Coordination chemistry of di-2-pyridylketone. Synthesis, spectroscopic investigations, X-ray studies and DFT calculations of Re(III) and Re(V) complexes

The paper presents a combined experimental and computational study of Re(III) and Re(V) complexes containing di-2-pyridylketone and its gem-diol form – [ReCl₃(dpk-N,O)(PPh₃)] (1), [ReCl₃(dpk-N,N′)(OPPh₃)] (2) and [ReOBr₃(dpk-OH)]·2(dpkH⁺Br⁻) (3). All the complexes have been characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The complex 2 has been additionally studied by magnetic measurement. The magnetic behavior of 2 is characteristic of mononuclear octahedral Re(III) complex with d⁴ low-spin (³T_1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state. DFT and time-dependent (TD)DFT calculations have been carried out for [ReCl₃(dpk-N,N′)(OPPh₃)] and [ReOBr₃(dpk-OH), and their UV–vis spectra have been discussed on this basis.     

Olefin epoxidation catalyzed by [Ru(TDL)(tmeda)H2O] complexes (TDL = tridentate Schiff-base ligand; tmeda = tetramethylethylenediamine)

Mixed-chelate complexes of ruthenium have been synthesized using tridentate Schiff-base ligands (TDLs) derived from condensation of 2-aminophenol or 2-aminobenzoic acid with aldehydes (salicyldehyde, 2-pyridinecarboxaldehyde), and tmeda (tetramethylethylenediamine). [Ru^III(hpsd)(tmeda)(H₂O)]⁺ (1), [Ru^III(hppc)(tmeda)(H₂O)]²⁺ (2), [Ru^III(cpsd)(tmeda)(H₂O)]⁺ (3) and [Ru^III(cppc)(tmeda)(H₂O)]²⁺ (4) complexes (where hpsd²⁻ = N-(hydroxyphenyl)salicylaldiminato); hppc⁻ = N-(2-hydroxyphenylpyridine-2-carboxaldiminato); cpsd²⁻ = (N-(2-carboxyphenyl)salicylaldiminato); cppc⁻ = N-2-carboxyphenylpyridine-2-carboxaldiminato) were characterized by microanalysis, spectral (IR and UV–vis), conductance, magnetic moment and electrochemical studies. Complexes 1–4 catalyzed the epoxidation of cyclohexene, styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-nitrostyrene, cis- and trans-stilbenes effectively at ambient temperature using tert-butylhydroperoxide (t-BuOOH) as terminal oxidant. On the basis of Hammett correlation (log k_rel vs. σ⁺) and product analysis, a mechanism involving intermediacy of a [Ru–O–OBu^t] radicaloid species is proposed for the catalytic epoxidation process.     

An unprecedented Cu–Schiff base complex existing as two different trinuclear units with strong antiferromagnetic couplings

A new tetradentate N₂O₂ donor Schiff base ligand [OHC₆H₄CHNCH₂CH₂CH(CH₂CH₃)NCHC₆H₄OH = H₂L ] was obtained by 1:2 condensation of 1,3-diaminopentane with salicylaldehyde and has been used to synthesise an unusual copper(II) complex whose asymmetric unit presents two structurally different almost linear trinuclear units [Cu₃(μ-L)₂(ClO₄)₂] [Cu₃(μ-L)₂(H₂O)(ClO₄)₂] (1). The ligand and the complex were characterised by elemental analysis, FT-IR, ¹H NMR and UV–Vis spectroscopy in addition electrochemical and single crystal X-ray diffraction studies were performed for the complex. The magnetic properties of 1 reveal the presence of strong intra-trimer (J₁ = −202(3) cm⁻¹ and J₂ = −233(3) cm⁻¹) as well as very weak inter-trimer (zJ′ = −0.11(1) cm⁻¹) antiferromagnetic interactions.     

