Spectral study of the structure of compartmental complexes of europium and copper

Compartmental complexes [EuH₂(fsa)₂en]Cl·3H₂O and [CuH₂(fsa)₂en]·0.5H₂O have been synthesized and characterized. The compartmental ligand (H₄(fsa)₂en) is N,N′-bis(3-carboxysalicy- lidene)ethylenediamine. Spectral study indicates that Eu(III) and Cu(II) are coordinated by the ---O₂O₂ coordinating atoms (outside) and the ---N₂O₂ coordinating atoms (inside), respectively. Since there is a considerable difference in the ligand field strength between the “outside” and “inside” coordination spheres, their different fluorescence properties have been investigated by photoacoustic spectroscopy and fluorescence spectroscopy.     

Coordination geometry of tetradentate Schiff’s base nickel complexes: the effects of donors, backbone length and hydrogenation

The X-ray crystal structures of (N,N′-bis-(o-amidobenzilidene)-1,3-diaminopropane)nickel (Niambpr), (N,N′-bis-(o-amidobenzilidene)-1,4-diaminobutane)nickel (Niambut), (N,N′-bis-(o-thiobenzilidene)-1,4-diaminobutane)nickel(II) (Nitsalbut), bis-acetonitrile-(N,N′-bis-(o-aminobenzyl)-1,2-diaminoethane) nickel(II) tetrafluoroborate [Ni(H₄amben)(MeCN)₂] [BF₄]₂, bis-O-acetato-(N,N′-bis-(o-aminobenzyl)-1,2-diaminoethane) nickel(II) [Ni(H₄amben)(OAc)₂ · H₂O] and bis-O-acetato-(N,N′-bis-(o-aminobenzyl)-1,3-diaminopropane) nickel(II) [Ni(H₄ambpr)(OAc)₂] are presented. These structures complete the structural characterisation of the simple unsubstituted Schiff’s base complexes with N₄ and N₂S₂ donor sets and allow us to assess the effects of donor groups and polymethylene chain length on the coordination geometries of nickel(II). The hydrogenated N₄ complexes offer an insight into the effects of increased flexibility and character of the internal nitrogen donors. Unlike the parent N₄ imine species the hydrogenated amine species do not deprotonate at the peripheral nitrogen donors and do not seem to be restricted to the meridial plane of the nickel.     

Neutral pyridylmethylamide ligands and their mononuclear copper(II) complexes

Mononuclear copper(II) complexes of a family of pyridylmethylamide ligands HL, HL^Me, HL^Ph, HL^Me3 and HL^Ph3, [HL = N-(2-pyridylmethyl)acetamide; HL^Me = N-(2-pyridylmethyl)propionamide; HL^Ph = 2-phenyl-N-(2-pyridylmethyl)acetamide; HL^Me3 = 2,2-dimethyl-N-(2-pyridylmethyl)propionamide; HL^Ph3 = 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide], were synthesized and characterized. The reaction of copper(II) salts with the pyridylmethylamide ligands yields complexes [Cu(HL)₂(OTf)₂] (1), [Cu(HL^Me)₂](ClO₄)₂ (2), [Cu(HL)₂Cl]₂[CuCl₄] (3), [Cu(HL^Me3)₂(THF)](OTf)₂ (4), [Cu(HL^Me3)₂(H₂O)](ClO₄)₂ (5a and 5b), [Cu(HL^Ph3)₂(H₂O)](ClO₄)₂ (6), [Cu(HL)(2,2′-bipy)(H₂O)](ClO₄)₂ (7), and [Cu(HL^Ph)(2,2′-bipy)(H₂O)](ClO₄)₂ (8). All complexes were fully characterized, and the X-ray structures vary from four-coordinate square-planar, to five-coordinate square-pyramidal or trigonal-bipyramidal. The neutral ligands coordinate via the pyridyl N atom and carbonyl O atom in a bidentate fashion. The spectroscopic properties are typical of mononuclear copper(II) species with similar ligand sets, and are consistent their X-ray structures.     

Synthesis and magnetism of the first tetranuclear copper(II)–iron(III) complexes of macrocyclic oxamides

Four novel tetranuclear macrocyclic complexes of the formula [(CuLⁱ)₃Fe](ClO₄)₃·3H₂O (i=1–4, Lⁱ are the dianions of the [14]N₄ and [15]N₄ macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL¹)₃Fe](ClO₄)₃·3H₂O (1) and [(CuL³)₃Fe](ClO₄)₃·3H₂O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm⁻¹ for 1 and J=−28.7 cm⁻¹ for 3 based on . The interaction parameters have been compared with that of the related [Cu₃Mn] compound.     

