Search

Carbon dioxide fixation by [Cu(bpca)(H2O)]2+ resulted in a chain having CO32− and HCO3− as ligands that shows a weak intrachain ferromagnetic interaction.

Two series of chlorine or fluorine derivatives containing monooxamato ligands result in diamagnetic complexes of Y3+ and La3+ and paramagnetic complexes of Nd3+ and Ho3+ that behave as single-ion magnets at lower temperatures.

Three new air-stable coordination compounds [Cu(HL)2(H2O)2]2·2H2O (1), [Cu(HL)2]n (1a), and [Zn(HL)2(H2O)2] (2), where HL = N-(4-hydroxyphenyl)oxamate, were successfully synthesized and characterized. Single-crystal X-ray analysis reveals 1 as a dinuclear copper(II) complex, in which the metal ions are connected through the carboxylate moieties of the oxamate ligands. The crystal structure of 1a is solved using powder X-ray diffraction data and stands for an anhydrous mononuclear copper(II) oxamate complex. 2 corresponds to the first example of a mononuclear Zn2+ oxamate complex containing both ligands and water solvent molecules in the cis arrangement. The presence of a phenol group in the oxamate ligand leads to different hydrogen bond patterns in the crystal packing in 1, 1a, and 2, resulting in supramolecular 3D architectures. Magnetic measurements of 1 reveal a ferromagnetic coupling between the copper(II) ions through the carboxylate–oxamate bridge [J = +0.829 cm−1, g = 2.101, zJ = +0.154 cm−1; H = −JSCu1·SCu2, where SCu1 = SCu2 = 1/2]. DFT calculations based on the broken symmetry formalism (DFT-BS) were performed to provide insight into the magnetic behavior.

We report improvement in the perovskite solar cell efficiency and stability after passivation with an organic molecule decorated with two anilinium cations. We compare this salt with its neutral analog and found that the change in the electron density distribution upon protonation and the presence of the halide anion are key to explaining the better passivation ability of the salt. In addition, we show that the counteranion has a significant impact on the performance of the device.

This work describes the synthesis, crystal structures and direct current (dc) magnetic properties of two air-stable oxamato-containing cobalt(II) complexes, [Co(H2edpba)(dmso)2]·dmso·H2O (1) and [Co(H2edpba)(H2O)2]n·n(dmso) (2) [H4edpba = N,N′-2,2′-ethylenediphenylenebis(oxamic acid); dmso = dimethylsulfoxide]. 1 is a mononuclear compound, whereas 2 is a neutral chain. Cobalt(II) ions in both compounds are six-coordinate by six oxygen atoms, four of them from two monodeprotonated oxamate groups and the other two from dmso (1)/water (2) molecules in cis (1) and trans (2) positions. Hydrogen bonds between monodeprotonated oxamate fragments of adjacent mononuclear units in 1 lead to a supramolecular chain growing along the crystallographic c axis. Hydrogen bonds involving coordinated water molecules and monodeprotonated oxamate fragments from adjacent chains in 2 result in a supramolecular 2D network. Cryomagnetic measurements reveal the occurrence of magnetically isolated high-spin cobalt(II) ions in agreement with the large values of the shortest intramolecular (1)/intrachain (2) metal···metal separation [ca. 10.3 (1) and 10.4 Å (2)]. Simultaneous simulation of the χMT versus T and M against H data through the Griffith–Figgis Hamiltonian led to the best-fit parameters: λ = −141.1 (1)/–174.8 cm−1 (2), σ = −1.45 (1)/–1.25 (2) and ν = −121.42 (1)/−247.29 cm−1 (2).

Despite high photo-conversion efficiency, the short long-term stability and toxicity issues have prevented lead-based perovskites from becoming the standard in high efficiency solar cells. Hence, lead-free perovskites with low inorganic framework dimensionality have attracted great attention because of their optoelectronic properties and superior stability. In this work, we present a combined experimental and theoretical investigation of the structural and optoelectronic properties of three novel highly stable zero-dimensional perovskites (discrete connectivity of the inorganic framework), where fused octahedra [BixIy]z− are interspersed by large organic cations: H2bpy2+ for 1, Hdmphen+ for 2 and the combination of H2terpy+2 and Hterpy+ for 3 (bpy = 4,4-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline, terpy = 2,2′;6′,2′′-terpyridine). In each of these compounds, the inorganic moieties display different morphologies, either edge-sharing bi-octahedra (Bi2I104−, 1), face-sharing bi-octahedra (Bi2I93−, 2) or isolated octahedra (BiI63−, 3). The consistent results of experimental and theoretical characterization reveal that distortions in the coordination octahedra are most prominent as the number of shared iodide species increases. The experimental optical response presents similar trends between all three materials, which is dominated by transitions inside the octahedron, while the transitions between cations and anionic bismuth-iodide clusters displayed very low intensity at a lower photon energy, an aspect that was described qualitatively well by theoretical characterization. Overall, these materials show different potential prospects, such as application in hybrid dimensional materials, acting as dielectrics for instance, or as a source of Bi for the synthesis of other lead-free perovskites.

Ruddlesden–Popper organic lead halides (RPOLHs) are in the material science spotlight because of their remarkable optoelectronic properties, tailorable compositions, and improved ambient stability over their three-dimensional perovskite analogues. In this report, we introduce a new synthesis method for RPOLHs with general composition L2[FAPbI3]n−1PbI4 [L = butylammonium (BA) or benzylammonium (BZA), FA = formamidinium, and n = 1 and 2]. Our method yields polycrystalline materials useful for thin-film fabrication for optoelectronic applications. Furthermore, we report the growth dynamics of BA2[FAPbI3]PbI4 using in situ small-angle X-ray scattering, revealing that the slabs grow within the first seconds of the reaction and then self-assemble into bulk crystallites.