Chelate structures of 5-(H/Br)-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazones (H2L): Synthesis and structural characterizations of [Ni(L)(PPh3)] and [Ru(HL)2(PPh3)2]

The reactions of 5-R-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazone {R: H (L¹); Br (L²)} with [M^II(PPh₃)nCl₂] (M = Ni, n = 2 and M = Ru, n = 3) in a 1:1 molar ratio have given stable solid complexes corresponding to the general formula [Ni(L)(PPh₃)] and [Ru(HL)₂(PPh₃)₂]. While the 1:1 nickel complexes are formed from an ONS donor set of the thiosemicarbazone and the P atom of triphenylphosphine in a square planar structure, the 1:2 ruthenium complexes consist of a couple from each of N, S and P donor atoms in a distorted octahedral geometry. These mixed-ligand complexes have been characterized by elemental analysis, IR, UV–Vis, APCI-MS, ¹H and ³¹P NMR spectroscopies. The structures of [Ni(L²)(PPh₃)] (II) and [Ru(L¹H)₂(PPh₃)₂] (III) were determined by single crystal X-ray diffraction.     

Hydrothermal synthesis and structural characterization of three inorganic–organic composite sandwich-type phosphotungstates

Three inorganic–organic composite sandwich-type phosphotungstates [Ni(tepa)(H₂O)]₄H₂[Ni₄(H₂O)₂(α-B-PW₉O₃₄)₂]·8H₂O (1), (enH₂)₃[Ni₂(H₂O)₁₀][Ni₄(H₂O)₂(α-B-PW₉O₃₄)₂]·en·8H₂O (2) and (enH₂)₁₀[Mn₄(H₂O)₂(α-B-PW₉O₃₄)₂]₂·20H₂O (3) (tepa=tetraethylenepentamine and en=ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ni²⁺ or Mn²⁺ ions in the presence of tepa or en and structurally characterized by IR spectra, elemental analysis, thermogravimetric analysis and variable temperature magnetic susceptibility. X-ray crystallographic analyses indicate that they all contain the classical tetra-M sandwiched polyoxoanions [M₄(H₂O)₂(α-B-PW₉O₃₄)₂]¹⁰⁻ (M=Ni²⁺ or Mn²⁺) and nickel-organoamine cations or organoamine cations work as the charge balance ions. The tetra-M clusters in 1, 2 and 3 exhibit the familiar structural type of a β-junction at the sites of metal incorporation. The study of magnetic property of 1 is indicative of a typical ferromagnetic coupling between Ni²⁺ cations.     

Nitric oxide and singlet oxygen photo-generation by light irradiation in the phototherapeutic window of a nitrosyl ruthenium conjugated with a phthalocyanine rare earth complex

The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] (H₂-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na₄[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] was obtained from cis-[Ru(H₂-dcbpy)₂Cl₂]·2H₂O, whereas Na₄[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] displays a band in the region of 305 nm (λ_max in 0.1 mol L⁻¹ HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na₄[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λ_max in H₂O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] FTIR spectrum displays a band at 1932 cm⁻¹ (Ru–NO⁺). The cyclic voltammogram of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO^+/0) and E = −0.50 V (NO^0/−) versus Ag/AgCl. The NO concentration and ¹O₂ quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L⁻¹ and ø_OS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L⁻¹ The photochemical pathway of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)]/Na₄[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy^-)₂(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and ¹O₂ could improve PDT and be useful in cancer treatment.     

Effect of chelating agent on the oxidation rate of PCP in the magnetite/H2O2 system at neutral pH