Synthesis, spectral properties, crystal structures and antimicrobial effects of copper(II) pyridinecarboxylate adducts with chelating ligands

The reaction of an ethanolic solution of copper(II) pyridinecarboxylates CuX₂·nH₂O (where X is nicotinate (nic) (n=0) or isonicotinate (isonic) (n=4)) with ethylenediamine (en) in a molar ratio of 1:2 lead to the isolation of solid tetragonally distorted octahedral complexes of the type [Cu(en)₂(H₂O)₂]X₂·nH₂O (n=1 for nic; n=0 for isonic). The analogous reaction of CuX₂·nH₂O with diethylenetriamine (dien) in a molar ratio of 1:1 leads to the formation of square-pyramidal pentacoordinated complexes of the type [CuX(dien)(H₂O)]X. On the other hand, the reaction of equimolar quantities of copper(II) nitrate and dien with nicotinate anions (equimolar quantities of pyridinecarboxylic acid and NaOH) in ethanolic solutions gives a solid monomeric complex [Cu(nic)(NO₃)dien)(H₂O)]·H₂O in which the coordination polyhedron around the Cu(II) atom is a (4+1+1) distorted tetragonal bipyramid. Based on the molecular structure the electronic and IR spectra are discussed. Moreover, the results of the quantitative determination of antimicrobial activity of the isonic complexes [Cu(isonic)₂(H₂O)₄], [Cu(en)₂(H₂O)₂](isonic)₂, [Cu(isonic)(dien)(H₂O)](isonic), as well as isonicotinic acid, ethylenediamine and diethylenetriamine alone are discussed.     

Thermal decomposition study on mixed ligand thymine complexes of divalent nickel(II) with dianions of some dicarboxylic acids

Thermal decomposition of mixed ligand thymine (2,4-dihydroxy-5-methylpyrimidine) complexes of divalent Ni(II) with aspartate, glutamate and ADA (N-2-acetamido)iminodiacetate dianions was monitored by TG, DTG and DTA analysis in static atmosphere of air. The decomposition course and steps of complexes [Ni(C₅H₆N₂O₂)(C₄H₅NO₄)²⁻(H₂O)₂]·H₂O, [Ni(C₅H₆N₂O₂)(C₅H₇NO₄)²⁻(H₂O)₂]·H₂O and [Ni(C₅H₆N₂O₂)(C₆H₈N₂O₅)²⁻(H₂O)₂]·1.5H₂O were analyzed. The final decomposition products are found to be the corresponding metal oxides. The kinetic parameters namely, activation energy (E*), enthalpy (ΔH*), entropy (ΔS*) and free energy change of decomposition (ΔG*) are calculated from the TG curves using Coats–Redfern and Horowitz–Metzger equations. The stability order found for these complexes follows the trend aspartate > ADA > glutamate.     

Three copper(II) complexes constructed from a new 1,3,5-triazine derivative ligand

Three new complexes {[Cu(dpdapt)(Hhbd)] · 6H₂O}_n (1) (dpdapt = N,N′-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd = 2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO₄)] · 2H₂O (2) and [Cu(dpdapt)(oxa)] · H₂O (3) (oxa = oxalate dianion) have been synthesized and structurally characterized. The non-covalent interactions of π–π stacking and hydrogen bonding extend complexes 1–3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels. The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.     

Ab initio study of 1,1-(methylphosphinylidene) bis(methanamine) and vibrational assignment of its N,N′-coordinated Pt(II) and Pd(II) chloro complexes

Infrared and Raman spectra of 1,1-(methylphosphinylidene) bis(methanamine) [mpbm, (CH₃)PO(CH₂NH₂)₂] and its N,N′-coordinated Pt(II) and Pd(II) have been studied in the 4000–200 cm⁻¹ frequency range. Ab initio calculations have been carried out for different conformations of the mpbm at HF/6-31G* level of the theory from which structural parameters, conformational stability and predicted infrared and Raman spectra have been obtained. A complete vibrational assignment of the lowest energy conformer, tttg⁻, as well as of its N,N′-coordinated Pt(II) and Pd(II) chloro-complexes was done on the basis of the calculated frequencies, relative infrared intensities, Raman activities and potential energy distribution (PED). The theoretical predictions are compared with the experimental results where appropriate.     

