Double End‐On Azido Copper(II) Dinuclear Complex with Oxazoline Ligand: Synthesis,Structure, Magnetic Properties and Theoretical Study

A double azido‐bridged Cu^II dinuclear complex with the chelating chiral ligand, [Cu₂(L)₂(N₃)₄] ( 1 ) [L = (+)‐2, 2′‐isopropylidene‐bis((4R)‐4‐benzyl‐2‐oxazoline)] was synthesized and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, magnetic measurements, and theoretical studies. The asymmetric double end‐on azido bridges in complex 1 lead to a weak antiferromagnetic behavior with J = –7.4 cm^–1. The exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –8.0 cm^–1) is in good agreement with the experimental value.     

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.     

Diverse structures and magnetism of cobalt(II) and manganese(II) compounds with mixed azido and carboxylato bridges induced by methylpyridinium carboxylates

Herein we present a systematic study of the structures and magnetic properties of six coordination compounds with mixed azide and zwitterionic carboxylate ligands, [M(N₃)₂(2‐mpc)] (2‐mpc=N‐methylpyridinium‐2‐carboxylate; M=Co for 1 and Mn for 2 ), [M(N₃)₂(4‐mpc)] (4‐mpc=N‐methylpyridinium‐4‐carboxylate; M=Co for 3 and Mn for 4 ), [Co₃(N₃)₆(3‐mpc)₂(CH₃OH)₂] ( 5 ), and [Mn₃(N₃)₆(3‐mpc)₂] ( 6 ; 3‐mpc=N‐methylpyridinium‐3‐carboxylate). Compounds 1 – 3 consist of one‐dimensional uniform chains with (μ‐EO‐N₃)₂(μ‐COO) triple bridges (EO=end‐on); 5 is also a chain compound but with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple and [(EO‐N₃)₂] double bridges; Compound 4 contains two‐dimensional layers with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple, [(μ‐EO‐N₃)(μ‐COO)] double, and (EE‐N₃) single bridges (EE=end‐to‐end); 6 is a layer compound in which chains similar to those in 5 are cross‐linked by a μ₃‐1,1,3‐N₃ azido group. Magnetically, the three Co^II compounds ( 1 , 3 , and 5 ) all exhibit intrachain ferromagnetic interactions but show distinct bulk properties: 1 displays relaxation dynamics at very low temperature, 3 is an antiferromagnet with field‐induced metamagnetism due to weak antiferromagnetic interchain interactions, and 5 behaves as a noninnocent single‐chain magnet influenced by weak antiferromagnetic interchain interactions. The magnetic differences can be related to the interchain interactions through π–π stacking influenced by different substitution positions in the ligands and/or different magnitudes of intrachain coupling. All of the Mn^II compounds show overall intrachain/intralayer antiferromagnetic interactions. Compound 2 shows the usual one‐dimensional antiferromagnetism, whereas 4 and 6 exhibit different weak ferromagnetism due to spin canting below 13.8 and 4.6 K, respectively.     

Two Diammonium Copper Azides with Similar Layerlike Magnetic Substructures Made of Chains of Serially Connected Cu6 Rings Show Cation‐Modulated Magnetism

We present here the first examples of Cu–azide compounds synthesized by using protonated diamine ions as cationic templates: (dmenH₂)[Cu₆(N₃)₁₄] and (trimenH₂)[Cu₆(N₃)₁₄] (dmenH₂²⁺: N,N′‐dimethylethylenediammonium; trimenH₂²⁺: N,N,N′‐trimethylethylenediammonium). Both compounds possess a similar, rarely observed anionic Cu–azide layer, which consists of [Cu₆(N₃)₁₄^2?]_n anionic chains linked by asymmetric end‐to‐end azido bridges. The chain, in turn, is made up of elongated Cu₆ rings, with double and single end‐on azido linkages between the square‐planar Cu²⁺ sites within the ring and double end‐on azido bridges serially connecting the rings. The molecular geometry results in ferromagnetic interactions within the Cu–azide layer in both compounds. The interlayer separations are determined by the cations, with the shortest interlayer Cu???Cu separations being 8.016 Å for the dmenH₂²⁺ compound and 9.106 Å for the trimenH₂²⁺ compound. These different interlayer separations tune the magnetic properties of the two materials. The dmenH₂²⁺ compound displays long‐range antiferromagnetic ordering at lowtemperature and short‐range ferromagnetic interaction at high temperature, while only short‐range ferromagnetism was observed in the trimenH₂²⁺compound at 2–300 K.     