The complex [Rh(CO)₂Cl]₂ reacts with two molar equivalent of pyridine carboxylic acids ligands Py-2-COOH(a), Py-3-COOH(b) and Py-4-COOH(c) to yield rhodium(I) dicarbonyl chelate complex [Rh(CO)₂(L^/)](1a) {L^/ = η²-(N,O) coordinated Py-2-COO⁻(a^/)} and non-chelate complexes [Rh(CO)₂ClL^//](1b,c) {L^// = η¹-(N) coordinated Py-3-COOH(b), Py-4-COOH(c)}. The complexes 1 undergo oxidative addition (OA) reactions with different electrophiles such as CH₃I, C₂H₅I, C₆H₅CH₂Cl and I₂ to give penta coordinated Rh(III) complexes of the types [Rh(CO)(CORⁿ)XL^/], {n = 1,2,3; R¹ = CH₃(2a); R² = C₂H₅(3a); X = I and R³ = CH₂C₆H₅ (4a); X = Cl}, [Rh(CO)I₂L^/](5a), [Rh(CO)(CORⁿ)ClXL^//] {R¹ = CH₃(6b,c); R² = C₂H₅(7b,c); X = I and R³ = CH₂C₆H₅ (8b,c); X = Cl} and [Rh(CO)ClI₂L^//](9b,c). The complexes have been characterized by elemental analysis, IR and ¹H NMR spectroscopy. Kinetic data for the reaction of 1a–b with CH₃I indicate a first order reaction. The catalytic activity of 1a–c for the carbonylation of methanol to acetic acid and its ester is evaluated and a higher turn over number (TON = 810–1094) is obtained compared with that of the well-known commercial species [Rh(CO)₂I₂]⁻ (TON = 653) at mild reaction conditions (temperature 130 ± 5 °C, pressure 35 ± 5 bar).     

Chelating, bridging, and chain structures within Ag(I) and Cu(I) complexes of bis(nicotinyloxy), bis(isonicotinyloxy), and bis(pyrimidine-5-carboxyloxy)-1,8-disubstituted anthraquinone ligands

Reaction of Ag(I) and Cu(I) [M(NCCH₃)₄]X (X = BF₄⁻ and PF₆⁻) salts with 1,8-bis(nicotinyloxy)anthracene-9,10-dione (1), 1,8-bis(isonicotinyloxy)anthracene-9,10-dione (2), and 1,8-bis(pyrimidine-5-carboxyloxy)anthracene-9,10-dione (3), yield new chelating and bridging complexes and two new coordination polymers. The bridging capabilities of ligands 1 and 2 have not been demonstrated before, and ligand 1, by itself, has the flexibility to produce either chelated or bridged structures and an unusual ladder coordination polymer. The tetradentate ligand 3 also produces a one-dimensional coordination polymer in the presence of one equivalent of Ag(I). All complexes have been characterized by X-ray crystallography.     

Heterometallic clusters arising from cubic Ni3M′O4 (M′=K and Na) entity: Solvothermal synthesis with/without the assistance of microwave

Solvothermal reaction assisted with microwave leads to the formation of two unique heterometallic cubic clusters [Ni₃M′(L)₃(OH)(CH₃CN)₃]₂·CH₃CN (M′=K for 1 and M′=Na for 2, where L is an anion of 2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-ethanesulfonate) with higher efficiency, yields and purity than those without it. The 6-metallacrown-3 [Ni₃(OH)(L)₃]⁻ groups exhibit interesting ion trapping and self-assembly of size-different Na⁺ and K⁺ through form recognition and coordination activity in 1 and 2. The magnetic studies for 1 and 2 suggest that the {Ni₃M′O₄} (M′=K and Na) cores both display dominant ferromagnetic interactions from the nature of the binding modes of μ₃-O (oxidophenyl) and μ₃-OH.     

Synthesis and structural characterisation of the oxo-rhenium(V) complexes with spirophosphorane derived bidentate ligand (PO). Crystal structure of trans-ReOCl2[OCMe2CMe2OP(OCMe2CMe2O)](PPh3)

The reactions of ReO(OEt)Cl₂L₂, L=py, PPh₃ or ReOCl₃(Me₂S)(OPPh₃), with spirohydrophosphorane HP(OCMe₂CMe₂O)₂ – abbreviated here as HPO – in toluene yield ReOCl₂(PO)L complexes, L=py (1), PPh₃ (2) and OPPh₃ (3), respectively. The encountered bidentate phosphite pinacolato (OCMe₂CMe₂O)POCMe₂CMe₂O⁻ ligand (PO⁻) is afforded by means of a spirophosphorane ring-opening reaction. All the pink–violet compounds 1–3 were characterised by NMR, IR and UV–Vis spectroscopies. The structure of trans-ReOCl₂(PO)PPh₃ (2) was determined crystallographically. The rhenium atom adopts distorted octahedral geometry with a trans multiply bonded terminal oxo ligand (Re–O_t=1.698(2) Å) trans to pinacolate oxygen (Re–O=1.880(2) Å). Two phosphorus atoms as well as two chlorides are mutually in a trans arrangement.     

