Syntheses,characterization, and crystal structures of ruthenium(II)/(III) complexes with tridentate salicylaldiminato ligands

Treatment of [Ru(PPh₃)₃Cl₂] with one equivalent of tridentate Schiff base 2-[(2-dimethylamino-ethylimino)-methyl]-phenol (HL) in the presence of triethylamine afforded a ruthenium(III) complex [RuCl₃(κ²-N,N-NH₂CH₂CH₂NMe₂)(PPh₃)] as a result of decomposition of HL. Interaction of HL and one equivalent of [RuHCl(CO)(PPh₃)₃], [Ru(CO)₂Cl₂] or [Ru(tht)₄Cl₂] (tht = tetrahydrothiophene) under different conditions led to isolation of the corresponding ruthenium(II) complexes [RuCl(κ³-N,N,O-L)(CO)(PPh₃)] (2), [RuCl(κ³-N,N,O-L)(CO)₂] (3), and a ruthenium(III) complex [RuCl₂(κ³-N,N,O-L)(tht)] (4), respectively. Molecular structures of 1·CH₂Cl₂, 2·CH₂Cl₂, 3 and 4 have been determined by single-crystal X-ray diffraction.     

Variation in coordinative property of two different N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL¹] · CH₃OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N₂O₂ tetradentate Schiff base ligand H ₂ L ¹ , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL²)₃] · (ClO₄)₃ · H₂O (2) was synthesised using an asymmetric N₂O₂ tetradentate Schiff base ligand HL ² on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N₂O₂ functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.     

Synthesis,crystal structures,thermal properties,and DNA-binding studies of transition metal complexes with imidazole ligands

A new series of complexes of transition metal (Cu, Zn, Ni) perchlorate with imidazole have been synthesized and characterized by elemental analysis, infrared (IR), UV-Vis spectroscopy, and single-crystal X-ray diffraction. Based on elemental and spectral data, the complexes are M(C₃H₄N₂) _x (ClO₄)₂ (M?=?Cu, Zn, x?=?4; M?=?Ni, x?=?6; C₃H₄N₂?=?imidazole). The crystal structures of Cu(C₃H₄N₂)₄(ClO₄)₂ (1) and Zn(C₃H₄N₂)₄(ClO₄)₂ (2) show metals surrounded by four nitrogens of imidazole, while the nickel complex Ni(C₃H₄N₂)₆(ClO₄)₂ (3) has six nitrogens of imidazole. Intra- and inter-molecular hydrogen bonds exist between hydrogen of imidazole and oxygen of perchlorate. The thermal stabilities of 1, 2, and 3 at different heating rates (β?=?5°C?min^?1, 10°C?min^?1, and 15°C?min^?1) show that all the complexes exhibit two thermal decomposition stages; the sequence of thermal stability is 2?>?1?>?3. 1, 2, 3, and imidazole display DNA binding ability, ascertained by UV-Vis titration.     

Different coordination modes of trans‐2‐{[(2‐methoxyphenyl)imino]methyl}phenoxide in rare‐earth complexes: influence of the metal cation radius and the number of ligands on steric congestion and ligand coordination modes

A simple and effective synthetic route to homo‐ and heteroleptic rare‐earth (Ln = Y, La and Nd) complexes with a tridentate Schiff base anion has been demonstrated using exchange reactions of rare‐earth chlorides with in‐situ‐generated sodium (E)‐2‐{[(2‐methoxyphenyl)imino]methyl}phenoxide in different molar ratios in absolute methanol. Five crystal structures have been determined and studied, namely tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐κ³O¹,N,O²)lanthanum, [La(C₁₄H₁₂NO₂)₃], ( 1 ), tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐κ³O¹,N,O²)neodymium tetrahydrofuran disolvate, [La(C₁₄H₁₂NO₂)₃]·2C₄H₈O, ( 2 )·2THF, tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato)‐κ³O¹,N,O²;κ³O¹,N,O²;κ²N,O¹‐yttrium, [Y(C₁₄H₁₂NO₂)₃], ( 3 ), dichlorido‐1κCl,2κCl‐μ‐methanolato‐1:2κ²O:O‐methanol‐2κO‐(μ‐2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐1κ³O¹,N,O²:2κO¹)bis(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato)‐1κ³O¹,N,O²;2κ³O¹,N,O²‐diyttrium–tetrahydrofuran–methanol (1/1/1), [Y₂(C₁₄H₁₂NO₂)₃(CH₃O)Cl₂(CH₄O)]·CH₄O·C₄H₈O, ( 4 )·MeOH·THF, and bis(μ‐2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐1κ³O¹,N,O²:2κO¹)bis(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐2κ³O¹,N,O²)sodiumyttrium chloroform disolvate, [NaY(C₁₄H₁₂NO₂)₄]·2CHCl₃, ( 5 )·2CHCl₃. Structural peculiarities of homoleptic tris(iminophenoxide)s ( 1 )–( 3 ), binuclear tris(iminophenoxide) ( 4 ) and homoleptic ate tetrakis(iminophenoxide) ( 5 ) are discussed. The nonflat Schiff base ligand displays μ₂‐κ³O¹,N,O²:κO¹ bridging, and κ³O¹,N,O² and κ²N,O¹ terminal coordination modes, depending on steric congestion, which in turn depends on the ionic radii of the rare‐earth metals and the number of coordinated ligands. It has been demonstrated that interligand dihedral angles of the phenoxide ligand are convenient for comparing steric hindrance in complexes. ( 4 )·MeOH has a flat Y₂O₂ rhomboid core and exhibits both inter‐ and intramolecular MeO—H…Cl hydrogen bonding. Catalytic systems based on complexes ( 1 )–( 3 ) and ( 5 ) have demonstrated medium catalytic performance in acrylonitrile polymerization, providing polyacrylonitrile samples with narrow polydispersity.     