The reaction between the ligand di(4-pyridyl)sulfide (dps) and two salts of divalent first row transition metals (M = Co2+, and Cu2+) resulted in three new compounds with formula: [Co(dps)4(H2O)2](ClO4)2⋅H2O (1), [Cu(dps)2(dmso)2]n(ClO4)2n (2) and [{Cu(dps)2(dmso)2}{Cu(dps)2(dmso)(H2O)}]n(ClO4)4n⋅2nH2O⋅n(dmso) (3). Crystal structures of 1–3 were determined using single-crystal X-ray diffraction. Crystal structure of 1 consists of a mononuclear complex, in which the dps ligand acts in a monodentate mode through one of the pyridyl nitrogen atoms. Compounds 2 and 3 present the dps ligands bridging metal centers leading to bidimensional coordination polymers. Magnetic properties in the polycrystalline samples of 1–3 in the 300–2 K temperature range were investigated. Complex 1 exhibits a field-induced slow magnetization behavior and behaves as a single-ion magnet with an effective energy barrier for the reversal of magnetization of 22.9 (1.1) K and τ0 = 5.3(1.2) × 10−7 s.

A series of lanthanide(III) oxamate complexes of formula Na[Eu(4-HOpa)4(H2O)]∙2H2O (1), Na[Gd(4-HOpa)4(H2O)]∙2H2O (2), Na[Dy(4-HOpa)4(H2O)]∙2H2O (3), and Na[Ho(4-HOpa)4(H2O)]∙2H2O (4) (4-HOpa = N-4-hydroxyphenyloxamate) were synthesized and characterized. The crystal structures of complexes 1–4, as well as the oxamate ligand in the ethyl ester acid form (Et[4-HOpa]), were elucidated by single crystal X-ray diffraction. 1–4 are isostructural, and they crystallize in the P21/n space group of the monoclinic system. The crystal structures of 1–4 consist of mononuclear lanthanide(III) complex anions, [Ln(4-HOpa)4(H2O)]− (Ln = Eu3+, Gd3+, Dy3+, and Ho3+), coordinated sodium(I) countercations, and crystallization water molecules, resulting in a 2D NaILnIII supramolecular coordination network. The coordination sphere of Ln3+ ions consists of square-face capped square antiprism (SAPRS-9). Magnetic properties were investigated for 1–4 in the 2–300 K temperature range using polycrystalline samples. Complex 2 exhibits an unusual and rare slow-relaxation of the magnetization for Gd3+ ions under DC applied field of 1.0 kOe, behaving as a field-induced single-ion magnet as occurs for the Dy3+ complex 3. The Eu3+ complex 1 has a nonmagnetic ground state, while the Ho3+ compound 4 behave as a paramagnet, and do not exhibit relaxation of the magnetization with or without an applied field.

We report the unique heterobimetallic dodecanuclear oxamate-based {CoII6CuII6} nanowheel obtained using an environmentally friendly synthetic protocol. The effective Hamiltonian methodology employed herein allows the rationalisation of magnetic isotropic or anisotropic metal clusters, being a significant advance for future studies of exciting properties only observed at low and ultralow temperatures.

Two air-stable, isostructural, mononuclear six-coordinate manganese(II) and cobalt(II) oxamate complexes, [M(4-HOpa)2(H2O)2] [4-HOpa = N-4-hydroxyphenyloxamate; M= Mn2+ (1) or Co2+ (2)], exhibit field-induced slow magnetic relaxation. A bottleneck process is observed throughout the temperature range of 2-20 K for 1, while for 2, it dominates only at low temperatures (2-4 K). Additionally, the Raman process [n = 6.9(2)] is responsible for an increase in the relaxation time at higher temperatures to 2.

Herein we describe the synthesis, structural characterization, physical/spectroscopic studies and evaluation of the antitumoral activity of a new copper(II) coordination polymer, [Cu(ndx)(8-hq)]n, where H(ndx) is nalidixic acid and H(8-hq) is 8-hydroxyquinoline. Single crystal X-ray diffraction shows a zigzag polymeric chain, where the adjacent copper atoms are connected via anti-anti μ-carboxylate bridge of ndx. This structural feature is quite different from those previously proposed for quinolone complexes. Variable-temperature magnetic susceptibility measurements showed weak antiferromagnetic interactions between the paramagnetic copper centers (−0.49 cm−1). In solution, the compound exists as neutral mononuclear species and it can inhibit the growth of a human chronic myelogenous leukemia cell line (K562) in a concentration-dependent manner with IC50 value lower than those of the corresponding free ligands. At similar doses, the compound does not alter the viability of human keratinocytes (HaCaT cell line). Spectroscopic data and viscosity measurements show that the compound binds to DNA (Kb = 2.47 × 105 M−1) interacting with it by a non-intercalative mode.

We report a sequential C–H iodination/organoyl-thiolation of naphthoquinones and their relevant trypanocidal activity. Under a combination of AgSR with a copper source, sulfur-substituted benzenoid quinones were prepared in high yields (generally >90%). This provides an efficient and general method for preparing A-ring modified naphthoquinoidal systems, recognized as a challenge in quinone chemistry.