Hydroformylation of oct-1-ene catalyzed by dinuclear gem-dithiolato-bridged rhodium(I) complexes and phosphorus donor ligands

The dinuclear gem-dithiolato bridged compounds [Rh₂(μ-S₂Cptn)(cod)₂] (1) (CptnS₂²⁻ = 1,1-cyclopentanedithiolato), [Rh₂(μ-S₂Chxn)(cod)₂] (2) (ChxnS₂²⁻ = 1,1-cyclohexanedithiolato), [Rh₂(μ-S₂CBn₂)(cod)₂] (3) (Bn₂CS₂²⁻ = 1,3-diphenyl-2,2-dithiolatopropane) and [Rh₂(μ-S₂CⁱPr₂)(cod)₂] (4) (ⁱPr₂CS₂²⁻ = 2,4-dimethyl-2,2-dithiolatopentane) dissolved in toluene in the presence of monodentate phosphine or phosphite P-donor ligands under carbon monoxide/hydrogen (1:1) atmosphere are efficient catalysts for the hydroformylation of oct-1-ene under mild conditions (6.8 atm of CO/H₂ and 80 °C). The influence of the gem-dithiolato ligand, the P-donor co-catalyst and the P/Rh ratio on the catalytic activity and selectivity has been explored. Aldehyde selectivities higher than 95% and turnover frequencies up to 245 h⁻¹ have been obtained using P(OMe)₃ as modifying ligand. Similar activity figures have been obtained using P(OPh)₃ although the selectivities are lower. Regioselectivities toward linear aldehyde are in the range 75–85%. The performance of the catalytic systems [Rh₂(μ-S₂CR₂)(CO)₂(PPh₃)₂]/PPh₃ has been found to be comparable to the systems [Rh₂(μ-S₂CR₂)(cod)₂] at the same P/Rh ratio. The system [Rh₂(μ-S₂CBn₂)(cod)₂] (3)/P(OPh)₃ has been tested in the hydroformylation-isomerization of trans-oct-2-ene. Under optimized conditions up to 54% nonanal was obtained. Spectroscopic studies under pressure (HPNMR and HPIR) evidenced the formation of hydrido mononuclear species under catalytic conditions that are most probably responsible for the observed catalytic activity.     

Interaction of N-(aryl)picolinamides with iridium. N–H and C–H bond activations

Reaction of N-(4-R-phenyl)picolinamide (R = OCH₃, CH₃, H, Cl and NO₂) with [Ir(PPh₃)₃Cl] in refluxing ethanol in the presence of a base (NEt₃) affords two yellow complexes (1-R and 2-R). The 1-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines, a chloride and a hydride. The 2-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines and two hydrides. Similar reaction of N-(naphthyl)picolinamide with [Ir(PPh₃)₃Cl] affords two organometallic complexes, 3 and 4. In complex 3 the amide ligand is coordinated to the metal center, via C–H activation of the naphthyl ring at the 8-position, as a dianionic tridentate N,N,C donor, along with two triphenylphosphines and one chloride. Complex 4 is similar to complex 3, except a hydride is bonded to iridium instead of the chloride. Structures of the 1-OCH₃, 2-Cl and 4 complexes have been determined by X-ray crystallography. All the complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ir^III–Ir^IV oxidation within 0.50–1.16 V vs. SCE and a reduction of the coordinated amide ligand within −1.02 to −1.25 V vs. SCE.     