Manganese(II), lead(II) and cadmium(II) coordination complexes containing a tetrazole‐based acylamide ligand: synthesis and the influence of the metal ions on the structures

Three new manganese(II), lead(II) and cadmium(II) coordination complexes have been prepared by reaction of N‐(1H‐tetrazol‐5‐yl)cinnamamide (HNTCA) with divalent metal salts (MnCl₂, PbCl₂ and CdCl₂) in a mixed‐solvent system, affording mononuclear to trinuclear structures namely, bis(methanol‐κO)bis[5‐(3‐phenylprop‐2‐enamido)‐1H‐1,2,3,4‐tetrazol‐1‐ido‐κ²N¹,O]manganese(II), [Mn(C₁₀H₈N₅O)₂(CH₃OH)₂], (1), bis[μ‐5‐(3‐phenylprop‐2‐enamido)‐1H‐1,2,3,4‐tetrazol‐1‐ido]‐κ³N¹,O:N²;κ³N²:N¹,O‐bis{aqua[5‐(3‐phenylprop‐2‐enamido)‐1H‐1,2,3,4‐tetrazol‐1‐ido‐κ²N¹,O]lead(II)}, [Pb₂(C₁₀H₈N₅O)₄(H₂O)₂], (2), and hexakis[μ₂‐5‐(3‐phenylprop‐2‐enamido)‐1H‐1,2,3,4‐tetrazol‐1‐ido‐κ³N¹,O:N²]tricadmium(II), [Cd₃(C₁₀H₈N₅O)₆], (3). The structures of these three compounds reveal that the nature of the metal ions and the side groups of the organic building blocks have a significant effect on the structures of the coordination compounds formed. Intermolecular hydrogen bonds link the molecules into two‐dimensional [complex (1)] and three‐dimensional hydrogen‐bonded networks. Complexes (2) and (3) show significant fluorescence, while complex (1) displays no fluorescence.     

Designing a heterotrinuclear CuII—NiII—CuII complex from a mononuclear CuII Schiff base precursor with dicyanamide as a coligand: synthesis,crystal structure,thermal and photoluminescence properties

Schiff bases are considered `versatile ligands' in coordination chemistry. The design of polynuclear complexes has become of interest due to their facile preparations and varied synthetic, structural and magnetic properties. The reaction of the `ligand complex' [CuL] {H₂L is 2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenol} with Ni(OAc)₂·4H₂O (OAc is acetate) in the presence of dicyanamide (dca) leads to the formation of bis(dicyanamido‐1κN¹)bis(dimethyl sulfoxide)‐2κO,3κO‐bis{μ‐2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenolato}‐1:2κ⁶O,O′:O,N,N′,O′;1:3κ⁶O,O′:O,N,N′,O′‐dicopper(II)nickel(II), [Cu₂Ni(C₁₇H₁₆N₂O₂)₂(C₂N₃)₂(C₂H₆OS)₂]. The complex shows strong absorption bands in the frequency region 2155–2269 cm⁻¹, which clearly proves the presence of terminal bonding dca groups. A single‐crystal X‐ray study revealed that two [CuL] units coordinate to an Ni^II atom through the phenolate O atoms, with double phenolate bridges between Cu^II and Ni^II atoms. Two terminal dca groups complete the distorted octahedral geometry around the central Ni^II atom. According to differential thermal analysis–thermogravimetric analysis (DTA–TGA), the title complex is stable up to 423 K and thermal decomposition starts with the release of two coordinated dimethyl sulfoxide molecules. Free H₂L exhibits photoluminescence properties originating from intraligand (π–π*) transitions and fluorescence quenching is observed on complexation of H₂L with Cu^II.     

