SYNTHESIS AND CRYSTAL STRUCTURE OF OXAMIDATO-BRIDGED BINUCLEAR COPPER(II) COMPLEXES

Abstract

The compounds [Cu(oxpn)] (1), [(bpy)(H₂O)Cu(μ-cis-oxpn)Cu(H₂O)] · 2NO₃ · 2H₂O (2) and [(Him)(NO₃)Cu(μ-trans-oxpn)Cu(Him)(NO₃)] (3), where oxpn is the dianion of N,N′-bis(3-aminopropyl)oxamide, bpy is bipyridine and Him is imidazole, were prepared and characterized by elemental analysis and IR spectra. Complex (2) was also studied by thermochemical analysis and its structure determined by X-ray crystallography. The structure of complex (2) consists of binuclear copper(II) molecules in which the copper(II) atoms are bridged by an oxamidato group in the cis conformation resulting a copper-copper distance of 5.21 Å. Both copper(II) ions are in square-pyramidal surroundings with almost coplanar basal planes and a water molecule occupying the apical positions. The N atoms of the oxamidato moiety are trigonal. Two lattice water molecules together with the two coordinated ones hydrogen bond with nitrate ions.     

Syntheses and crystal structures of copper(II) complexes derived from 2,4,6-tris(2-pyridyl)-1,3,5-triazine

Treatment of freshly precipitated Cu(OH)₂?·?xH₂O and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) with oxalic and malonic acids in methanol-water at room temperature gave [Cu(tptz)(C₂O₄)(H₂O)]?·?4H₂O (1) and [Cu(pma)(C₃H₂O₄)(H₂O)]?·?H₂O (2) (pma?=?2-aminocarbonylpyridine), respectively. Reaction in the absence of any acid resulted in [Cu(bpca)(tca)]?·?2H₂O (3) (bpca?=?bis(2-pyridylcarbonyl)amide anion; tca?=?2-pyridinecarboxylate anion). Complex 1 consists of [Cu(tptz)(C₂O₄)(H₂O)] and lattice H₂O molecules; the tridentate tptz ligand, bidentate oxalate dianion and an aqua ligand are bound to Cu with distorted octahedral geometry. Complex 2 is composed of [Cu(pma)(C₃H₂O₄)(H₂O)] and lattice H₂O molecules; the bidentate 2-aminocarbonylpyridine ligand, a bidentate malonate dianion and an aqua ligand are coordinated to Cu with a slightly distorted square pyramidal geometry. Complex 3 consists of [Cu(bpca)(tca)] and lattice H₂O molecules. Square pyramidally coordinated Cu atoms are surrounded by tridentate bpca with nitrogen donor atoms and a bidentate 2-pyridinecarboxylate anion.     

Synthesis and magnetic properties of binuclear cobalt(Ⅱ), nickel(Ⅱ) and copper(Ⅱ) complexes bridged by oxamidate group

Four binuclear Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes bridged by oxamidate (oxd) group have been synthesized, namely Co2(byp)2(oxd)(ClO4)2 (1), Co2(Me2bpy)2(oxd)(ClO4)2.H2O (2), Ni2(bpy)2(oxd)(ClO4)2.2H2O (3) and Cu2(Me2bpy)2(oxd)(NO3)2 (4). (bpy=2,2'-bipyridyl, Me2-bpy=4,4'-dimethylbipyridyl, oxd=oxamidate) The complexes are characterized by IR, UV spectra, EPR and variable-temperature magnetic susceptibility (4-300 K). The susceptibility data for. complexes 1 and 3 were least-squares fit to the susceptibility equation derived from the spin Hamiltonian H=-2J . S1 . S2. The exchange integral, J, was found to be equal to -3.62 cm-1 in 1 and -1.82 cm-1 in 3. This indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

Synthesis,structure and properties of a binuclear complex {[Mn(bpy)2(CuL)(H2O)2](ClO4)2} and its CuL precursor (H2L = 2,3-dioxo-5,6 : 14,15-dichlorobenzo-7,13-diphenyl-1,4,8,12-tetraazacyclo-pentadeca-7,12-diene)