Crystal structure and physico-chemical properties of diaquabis(1,10-phenanthroline)manganese(II) disaccharinate monohydrate

A novel manganese complex, [Mn(phen)₂(H₂O)₂](sac)₂·H₂O, was synthesized by the reaction of [Mn(sac)₂(H₂O)₄]·2H₂O with 1,10-phenantroline in aqueous solution and characterized by elemental analysis, IR spectral evidence, magnetic measurements, thermal analysis and single crystal X-ray diffraction. The compound crystallizes in triclinic system, space group P-1, with Z=2. The saccharinate ions do not coordinate the central metal, instead are present as the complementary anions. In the complex cation, Mn(II) is coordinated by two phen and two aqua ligands, and exhibits a distorted octahedral coordination with a high-spin configuration. The presence of lattice and coordinate water molecules are also confirmed by thermal analysis and IR spectroscopy.     

Solvothermal syntheses and crystal structures of two metal coordination polymers with double-chain structures

Two polymeric complexes, [Cu₂(btec)(phen)₂]_n·(H₂O)_n (1) and [Cd₄(btec)₂(phen)₄(H₂O)₄]_n (2) (H₄btec=1,2,4,5-benzenetetracarboxylic acid; PHEN=1,10-phenanthroline), were synthesized by solvothermal reactions at 140 °C. Both complex 1 and 2 possess infinite double-chain structures, in which each Cu(II) center has a tetrahedral configuration and the Cd(II) centers adopt triangular prismatic and square-based pyramidal configurations simultaneously. The inter-chain face to face π–π interactions among the aromatic rings of phen and the hydrogen bond interactions between aqua molecules and carboxyl O atoms result in 3-D networks in the two complexes. The ESR spectra study of complex 1 shows that there is negligibly small long-range super-exchange interactions between the Cu(II) atoms via benzenecarboxylate bridging.     

Constructions of a set of novel hydrogen-bonded supramolecules from reactions of cobalt(II) salt with bis(3,5-dimethylpyrazolyl)methane and different carboxylic acids

Reactions of CoX₂·6H₂O (X = Cl⁻, ClO₄⁻) with bis(3,5-dimethylpyrazolyl)methane (dmpzm) and formic acid, acetic acid, benzoic acid, salicylic acid, maleic acid, or fumaric acid under the presence of KOH solution produced a new family of Co(II)/dmpzm complexes, [Co(dmpzm)₂L]X·nH₂O (1: L = O₂CH, X = Cl, n = 2; 2: L = OAc, X = Cl, n = 3; 3: L = benzoate, X = ClO₄, n = 1/3; 4: L = salicylate, X = ClO₄, n = 1/3) and [Co₂(dmpzm)₄L](ClO₄)₂·nSolv (5: L = maleate, n = 3, Solv = H₂O; 6: L = fumarate, n = 2, Solv = MeOH). These compounds were structurally characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Compounds 1–4 are mononuclear while 5–6 are binuclear. Each cobalt atom of 1–6 is hexacoordinate, with a distorted octahedral CoN₄O₂ coordination geometry incorporating two N,N′-bidentate dmpzm ligands and one O,O′-bidentate carboxylate ligand. There are rich intra- and intermolecular hydrogen bonds in the crystals of 1–6, thereby forming either 2D hydrogen-bonded networks (1 and 2) or 3D hydrogen-bonded networks (3–6). In addition, the thermal behaviors of 1–6 were also investigated.     

Synthesis, crystal structures and magnetic properties of Cu(II) compounds bridged by the terephthalate ligand and hydrogen bonds

