Transition metal tetrapentafluorophenyl porphyrin catalyzed hydrogen evolution from acetic acid and water

The performance of Cu (1), Co (2) and Zn (3) complexes of meso-tetrakis(pentafluorophenyl)porphyrin in the electrocatalyzed evolution of hydrogen has been investigated. In acetic acid media, hydrogen evolution turnover frequency (TOF) values for complexes 1, 2 and 3 were 22.1, 19.8 and 18.1 h^?1, respectively, at an overpotential of 942 mV versus Ag/AgNO₃. In buffer solution at pH 7.0, the corresponding hydrogen evolution TOF values increased dramatically, to 266, 234, 218 h^?1 at a similar overpotential of 878 mV versus SHE. The Faradaic yields of 1, 2, and 3 for sustained proton reduction in catalytic experiments at a glassy carbon electrode over 72 h were 89.7, 90.4 and 91.0%, respectively, with no observable catalyst decomposition.     

Syntheses and luminescence of four supramolecular coordination complexes with flexible ligand

Four d ¹⁰-based complexes with chemical formulae {[Zn(L¹)₂(H₂O)₂(4,4′-Bipy)₂] (I), {[Zn₂(L¹)₄(Mi)] · 4H₂O} (II), {[Zn(L¹)₂(Phen)] · H₂O} (III) {[Cd(L¹)₂(Phen)] · 2H₂O} (IV) (HL¹ = p-hydroxy phenylacetic acid, 4,4′-Bipy = 4,4′-bipyridine, Phen = 1,10-phenanthroline, Mi = 1,4-bis(imidazol-1-yl)butane) have been synthesized and structurally characterized by single crystal X-ray diffraction (CIF files CCDC nos. 1047119 (I), 1047120 (II), 1047121 (III), 1047122 (IV)). The significant effect of assistant ligands and metal ions on assembly of I?IV has been demonstrated, which leads to the formation of distinct crystalline products. Complexes I?IV show various coordination motifs with different existing forms and coordination modes of the organic ligands. Furthermore, extend supramolecular networks are connected by secondary interactions such as hydrogen-bonding and aromatic stacking. The thermal stability and luminescent properties of the compounds were discussed in detail.     

The thermodynamic properties of alkylated γ-lactones

The enthalpies of formation of γ-pentanolactone (I), γ-hexanolactone (II), and γ-nonanolactone (III) were determined by combustion calorimetry. The enthalpies of vaporization of these lactones were measured by the transfer method. Conformational analysis was performed and equilibrium structures, sets of fundamental vibrations, moments of inertia, and total energies of the stablest conformers of I, II, and III were calculated by the B3LYP/6-311G(d,p), G3MP2, and CBS-QB3 methods. The experimental IR spectra and calculated vibrational frequencies were used to obtain sets of fundamental vibrations of the stablest conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. Additive and quantum-chemical methods were applied to estimate the Δ_f H ^o(g) values of a number of γ-lactones. Composite quantum-chemical methods were used to obtain the energies of monomethyl γ-butyrolactones and estimate their relative stability depending on the position of the methyl substituent in the ring.     

Study of lithium complexes with benzo-15-crown-5 ether by X-ray diffraction and IR spectroscopy

The complex formation of lithium with benzo-15-crown-5 (B15C5) was investigated. The complexes LiB15C5H₂OX, where X = Cl^? (1), I^? (2), (3), (5), and LiBF₄B15C5 (4) were synthesized and studied by IR spectroscopy. Complexes 1–4 were examined by X-ray diffraction. According to IR spectroscopy data, the crown ether conformation changes upon dissolution. The interaction of the extracted complex with the solvent was identified.     

Directed assembly of cobalt(II) 1-H-indazole-3-carboxylic acid coordination networks by bipyridine and its derivatives: structural versatility,electrochemical properties,and antifungal activity

This paper describes the hydrothermal synthesis, full characterization, and architectural diversity of three intriguingly bioactive cobalt–organic frameworks, namely, 3D [Co(HL ^? )₂(BPY)] _n ·4nH₂O (1), 2D [Co(HL ^? )₂(BPE)] _n (2), and 2D [Co(HL ^? )₂(DPP)] _n (3) coordination polymers, synthesized through a mixed ligand strategy using H ₂ L (1-H-indazole-3-carboxylic acid) as a main structural block and the flexible bipyridine and its derivatives (BPY = 4,4′-bipydine, BPE = 1,2-bis(4-pyridyl)ethane, DPP = 1,3-bis(4-pyridyl)propane) as auxiliary ligand sources. Complexes 1–3 were isolated as air stable and slightly soluble crystalline solids and characterized using elemental analysis, FT-IR, electrochemical technique, thermogravimetric analysis, powder X-ray diffractometer, and single-crystal X-ray crystallography. The bipyridine derivatives played key roles in defining the structural space group and dimensionality feature of the obtained networks. The abundant H-bonding and π–π stacking interactions in complexes 1–3 gave rise to their intricate metal–organic structures of 3D (1), 2D (2), and 2D (3). In addition, the solutions of complexes 1–3 showed profound antifungal activities against the selected strain of Colletotrichum musae compared with the controlled group using benomyl as a traditional agrochemical fungicide.     