A binuclear complex {[Mn(bpy)₂(CuL)(H₂O)₂](ClO₄)₂} (2) and its CuL (1) precursor (H₂L?=?2,3-dioxo-5,6?:?14,15-dichlorobenzo-7,13-diphenyl-1,4,8,12-tetraazacyclo-pentadeca-7,12-diene; bpy?=?2,2′-dipyridyl) have been synthesized and characterized structurally. Complex 1 consists of the neutral [CuL] fragments and methanol molecules. In complex 2, [Mn(bpy)₂(CuL)]²⁺ cation, two water molecules and two perchloric anions make up of the crystal. Mn(II) is coordinated by four nitrogen atoms from two 2,2′-dipyridyl and two oxygen atoms from the Cu(II) precursor. Magnetic characterization of 2 exhibits an antiferromagnetic interaction between Cu(II) and Mn(II) ions, with J?=??74.1?cm^?1.     

Syntheses and characterization of nickel(II), zinc(II) and palladium(II) complexes derived from three pyrazole-based polydentate ligands

Two pyrazole-based polydentate ligands, 1,3-bis(5-methyl-3-phenylpyrazol-1-yl)-propan-2-ol (Hmppzpo) and 1,3-bis(5-methyl-3-p-isopropylphenylpyrazol-1-yl)-propan-2-ol (Hmcpzpo), have been synthesized. A third ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (Hdmpzpo), has been synthetically modified. Seven new M(II) coordination compounds of general formula M₂L₂X₂ (M?=?Zn, Ni; X?=?NO₃ or ClO₄; L?=?dmpzpo, mppzpo or mcpzpo) or MLX (M?=?Pd; L?=?dmpzpo; X?=?Cl) were synthesized and structurally characterized by elemental analysis and FT-IR analysis. The crystal structures of [Zn₂(μ-dmpzpo-O,N,N′)₂(NO₃)₂]?·?2H₂O (1?·?2H₂O), [Ni₂(μ-dmpzpo-O,N,N′)₂(CH₃CN)₂](ClO₄)₂ (2) and Pd(μ-dmpzpo-N,N′)Cl₂ (4) were determined by single-crystal X-ray crystallography. The crystal structures show that complexes 1?·?2H₂O and 2 are center-symmetric dinuclear compounds, with two metal ions bridged by two alkoxo groups and each metal ion with a distorted square-pyramidal environment. The palladium complex, 4, displayed square-planar coordination geometry around the Pd(II) ion with trans arrangement.     

Synthesis and Crystal Structure of a Fumaratocopper(II) Complex with Bipyridine

The title complex [Cu₂(C₄H₂O₄)₂(bipy)₂(H₂O)₃] · 3H₂O (bipy = 2,2'-bipyridine) was prepared and its crystal structure determined by X-ray diffraction methods. Both Cu(II) atoms of the binuclear complex assume square pyramidal coordination. The fumarate groups display different coordination modes. One fumarate group bridges two Cu(II) ions to form a binuclear complex while another fumarate group terminally coordinates to a Cu(II) atom with one carboxyl group free from coordination. The terminally coordinated fumarate showed unusual disorder, which may be due to an intermolecular H-bonding interaction. Close stacking of bipy rings is observed as verified by the distance of 3.46 Å between parallel ring planes. IR spectra were assigned based on the molecular structure.     

Synthesis and crystal structure of heteronuclear La( III )‐Cu(II ) complex { [LaCu2(NTA)2(4,4′‐bpy)(H2O)3]NO3·5H2O}n

A novel La( III )‐Cu( II ) heterometallic coordination polymer {[LaCu₂(NTA)₂(4,4′‐bpy)(H₂O)₃]NO₃·5H₂O]_n, where H₃NTA denotes nitrilotriacetic acid and 4,4′‐bpy denotes 4, 4‐bipyridine, was synthesized and characterized by IR spectrum, elemental analysis and X‐ray diffraction. The complex crystallizes in the triclinic space group Pi with cell parameters a = 1.33710(10) nm, b = 1,44530(10) nm, c =1.0949(2) nm, α = 71.905(7)°, β = 74.327(7)°, γ = 64.427(9)°, V = 1.7912(4) nm³and Z = 2. It consists of heterometallic units, in which each La( II ) ion is coordinated in a distorted monocapped square antiprism by three oxygen atoms from water molecules and six carboxyl oxygen atoms from five NTA^3? ions, and each Cu( I ) ion is coordinated by one nitrogen atom from 4,4′‐bpy and one nitrogen atom, three oxygen atoms from NTA^3?. In the title complex, La( I ) ions and Cu( II ) ions are connected by the heterometallic bridging of NTA^3?, constructing a two‐dimensional network structure along the [110]. And it is extended into an infinite three‐dimensional network structure by the formation of homometallic bridging of Cu‐4, 4′‐bpy‐Cu, exhibiting a certain inclusion ability.     