A 3D network [Cu(tmen)(tp)(H₂O)₂]_n (1) (tmen = N,N,N′,N′-tetramethylethylenediamine; tp = terephthalate) and a 2D sheet [Cu(pyrazole)₂(tp)]_n (2), featuring 1D chains interwoven by hydrogen bonds, have been prepared and characterized by means of X-ray analyses and magnetic measurements. For 1, coordinative zigzag chains contain Cu(II) centers capped by the chelate ligand tmen, in which the tetragonal structure is elongated due to Jahn–Teller distortion. Coordinated water molecules are hydrogen-bonded to two free carboxylate oxygens of tp bridges, leading to the observed 3D structure. The use of the non-chelating capping ligand pyrazole produced the covalent-bonded 1D linear compound 2 with hydrogen bonds. A severe octahedral distortion of the Cu(II) center arises from a small bite angle (52.3(1)°) of two carboxylate oxygen atoms of tp, which are in turn hydrogen-bonded to the N–H groups of pyrazole ligands coordinated to Cu(II) atoms in neighboring chains. Magnetic data were fitted with the high-temperature series expansion for the Heisenberg chain spin Hamiltonian H = −J∑_iS_i · S_i + 1 together with consideration of the molecular field approximation (zJ′). Both compounds interestingly exhibit ferromagnetic interactions with g = 2.17, J = 4.08 cm⁻¹, zJ′ = −0.28 cm⁻¹ for 1 and g = 2.09, J = 1.47 cm⁻¹, zJ′ = −0.04 cm⁻¹ for 2. By taking into account structural parameters of distances between Cu atoms, it is reasonably assigned that the ferromagnetic couplings (J > 0) in these systems originate from the hydrogen bonds. The spin density of the d_x²-y² orbital on a Cu(II) atom in a chain is propagated and induced over the d_z² orbital of another Cu(II) atom in an adjacent chain. This orbital orthogonality gives rise to such interactions. The negative zJ′ term suggests that the tp bridges communicate only tiny antiferromagnetic interactions.     

Structural, spectral and thermal properties of a polymeric nickel(II) complex containing two-dimensional network

The structure of the complex [Ni(hmt)(NCS)₂(H₂O)₂]_n, assembled by hexamethylenetetramine (hmt) and octahedral Ni(II), is reported. Crystal data: Fw 351.07, a=9.885(10) Å, b=12.06(1) Å, c=12.505(8) Å, β=114.41(4)°, V=1357(1) ų, Z=4, space group=C2/c, T=173 K, λ(Mo−K)=0.71070 Å, ρ_calc=1.718 gcm⁻¹, μ=17.44 cm⁻¹, R=0.099, Rw=0.145. The tetrahedral assembling template effect of the hmt molecule is completed by two coordination bonds and two hydrogen interactions. The UV–vis absorption spectrum of this complex [Ni(hmt)(NCS)₂(H₂O)₂]_n with a two-dimensional network is determined in the range of 5000–35000 cm⁻¹ at room temperature. The observed spectrum is discussed and explained perfectly by the scaling radial theory proposed by us. The two-dimensional structure has no apparent effects on the d–d transitions of the central Ni(II) ion. The IR spectrum and the GT curve of the complex were also measured and clearly reflect its structural properties.     

Coordination geometry of chromium(VI) species. The first example of cis-bridging chromate ions in helically structured catena(μ-CrO4-O,O′)[Ni(HIm)3H2O]

Nickel(II) chromate complex with imidazole (HIm) was isolated from the [Ni²⁺–HIm–CrO₄²⁻] system in various experimental conditions, i.e. reagent molar ratios and nickel(II) salts. The catena(μ-CrO₄-O,O′)[Ni(HIm)₃H₂O] (1) crystallizes in monoclinic crystal system—space group P2₁/n with cell parameters: a=11.784(2), b=8.899(2), c=13.934(3) (Å), β=95.19(3) (°). The unit cell contains two independent helixes, left- and right-handed, stabilized by intrahelical and interhelical hydrogen bonds (HB) and π–π interactions. The cis coordination of the CrO₄²⁻ anions and the HB systems appeared to be the main determinants of the helical architecture. To the best of our knowledge the cis-chromate coordination was observed for the first time. The cis coordination causes the distortion of the nickel octahedron, which was analysed by 4 K single crystal electronic spectra with D_4h symmetry approximation (gaussian resolution and crystal field parameters). This symmetry was also confirmed with the polarised electronic spectra. The magnetic properties of the complex suggest the occurrence of weak intrachain antiferromagnetic interactions between the magnetic Ni^II center. The computational DFT studies of complex 1 assuming three possible isomers mer[(HIm)₃]–cis[(CrO₄²⁻)₂], mer–trans and fac–cis suggested that the main contribution to the stability of 1 might have interhelical and intrahelical hydrogen bonds.     