Structural features of monomeric octahedral <Emphasis Type="Italic">d</Emphasis><Superscript>2</Superscript>-rhenium(V) monooxo complexes with oxygen atoms of bidentate-chelating acido (O,O)-ligands

The structural features of 39 mononuclear octahedral d ²-rhenium(V) monooxo complexes (I–ХХХIХ) with oxygen atoms of bidentate-chelating (O,O) acido ligands (Lig) are considered. In 21 complexes (I–ХХI), the O(lig) atoms are both in trans and cis positions to oxo ligands. In the other 18 complexes (XXI–XXXIX), both O(lig) atoms are in cis positions to the O(oxo) ligands.     

Paramagnetic Cu<Superscript>II</Superscript> complexes with 1-(hetarylmethyl)silatranes

The structures of paramagnetic complexes CuCl₂?L with L = HetCH₂Si(OCH₂CH₂)₃N [Het = pyrrol-1-yl (1), indol-1-yl (2), carbazol-9-yl (3), imidazole-1-yl (4), 3,5-dimethylpyrazol-1-yl (5), 1,2,4-triazol-1-yl (6), benzimidazol-1-yl (7), and 1,2,3-benzotriazol-1-yl (8)] were studied by the ESR and quantum chemical methods in terms of the density functional theory (DFT) approximation. The difference in structures of complexes CuCl₂?1—CuCl₂?8 is mainly determined by the nature of the five-membered heterocycle. The ESR spectra at room temperature are typical of the mononuclear complexes of Cu^II of axial symmetry with various types of distortions. In complexes CuCl₂?1—CuCl₂?3, narrow symmetric signals of zero-valent copper are recorded. These signals remain in the spectra for at least six months, which can characterize them as efficient stabilizing matrices of nanoparticles.     

Effect of the air humidity on the proton conductivity of some aminobenzenesulfonic acids

Effects of environment conditions (humidity and temperature) on the proton conductivity of aminobenzenesulfonic acids: 2-amino-(orthanilic) acid (I), 3-amino-(metanilic) acid (II), 4-amino-(sulfanilic) acid (III), their general formula NH₂C₆H₄SO₃H, and 3-amino-4-hydroxobenzenesulfonic acid (IV) [NH₂(OH)C₆H₃SO₃H), as well as (for sake of comparison) inorganic aminosulfonic acid [sulphamic acid (NH₂SO₃H)] (V) are studied. All above-listed compounds are zwitter-ions: they contain a fragment NH ₃ ⁺ SO ₃ ^? . The presence of this structural fragment affects the thermal stability of the compounds; according to the mass-spectrometry analysis data, the decomposition of the SO₃-fragment begins at the following temperatures: (I) ?339, (II) ?370, (III) ?320, (IV) ?278, and (V) ?220°C. It is shown that the increase of the environment relative humidity up to 95% results in the increase of the aminobenzenesulfonic acids proton conductivity from 10^?9–10^?8 to 10^?5 S cm^?1; sulphamic acid, to 10^?4 S cm^?1. At that, the amount of adsorbed water does not exceed 0.2 moles per 1 sulfo group in all cases. The conductance activation energy equals 0.2 eV at a relative humidity of 95%.     

Syntheses and structures of tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)-, tris(3-fluorophenyl)-, and tris(4-fluorophenyl)antimony dioximates

Tris(para-tolyl)antimony bis(2-oxybenzaldoximate) (I), tris(para-tolyl)antimony bis(2-nitrobenzaldoximate) (II), tris(para-tolyl)antimony bis(2-bromobenzaldoximate) (III), tris(3-fluorophenyl)antimony bis(2-oxybenzaldoximate) (IV), tris(4-fluorophenyl)antimony bis(2-bromobenzaldoximate) (V), and tris(4-fluorophenyl)antimony bis(2-nitrobenzaldoximate) (VI) are synthesized by the reactions of tris(paratolyl)-, tris(3-fluorophenyl)-, and tris(4-fluorophenyl)antimony with 2-oxy-, 2-nitro-, and 2-bromobenzaldoxime in diethyl ether in the presence of tert-butyl hydroperoxide. The Sb atoms in complexes I–VI have a distorted trigonal bipyramidal coordination mode with the oximate ligands in the axial positions. CIF files CCDC nos. 1062231 (I), 1059962 (II), 1465384 (III), 1465109 (IV), 1471948 (V), and 1060387 (VI).     

