; and NITPh‐Ph = 4′‐biphenyl‐4, 4, 5, 5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide] were synthesized and characterized by X‐ray diffraction, elemental analysis, magnetic measurements, as well as IR and UV/Vis spectroscopy. X‐ray crystal structure analysis revealed that the structures of both complexes are isomorphous, the central Ln^III ions are coordinated by six oxygen atoms from three hfac ligand molecules and two oxygen atoms from nitronyl radicals. The temperature dependencies of the magnetic susceptibilities were studied. They showed that in the Gd^III complex, ferromagnetic interactions between Gd^III and the radicals and antiferromagnetic interactions between the radicals coexist in this system (with J_Rad–Gd = 0.1 cm^–1, J_Rad–Rad = –0.309 cm^–1).     

Intramolecular and Intermolecular Magnetic Coupling Mechanism of a Dinuclear Copper(II) Complex

Abstract. A new dinuclear complex, [Cu₂(μ_{1, 3}‐NCS)₂(Ophen)₂(OH₂)₂], (HOphen = 1, 10‐phenanthrolin‐2‐ol) was synthesized and its crystal structure was determined by X‐ray crystallography. In the complex, the Cu^II ion assumes a distorted square pyramidal arrangement and the thiocyanate anion functions as bridged ligand and Ophen as capped ligand. The analysis of the crystal structure shows that there exists a π–π stacking interaction between the adjacent complexes. The theoretical calculations reveal that the magnetic coupling pathways from the thiocyanate anions bridge ligand and the π–π stacking magnetic coupling pathway resulted in the weak ferromagnetic interactions with 2J = 18.46 cm^–1 and 2J = 10.46 cm^–1, respectively. The calculations also display that the spin delocalization and the spin polarization occur in the bridge magnetic coupling system and the π–π stacking magnetic coupling system, and the magnetic coupling mechanism of the π–π stacking can be explained with McConnell I spin‐polarization mechanism. The fitting for the data of the variable‐temperature magnetic susceptibility with dinuclear Cu^II formula gave the magnetic coupling constant 2J = 2.84 cm^–1 and zJ′ = 0.03 cm^–1, in which the 2J = 2.84 cm^–1 is attributed to the magnetic coupling from the bridge dinuclear Cu^II unit and the zJ′ = 0.03 cm^–1 is ascribed to the π–π stacking magnetic coupling system. The study may benefit to understand the magnetic coupling mechanism of π–π stacking system.     

Synthesis,crystal structure,and properties of copper(II) and manganese(II) complexes with azide and 3,4-di(2′-pyridyl)-1,2,5-oxadiazole

Two transition metal complexes with azide and 3,4-di(2′-pyridyl)-1,2,5-oxadiazole (dpo), [Cu₂(dpo)₂(N₃)₄] (1), and [Mn(dpo)₂(N₃)₂] (2), have been synthesized and characterized by single-crystal X-ray diffraction. The Cu(II) complex is binuclear with double end-on (EO) azido bridges, in which each Cu(II) ion assumes a distorted square pyramidal geometry, and each EO azido bridge adopts a quasi-symmetric fashion. In contrast, the Mn(II) complex is mononuclear, in which the Mn(II) ion is ligated by two dpo ligands and two terminal azide ions, with a distorted octahedron geometry. Magnetic studies on the Cu(II) complex revealed that the double EO azido bridge mediates ferromagnetic coupling with J=12.8 cm⁻¹.     

Synthesis,Characterization, and Electrocatalytic Behavior for Hydrogen Evolution of a Dinuclear Copper(II) Complex of 1-[(2-Carboxymethyl) benzene]-3-[2-carboxybenzene] triazene

A dinuclear copper(II) complex, [Cu^II₂(L)₂] is afforded by the reaction of CuCl₂ · 2H₂O with a triazenido ligand, 1-[(2-carboxymethyl) benzene]-3-[2-carboxybenzene] triazene (H₂L). Structural investigation shows that the copper-copper distance [2.3985(7) Å] is significantly shorter than the sum of the van der Waals radii of Cu (1.40 Å), suggesting that there are metal-metal bonds in [Cu^II₂(L)₂]. In solid, there is a strong antiferromagnetic interaction between copper(II) ions (J = –135.6 cm^–1). In homogeneous environment, [Cu^II₂(L)₂] shows electrocatalytic activities for hydrogen generation both from acetic acid with a turnover frequency (TOF) of 32 mol of hydrogen per mole of catalyst per hour [mol(H₂) · mol^–1(catalyst) · h^–1] at an overpotential (OP) of 941.6 mV, and neutral buffer with a TOF of 512 mol(H₂) · mol^–1(catalyst) · h^–1 at an OP of 836.7 mV.     