Ligand assembly and metal ion complexation: syntheses and X-ray structures of Ni(II) and Cu(II) benzoate and 4-tert-butylbenzoate complexes of cyclam

The syntheses and X-ray structures of trans-[Ni(O-benzoato)₂(cyclam)], trans-[Cu(H₂O)₂(cyclam)]-(benzoate)₂·2H₂O and trans-[Cu(H₂O)₂(cyclam)](4-t-butyl-benzoate)₂ (where cyclam is 1,4,8,11-tetraazacyclotetradecane) are described. The nickel complex has a tetragonally distorted octahedral coordination geometry with cyclam occupying the equatorial plane in a stable trans-III arrangement, with benzoate ligands filling the axial positions. The structure closely resembles the arrangement in the previously described hydrogen-bonded (metal-free) ligand assembly [(cyclamH₂)·(4-t-butyl benzoate)₂]·2(benzoic acid) if the latter benzoic acid moieties, which do not interact directly with the cyclam moiety, are ignored. The 2?:?1 fragment thus may be viewed as a ligand assembly “preorganized” for nickel ion complexation. In contrast to the nickel structure, the two trans-axial sites in both copper structures are occupied by aqua rather than O-carboxylate ligands. Although they do not form part of the inner coordination sphere in either complex, the two carboxylate anions remain hydrogen bound to the (coordinated) cyclam ligand, with the mode of packing being generally similar in each complex.     

Copper(II), Cobalt(II), and Nickel(II) Complexes of two Novel Pyridine‐derived Macrocyclic Ligands bearing o‐ and pNitrobenzyl Pendant Groups

The pendant‐armed ligands L¹ and L² were synthesized by N‐alkylation of the four secondary amine groups of the macrocyclic precursor L using o‐nitrobenzylbromide (L¹) and p‐nitrobenzylbromide (L²). Nitrates and perchlorates of Cu^II, Ni^II and Co^II were used to synthesize the metal complexes of both ligands and the complexes were characterized by microanalysis, MS‐FAB, conductivity measurements, IR and UV‐Vis spectroscopy and magnetic studies. The crystal structures of L¹, [CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN, [CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH and [NiL²](ClO₄)₂·3CH₃CN·H₂O were determined by single crystal X‐ray crystallography. These structural analysis reveal the free ligand L¹, three mononuclear endomacrocyclic complexes {[CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN and [NiL²](ClO₄)₂·3CH₃CN·H₂O} and one binuclear complex {[CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH} in which one of the metals is in the macrocyclic framework and the other metal is outside the ligand cavity and coordinated to four nitrate ions.     

Low‐dimensional compounds containing cyano groups. II. catena‐Poly[[(2,2′‐bipyridine‐κ2N:N′)(dicyanamido‐κN)copper(II)]‐μ‐dicyanamido‐κ2N:N′]

The crystal structure of the title compound, [Cu(C₂N₃)₂(C₁₀H₈N₂)]_n, is formed by neutral zigzag chains of the [–NC–N–CN–Cu{(bpy)N(CN)₂}–NC–N–CN–] type run­ning along the c axis (bpy is 2,2′‐bi­pyridine). The Cu atoms in the chains are pentacoordinated in the form of a distorted tetragonal pyramid, with a CuN₅ chromophore. The coordination sites are occupied by two N atoms of one bpy mol­ecule in the basal plane [Cu—N 2.018 (4) and 2.025 (2) Å] and by three terminal N atoms of two dicyan­amide ligands. One of the dicyan­amide ligands is coordinated in a monodentate fashion through a nitrile N atom in the basal plane [Cu—N 1.963 (4) Å]. The second acts as an end‐to‐end bridging ligand to a neighbouring Cu atom and is coordinated by one nitrile N atom in the basal plane [Cu—N 2.001 (2) Å], while the second nitrile N atom occupies the apical position [Cu—N 2.159 (2) Å] and originates from the bridge connecting another Cu atom. The shortest intrachain Cu?Cu distance is 8.212 (1) Å, as a consequence of the large bridging ligand, whereas the minimum interchain distance between Cu atoms is only 5.77 (7) Å, because of the interdigitation of the chains.     