Synthesis, chemical characterization and crystal structure of the (oxalato-O,O′)bis(1,10-phenanthroline)copper(II) pentahydrate

Violet single-crystals of the complex [Cu(ox)(phen)₂]·5H₂O (1), where ox²⁻ is oxalate and phen is 1,10-phenanthroline, were obtained by slow evaporation of a solution previously prepared by dissolving Cu(ox)·1/3H₂O in a water–acetonitrile solution of phenantroline. Its crystal structure consists of neutral mononuclear [Cu(ox)(phen)₂] units and crystallization water molecules which are held together by face-to-face stacking interactions between the phenantroline aromatic rings and an extensive three-dimensional network of O_w–HO/O_w hydrogen bonds. The copper atom is hexaco-ordinated to two oxygen atoms of a bidentate oxalato ligand and to four nitrogen atoms belonging to two phen ligands in a distorted octahedral cis arrangement. The e.p.r. Q-band spectrum of 1 shows an axial-type signal with g-tensor values of g=2.28 and g=2.06, which is consistent with the axially elongated octahedral geometry of the copper(II) chromophore found in the structural work. The relation gg>2.0 indicates a d(x²−y²) ground state. Variable temperature susceptibility measurements (5–300 K) reveals the occurrence of magnetically isolated paramagnetic centers in the crystal structure. Thermal degradation of the compound 1 under synthetic air atmosphere starts between 50 and 110°C with an endothermic process attributable to the release of the crystallization water molecules.     

Optimised hydrothermal synthesis of multi-dimensional hybrid coordination polymers containing flexible organic ligands

In this paper, we summarise our recent research interest in the hydrothermal synthesis and structural characterisation of multi-dimensional coordination polymers. The use of N-(phosphonomethyl)iminodiacetic acid (also referred to as H₄pmida) in the literature as a versatile chelating organic ligand is briefly reviewed. This molecule plays an important role in the formation of centrosymmetric dimeric [V₂O₂(pmida)₂]⁴⁻ anionic units, which were first used by us as building blocks to construct novel coordination polymers. Starting with [V₂O₂(pmida)₂]⁴⁻ in solution, we have isolated [M₂V₂O₂(pmida)₂(H₂O)₁₀] species (where M²⁺ = Mn²⁺, Co²⁺ or Cd²⁺) via the hydrothermal synthetic approach, which were then employed for the construction of [CdVO(pmida)(4,4′-bpy)(H₂O)₂]·(4,4′-bpy)_0.5·(H₂O), [CoVO(pmida)(4,4′-bpy)(H₂O)₂]·(4,4′-bpy)_0.5, [Co(H₂O)₆][CoV₂O₂(pmida)₂(pyr)(H₂O)₂]·2(H₂O) and [Cd₂V₂O₂(pmida)₂(pyr)₂(H₂O)₄]·4(H₂O) by the inclusion of bridging organic ligands in the reactive mixtures, such as pyrazine (pyr) and 4,4′-bipyridine (4,4′-bpy). These materials can contain channel systems, and exhibit magnetic behaviour, not only due to the V⁴⁺ centres but also to the transition metal centres which establish the links between neighbouring dimeric [V₂O₂(pmida)₂]⁴⁻ anionic units. A closely related anionic moiety, [Ge₂(pmida)₂(OH)₂]²⁻, was engineered to allow the study of such crystalline hybrid materials using one- and two-dimensional high-resolution solid-state NMR.     

2D Cu(I) and 3D mixed-valence Cu(I)/Cu(II) coordination polymers: Synthesis and structural characterization of [CuCl(pyz-H)2]·2H2O and [Cu2Cl2(pyz)(H2O)]·H2O (pyz-H = pyrazinic acid)

Two new coordination polymers of copper(I) chloride and pyrazinic acid (pyz-H), namely [CuCl(pyz-H)₂]·2H₂O (1) and [Cu₂Cl₂(pyz)(H₂O)]·H₂O (2) have been prepared and characterized by spectroscopic, magnetic and crystallographic methods. The overall physical measurements suggest that 1 is diamagnetic and contains monodentate N-pyrazinic acid, whereas 2 is paramagnetic and contains tridentate N,N′,O- chelating bridging pyrazinato anion. In the structure of 1 as elucidated by X-ray single crystal analysis, the asymmetric units [CuCl(pyz)₂] are linked together forming a zigzag chain with tetrahedral copper(I) environment. The two lattice water molecules form hydrogen bonds with the uncoordinated N atom and carboxylate group O atom of pyz-H molecules. The Cu–N bond lengths are 2.009(6) Å and Cu–Cl distances are 2.337(2) Å. Complex 2 has a three-dimensional structure with the chains [Cu(I)Cu(II)(C₅H₃N₂O₂)Cl₂(H₂O)] interconnected by [Cu(I)Cl₂N] tetrahedral unit and [Cu(II)NO₂Cl₂] polyhedra. The Cu(I)–Cl and Cu(I)–N distances are 2.327(2)–2.581(2) Å and 1.988(6) Å, respectively, whereas the Cu(II)–Cl and Cu(II)–N bond lengths are 2.258(2), 2.581(2) Å, and 2.017(6) Å, respectively. Hydrogen bonds of the type O–HO are formed between lattice and coordinated water, and carboxylate oxygens of pyrazinato ligand giving rise to a three-dimensional network. The Cl⁻ anions act as bridging ligands in both complexes. The magnetic data of complex 2 have been measured from 2 to 300 K and discussed.     