Structure and magnetic properties of the copper(II) complexes with diacyl hydrazides of salicylic acid

The structures and results of the static magnetic susceptibility investigation of the copper(II) binuclear complex with salicylic acid diacyl hydrazide (H₂L), [Cu₂(L)(Py)₄] (I), and the copper(II) trinuclear complex with diacyl dihydrazide of salicylic and glutaric acids (H₆L′), [Cu₃(L′)(Py)₄] · 2Py (II), are described. The exchange antiferromagnetic interactions between the paramagnetic centers with the exchange interaction parameter −2J = 119 cm⁻¹ for dimer I and 14 cm⁻¹ for trinuclear complex II are detected.     

Crystal Structures,Magnetic Properties and Catecholase‐Like Activities of μ‐Alkoxo‐μ‐Carboxylato Double Bridged Dinuclear and Tetranuclear Copper(II) Complexes

One μ‐alkoxo‐μ‐carboxylato bridged dinuclear copper(II) complex, [Cu₂(L¹)(μ‐C₆H₅CO₂)] ( 1 )(H₃L¹ = 1,3‐bis(salicylideneamino)‐2‐propanol)), and two μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear copper(II) complexes, [Cu₄(L¹)₂(μ‐C₈H₁₀O₄)(DMF)₂]·H₂O ( 2 ) and [Cu₄(L²)₂(μ‐C₅H₆O₄]·2H₂O·2CH₃CN ( 3 ) (H₃L² = 1,3‐bis(5‐bromo‐salicylideneamino)‐2‐propanol)) have been prepared and characterized. The single crystal X‐ray analysis shows that the structure of complex 1 is dimeric with two adjacent copper(II) atoms bridged by μ‐alkoxo‐μ‐carboxylato ligands where the Cu···Cu distances and Cu‐O(alkoxo)‐Cu angles are 3.5 11 Å and 132.8°, respectively. Complexes 2 and 3 consist of a μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear Cu(II) complex with mean Cu‐Cu distances and Cu‐O‐Cu angles of 3.092 Å and 104.2° for 2 and 3.486 Å and 129.9° for 3 , respectively. Magnetic measurements reveal that 1 is strong antiferromagnetically coupled with 2J =‐210 cm^?1 while 2 and 3 exhibit ferromagnetic coupling with 2J = 126 cm^?1 and 82 cm^?1 (averaged), respectively. The 2J values of 1–3 are correlated to dihedral angles and the Cu‐O‐Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ) catalyzed by 1–3 was studied. Complexes 1–3 exhibit catecholase‐like active at above pH 8 and 25 °C for oxidation of 3,5‐di‐tert‐butylcatechol.     

Binuclear Copper(II) Complexes with Robsori-Type Ligands. Synthesis,characterization, crystal structure,and magnetic properties

Three binuclear copper(II) complexes, [Cu₂(μ-L)(μ-N₃)](ClO₄)2′ 1-5 EtOH (1), [Cu₂(μ-L)(μ-MeO)(ClO₄)]-ClO₄ - EtOH ( 2 ) and [Cu₂(μ-L)(μ-C₃H₃N₂)](ClO₄)₂ · 2H₂O, ( 3 ) where L is the pentadentale bridging ligand derived from 5-(tert-butyl)-2-hydroxybenzene-1, 3-dicarbaldehyde bis(benzoylhydrazone) ( HL ) were synthesized and characterized. The crystal-structure determination of complex 2 provided the following crystal data: monoclinic, space group P2₁}/a, a = 11.412(2), b = 24.509(4), c = 14.833(4) Å, β = 104.41(2)°, K = 4018(3) ų, Z = 4. The structure shows that the Cu^II ions are bridged by the endogenous phenolato O-atom and by an exogenous bridge CH₃O^?. The analysis of variable-temperature magnetic susceptibility data (4-300 K.) indicates that there is an antiferromagnetic interaction between the Cu^II ions in these complexes with an exchange parameter (2J) of ?119.1 cm^?1 for complex 1 and ?361.8 cm^?1 for complex 3 . The effect of some exogenous bridging ligands on magnetic coupling for this type of complex is suggested.     

Structure and Magnetic Properties of a 2D Paddle‐wheel Dinuclear[Cu2] Cluster‐based Polymer with 1,1‐Cyclohexanediacetate Ligand

One new two‐dimensional (2D) Cu^II polymer [Cu(CHDA)(H₂O)]_n ( 1 ) was synthesized solvothermally based on 1,1‐cyclohexanediacetic acid (H₂CHDA) ligand. Single‐crystal X‐ray diffraction analysis reveals that 1 has a 2D framework structure consisting of paddle‐wheel dinuclear [Cu₂] cluster unit and CHDA^2– connector, which bears a 4‐connected sql network with Schläfli symbol of (4⁴.6²). Magnetic studies indicate the presence of strong antiferromagnetic coupling (J = –302 cm^–1) between the two Cu^II ions in the paddle‐wheel dicopper(II) entity.     