Copper(II) and zinc(II) complexes of pyridine‐2,6‐di­carboxyl­ic acid

The title compounds, bis­(pyridine‐2,6‐di­carboxyl­ato‐N,O,O′)copper(II) monohydrate, [Cu(C₇H₄NO₄)₂]·H₂O, andbis(pyridine‐2,6‐dicarboxylato‐N,O,O′)zinc(II) trihydrate, [Zn(C₇H₄NO₄)₂]·3H₂O, have distorted octahedral geometries about the metal centres. Both metal ions are bonded to four O atoms and two pyridyl‐N atoms from the two terdentate ligand mol­ecules, which are nearly perpendicular to each other. The copper(II) complex has twofold crystallographic symmetry and contains two different ligand mol­ecules, one of which is neutral and another doubly ionized. In contrast, the zinc(II) complex contains two identical singly ionized ligand mol­ecules. Both crystal structures are stabilized by O—H?O intermolecular hydrogen bonds between the complex and the water mol­ecules.     

Spectroscopic and structural studies of 6,6′-bis(N-methylhydrazine)-2,2′-bipyridine and its mononuclear copper(II) complex

The tetradentate ligand, 6,6′-bis(N-methylhydrazine)-2,2′-bipyridine (L) and its mononuclear copper(II) complex [Cu(L)](ClO₄)₂] (1) have been synthesized and characterized. The crystal structures of L and 1 have been determined by single-crystal X-ray diffraction. Both crystallize in the centrosymmetric monoclinic space group with crystallographic inversion symmetry. The ligand adopts a planar transoid configuration in the solid state. In 1, the Cu(II) is six-coordinate octahedral, defined by N₄O₂ donors from ligand and two perchlorates. The molecular units are connected by intermolecular H-bonds between the hydrazino group of the one unit and coordinated perchlorate of the neighboring two units via N–H ··· O to furnish a 2-D network. Coordinated perchlorates also form an intramolecular H-bond with hydrazine influencing the crystal packing.     

An Aqua‐Bridged Helical‐Chain Copper(II)‐Saccharinato Polymer Linked into a Two‐Dimensional Supramolecular Framework

A new assembly [Cu₂(sac)₂(μ‐dmea)₂(μ‐H₂O)]_n (sac = saccharinate and Hdmea = 2‐dimethylaminoethanol) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X‐ray diffraction. The complex crystallizes in the monoclinic space group C2/c and consists of dinuclear modules of [Cu₂(sac)₂(dmea)₂]. The sac ligand is N‐coordinated, while the dmea ligand is in the deprotanated form by losing the ethanol hydrogen atom and acts as a bidentate donor through the alkoxo group and N atom. The alkoxo group also serves as a bridge between two copper(II) ions, leading to an intra‐dimer Cu···Cu separation of 3.0229(7) Å. The dimeric units are bridged by aqua ligands to generate a one‐dimensional water‐bridged helical chain, in which the copper(II) ions exhibit a distorted square‐pyramidal CuN₂O₃ coordination. The Cu–Cu distance in the chain separated by the bridging aqua ligands is 5.297Å. The polymeric chains are further linked by π(sac)···π(sac) and C–H···π(sac) interactions into a two‐dimensional supramolecular network.     