Salicylaldoxime in manganese(III) carboxylate chemistry: Synthesis, structural characterization and physical studies of hexanuclear and polymeric complexes

The use of salicylaldehyde oxime (H₂salox) in manganese(III) carboxylate chemistry has yielded new members of the family of hexanuclear compounds presenting the [Mn₆(μ₃-O)₂(μ₂-OR)₂]¹²⁺ core, complexes [Mn^III₆(μ₃-O)₂(O₂CPh)₂(salox)₆(L₁)₂(L₂)₂] (L₁ = py, L₂ = H₂O (1); L₁ = Me₂CO, L₂ = H₂O (2); L₁ = L₂ = MeOH (3)). Addition of NaOMe to the acetonitrile reaction mixture, afforded the 1D complex [Mn^III₃Na(μ₃-O)(O₂CPh)₂(salox)₃(MeCN)]_n (4), whereas addition of NaClO₄ to the acetone reaction mixture afforded an analogous 1D complex [Mn^III₃Na(μ₃-O)(O₂CPh)₂(salox)₃(Me₂CO)]_n (5). The structures of 1–3 present the [Mn₆(μ₃-O)₂(μ₂-OR)₂]¹²⁺ core and can be described as two [Mn₃(μ₃-O)]⁷⁺ triangular subunits linked by two μ₂-oximato oxygen atoms of the salox²⁻ ligands, which show the less common μ₃-κ²O:κO′:κN coordination mode. The benzoato ligands are coordinated through the usual syn,syn-μ₂-κO:κO′ mode. The 1D polymeric structures of 4 and 5 consist of alternating [Mn₃(μ₃-O)]⁷⁺ subunits and Na⁺ atoms linked through two μ₃-κ²O:κO′:κN and one μ₄-κ²O:κ²O′:κN salox²⁻ ligands as well as one syn,anti-μ₂-κO:κO′ benzoato ligand. DC and AC magnetic susceptibility studies on 1 revealed the stabilization of an S = 4 ground state, and indications of single-molecule magnetism behavior, whereas the DC experimental data from polycrystalline sample of 5 are indicative of antiferromagnetic interactions within the [Mn₃] subunit. Solid state ¹H NMR data of 1 were used to probe the spin-lattice relaxation of the system.     

Spectral and electrochemical studies of ruthenium(II) complexes with N-methyl-4-nitrobenzaldehyde and N-methyl-4-nitrobenzophenone thiosemicarbazone: Potential anti-trypanosomal agents

N⁴-Methyl-4-nitrobenzaldehyde thiosemicarbazone (H4NO₂Fo4M), N⁴-methyl-4-nitrobenzophenone thiosemicarbazone (H4NO₂Bz4M) and their ruthenium(II) complexes [Ru(4NO₂Fo4M)₂(PPh₃)₂] (1), [Ru(4NO₂Bz4M)₂(PPh₃)₂] (2), [Ru(4NO₂Fo4M)₂(dppb)] (3) and [Ru(4NO₂Bz4M)₂(dppb)] (4) (dppb = 1,4-bis(diphenylphospine)butane) were obtained and characterized. The crystal structure of H4NO₂Fo4M has been determined. Electrochemical studies have shown that the nitro anion radical, one of the proposed intermediates in the mechanism of action of nitro-containing anti-trypanosomal drugs, is formed at approximately −1.00 V in the free thiosemicarbazones as well as in their corresponding ruthenium(II) complexes, suggesting their potential to act as antitrypanosomal drugs. The natural fluorescence of H4NO₂Fo4M, H4NO₂Bz4M and complexes (1)–(4) provides a way to identify and to monitor their concentration in biological systems.     