Synthesis,characterization and X-ray crystal structure of novel nickel Schiff base complexes and investigation of their catalytic activity in the electrocatalytic reduction of alkyl and aryl halides

Novel potentially bidentate NO Schiff base ligands, HL ¹ and HL ² derived from condensation reaction of 2′-methoxyphenyl-2-ethylamine with salicylaldehyde (HL ¹ ) and with 2-hydroxy-4-methoxybenzaldehyde (HL ² ), and their nickel complexes were synthesized and characterized by usual spectroscopic techniques such as FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and elemental analysis. It was revealed that the bidentate Schiff base ligands coordinate with Ni(II) ions yielding mononuclear complexes with 1:2 (metal/ligand) stoichiometry. This result has been determined by using X-ray crystallographic technique of HL ² and the nickel complex derived from HL ¹ (Ni(II)-2L ¹ ). So, the structural studies showed that the two Ni(II) complexes adopt a square-planar geometry around the central metal ion. Cyclic voltammetry studies were investigated in 0.1 M TBAP in DMF solution and indicate that the nickel complexes show one reduction wave related to Ni(II)/Ni(I) redox couple. The electrocatalytical properties of these complexes were also studied in the same electrolyte medium. Their electrocatalytic performances have been tested toward the electroreduction reaction of bromocyclopentane and iodobenzene, showing a promoted activity in the case of the Ni(II)-2L ² complex.     

Synthesis and structure of bischelate gallium complexes (dpp-bian)Ga(acac) and (dpp-bian)Ga(2,2´-bipy) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)

A reaction of digallane [(dpp-bian)Ga—Ga(dpp-bian)] (1) (dpp-bian is the 1,2-bis[(2,6-disopropylphenyl)imino]acenaphthene) with one equivalent of I₂ leads to oxidation of (dpp-bian)^2– in compound 1 to (dpp-bian)–and gives [(dpp-bian)GaI—GaI(dpp-bian)] (2). In the reaction of compound 2 with two equivalents of (acac)Na, not only exchange of the iodide and acetylacetonate ions takes place, but also a transfer of electrons from the metal—metal bond to dpp-bian with the formation of the complex [(dpp-bian)Ga(acac)] (3), in which the dpp-bian ligand is a dianion. A reaction of digallane 1 with 2,2´-bipyridyl at 200 °C in toluene in a sealed tube leads to the reduction of 2,2´-bipyridyl and gives the complex [(dpp-bian)Ga(bipy)] (4), which contains two different chelate redox-active ligands. The new compounds were characterized by IR (3, 4), NMR (3), and ESR spectra (4), the structures of both derivatives were established by X-ray diffraction.     

The synthesis and structural characterization of transition metal coordination complexes of coumarilic acid

The coumarilate (coum^?) complexes of Co^II(1), Ni^II(2) Cu^II(3) and Zn^II(4) were synthesized and characterized by elemental analysis, magnetic susceptibility, solid-state UV–Vis, FTIR spectra, thermoanalytical TG–DTG/DTA and single-crystal X-ray diffraction methods. It was found that all of the complex structures have 2 mol (coum^?) ligand bonded as monoanionic monodentate in the structures of 1 and 2 while they were coordinated to metal cations as monoanionic bidentate in the complexes 3 and 4. There was not any hydrate water in the metal complexes. The complexes of 1 and 2 have four moles of aqua ligand, and the other complexes have two moles. Thermal decomposition of each complex starts with dehydration, and then the decomposition of organic parts goes. The thermal dehydration of the complexes takes place in one (for the compounds of 2, 3, 4) or two (for the compound 1) steps. The decomposition mechanism and the thermal stability of the complexes under investigation were determined on the basis of their structures. Metal oxides were obtained as the final decomposition product.     

Synthesis,characterization and antitumor activity of palladium(II) complexes of imidazolidine-2-thione

Complexes of the type cis-[PdX₂(imzt)(PPh₃)] {imzt = imidazolidine-2-thione; PPh₃ = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and ¹H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl₂(CH₃CN)₂], imidazolidine-2-thione and triphenylphosphine in CHCl₃/CH₃OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH₃OH showed that the coordination geometry around Pd^II is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by ¹H NMR spectroscopy, revealing that the coordination takes place via N7.     