Structural Study of Nickel(II), Copper(II), and Palladium(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Reduction of 2‐cyanopyridine by sodium in the presence of 3‐hexamethyleneiminylthiosemicarbazide produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim. Complexes with nickel(II), copper(II) and palladium(II) have been prepared and the following complexes structurally characterized: [Ni(Amhexim)OAc], [{Cu(Amhexim)}₂C₄H₄O₄]·2DMSO·H₂O, [Cu(HAmhexim)Cl₂] and [Pd(Amhexim)Cl]. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur atom when coordinating as the anionic or neutral ligand, respectively. [{Cu(Amhexim)}₂C₄H₄O₄] is a binuclear complex with the two copper(II) ions bridged by the succinato group in [Cu‐(HAmhexim)Cl₂] the Cu atom is 5‐coordinate and close to a square pyramid structure and in [Ni(Amhexim)OAc] and [Pd(Amhexim)Cl] the metal atoms are planar, 4‐coordinate.     

Synthesis,crystal structure and spectroscopic properties of a chiral cyano-bridged heterobinuclear complex, (4 S ,11 S )-[Cu(1,7-CT)( μ -CN)Fe(CN)4NO] · H2O

The chiral complex, (4S,11S)-[Cu(1,7-CT)(μ-CN)Fe(CN)₄NO] ·?H₂O (1,7-CT =?5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,7-diene), and its enantiomer have been synthesized by reaction and conglomerate crystallization. They consist of heterobinuclear species in which the Cu and Fe centers are linked by a cyanide bridge and crystalline water. The Cu(II) is coordinated by five N atoms and exhibits a distorted square-pyramidal geometry, in which two hydrogen atoms on secondary amines lie in the inward side of the macrocyclic plane, while on the other moiety the Fe(II) is a slightly distorted octahedral structure. The binuclear molecules are linked through intermolecular O2–H2A···N1 and O2–H2B···N4 hydrogen bonds, forming two different waved chains that oriented the molecules for optical activity. IR spectrum shows the existence of bridging cyanide ligand. In methanol the specific rotations of enantiomers are ±205 deg ·?cm² ·?(10 g)^?1, the peak positions of their circular dichroism spectra are close to that of their UV-Vis spectra and present up and down symmetric signals.     

Studies on mononuclear transition metal chelates derived from a novel ( E,E )-dioxime: synthesis,characterization and biological activity

A novel vic-dioxime ligand with a thiourea moiety, (4E,5E)-1,3-bis{4-[(4-bromophenylamino)methylene]phenyl}-2-thiooxaimidazoline-4,5-dione dioxime (4) (bmdH₂) has been synthesized from N,N′-bis{4-[(4-bromophenylamino)methylene]phenyl}thiourea and (E,E)-dichloroglyoxime. The bmdH₂ ligand (4) forms transition metal complexes [M(bmdH)₂] with a metal?:?ligand ratio of 1?:?2 with M?=?Ni(II), Co(II), and Cu(II). The mononuclear Ni(II), Co(II) and Cu(II) complexes, [Ni(bmdH)₂] (5), [Co(bmdH)₂] (6) and [Cu(bmdH)₂] (7) have the metal ions coordinated through the two N,N atoms, as do most vic-dioximes. Elemental analyses, molar conductivity, magnetic susceptibility, IR, ¹H NMR spectra, and UV-Visible spectroscopy were used to elucidate the structures of the ligand and its complexes. Conductivity measurements have shown that the mononuclear complexes are non-electrolytes. In addition, the ligands and metal complexes were screened for antibacterial and antifungal activities by agar well diffusion techniques using DMF as solvent.     

Crystal Structures of [Cu2(bpy)2(H2O)(OH)2(SO4)]·4H2O and [Cu(bpy)(H2O)2]SO4 with bpy = 2, 2′‐Bipyridine

Two sulfato Cu^II complexes [Cu₂(bpy)₂(H₂O)(OH)₂(SO₄)]· 4H₂O ( 1 ) and [Cu(bpy)(H₂O)₂]SO₄ ( 2 ) were synthesized and structurally characterized by single crystal X—ray diffraction. Complex 1 consists of the asymmetric dinuclear [Cu₂(bpy)₂(H₂O)(OH)₂(SO₄)] complex molecules and hydrogen bonded H₂O molecules. Within the dinuclear molecules, the Cu atoms are in square pyramidal geometries, where the equatorial sites are occupied by two N atoms of one bpy ligand and two O atoms of different μ₂—OH groups and the apical position by one aqua ligand or one sulfato group. Through intermolecular O—H···O and C—H···O hydrogen bonds and intermolecular π—π stacking interactions, the dinuclear complex molecules are assembled into layers, between which the hydrogen bonded H₂O molecules are located. The Cu atoms in 2 are octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two H₂O molecules and two sulfato groups with the sulfato O atoms at the trans positions and are bridged by sulfato groups into ¹[Cu(bpy)(H₂O)₂(SO₄)_2/2] chains. Through the interchain π—π stacking interactions and interchain C—H···O hydrogen bonds, the resulting chains are assembled into bi—chains, which are further interlinked into layers by O—H···O hydrogen bonds between adjacent bichains.     