Crystal chemistry of three new monodimensional fluorometalates templated with ethylenediamine

Three new monodimensional hybrid metal (Ti, In, Al) fluorides are synthesized with ethylenediamine (en) as a templating agent in solvothermal conditions assisted by microwave heating. All structures involve inorganic chains built up from TiO₂F₄ octahedra connected by two opposite O²⁻ vertices in [H₂en]·(TiOF₄) (I), from InF₆(H₂O) pentagonal bipyramids linked by F–F edges in [H₂en]·(InF₄(H₂O))₂·H₂O (II) and from (Al₇F₃₀)⁹⁻ polyanions sharing two opposite AlF₆ octahedra in [H₂en]₃·(Al₆F₂₄) (III). I is tetragonal, P4/ncc, a = 12.761(3) Å, c = 8.041(3) Å; II is orthorhombic, F2dd, a = 6.904(5) Å, b = 16.559(5) Å, c = 19.777(4) Å and III is monoclinic, P2₁/n, a = 9.387(2) Å, b = 6.710(2) Å, c = 21.513(6) Å, β = 97.18(3)°.     

Molybdenum(VI) network polymers based on anion–π interaction and hydrogen bonding: Synthesis, crystal structures and oxidation catalytic application

A crystallographic investigation of anion–π interactions and hydrogen bonds on the preferred structural motifs of molybdenum(VI) complexes has been carried out. Two molybdenum(VI) network polymers MoO₂F₄·(Hinca)₂ (1) and MoO₂F₃(H₂O)·(Hinpa) (2), where inca = isonicotinamide and inpa = isonipecotamide, have been synthesized, crystallographically characterized and successfully applied to alcohol oxidation reaction. Complex 1 crystallizes in the monoclinic space C2/c: a = 16.832(3) Å, b = 8.8189(15) Å, c = 12.568(2) Å, β = 118.929(3)°, V = 1560.1(5) Å³, Z = 4. Complex 2 crystallizes in the triclinic space P-1: a = 5.459(2) Å, b = 9.189(4) Å, c = 12.204(5) Å, α = 71.341(6)°, β = 81.712(7)°, γ = 77.705(7)°, V = 564.8(4) Å³, Z = 2. Complex 1 consists of hydrogen bonding and anion–π interactions, both of which are considered as important factors for controlling the geometric features and packing characteristics of the crystal structure. The geometry of the sandwich complex of [MoO₂F₄]²⁻ with two pyridine rings indicates that the anion–π interaction is an additive and provides a base for the design and synthesis of new complexes. For complex 2, the anions and the protonated inpa ligands form a 2D supramolecular network by four different types of hydrogen contacts (N–HF, N–HO, O–HF and O–HO). The catalytic ability of complexes 1 and 2 has also been evaluated by applying them to the oxidation of benzyl alcohol with TBHP as oxidant.     

Synthesis of new Cu(II), Ni(II) and Co(II) complexes with a bis-amide ligand functionalized with pyridine moieties: Spectral, magnetic and electrochemical studies

Three new copper(II), nickel(II) and cobalt (II) dinuclear complexes with a bis-amide ligand derived from tartaric acid have been prepared and characterized. For this purpose, the ligand (R,R)-(+)-di-N,N′-methylpyridino-tartramide (dmpt) was synthesized via the classical aminolysis of (R,R)-(+)-dimethyltartrate with pyridylmethylamine. The molecular structures of the complexes Na[Cu₂(dmptH₋₃)(CO₃)] · 8H₂O (1) and [Ni₂(dmptH₋₂)₂] · 9.75H₂O (2) were elucidated by X-ray diffraction, and the complex [Co₂(dmptH₋₃)(μ-OH)] · NaClO₄ · 5H₂O (3) by XAS. The crystal structure of (1) shows that the two metallic centres are in a square planar environment. Each copper(II) is bound to pyridyl and deprotonated amidic nitrogen atoms and to the oxygen atoms of hydroxyl and carbonato groups. In complex (2), both nickel atoms are in a distorted octahedral environment with an identical set of donors atoms, N₄O₂, coming from four nitrogen atoms of two pyridylmethylamido moieties and two oxygen donor atoms of alcohol groups. XAS analysis of complex (3) allows us to propose a CoN₂O₄ chromophore, with two nitrogen atoms coming from pyridyl and amidic groups and two bridged oxygen atoms from a deprotonated alcohol group and an hydroxyl group; the hexacoordination is achieved by two water molecules. The spectroscopic, electrochemical and magnetic properties of these complexes were investigated.     