A new series of {FeIII2LnIII2} heterobimetallic squares of general formula [FeIII{HB(pz)3}(CN)(μ-CN)2Ln(pyim)x(NO3)2(H2O)y]2·zH2O [Ln = La (1), Gd (2), Tb (3) and Dy (4); {HB(pz)3}− = hydrotris(pyrazolyl)borate and pyim = 2-(1H-imidazol-2-yl)pyridine; x = 2, y = 0 (1), x = y = 1 (2–4) and z = 10 (1), 6 (2), 2.76 (3), 4 (4)] were synthesized by reacting the low-spin [FeIII{HB(pz)3}(CN)3]− complex anion with the preformed [LnIII(pyim)x(NO3)2(H2O)y]+ complex cation [formed in situ by mixing the lanthanide(III) salt and the pyim ligand]. Single-crystal X-ray diffraction shows that 1–4 crystallize in the P triclinic space group, 2–4 being isomorphous. In all cases, the structure comprises neutral cyanido-bridged {FeIII2LnIII2} molecular squares in which two [FeIII{HB(pz)3}(CN)3]− units act as bis-monodentate ligands towards two [LnIII(pyim)x(NO3)2(H2O)y]+ moieties through two of the three cyanide groups. The iron(III) and lanthanide(III) cations regularly alternate in the corners of the square and the edges are defined by the cyanide bridges. Each iron(III) ion in 1–4 is six-coordinate in a distorted octahedral surrounding with a tridentate tris(pyrazolyl)borate ligand and three cyanide groups in an approximately C3v symmetry. The lanthanum(III) ion in 1 is ten-coordinate in a rare distorted sphenocorona environment, while the lanthanide(III) ions in 2–4 are all nine-coordinate with a muffin-like geometry. The values of the FeIII⋯LnIII distances across the cyanide bridges are 5.579(1) and 5.687(1) A (1), 5.4695(20) and 5.4781(29) A (2), 5.4550(12) and 5.4464(14) A (3), 5.4463(10) and 5.4478(12) A (4). The tetranuclear units in 1–4 are further interconnected through hydrogen bonds, π–π stacking and very weak C–H⋯π type interactions leading to supramolecular three-dimensional networks with different topologies. Solid-state direct-current magnetic susceptibility analyses in the temperature range 1.9–300 K reveal the occurrence of weak intra- and intermolecular antiferromagnetic interactions in 1 [JFeFe′ = −2.32(3) cm−1, gFe = 2.198(4), θ = −0.650(7) K and χTIP = 266(5) × 10−6 cm3 mol−1, the Hamiltonian being defined as H = −JFeFe′SFeSFe′ + gβH(SFe + SFe′)] and 2 [JFeFe′ = −2.06(3) cm−1, JFeGd = −0.210(4) cm−1, gFe = 2.23(1), gGd = 2.0 (fixed), θ = −0.450(5) K and χTIP = 280(5) × 10−6 cm3 mol−1]. The coexistence of the spin–orbit coupling of the low-spin iron(III) and lanthanide(III) ions [TbIII (3) and DyIII (4)], together with the ligand field effects, masked the visualization of the possible magnetic interactions in 3 and 4. The small antiferromagnetic couplings in 1 and 2 are in line with previously reported weak antiferromagnetic interactions for these couples of ions through single cyanide bridges.

This paper describes the synthesis, physical characterization, X-ray crystal structures and antitumoral activity against human carcionogenic cells of three new diethyl ester acid derivatives of phenylene bis-monothiooxamate compounds, namely Et2H2opbta (1), Et2H2mpbta (2) and Et2H2ppbta (3) [opbta = N,N′-1,2-phenylenebis(2-thiooxamate), mbpta = N,N′-1,3-phenylenebis(2-thiooxamate) and ppbta = N,N′-1,4-phenylenebis(2-thiooxamate)]. Compounds 1–3 were obtained under mild conditions by reaction of the corresponding N,N′-phenylenebis(oxamate) analogues and Lawesson's reagent resulting in the formation of C S bonds at the carbonyl amide functions. Crystal structures of 1–3 consist of 1D supramolecular assemblies of centrosymmetric H2Et2ppbta (3) or noncentrosymmetric chiral H2Et2opbta (1) and H2Et2mpbta (2) molecules with opposite helical chirality (M and P enantiomers) resulting from intermolecular N H⋯O (1 and 3) or N H⋯S (2) hydrogen bonds between the amide hydrogen atoms and the carbonyl ester oxygen or thionyl amide sulfur atoms from the thiooxamate moieties respectively, together with weak S⋯S bonds between the thionyl amide sulfur atoms (1). The cytotoxicity of H2Et2xpbta [x = o (1), m (2) and p (3)] against chronic myelogenous leukemia cells was evaluated and the bioactivity follows the order 1 ≫ 2 > 3, compound 1 being six and ten times more active than 2 and 3, respectively.

Salacia crassifolia traditionally known as “Bacupari-do-Cerrado” is used to treat kidney problems, and as a healing agent for coughs and malaria. The phytochemical study of the S. crassifolia roots led to the isolation of thirteen compounds: abruslactone-A (1), urs-12-ene-3β,25,30-triol (2), carioprystimerin (3), β-sitosterol (4), pristimerin (5), dispermoquinone (6), netzahualcoyonol (7), 20-hydroxy-20-epi-tingenone (8), 6-oxo-pristimerol (9), 9β,10β-epoxi-3β-hydroxy-1βH,4βH,5βH,7βH,11αH-guaian-12,8β-olide (10), 3-O-b-D-glucosyl-b-sitosterol (11), 4`-O-methylepigalocatechin (12) and cerebroside (13). The chemical structures of 1-13 were determined by IR, 1D/2D NMR together with X-ray diffractometry. Compounds 2 and 10 are herein described for the first time. Extracts of S. crassifolia and compounds 3, 5, 8 and 9 were evaluated on acetylcholinesterase inhibition, in vitro cytotoxic activity and in vivo toxicity tests using Caenorhabditis elegans model. All tested compounds inhibited acetylcholinesterase, and compounds 3, 8 and 9 demonstrated a greater potential when compared to the standard eserine. The tested compounds showed low cytotoxicity against the THP-1, K562 and MDA-MB-231 cancer cell lines. None of the tested compounds and extracts were toxic against C. elegans since the larvae survival rate in L1 stage was higher than 90%.