Synthesis and properties of copper(II) complexes with a chiral dioxatetraazamacrocyclic ligand based on a natural monoterpene, (+)-3-carene

The copper(II) compounds [CuL](NO₃)₂ · H₂O (I), [CuL](ClO₄)₂ · H₂O (II), CuLCl₂ · 3H₂O (III), and CuLBr₂ · 4H₂O (IV), where L is a chiral dioxatetraazamacrocyclic ligand based on the natural monoterpene (+)-3-carene, have been synthesized. According to IR and EPR spectroscopy, L acts as a tetradentate chelating ligand coordinated through the N atoms of the NH and C=N groups. The NO ₃ ^? anions in I and the ClO ₄ ^? anions in II are outer-sphere. I and II have a planar coordination core CuN₄, III has a CuN₄ClO coordination core, and IV has a CuN₄Br₂ coordination core.     

Lanthanide complexes with the Schiff base containing sterically hindered phenol: Synthesis,structure, and luminescence properties

The syntheses of the 2,6-di-tert-butyl-4-(2-hydroxybenzylideneamino)phenolate (L) complexes of Gd (I), Nd (II), Er (III), Yb (IV), Tm (V), Sm (VI), and Tb (VII) are described. The structures of the Gd and Er complexes are determined by X-ray diffraction analysis (CIF files CCDC nos. 1558820 (I) and 1558819 (III)). All synthesized compounds exhibit ligand-centered photoluminescence in a range of 405–485 nm. In addition, the luminescence spectra of solid samples of the neodymium and ytterbium complexes contain narrow bands of f–f transitions characteristic of Nd³⁺ and Yb³⁺ ions.     

The conformational spaces of dinaphthyl ketones,dinaphthyl thioketones,and dinaphthyl diazomethanes: 1-substituted naphthalenes versus 2-substituted naphthalenes

1,1′-Dinaphthyl ketone (15), 1,2′-dinaphthyl ketone (18), 2,2′-dinaphthyl ketone (19), 1,1′-dinaphthyl thioketone (16), 1,2′-dinaphthyl thioketone (20), 2,2′-dinaphthyl thioketone (21), 1,1′-dinaphthyldiazomethane (17), 1,2′-dinaphthyldiazomethane (22), and 2,2′-dinaphthyldiazomethane (23) have been synthesized. Ketone 15 has been prepared from di(1-naphthyl)methanol; ketone 18 has been prepared by a Friedel–Crafts acylation of naphthalene with 2-naphthoyl chloride; ketone 19 has been prepared by a Grignard reaction of 2-naphthylmagnesium bromide with 2-naphthoyl chloride. Thioketones 16, 20, and 21 have been prepared by reactions of the corresponding ketones 15, 18, and 19 with Lawesson’s reagent. The diazomethane derivatives 17, 22, and 23 have been prepared by the HgO oxidation of the respective hydrazones 25, 27, and 28 (prepared from the respective thioketones 16, 20, and 21). The crystal and molecular structures of ketones 15, 18, and 19 and of thioketone 16 have been determined. A variety of conformations in the crystal structures is noted: 1Z,1′Z (15), 1E,1′Z (16), 1E,2′E (18), 2Z,2′Z (19). The NMR experiments have demonstrated the downfield shifts of the protons peri to the carbonyl and the thiocarbonyl groups in 15, 16, and 18, but not in 20. A systematic DFT study (B3LYP/6-31G(d)) of the conformational spaces of 15–23 and their ¹H and ¹³C NMR chemical shifts has been performed. In each series of constitutional isomers, the order of stabilities is 2,2′-(NA)₂C=X > 1,2′-(NA)₂C=X > 1,1′-(NA)₂C=X. The decrease in the stabilities of 1-naphthyl derivatives relative to 2-naphthyl derivatives is attributed to the increased overcrowding and the increased twist angles in 1-naphthyl derivatives. The increased stabilization of E-conformations with the increase of the radius of a heteroatom at C⁹ due to the steric reasons is noted. The DFT calculations satisfactorily describe the X-ray conformations of 15, 16, 18, and 19.     