Synthesis,Structure, and Magnetic Properties of a Random Bimetallic One‐dimensional CoII‐MnII Coordination Polymer with Mixed Azide‐carboxylate Bridges

The 3d–3d random bimetallic compound [Co_2.28Mn_0.72(N₃)₆(mpc‐3)₂(CH₃OH)₂] ( 1 ) (mpc‐3 = N‐methylpyridinium‐3‐carboxylate) was synthesized by partly substituting the Co^II ions in the homometallic compound by Mn^II. Complex 1 was structurally and magnetically characterized. It consists of one‐dimensional chains with the neighboring metal ions being linked alternatively by [(μ‐EO‐N₃)₂(μ‐COO)] (EO = end‐on) triple bridges and double EO azide bridges. Hydrogen‐bonding interactions and π–π interactions are involved in the formation of a three‐dimensional supramolecular network. Magnetic measurements revealed that complex 1 exhibits slow relaxation, which is similar to the homometallic Co^II parent compound whereas the T_B is lower than that of the Co^II analog.     

Copper(II) Halide Complexes with 1‐tert‐Butyl‐1H‐1,2,4‐triazole and 1‐tert‐Butyl‐1H‐tetrazole

1‐tert‐Butyl‐1H‐1,2,4‐triazole (tbtr) was found to react with copper(II) chloride or bromide to give the complexes [Cu(tbtr)₂X₂]_n and [Cu(tbtr)₄X₂] (X = Cl, Br). 1‐tert‐Butyl‐1H‐tetrazole (tbtt) reacts with copper(II) bromide resulting in the formation of the complex [Cu₃(tbtt)₆Br₆]. The obtained crystalline complexes as well as free ligand tbtr were characterized by elemental analysis, IR spectroscopy, thermal and X‐ray analyses. For free ligand tbtr, ¹H NMR and ¹³C NMR spectra were also recorded. In all the complexes, tbtr and tbtt act as monodentate ligands coordinated by Cu^II cations via the heteroring N⁴ atoms. The triazole complexes [Cu(tbtr)₂Cl₂]_n and [Cu(tbtr)₂Br₂]_n are isotypic, being 1D coordination polymers, formed at the expense of single halide bridges between neighboring copper(II) cations. The isotypic complexes [Cu(tbtr)₄Cl₂] and [Cu(tbtr)₄Br₂] reveal mononuclear centrosymmetric structure, with octahedral coordination of Cu^II cations. The tetrazole compound [Cu₃(tbtt)₆Br₆] is a linear trinuclear complex, in which neighboring copper(II) cations are linked by single bromide bridges.     

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).     

Direct Synthesis and Characterization of New Copper(II) and Zinc(II) 5‐R‐Tetrazolato Complexes [R = Me,Ph, 4‐Py] with Ethylenediamine and DMSO as Coligands

Three novel 5‐R‐tetrazolato complexes (R = Me, Ph, 4‐Py), namely [Zn₂(MeCN₄)₄(DMSO)₂] ( 1 ), [Cu₂(PhCN₄)₄(en)₂] · 2DMSO ( 2 ), and [Cu(4‐PyCN₄)₂(DMSO)₂] · 4DMSO ( 3 ), were isolated as unexpected products under attempts to prepare heterometallic tetrazolates using a direct synthesis strategy in the Cu⁰‐ZnO‐en‐RCN₄H‐DMSO system (en = ethylenediamine). The prepared compounds were characterized by elemental, single‐crystal X‐ray, and thermal analyses, and IR spectroscopy. Variation of the 5‐substituent of the tetrazole ring causes different composition of complexes 1 – 3 and diverse coordination modes of 5‐R‐tetrazolato ligands. Complex 1 is a 3D coordination polymer due to N1, N4‐bridging of 5‐methyltetrazolato anions. Complex 2 , with en as a coligand, has a dinuclear structure with two copper atoms linked together by two 5‐phenyltetrazolato ligands by tetrazole N2, N3 bridges. Complex 3 represents a 2D coordination polymer, formed due to 5‐(4‐pyridyl)tetrazolato bridges between adjacent copper atoms (with the tetrazole and pyridine rings nitrogen atoms as coordination centers). DMSO molecules, included in all the compounds, are solvate and/or coordinated ones.     