Syntheses and X-ray structural studies of the novel complexes [Ni(en)2(3-pyt)2] and [Cu(en)2](3-pyt)2 based on 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione

Two novel mononuclear mixed-ligand complexes [Ni(en)₂(3-pyt)₂] (1) and [Cu(en)₂](3-pyt)₂ (2), derived from potassium [N′-(pyridine-3-carbonyl)-hydrazinecarbodithioate [K⁺(H₂L)⁻] and containing en as a co-ligand, have been synthesized. The [K⁺(H₂L)⁻] undergoes cyclization in the presence of ethylenediamine (en) and is converted to 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione (3-pyt)⁻. [Ni(en)₂(3-pyt)₂] and [Cu(en)₂](3-pyt)₂ have been characterized with the aid of elemental analyses, IR, UV–Vis, magnetic susceptibility and single crystal X-ray studies. The complexes 1 and 2 crystallize in the orthorhombic and monoclinic systems with space groups Pca2(1) and C2/c, respectively. The single crystal X-ray diffraction studies of both complexes indicate that (3-pyt)⁻ adopts a thione form in 1 but is present as a thiolato form in 2.     

Synthesis, spectroscopic and electrochemical properties of manganese, nickel and iron octakis-(2-diethylaminoethanethiol)-phthalocyanine

The syntheses, spectroscopic and electrochemical properties of manganese (3), nickel (4) and iron (5) phthalocyanine complexes, octa-substituted at the peripheral positions with diethlyaminoethanethiol substituent, are reported. The electrochemistry of these complexes and the corresponding cobalt complex (6) are reported. Complex 3 showed two reversible reduction couples attributed to the Mn^IIIPc⁻²/Mn^IIPc⁻² (E_½ = −0.12 V versus Ag|AgCl) and Mn^IIPc⁻²/Mn^IIPc⁻³ (E_½ = −0.82 V versus Ag|AgCl) species. Two ring-based reduction couples were also observed for complex 4. Two reduction couples, assigned to the Fe^IIPc⁻²/Fe^IPc⁻² (E_½ = −0.35 V versus Ag|AgCl) and Fe^IPc⁻²/Fe^IPc⁻³ (E_½ = −0.96 V versus Ag|AgCl) species, and an oxidation couple, attributed to Fe^IIIPc⁻²/Fe^IIPc⁻² (E_½ = 0.26 V versus Ag|AgCl) species, were observed. For complex 6, two reductions and one oxidation were also observed with the potential range of 1.2 to −1.8 V versus Ag|AgCl Spectroelectrochemical studies were used to confirm some of the assigned processes.     

Synthesis, crystal structure and properties of cobalt(II) and nickel(II) coordination polymers supported by functionalized dicarboxylate ligands

Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands, namely, [Co^IIL¹(2,2′-bpy)(H₂O)] (1), [Ni^IIL¹(2,2′-bpy)(H₂O)]·H₂O (2), [Co^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (3) and [Ni^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (4), where H₂L¹ = 2,5-dibenzoylterephthalic acid, H₂L² = 4,6-bis(4-methylbenzoyl)isophthalic acid and 2,2′-bpy = 2,2′-bipyridine, were synthesized and characterized by elemental analysis, IR spectra and thermogravimetric analysis. Complex 1 exhibits a zigzag chain with a C–Hπ interaction between the phenyl ring proton and the phenyl ring of an adjacent chains to form a 2D supramolecular sheet. Complex 2 contains two helical chains which extend into 2D via a C–Hπ interaction between the pyridine ring proton and the pyridine ring. Complexes 3 and 4 are isomorphous with helical chains that extend in the same direction and further link to one another by supramolecular forces into a 2D structure. Moreover, magnetic and luminescence properties have been investigated for 1 and 2, respectively.