We report a new method for A-ring selenation of naphthoquinones and anthraquinones and discuss the relevant trypanocidal activity of the synthesized compounds. We have demonstrated three efficient strategies for the preparation of the target selenium derivatives, i.e. (a) copper(I) thiophene-2-carboxylate and in situ generated Santi's reagent were used to prepare selenium-substituted benzenoid quinones, (b) copper complexes and (c) carbon nanotube-supported copper ferrite as catalysts in the presence of AgSeR-salts were also used for the synthesis of selenium-containing quinoidal derivatives. These new methods provide efficient and practical strategies for the preparation of selenium-based quinones. In addition, we have discovered nine compounds with potent trypanocidal activity. The derivatives 2a–2e showed potent trypanocidal activity with IC50 values in the range of 13.3 to 37.0 μM.

Two new compounds, caryopristimerin and 2α,3α,22β-trihydroxy-21-oxo-29-nor-friedelan-24-oic acid, were isolated from the hexane/ethyl ether extract of Salacia crassifolia roots. Caryopristimerin represents the first example of a homo Diels-Alder adduct of a sesquiterpene and a triterpene, and the new 29-nor-friedelane displays a highly oxygenated A ring with a carboxylic group at the unusual C-5 position. The new compounds were elucidated by infrared (IR), high-resolution-atmospheric pressure chemical ionization-mass spectrometry (HR-APCI-MS), 1D/2D nuclear magnetic resonance (NMR) and single crystal X-ray diffraction analysis. Additionally, the known compounds 3-oxo-29-hydroxyfriedelane, pristimerin, tingenone and netzahualcoyonol are herein reported for the first time as constituents of S. crassifolia. Their structures were established by spectroscopic analysis.

This work describes the synthesis and characterization of a new class of oxamic acid derivatives containing pyrazole and isoxazole as substituents to investigate their ability to form hydrogen bonds aiming at applying them in crystal engineering and molecular self-recognition. In this respect, we report a new synthesis of 2-(4-nitrophenyl)-1,3-propanedial (1) in high yield using SOCl2 as a chlorinating agent. The new oxamic esters 4-(1H-pyrazol-4-yl)phenylene-N-(ethyloxamate) (2d) and 4-(1,2-oxazol-4-yl)phenylene-N-(ethyloxamate) (3d) were prepared from 1. The synthetic route consists of the cyclisation of 1 either with hydrazine to afford 4-(-aminophenyl)-1H-pyrazole (2a) or with hydroxylamine to obtain the isoxazole-based molecule 4-(4-nitrophenyl)-1,2-oxazole (3a). The reduction of 2a and 3a was carried out in an acidic/tin solution to yield 4-(4-ammoniophenyl)-1H-pyrazol-2-ium trichlorostannate(II) chloride monohydrate (2b) and 4-(4-ammoniophenyl)-1,2-oxazole hexachlorostannate(IV) (3b). Basic extraction of 3b provided 4-(4-aminophenyl)-1,2-oxazole (3c). The reduction of 2a to 4-(4-aminophenyl)-1H-pyrazole (2c) was achieved by means of hydrazine associated with supported palladium on carbon. The condensation of 2c and 3c with ethyl chlorooxoacetate delivers oxamic esters 2d and 3d. In n-tetrabutylammonium hydroxide solution 2d is fully hydrolyzed, obtaining the n-tetrabutylammonium salt of 4-(1H-pyrazole-4-yl)phenylene-N-oxamate as a hemihydrate (2e). The low stability of isoxazole molecules in basic solutions was proved by crystallizing the n-tetrabutylammonium salt of 1-cyano-1-(4-nitrophenyl)-2-oxoethanide (3f) (obtained by cleavage of 3d with n-Bu4NOH) and preparing its conjugated acid 2-(4-nitrophenyl-3-oxopropanenitrile (3e). The structures of 2b, 3b, 3d and 2e were solved by single crystal X-ray diffraction techniques. The analysis of their crystal packing reveals hydrogen bond features compatible for all compounds as well as some differences depending on the pH of the crystallization solution and the presence or absence of the oxamate group due to the increase of hydrogen bond donors and acceptors.

Aromatic carboxylates have been vastly applied as building blocks for the assembly of robust molecular-based materials owing to their potential application in various fields. In this family, 1,3-benzenedicarboxylate (1,3-bdc), which possesses a “V”-type configuration, has been distinguished. Over the past 20 years, the number of compounds based on 1,3-bdc rapidly expanded due to its multifaceted coordination chemistry and the possibility to generate materials with diversified applications. Therefore, the main purpose of this study is to explore the structural aspects, diversity, and the factors that influence coordination modes of 1,3-bdc by comparison of a series of structurally related compounds. In this sense, we highlight some aspects that can assist in a more rational design of coordination networks based on 1,3-bdc. We also discuss the structural-spectroscopic correlation of the metal-carboxylate bonds aimed at providing support for further investigation on multifunctional materials based on 1,3-bdc, including the amorphous solids. As a direct application of this knowledge, we produced two new CuII-based compounds by the combination of 1,3-bdc and 1,10-phenanthroline (phen). We obtained a discrete complex formed by two cocrystallized mononuclear complexes, {[Cu(1,3-Hbdc)(phen)(H2O)2]ClO4·[Cu(1,3-bdc)(phen)(H2O)2]·2(H2O)} (1), and a coordination polymer, {[Cu(1,3-bdc)(phen)(H2O)]·DMF}n (2), and we provided a further investigation of the nature and features of these compounds based on the discussion raised in this systematic study.