A tetrazol‐5‐yl analogue of glycine, 5‐ammoniomethyl‐1H‐tetrazolide,and its copper(II) complex

A nonclassical tetrazole isostere of glycine, viz. zwitterionic 5‐ammoniomethyl‐1H‐tetrazolide, C₂H₅N₅, (I), crystallizes in the chiral P3₁ space group, similar to γ‐glycine. The crystal packing of (I) is determined by a set of classical hydrogen bonds, forming a three‐dimensional network that is practically the same as that in γ‐glycine. The Cu^II complex of (I), poly[[bis(μ₂‐5‐aminomethyl‐1H‐tetrazolido‐κ³N¹,N⁵:N⁴)copper(II)] dihydrate], {[Cu(C₂H₄N₅)₂]·2H₂O}_n, (II), is a layered coordination polymer formed as a result of tetrazole ring bridges. The Cu^II cations lie on inversion centres, are surrounded by four anions and adopt elongated octahedral coordination. Water molecules are located in the interlayer space and connect the layers into a three‐dimensional network via a system of hydrogen bonds.     

Syntheses,Structures, and Electrochemical Properties of Two Bis‐triazole‐bis‐amide‐based Copper(II) Pyridine‐2,3‐dicarboxylate Coordination Polymers

Abstract. Two bis‐triazole‐bis‐amide‐based copper(II) pyridine‐2,3‐dicarboxylate coordination polymers (CPs), [Cu(2,3‐pydc)(dtb)_0.5(DMF)] · 2H₂O ( 1 ) and [Cu(2,3‐pydc)(dth)_0.5(DMF)] · 2H₂O ( 2 ) (2,3‐H₂pydc = pyridine‐2,3‐dicarboxylic acid, dtb = N,N′‐bis(4H‐1,2,4‐triazole)butanamide, and dth = N,N′‐bis(4H‐1,2,4‐triazole)hexanamide), were synthesized under solvothermal conditions. CPs 1 and 2 show similar two‐dimensional (2D) structures. In 1 , the 2,3‐pydc anions bridge the Cu^II ions into a one‐dimensional (1D) chain. Such 1D chains are linked by the dtb ligands to form a 2D layer. The adjacent 2D layers are extended into a three‐dimensional (3D) supramolecular architecture by hydrogen‐bonding interactions. The electrochemical properties of 1 and 2 were investigated.     

Structure and magnetic properties of a copper(II) coordination polymer based on azide,pyridine and homophthalic acid

The azide anion is a short bridging ligand that has been used extensively to construct magnetic coordination polymers, and fundamental magneto‐structural correlations have been substantiated by theoretical calculations. The copper(II) coordination polymer poly[bis(μ‐azido‐κ²N¹:N¹)(μ₄‐homophthalato‐κ⁴O:O′:O′′:O′′′)bis(pyridine‐κN)dicopper(II)], [Cu₂(C₉H₆O₄)(N₃)₂(C₅H₅N)₂]_n, was synthesized from homophthalic acid (2‐carboxyphenylacetic acid), pyridine and azide (N₃⁻) by a hydrothermal reaction. Single‐crystal structure analysis indicated that it features a one‐dimensional chain structure which is comprised of (μ_1,1‐N₃⁻)(μ‐syn–syn‐COO⁻)₂‐ and (μ_1,1‐N₃⁻)₂‐bridged tetranuclear Cu^II units. Magnetic measurements revealed that the compound exhibits dominant antiferromagnetic behaviour.     

Designing a heterotrinuclear CuII—NiII—CuII complex from a mononuclear CuII Schiff base precursor with dicyanamide as a coligand: synthesis,crystal structure,thermal and photoluminescence properties

Schiff bases are considered `versatile ligands' in coordination chemistry. The design of polynuclear complexes has become of interest due to their facile preparations and varied synthetic, structural and magnetic properties. The reaction of the `ligand complex' [CuL] {H₂L is 2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenol} with Ni(OAc)₂·4H₂O (OAc is acetate) in the presence of dicyanamide (dca) leads to the formation of bis(dicyanamido‐1κN¹)bis(dimethyl sulfoxide)‐2κO,3κO‐bis{μ‐2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenolato}‐1:2κ⁶O,O′:O,N,N′,O′;1:3κ⁶O,O′:O,N,N′,O′‐dicopper(II)nickel(II), [Cu₂Ni(C₁₇H₁₆N₂O₂)₂(C₂N₃)₂(C₂H₆OS)₂]. The complex shows strong absorption bands in the frequency region 2155–2269 cm⁻¹, which clearly proves the presence of terminal bonding dca groups. A single‐crystal X‐ray study revealed that two [CuL] units coordinate to an Ni^II atom through the phenolate O atoms, with double phenolate bridges between Cu^II and Ni^II atoms. Two terminal dca groups complete the distorted octahedral geometry around the central Ni^II atom. According to differential thermal analysis–thermogravimetric analysis (DTA–TGA), the title complex is stable up to 423 K and thermal decomposition starts with the release of two coordinated dimethyl sulfoxide molecules. Free H₂L exhibits photoluminescence properties originating from intraligand (π–π*) transitions and fluorescence quenching is observed on complexation of H₂L with Cu^II.     