On the Controversial Fitting of Susceptibility Curves of Ferromagnetic CuII Cubanes: Insights from Theoretical Calculations

This paper reports a theoretical analysis of the electronic structure and magnetic properties of a tetranuclear Cu^II complex, [Cu₄(HL)₄], which has a 4+2 cubane‐like structure (H₃L=N,N′‐(2‐hydroxypropane‐1,3‐diyl)bis(acetylacetoneimine)). These theoretical calculations indicate a quintet (S=2) ground state; the energy‐level distribution of the magnetic states confirm Heisenberg behaviour and correspond to an S₄ spin–spin interaction model. The dominant interaction is the ferromagnetic coupling between the pseudo‐dimeric units (J₁=22.2 cm^?1), whilst a weak and ferromagnetic interaction is found within the pseudo‐dimeric units (J₂=1.4 cm^?1). The amplitude and sign of these interactions are consistent with the structure and arrangement of the magnetic Cu 3d orbitals; they accurately simulate the thermal dependence of magnetic susceptibility, but do not agree with the reported J values (J₁=38.4 cm^?1, J₂=?18.0 cm^?1) that result from the experimental fitting. This result is not an isolated case; many other polynuclear systems, in particular 4+2 Cu^II cubanes, have been reported in which the fitted magnetic terms are not consistent with the geometrical features of the system. In this context, theoretical evaluation can be considered as a valuable tool in the interpretation of the macroscopic behaviour, thus providing clues for a rational and directed design of new materials with specific properties.     

Syntheses,Crystal Structure,and Magnetic Properties of a Self‐assembling Dicopper(II) Helicate with Novel Bipyridine Ligand

A novel double helical dicopper(II) complex was synthesized by reaction of a polydentate ligand L = 2,2′‐bipyridyl‐6,6′‐bis(2‐acetylpyrazinohydrazone) with copper(II) perchlorate in CH₃CN. The self‐assembling process was studied by UV‐Vis spectrometric titration experiments which revealed the formation of dinuclear complexes [Cu₂L₂](ClO₄)₄. The structure of dicopper double‐helicate was confirmed by X‐ray diffractometry. Each copper(II) center occupies a distorted octahedral environment. Variable‐temperature magnetic measurements reveal weak antiferromagnetic interactions between Cu(II) ion centers with J = ?0.63 cm^?1.     

Ion‐Directed Coordinative Polymerization of Copper(II) Pyridyl‐Alcohol Complexes Through Thiane Functionalities

A mononuclear complex [Cu(HL · S)₂(NO₃)₂] ( 1 ) and a one‐ dimensional coordination polymer [Cu(HL · S)Cl₂]_n ( 2 ) [HL · S = 4‐(pyridin‐2‐ylmethyl)tetrahydro‐2H‐thiopyran‐4‐ol] showcase the structure‐directing role of the counterions in their formation reaction: monodentate ligation of NO₃^– and Cl^– induces an octahedral (with two HL · S per Cu in 1 ) or trigonal‐bipyramidal (with one HL · S per Cu in 2 ) Cu^II coordination environment. In contrast to 1 exhibiting no coordinative metal–sulfur bonds in the crystal lattice (space group P2₁/c), 2 (P2₁/c) features intermolecular Cu–S contacts of 2.3188(7) Å. The coordination compounds are thermally stable up to ca. 160 °C. Whereas 1 demonstrates the spin‐like behavior of an isolated central Cu^II ion, compound 2 exhibits weak antiferromagnetic intra‐chain coupling with J ≈ –2.1 cm^–1 between neighboring Cu^II ions.     

Different Metal Aggregation in Copper Acetate Chain Coordination Polymers with Dipyridyl Tethers Bearing Hydrogen Bonding Capable Functional Groups

Hydrothermal synthesis has afforded a pair of divalent copper acetate coordination polymers containing either 4, 4′‐dipyridylamine (dpa) or 4‐pyridylisonicotinamide (4‐pina), both of which hydrogen‐bonding capable central functional groups. X‐ray crystallography revealed that both exhibit a 1D chain dimensionality. Use of the kinked tethering ligand dpa produced [Cu(OAc)₂(dpa)]_n ( 1 ), which possesses a simple chain based on dpa linkage of isolated copper ions. On the other hand, employing the straighter amide ligand 4‐pina generated {[Cu(OAc)₂(4‐pina)] · 0.5H₂O}_n ( 2 ), which exhibits {Cu₂O₂} rhomboid dimers formed through bridging acetate ligands. Weak antiferromagnetic coupling [g = 1.984(3), J = –3.2(3) cm^–1] was observed within the axial‐equatorial bridged {Cu₂O₂} dimers in 2 , with possible ferrimagnetism due to spin canting below 11 K.