In the series described in this work, the hydrothermal synthesis led to oxidation of the 5-methyl-pyrazinecarboxylate anion to the 2,5-pyrazinedicarboxylate dianion (2,5-pzdc) allowing the preparation of three-dimensional (3D) lanthanide(III) organic frameworks of formula {[Ln2(2,5-pzdc)3(H2O)4]·6H2O}n [Ln = Ce (1), Pr (2), Nd (3), and Eu (4)] and {[Er2(2,5-pzdc)3(H2O)4]·5H2O}n (5). Single-crystal X-ray diffraction on 1–5 reveals that they crystallize in the triclinic system, P1 space group with the series 1–4 being isostructural. The crystal structure of the five compounds are 3D with the lanthanide(III) ions linked through 2,5-pzdc2– dianions acting as two- and fourfold connectors, building a binodal 4,4-connected (4·648)(426282)-mog network. The photophysical properties of the Nd(III) (3) and Eu(III) (4) complexes exhibit sensitized photoluminescence in the near-infrared and visible regions, respectively. The photoluminescence intensity and lifetime of 4 were very sensitive due to the luminescence que...

This work is devoted to the investigation of the thermally induced spin-crossover behavior from a high-spin state (HS, S = 3/2) at higher temperatures to a low-spin phase (LS, S = 1/2) at lower temperatures of the six-coordinate cobalt(II) complex in the compound [Co(terpy)2]3[NbO(C2O4)3]2·3CH​3OH·4H2O (2). The crystal structure of 2 together with that of its counterion as tetraphenylarsonium(V) salt (AsPh4)3[NbO(C2O4)3]·9H2O (1) are also included. The spin-crossover process was followed by the thermal variation of the χMT product between 2.0 and 400 K under the warming mode, with the LS configuration being achieved at T ⩽ 200 K and the LS → HS interconversion being incomplete at 400 K. X-band EPR measurements both in solution and in the solid state were used to characterize the LS state. In order to substantiate the phenomenon in 2, an analytical expression was presented based on the combination of the spin–orbit coupling and both first- and second-order Zeeman effects for a d7 electronic configuration. The best-fit parameters were Cvib = 0.0249, λ = −163 cm−1, α = 1.06, Δ = 1532 cm−1, with a fixed value of gLS = 2.11 determined from the fit of the EPR spectrum at 10 K.

The synthesis, crystal structure and magnetic properties of the coordination polymers of formula [EDAP{Li6(H2O)8[(Cu2(&mu, mpba)2)2(H2O)2]}]n (1) and [(EDAP)2{K(H2O)4[Cu2(&mu, mpba)2(H2O)2]}Cl&middot, 2H2O]n (2), in which mpba = N,N&prime, 1,3-phenylenebis(oxamate) and EDAP2+ = 1,1&prime, ethylenebis(4-aminopyridinium) are described. Both compounds have in common the presence of the [Cu2(mpba)2]4&minus, tetraanionic unit which is a [3,3] metallacyclophane motif in which the copper(II) ions are five-coordinate in a distorted square pyramidal surrounding. The complex anion in 1 is dimerized through double out-of-plane copper to outer carboxylate-oxygen atoms resulting in the centrosymmetric tetracopper(II) fragment [Cu4(&mu, mpba)4(H2O)2]8&minus, which act as a ligand toward six hydrated lithium(I) cations leading to anionic ladder-like double chains whose charge is neutralized by the EDAP2+ cations. In the case of 2, each dicopper(II) entity acts as a ligand towards tetraquapotassium(I) units to afford anionic zig zag single chains of formula {K(H2O)4[Cu2(&mu, mpba)2(H2O)2]}n3n&minus, plus EDAP2+ cations and non-coordinate chloride anions. Cryomagnetic measurements on polycrystalline samples 1 and 2 show the occurrence of ferromagnetic interactions between the copper(II) ions across the &ndash, Namidate&ndash, (C&ndash, C&ndash, C)phenyl&ndash, exchange pathway [J = +10.6 (1) and +8.22 cm&minus, 1 (2)] and antiferromagnetic ones through the double out-of-plane carboxylate-oxygen atoms [j = &minus, 0.68 cm&minus, 1 (1), the spin Hamiltonian being defined as H = &minus, J ( S C u 1 &middot, S C u 2 + S C u 2 i &middot, S C u 1 i ) &minus, j ( S C u 2 &middot, S C u 2 i ) ].

Three new coordination compounds of formula (edap)2[Cu(opba)]2·4H2O (1), (edap)[{Na2(H2O)4}{Cu2(opba)2}]·2H2O (2), and (edap)[{K2(H2O)2}{Cu2(opba)2}]·3H2O (3) (edap = 1,1′-ethylenebis(4-aminopyridinium) and opba = 1,2-phenylenebis(oxamate)) were synthesized through the metathesis reaction involving A2[Cu(opba)] (A = Li+, Na+, and K+) and (edap)Cl2·2H2O. Crystal structures of 1–3 and edap(IO3)2·4H2O compound were elucidated by single crystal X-ray diffraction. Compounds 1–3 are built up from dinuclear copper(II) entities, {[Cu(opba)]2}4– with an asymmetric bis(monatomic oxygen) bridge resulting from the parallel “out-of-plane” disposition of the planar mononuclear [Cu(opba)]2–. They possess distinct supramolecular arrangements of varying dimensionality (nD with n = 0 (1), 1 (2), and 2 (3)) in the solid state depending on the nature of the coordinated alkaline ion present alongside edap2+ counterions. While the {[Cu(opba)]2}4– building blocks are well-isolated in 1, they form either double chains or corruga...