A novel tetrazolate‐ and cyanide‐bridged three‐dimensional heterometallic coordination polymer: crystal structure,thermal stability and magnetic properties

By using environmentally friendly K₃[Co(CN)₆] as a cyanide source, the solvothermal reaction of CuCl₂ and tetrazole (Htta) led to a novel tetrazolate‐ and cyanide‐bridged three‐dimensional heterometallic Cu^II–Co^III complex, namely poly[[hexa‐μ₂‐cyanido‐κ¹²C :N‐pentakis(μ₃‐tetrazolato‐κ³N ¹:N ²:N ⁴)cobalt(III)tetracopper(II)] monohydrate], {[Co^IIICu^II₄(CHN₄)₅(CN)₆]·H₂O}_n , (I). The crystal structure analysis reveals that it is the first example of a (6,8,8)‐connected three‐dimensional framework with a unique topology, constructed from anionic [Co(CN)₆]³⁻ and cationic [(Cu1)₂(tta)₂]²⁺ and [(Cu2Cu3)(tta)₃]⁺ units through μ₂‐cyanide and μ₃‐tetrazolate linkers. The compound was further characterized by thermal analysis, vibrational spectroscopy (FT–IR), scanning electron microscopy/energy‐dispersive X‐ray spectroscopy (SEM–EDS) and magnetic measurements. The magnetic investigation indicates that the complex exhibits antiferromagnetic coupling between adjacent Cu^II cations.     

(2‐Aminopyrimidine‐κN1)aqua(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)copper(II): X‐ray and DFT calculated structure

In the title compound, [Cu(C₇H₃N₂O₄)(C₄H₅N₂)(H₂O)], (I), pyridine‐2,6‐dicarboxylate (pydc²⁻), 2‐aminopyrimidine and aqua ligands coordinate the Cu^II centre through two N atoms, two carboxylate O atoms and one water O atom, respectively, to give a nominally distorted square‐pyramidal coordination geometry, a common arrangement for copper complexes containing the pydc²⁻ ligand. Because of the presence of Cu...X_bridged contacts (X = N or O) between adjacent molecules in the crystal structures of (I) and three analogous previously reported compounds, and the corresponding uncertainty about the effective coordination number of the Cu^II centre, density functional theory (DFT) calculations were used to elucidate the degree of covalency in these contacts. The calculated Wiberg and Mayer bond‐order indices reveal that the Cu...O contact can be considered as a coordination bond, whereas the amine group forming a Cu...N contact is not an effective participant in the coordination environment.     

Poly[diaquabis(μ‐4,4′‐bipyridine‐κ2N:N′)bis(ethane‐1,2‐diol)di‐μ‐sulfato‐dicopper(II)]

The title compound, [Cu₂(SO₄)₂(C₁₀H₈N₂)₂(C₂H₆O₂)₂(H₂O)₂]_n, contains two crystallographically unique Cu^II centres, each lying on a twofold axis and having a slightly distorted octahedral environment. One Cu^II centre is coordinated by two bridging 4,4′‐bipyridine (4,4′‐bipy) ligands, two sulfate anions and two aqua ligands. The second is surrounded by two 4,4′‐bipy N atoms and four O atoms, two from bridging sulfate anions and two from ethane‐1,2‐diol ligands. The sulfate anion bridges adjacent Cu^II centres, leading to the formation of linear ...Cu1–Cu2–Cu1–Cu2... chains. Adjacent chains are further bridged by 4,4′‐bipy ligands, which are also located on the twofold axis, resulting in a two‐dimensional layered polymer. In the crystal structure, extensive O—H...O hydrogen‐bonding interactions between water molecules, ethane‐1,2‐diol molecules and sulfate anions lead to the formation of a three‐dimensional supramolecular network structure.     