Cobalt(II) complexes with pentadentate Schiff bases 2,6-diacetylpyridine hydrazones: Syntheses and structures

Seven new cobalt(II) complexes based on the Schiff bases, 2,6-diacetylpyridine bis(isonicotinoylhydrazone) (H₂L¹) and 2,6-diacetylpyridine bis(nicotinoylhydrazone) (H₂L²), are synthesized and studied by X-ray diffraction analysis: [Co(H₂L¹)(NCS)₂] · 2.25H₂O (I), [Co(H₂L²)(NCS)₂] · CH₃OH (II), [Co(H₂L²)(NCS)(H₂O)]NCS (III), [Co(H₄L¹)(NCS)₂](NO₃)₂ · 2H₂O (IV), [Co(H₄L¹)(NCS)₂][Co(NCS)₄] · 0.75H₂O (V), [Co(H₄L²)(NCS)₂][Co(NCS)₄] · 1.75H₂O (VI), and [Co(H₂L²)(NCS)(CH₃OH)]₂[Co(NCS)₄] · 2CH₃OH (VII) (CIF files CCDC 941186 (I), 1457906 (Ia), 1457905 (II), 941187 (III), 1457907 (IV), 1457908 (V), 1457909 (VI), and 941188 (VII)). The organic ligands in the complexes act as pentadentate neutral H₂L or doubly protonated (H₄L)²⁺ coordinated through the same set of donor atoms N₃O₂. In all compounds I–VII, the coordination polyhedron of the Co²⁺ ion in a complex with the Schiff bases has a shape of a pentagonal bipyramid. The hydrazones are arranged in the equatorial plane of the bipyramid. Its axial vertices are occupied by the nitrogen atoms of the NCS￣ anions in compounds I, II, and IV–VI and by the nitrogen atoms of NCS￣ and oxygen of the water molecule in compound III or methanol in compound VII. The NO ₃ ^- anions or [Co(NCS)₄]^2￣ complex anions obtained by the reactions are involved along with the NCS￣ anions in the formation of compounds IV–VII.     

Binding of carboxylate and trimethylammonium salts to octa-acid and TEMOA deep-cavity cavitands

In participation of the fifth statistical assessment of modeling of proteins and ligands (SAMPL5), the strength of association of six guests (3–8) to two hosts (1 and 2) were measured by ¹H NMR and ITC. Each host possessed a unique and well-defined binding pocket, whilst the wide array of amphiphilic guests possessed binding moieties that included: a terminal alkyne, nitro-arene, alkyl halide and cyano-arene groups. Solubilizing head groups for the guests included both positively charged trimethylammonium and negatively charged carboxylate functionality. Measured association constants (K _a ) covered five orders of magnitude, ranging from 56 M^?1 for guest 6 binding with host 2 up to 7.43 × 10⁶ M^?1 for guest 6 binding to host 1.     

Investigation of Structural,Electronic and Biological Properties of Two Zn(II) Complexes with Pentaaza Macrocyclic Schiff-Base Ligand: A DFT Approach

Two zinc(II) complexes, [ZnL¹Br]⁺ (1), and [ZnL²]²⁺ (2), are optimized by using density functional theory at B3LYP method with mix basis sets which are LANL2DZ/6–31G(d,p) and LANL2TZ+/6–31++G(d,p) basis sets. L¹ and L² are pentadentate macrocyclic Schiff-base ligands containing piperazine moiety. The optimized structures and structural parameters are obtained by using each basis set. IR and UV–VIS spectra of complex (1) and (2) are investigated in detail. NLO properties of Zn(II) complexes are investigated and it is found that NLO properties of complex (2) is better than complex (1). Solvent effects on biological activity are investigated in gas phase, water and chloroform for studied complexes and no solvent effects are monitored for complex (1) and (2). Biological reactivity of complex (1) is higher than that of complex (2).     

Ruthenium(II) complexes of azoimine and α-diimine ligands: synthesis,spectroscopic and electrochemical properties,crystal structures and DFT calculations

Five octahedral ruthenium(II) complexes with azoimine–quinoline (Azo) and α-diimine (L) ligands having the general formula [Ru^II(L)(Azo)Cl](PF₆) (1–5) {Azo: PhN=NC(COMe)=NC₉H₆N, L = 4,4′-dimethoxy-2,2′-bipyridine (dmeb) (1), 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H₂Azo) and α-diimine (L) pro-ligands to RuCl₃ in refluxing EtOH. The tridentate azoimine–quinoline ligands coordinate to ruthenium via the Azo-N′, N′-imine and N″-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, ¹H, ¹³C and ¹⁹F NMR) and electrochemical behavior of complexes 1–5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong π-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63–1.72 V versus NHE. The electronic spectra in MeCN and IR spectra in CH₂Cl₂ for complex 3 in its oxidized 3 ⁺ and reduced 3 ^? forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV–Vis absorption bands.