This work concerns the oxalate delivery process that occurs when using (NH4)3[NbO(C2O4)3]·6H2O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C2O4)(H2O)] (1) and [{Cu(dmphen)(CH3OH)}2(μ-C2O4)](ClO4)2 (2) (dmphen = 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)3}(CN)2(μ-CN)]2[{Cu(dmphen)}2(μ-C2O4)]}∙xCH3OH (3) (2.0 ≤ x ≤ 2.4) was obtained by reacting 2 and PPh4[Fe{HB(pz)3}(CN)3]∙H2O [ = tetraphenylphosphonium and = tris(pyrazolyl)borate]. Crystal structures of 1–3 have been determined by single-crystal X-ray diffraction experiments: 1 is a mononuclear trigonal bipyramidal copper(II) species, 2 is a centrosymmetric oxalato-bridged dicopper(II) complex, and 3 consists of centrosymmetric tetranuclear units with intramolecular iron–copper and copper–copper distances around 5.010(1) and 5.1833(9) Å, respectively. Variable-temperature magnetic measurements of 2 and 3 were carried out from 50 to 350 (1) and 1.9 to 300 K (3). A strong antiferromagnetic interaction between copper(II) ions occurs in 2 (J = −340 cm−1, the spin Hamiltonian being defined as ). Analysis of the magnetic data of 3 shows magnetic interactions across the oxalate (J1 = −341 cm−1) and single cyanide (J2 = +12.9 cm−1) … (J2 = +12.9 cm−1) bridges . Simple symmetry considerations of the interacting magnetic orbitals in 2 and 3 provide a clear picture of the exchange pathways involved in these complexes.

Two new oxamate-containing manganese(II) complexes, [{Mn(H2edpba)(H2O)2}2]n (1) and [Mn(H2edpba)(dmso)2]∙dmso∙CH3COCH3∙H2O (2) (H4edpba = N,N′-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of 1 and 2 were characterized by single crystal X-ray diffraction. The structure of 1 consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H2edpba2− ligand and two carboxylate–oxygens from two other H2edpba2− ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an anti-syn conformation. A dmso solution of single crystals of 1 was placed under acetone atmosphere affording 2, whereas putting 2 in equimolar water:ethanol mixture results in 1. The molecular structure of 2 is made up of mononuclear manganese(II) units which are interlinked by weak C–H⋯π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic b axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through anti-syn carboxylate bridges for 1 [J = −1.18 cm−1, the Hamiltonian being defined as H = −J S1.S2] and very weak intrachain ferromagnetic interactions in 2 [J = + 0.046 cm−1, H = −J ∑iSi.Si + 1].

Five new complexes of formula K4[Pd2(mpba)2] · 4H2O (1), {[K4(H2O)(dmso)][Pd2(mpba)2]} (2), {[Cu(bpca)]4[Pd2(mpba)2]} · 6H2O (3), {[Cu(bpca)]2[Pd(opba)]} · 1.75dmso · 0.25H2O (4), {[Cu(bpca)]2[Pd(opba)]}n · ndmso (5) [H4mpba =1,3-phenylenebis(oxamic acid), H4opba = 1,2-phenylenebis(oxamic acid), Hbpca = bis(2-pyridylcarbonyl)amide, and dmso = dimethyl sulfoxide] have been prepared and investigated by infrared spectroscopy, thermal analysis, single crystal X-ray diffraction, and magnetic susceptibility techniques. The structure of 2 consists of a [Pd2(mpba)2]4– anionic entity in which the palladium(II) cations are coordinated by two mpba ligands resulting in a dipalladium(II) unit that acts as a ligand toward potassium(I) cations leading to a neutral three-dimensional network. Compound 3 is a neutral hexanuclear complex where the dinuclear [Pd2(mpba)2]4– unit adopts a tetrakis(bidentate) coordination mode toward four [Cu(bpca)]+ end-cap entities. This compound can be viewed as a “dimer of trimers” in which...

The synthesis, crystal structure and preliminary magnetic characterization of a new heterobimetallic [MnII5CuII5] wheel containing a flexible bis-oxamate type ligand are described. This decanuclear compound exhibits a relatively strong intra-wheel antiferromagnetic interaction leading to a ground spin state S = 10.

Single crystals of the mononuclear bis-oxamate nickel(II) complex [Ni(bipy)(H2edpba)]·dmso (1) are obtained by reacting [Ni(bipy)Cl2]·H2O and the flexible K2(H2edpba) ligand [bipy = 2,2′-bipyridine; H4edpba = N,N′-2,2′-ethylenediphenylenebis(oxamic acid)]. The reaction of 1 with copper(II) ions resulted in two products in which the replacement of the nickel(II) ion by copper(II) took place: the chain compound [Cu(bipy)(H2edpba)]n·3nH2O·ndmso [dmso = dimethyl sulfoxide] (2) and the analogous chain compound without dmso crystallization molecules [Cu(bipy)(H2edpba)]n·1.5nH2O (3a) in its polycrystalline form. The reaction of [Cu(bipy)Cl2] and K2(H2edpba) yielded single crystals of [Cu(bipy)(H2edpba)]n·1.5nH2O (3b). The H2edpba2– ligand exhibits the anti conformation in 1, 2, and 3b, but it adopts different coordination modes: terminal bis-bidentate (1) and bridging bis-bidentate (2 and 3b) through the two pairs of carbonyl-oxygen atoms of the two oxamate arms. Magnetic susceptibility measurements carried out ...