Cu3(CN)4(NH3)2Hg(CN)2: a novel inter­penetrating framework formed from CuI,CuII, HgII and cyanide bridges

The title compound, poly[diammine­hexa‐μ‐cyano‐di­copper(I)­copper(II)­mercury(II)], [Cu₃Hg(CN)₆(NH₃)₂]_n, has a novel threefold‐inter­penetrating structure of three‐dimensional frameworks. This three‐dimensional framework consists of two‐dimensional network Cu₃(CN)₄(NH₃)₂ complexes and rod‐like Hg(CN)₂ complexes. The two‐dimensional network complex contains trigonal–planar Cu^I (site symmetry m) and octa­hedral Cu^II (site symmetry 2/m) in a 2:1 ratio. Two types of cyanide group form bridges between three coordination sites of Cu^I and two equatorial sites of Cu^II to form a two‐dimensional structure with large hexa­gonal windows. One type of CN⁻ group is disordered across a center of inversion, while the other resides on the mirror plane. Two NH₃ mol­ecules (site symmetry 2) are located in the hexa­gonal windows and coordinate to the remaining equatorial sites of Cu^II. Both N atoms of the rod‐like Hg(CN)₂ group (Hg site symmetry 2/m and CN⁻ site symmetry m) coordinate to the axial sites of Cu^II. This linkage completes the three‐dimensional framework and penetrates two hexa­gonal windows of two two‐dimensional network complexes to form the threefold‐inter­penetrating structure.     

Four‐ and five‐coordinate copper(II) complexes with N‐(4,4‐diphenyl‐5‐oxo‐4,5‐dihydro‐1H‐imidazol‐2‐yl)glycine

The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂]·2C₃H₇NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂(H₂O)]·2C₃H₇NO, (II). In (I), the Cu^II ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the Cu^II ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks.     

A two‐dimensional mixed‐valence CuII/CuI coordination polymer constructed from 2‐(pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylate

Coordination polymers are a thriving class of functional solid‐state materials and there have been noticeable efforts and progress toward designing periodic functional structures with desired geometrical attributes and chemical properties for targeted applications. Self‐assembly of metal ions and organic ligands is one of the most efficient and widely utilized methods for the construction of CPs under hydro(solvo)thermal conditions. 2‐(Pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylate (HPIDC²⁻) has been proven to be an excellent multidentate ligand due to its multiple deprotonation and coordination modes. Crystals of poly[aquabis[μ₃‐5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylato‐κ⁵N¹,O⁵:N³,O⁴:N²]copper(II)dicopper(I)], [Cu^IICu^I₂(C₁₀H₅N₃O₄)₂(H₂O)]_n, (I), were obtained from 2‐(pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PIDC) and copper(II) chloride under hydrothermal conditions. The asymmetric unit consists of one independent Cu^II ion, two Cu^I ions, two HPIDC²⁻ ligands and one coordinated water molecule. The Cu^II centre displays a square‐pyramidal geometry (CuN₂O₃), with two N,O‐chelating HPIDC²⁻ ligands occupying the basal plane in a trans geometry and one O atom from a coordinated water molecule in the axial position. The Cu^I atoms adopt three‐coordinated Y‐shaped coordinations. In each [CuN₂O] unit, deprotonated HPIDC²⁻ acts as an N,O‐chelating ligand, and a symmetry‐equivalent HPIDC²⁻ ligand acts as an N‐atom donor via the pyridine group. The HPIDC²⁻ ligands in the polymer serve as T‐shaped 3‐connectors and adopt a μ₃‐κ²N,O:κ²N′,O′:κN′′‐coordination mode, linking one Cu^II and two Cu^I cations. The Cu cations are arranged in one‐dimensional –Cu1–Cu2–Cu3– chains along the [001] direction. Further crosslinking of these chains by HPIDC²⁻ ligands along the b axis in a –Cu2–HPIDC²⁻–Cu3–HPIDC²⁻–Cu1– sequence results in a two‐dimensional polymer in the (100) plane. The resulting (2,3)‐connected net has a (12³)₂(12)₃ topology. Powder X‐ray diffraction confirmed the phase purity for (I), and susceptibilty measurements indicated a very weak ferromagnetic behaviour. A thermogravimetric analysis shows the loss of the apical aqua ligand before decomposition of the title compound.     