Dinuclear Zn(II) and Hg(II) complexes of an angular dipyridyl ligand: syntheses,crystal structures,and properties

The angular polytopic dipyridyl ligand 2,6-bis(quinoline-2-carboxamido)pyridine (H₂L) was prepared. Assemblies of H₂L with ZnAc₂ and HgAc₂ resulted in two new dinuclear complexes [Zn₂(L)(Ac)₂]?·?1.5H₂O?·?0.5CH₃OH (1) and [Hg₂(L)(Ac)₂]?·?5H₂O?·?CH₃OH (2) where the doubly deprotonated L^2? bi-chelate as μ-kN,N′?:?kN″,N″′, bridging the two metal centers (Ac?=?acetate). In 1, the two Zn(II) ions are also doubly bridged by two Ac ions in a μ-kO?:?kO′ coordination, and thus each metal center adopts a distorted tetrahedral geometry. In 2, each Ac ion is only terminal to Hg(II), in a rare distorted triangular or T-shaped coordination geometry. Free H₂L, 1, and 2 emit interesting bluish-green fluorescence with strong intensities. Thermogravimetric analysis of 1 shows that the dinuclear structure of 1 is stable to 382°C.     

Complexes of 2, 6‐Bis(hydroxymethyl)pyridine with Different Copper(II) Salts Involving the Anions Chloride,Perchlorate, Nitrate and Acetate. Synthesis and Crystal Structures of the Complexes

Complexes of 2, 6‐bis(hydroxymethyl)pyridine (dhmp) with different Cu^II salts [CuCl₂·6H₂O, Cu(ClO₄)₂·6H₂O, Cu(NO₃)₂·3H₂O, Cu(CH₃COO)₂·H₂O] are prepared ( 1 — 5 , respectively), studied by IR, and their crystal structures reported. Dependent on the anion kind, influences on the distortion of the co‐ordination polyhedron, the distribution of donor sites, the formation of a mono‐ or binuclear complex, and the resultant packing structure of the complex are observed, although in no case the counterions of the used Cu^II salts or water of hydration were found in the co‐ordination sphere. Crystal structures of 1 — 5 indicate hexaco‐ordination of the Cu^II ions with N₂O₄‐environment and show that 1 — 4 are mononuclear 2:1 (L:M) complexes, but 5 is a binuclear 4:2 complex. Crystallization of Cu(ClO₄)₂·6H₂O with dhmp yielded two different complexes ( 2 / 3 ). In 3 , one of the dhmp components is mono‐deprotonated and acts as an anionic ligand. The same behavior is found in 5 . Whereas in the neutral ligand complexes 1 , 2 and 4 the basal planes are occupied by O donors, and N atoms are in the axial positions of the octahedrons, in 3 and 5 the bases are formed by two O and two N donor atoms, and O atoms are in the axes. Moreover, complex 3 shows the N atoms in trans position, but 5 in cis position. The packing of the cationic complex units is typical of strong and weak H bond interactions involving the counterions and hydroxylic or aromatic hydrogen atoms to yield complex network structures.     

Synthesis and properties of nickel(II) and copper(II) complexes of a di-N-acetamide tetraaza macrocycle

The syntheses of the hexadentate ligand 2,13-bis(acetamido)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane (L²) and its complexes with Ni(II) and Cu(II) are described. Crystal structures of H₂L²·2HClO₄ (1), [Ni(L²)](ClO₄)₂ (2) and [Cu(L²)](ClO₄)₂ (3) are reported. The two pendant acetamide groups of the macrocyclic ligand 1 are trans to each other and the absolute configuration is a trans-IV in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant acetamide groups at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.