The cytotoxic activity against human carcinogenic cells of five compounds, three of them containing palladium(II) and one containing platinum(II) was evaluated for the first time. These compounds were synthesized and characterized and present the formula K2(H2opba)·2H2O (1), K2[Pd(opba)]·2H2O (2), [Pd(NH3)4]Cl2·2H2O (3), [Pd(NH3)4][Pd(opba)] (4) and [Pt(H2opba)]·H2O (5), where opba = 1,2-phenylenebis(oxamate). Compounds 4 and 5 are novel and their synthesis and characterization are discussed in detail in this paper. The crystal structure of 4 was elucidated by single crystal X-ray diffraction and consists of discrete [Pd(NH3)4]2+cations interacting via hydrogen-bonds with [Pd(opba)]2− anions. Despite the fact that compound 1 has no significant effect on the growth of chronic myelogenous leukemia cells, its PdII and PtII complexes inhibit cellular growth in the following order of activity 2 ∼ 4 > 5. Compounds 2 and 4 are approximately 20 times more cytotoxic against leukemia cells than the free ligand.

In this paper, an artificial intelligence solution to diagnose faults before acquisition of submersible petroleum motor pump systems is presented. Proper fault identification is time consuming and demands highly trained human experts. The diagnosis system is intended to facilitate the work of the human component of this important process by replicating the decision of highly trained experts through a classifier. To perform the automatic diagnosis, firstly intermediate features are extracted as the vibration spectra. Subsequently, high level features are extracted and fed into a classifier that outputs the final diagnose. To validate our proposal and to select the best classifier (among K-Nearest-Neighbour, Random Forest, Support Vector Machine and Decision Tree) for this problem, we performed a comparative study using real data acquired in tests accomplished before acquisition of submersible motor pumps. Our dataset comprises thousands of entries of accelerometer sensors (vertically distributed along the particular system components) data labelled by an human expert to one of the considered scenarios (normal pump, faulty sensor, faulty pump with rubbing, misalignment or unbalance). Results have showed that the evaluated classifiers have equivalent performance for the given problem, and that the standardization procedure can improve the performance of some classifiers. The performance of the classifiers is sufficient to facilitate the work performed by humans and consequently reduce the time spent in the pump fault diagnosis process.

Two new mononuclear oxamato-containing palladium(II) complexes of formula K2[Pd(opba)]·2H2O (1) and (PPh4)2[Pd(opba)]·2H2O (2) and the heterodimetallic palladium(II)–cobalt(II) chain {[Co(H2O)2Pd(opba)]·dmso}n (3) [opba = 1,2-phenylenebis(oxamate), PPh4+ = tetraphenylphosphonium cation and dmso = dimethyl sulfoxide] have been prepared, and the structures of two of them (compounds 2 and 3) were determined by X-ray diffraction analysis of single crystals. The structure of 2 consists of discrete anions of [Pd(opba)2]2– and PPh4+ cations. Each PdII ion in 2 is surrounded by two oxamate nitrogen atoms and two carboxylate oxygen atoms in a square-planar surrounding. Compound 3 is a neutral chain with regular alternating PdII and CoII ions, the [Pd(opba)]2– entity acting as a bis(bidentate) ligand towards trans-diaquacobalt(II) fragments, and dmso molecules of crystallization. Compound 3 exhibits a single-crystal-to-single-crystal phase transition between monoclinic C2/c (α phase) and triclinic P (β phase) space groups. Within the α phase the dmso molecule of crystallization is disordered, but it becomes ordered below 215 K in the β phase. The ordering process of the dmso molecule is followed by a reduction in the unit cell volume. The magnetic properties of 3 are barely affected by the structural phase transition, and they indicate an important spin–orbit coupling of the high-spin octahedral CoII ion [α = 1.245, λ = –151 cm–1, Δ = 494 cm–1, the spin Hamiltonian being defined as H = –αλLS + Δ(Lz2–2/3) + βH(–αL + geS)] with an almost negligible intra- [through the diamagnetic square-planar PdII centre] and interchain antiferromagnetic interactions (θ = –0.32 K).