The coordination chemistry of two symmetric double‐armed oxadiazole‐bridged organic ligands with copper salts

Two new symmetric double‐armed oxadiazole‐bridged ligands, 4‐methyl‐{5‐[5‐methyl‐2‐(pyridin‐3‐ylcarbonyloxy)phenyl]‐1,3,4‐oxadiazol‐2‐yl}phenyl pyridine‐3‐carboxylate (L1) and 4‐methyl‐{5‐[5‐methyl‐2‐(pyridin‐4‐ylcarbonyloxy)phenyl]‐1,3,4‐oxadiazol‐2‐yl}phenyl pyridine‐4‐carboxylate (L2), were prepared by the reaction of 2,5‐bis(2‐hydroxy‐5‐methylphenyl)‐1,3,4‐oxadiazole with nicotinoyl chloride and isonicotinoyl chloride, respectively. Ligand L1 can be used as an organic clip to bind Cu^II cations and generate a molecular complex, bis(4‐methyl‐{5‐[5‐methyl‐2‐(pyridin‐3‐ylcarbonyloxy)phenyl]‐1,3,4‐oxadiazol‐2‐yl}phenyl pyridine‐3‐carboxylate)bis(perchlorato)copper(II), [Cu(ClO₄)₂(C₂₈H₂₀N₄O₅)₂], (I). In compound (I), the Cu^II cation is located on an inversion centre and is hexacoordinated in a distorted octahedral geometry, with the pyridine N atoms of two L1 ligands in the equatorial positions and two weakly coordinating perchlorate counter‐ions in the axial positions. The two arms of the L1 ligands bend inward and converge at the Cu^II coordination point to give rise to a spirometallocycle. Ligand L2 binds Cu^I cations to generate a supramolecule, diacetonitriledi‐μ₃‐iodido‐di‐μ₂‐iodido‐bis(4‐methyl‐{5‐[5‐methyl‐2‐(pyridin‐4‐ylcarbonyloxy)phenyl]‐1,3,4‐oxadiazol‐2‐yl}phenyl pyridine‐4‐carboxylate)tetracopper(I), [Cu₄I₄(CH₃CN)₂(C₂₈H₂₀N₄O₅)₂], (II). The asymmetric unit of (II) indicates that it contains two Cu^I atoms, one L2 ligand, one acetonitrile ligand and two iodide ligands. Both of the Cu^I atoms are four‐coordinated in an approximately tetrahedral environment. The molecule is centrosymmetric and the four I atoms and four Cu^I atoms form a rope‐ladder‐type [Cu₄I₄] unit. Discrete units are linked into one‐dimensional chains through π–π interactions.     

Mixed‐ligand MnII and CuII complexes with alternating 2,2′‐bipyrimidine and terephthalate bridges

The novel polymeric complexes catena‐poly[[diaquamanganese(II)]‐μ‐2,2′‐bipyrimidine‐κ⁴N¹,N^1′:N³,N^3′‐[diaquamanganese(II)]‐bis(μ‐terephthalato‐κ²O¹:O⁴)], [Mn₂(C₈H₄O₄)₂(C₈H₆N₄)(H₂O)₄]_n, (I), and catena‐poly[[[aquacopper(II)]‐μ‐aqua‐μ‐hydroxido‐μ‐terephthalato‐κ²O¹:O^1′‐copper(II)‐μ‐aqua‐μ‐hydroxido‐μ‐terephthalato‐κ²O¹:O^1′‐[aquacopper(II)]‐μ‐2,2′‐bipyrimidine‐κ⁴N¹,N^1′:N³,N^3′] tetrahydrate], {[Cu₃(C₈H₄O₄)₂(OH)₂(C₈H₆N₄)(H₂O)₄]·4H₂O}_n, (II), containing bridging 2,2′‐bipyrimidine (bpym) ligands coordinated as bis‐chelates, have been prepared via a ligand‐exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht²⁻) anions were found. In (I), two tpht²⁻ anions acting as bis‐monodentate ligands bridge the Mn^II centres in a parallel fashion. In (II), the tpht²⁻ anions act as endo‐bridges and connect two Cu^II centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn₂(tpht)₂(bpym)(H₂O)₄] entity in (I) and the trinuclear [Cu₃(tpht)₂(OH)₂(bpym)(H₂O)₄]·4H₂O coordination entity in (II) build up one‐dimensional polymeric chains along the b axis. In (I), the Mn^II cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central Cu^II cation is also on a special position (site symmetry ). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face‐to‐face π–π interactions [in (I)], forming three‐dimensional metal–organic frameworks. The Mn^II cation in (I) has a trigonally deformed octahedral geometry, whereas the Cu^II cations in (II) are in distorted octahedral environments. The Cu^II polyhedra are inclined relative to each other and share common edges.