Zn(II) complexes with pyridine derived N6 and N8 donor azamacrocyclic ligands

A novel N6 macrocyclic ligand, L¹ (2,8,14,20-tetramethyl-3,7,15,19,25,26-hexaaza-tricyclo[19.3.1.1^9,13]hexacosa-1(24),9,11,13(26),21(25),22-hexaene), was obtained by reduction of the 2 + 2 condensation product of 2,6-diacetylpyridine and propane-1,3-diamine. Zinc(II) complexes of L¹, of a related N8 macrocycle, L³ (3,6,9,17,20,23,29,30-octaaza-tricyclo[23.3.1.1[11,15]]triaconta-1(28),1,13,15(30),25(29),26-hexaene), similarly prepared by 2 + 2 condensation of 2,6-diformylpyridine and diethylenetriamine and of a tetra N-2-cyanoethyl derivative of a homologue of L¹ prepared from diformyl pyridine and ethane-1,2-diamine, L² (3-[6,14,17-tris-(2-cyano-ethyl)-3,6,14,17,23,24-hexaaza-tricyclo[17.3.1.1^8,12] tetracosa-1(23),8(24),9,11,19,21-hexaen-3-yl]-propionitrile), were prepared. Structures were determined for [ZnL¹](ClO₄)₂ · H₂O, [ZnL²](NO₃)₂ and [Zn₂L³(NO₃)₂](NO₃)₂ · H₂O. The [ZnL¹](ClO₄)₂ · H₂O and [ZnL²](NO₃)₂ complexes present a mononuclear endomacrocyclic structure with the metal in an octahedral distorted environment coordinated by the six donor nitrogen atoms from the macrocyclic backbone while the complex [Zn₂L³(NO₃)₂](NO₃)₂ · H₂O is dinuclear with both metal atoms into the macrocyclic cavity coordinated by four donor nitrogen atoms from the macrocyclic framework and one oxygen atom from one monodentate nitrate anion, in a distorted square pyramidal arrangement.     

Supramolecular architecture of cadmium(II)–terephthalate complexes having a tridentate or tetradentate Schiff base as blocking coligand

Two new cadmium(II)–terephthalate complexes, _∞¹{[Cd₂(μ-terephthalate)₂(L¹)₂]·9H₂O} (1) and [{Cd(H₂O)(L²)}₂(μ-terephthalate)](terephthalate) · 10H₂O (2), where L¹ = (E)-N¹,N¹-diethyl-N²-(1-(pyridin-2-yl)ethylidene)ethane-1,2-diamine; L² = N,N′-bis-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine; have been synthesized by a conventional solution method. Characterization by single crystal X-ray crystallography shows that compound 1 is composed of 1-D polymeric zig-zag chains with distorted pentagonal-bipyramidal cadmium centers. Compound 2 consists of centrosymmetric dinuclear complexes with a distorted pentagonal-bipyramidal cadmium center in which one terephthalate ligand bridges the metal centres and another terephthalate anion with water of crystallization forms a H-bonding network.     

Hydrothermal synthesis, structural characterisation and magnetic behaviour of hybrid complexes of N-(phosphonomethyl)iminodiacetate

Two new compounds containing multidentate chelating organic residues of N-(phophonomethyl)iminodiacetic acid (H₄pmida), [M(pyr)(H₂O)₄][M₂(Hpmida)₂(pyr)(H₂O)₂]·2(H₂O) (where pyr=pyrazine and M=Co²⁺ or Ni²⁺ for I and II, respectively) have been synthesised and structurally characterised by single-crystal and powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermal analysis and solid-state ³¹P MAS NMR. The compounds contain discrete binuclear anionic [M₂(Hpmida)₂(pyr)(H₂O)₂]²⁻ units in which one pyrazine ligand bridges two M²⁺ cations which are completely trapped inside three five-membered chelate rings formed by the Hpmida³⁻ ligands. These moieties close pack in the ac plane via a series of strong and highly directional O–HO hydrogen bonds leading to the formation of anionic layers. One-dimensional cationic coordination polymers are placed in-between and strongly hydrogen-bonded to these layers. The magnetic properties of these two materials are also reported.