A novel series of copper(II) coordination polymers [Cu2(O2CC8H9)4(pyz)]n (1), [Cu2(O2CC8H9)4(dps)]n (2), {[Cu(O2CC8H9)2(dps)(H2O)]·H2O}n (3), {[NaCu(O2CC8H9)2(bpm)(NO3)]·H2O}n (4), and [Cu4(O2CC8H9)6(OH)2(bpp)2]n (5) [O2CC8H9− = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2′-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [CuII2(μ-O2CC8H9)4] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[CuII(O2CC8H9)2] units linked by the bis-monodentate dps ligand. Compound 4 consists of heterobimetallic chains where [NaI2CuII2(μ-O2CC8H9)4(NO3)2] units are doubly bridged by bis-bidentate bpm ligands. Compound 5 is also a chain compound whose structure is made up by tetranuclear [CuII4(μ3-OH)2(μ-O2CC8H9)4(O2CC8H9)2] units which are doubly bridged by bis-monodentate bpp ligands. The magnetic properties were investigated in the temperature range 1.8–300 K. Strong antiferromagnetic interactions across the quadruple syn–syn carboxylate are observed in 1 and 2 [J = −378 (1) and −348 cm−1 (2)] whereas a weak ferromagnetic coupling through the double out-of-plane oxo(carboxylate) bridge occurs in 4 [J = +2.66 cm−1], the spin Hamiltonian being defined as H = −JS1·S2 with S1 = S2 = SCu = 1/2. A quasi Curie law is observed for 3 (θ = −0.36 cm−1), the bis-monodentate dps ligand being a very poor mediator of magnetic interactions. The analysis of the magnetic properties of 5 is quite complex because of the presence of two crystallographically independent tetracopper(II) units with single-μ-hydroxo, di-μ-hydroxo, μ3-hydroxo and single-μ-hydroxo plus double syn,syn carboxylate bridges in each one. The nature and values of the magnetic couplings for 5 obtained by fitting (intermediate, strong and weak antiferromagnetic interactions for the three former exchange pathways respectively, and intermediate ferromagnetic interactions for the latter one) were substantiated by DFT type calculations.

A relatively large antiferromagnetic interaction between the two chromium(III) ions from the molecular square [{Cr(dmso)4}2{Nb(μ-O)2(C2O4)2}2] () (J = -12.0 cm(-1)) is mediated by the diamagnetic oxo-Nb(V)-oxo pathway, its nature and magnitude being substantiated by DFT type theoretical calculations.

The synthesis, crystal structure and preliminary magnetic characterization of a new heterobimetallic [Mn₅(II)Cu₅(II)] wheel containing a flexible bis-oxamate type ligand are described. This decanuclear compound exhibits a relatively strong intra-wheel antiferromagnetic interaction leading to a ground spin state S = 10.

In this work, an efficient heterogeneous acid catalyst for the esterification of oleic acid was prepared directly from oilseed cake by a simple sulfonation with concentrated H 2 SO 4 . Characterization by SEM/EDS, IR, Raman, TG, TG/MS, potentiometric titration showed that treatment with H 2 SO 4 for 1, 2 and 4 h at 120 °C partially dehydrates the cake to form a carbon/cellulose composite which is sulfonated to produce strong SO 3 H acidic sites. These surface sites were active for the esterification of oleic acid with yields ca. 84%, 88% and 94% in the presence of 5, 10 and 20 wt% catalyst, respectively. These results are comparable to 98% yield obtained with 1 wt% H2SO4 and higher than 75% observed for a high surface area (880 m 2 g −1 ) sulfonated activated carbon with similar number of SO3H active groups. These results are discussed in terms of two effects: (i) the number of sulfonic surface acidic groups and (ii) the presence of a hydrophilic cellulosic fraction in the catalyst that adsorbs/traps water formed in the reaction shifting the esterification equilibrium and improving the yield.

For the new organic salt 1H-imidazol-3-ium 1,4-dioxo-1,4-dihydronaphthalen-2-olate, C3H5N2+·C10H5O3−,ab initiocalculations of the gas-phase structures of the lawsonate and imidazolium ions were performed to help in the interpretation of the structural features observed. Three different types of hydrogen bond are responsible for the three-dimensional packing of the salt.

Hydrogen bonds have been exhaustively investigated in order to understand their role in intermolecular interactions [1]. The importance of the hydrogen bonds follows from their particular role in the molecular association thanks to their variable strength and geometry. Indeed depending on the chemical nature of the donor/acceptor as well as on the physical parameters such as temperature and pressure, hydrogen bonds can give rise to directional and/or to hydrophilic like interactions which play a crucial role both in stabilizing static structures and in mediating dynamic biological processes. Among the hydrogen bonds the less common ones are the strongest (and shortest) ones, characterized by donor–acceptor interatomic distances shorter than 2.6 Å with D–H...A angle close to 180° [2]. Most of the short hydrogen bonds observed and reported so far are intramolecular interactions, nevertheless, both the bridging as well as the coordination of the metal ions by carboxylate groups and oxalate anions can provide the possibility of short interactions [3]. During the refinement of the structure of the potassium-monodeprotonated salt of 1,4-butodioxybis(4'-benzoic) acid it was observed a high electron density maxima over the mirror symmetry element. This electron density indicates a hydrogen atom doing an ultra short intermolecular hydrogen bond (2.4846(1) Å) between the deprotonated and non-deprotonated carboxylic acid groups. The seven fold coordinate potassium atom ties the organic moieties pushing the hydrogen atom closer to the deprotonated and negatively charged, carboxylate oxygen atom. The hydrogen atomic displacement parameter suggests, however, a possible positional disorder, which could be interpreted both as symmetrical O–H–O or asymmetrical O–H...O interaction.

A discrete dicopper(II) system, [Cu(bipy)(H2mpba)]2·2H2O (1), and its isomeric chain, [Cu(bipy)(H2mpba)]·dmso (2) [bipy = 2,2′-bipyridine and H4mpba = N,N′-1,3-phenylenebis(oxamic acid)], were obtained by modifying the ratio of the H2O–dmso solvent mixture, and their interconversion was also monitored by changing the solvents during the synthesis. The solvents play an essential role in the formation and crystallization of these complexes, presenting different dimensionalities and connectivities. The double deprotonated H2mpba2− adopts the bidentate/monodentate (1) and bis-bidentate (2) bridging modes toward the (2,2′-bipyridyl)copper(II) units affording a dinuclear compound (1) and a linear chain (2), respectively. Variable-temperature magnetic measurements show the occurrence of weak intradinuclear (1) and intrachain (2) antiferromagnetic interactions.