Hydrothermal synthesis, crystal structure, and thermal analysis of a Novel trinuclear manganese complex: Mn3(C12H8N2)2(C10H11O5)6

A novel trinuclear manganese(II) complex, Mn₃(C₁₂H₈N₂)₂(C₁₀H₁₁O₅)₆ (I), has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P2₁/n, with cell parameters a = 12.1935(7), b = 19.0249(11), c = 18.0515(10)?, β = 105.0430(10)°, V = 4044.1(4)?³, Z = 2. Two of the three manganese atoms in the crystal structure are crystallographically equivalent and adopt N₂O₄ coordination mode, whereas the remaining manganese atom adopts O₆ coordination mode, which forms a nearly regular octahedron. The experimental result of thermal analysis shows that complex I remains stable below 300°C.     

Controllable assembly of a three‐dimensional metal–organic supramolecular framework displaying hydrogen‐bonding and π–π stacking interactions

The complex poly[[aqua(μ₂‐phthalato‐κ²O¹:O²){μ₃‐2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetato‐κ⁴N²,N³:O:O′}{μ₂‐2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetato‐κ³N²,N³:O}dizinc(II)] dihydrate], {[Zn₂(C₁₀H₈N₃O₂)₂(C₈H₄O₄)(H₂O)]·2H₂O}_n, has been prepared by solvothermal reaction of 2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetonitrile (PPAN) with zinc(II). Under hydrothermal conditions, PPAN is hydrolyzed to 2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetate (PPAA⁻). The structure determination reveals that the complex is a one‐dimensional double chain containing cationic [Zn₄(PPAA)₄]⁴⁺ structural units, which are further extended by bridging phthalate ligands. The one‐dimensional chains are extended into a three‐dimensional supramolecular architecture via hydrogen‐bonding and π–π stacking interactions.     

Catalytic oxyfunctionalization of saturated hydrocarbons by non-heme oxo-bridged diiron(III) complexes: role of acetic acid on oxidation reaction

Oxo-bridged diiron(III) complexes [Fe₂O(L¹)₂(H₂O)₂](ClO₄)₄ (1) and [Fe₂O(L²)₂(H₂O)₂](ClO₄)₄ (2), where L¹ and L² are tetradentate N-donor N,N′-bis(2-pyridylmethyl)-1,2-cyclohexanediamine and N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine respectively, have been isolated as synthetic models of non-heme iron oxygenases and characterized by physicochemical and spectroscopic methods. Both the complexes have been studied as catalysts for the oxyfunctionalization of saturated hydrocarbons using green hydrogen peroxide (H₂O₂) as oxidant under mild conditions. The selectivity (A/K) and regioselectivity (3°/2°) in oxidative C–H functionalization of alkanes suggests the involvement of metal-based intermediate in the oxygenation reaction. The catalytic efficiency is found to be strongly dependent on the presence of acetic acid. Remarkable increase in conversion and selectivity favoring the formation of alcohols in the oxidation of cyclohexane and cyclooctane and exclusive hydroxylation of adamantane with drastic enhancement of regioselectivity has been achieved by the addition of acetic acid in the presence of H₂O₂.

     

Two new dimeric cadmium(II) and zinc(II) sulfate complexes with 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and 2,2:6′,2′′‐ter­pyridine

The structures of two new sulfate complexes are reported, namely di‐μ‐sulfato‐κ³O,O′:O′′‐bis{aqua­[2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine‐κ³N¹,N²,N⁶]­cadmium(II)} tetra­hydrate, [Cd₂(SO₄)₂(C₁₆H₁₂N₆)₂(H₂O)₂]·4H₂O, and di‐μ‐sulfato‐κ²O:O′‐bis­[(2,2′:6′,2′′‐ter­pyridine‐κ³N¹,N^1′,N^1′′)­zinc(II)] dihydrate, [Cd₂(SO₄)₂(C₁₅H₁₁N₃)₂]·2H₂O, the former being the first report of a Cd(tpt) complex [tpt is 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine]. Both compounds crystallize in the space group P and form centrosymmetric dimeric structures. In the cadmium complex, the metal center is heptacoordinated in the form of a pentagonal bipyramid, while in the zinc complex, the metal ion is in a fivefold environment, the coordination geometry being intermediate between square pyramidal and trigonal bipyramidal. Packing of the dimers leads to the formation of planar structures strongly linked by hydrogen bonding.     

New thallium(III) chloride complexes with pyridine carboxylic acids: from molecular compounds to supramolecular associations

Reactions of TlCl₃ with picolinic acid (Hpic), nicotinic acid (Hnic), isonicotinic acid (Hinic) and 3-hydroxy-picolinic acid (H3hpic) afford the isolation of new chlorothallium(III) complexes. The compounds are characterized by IR, Raman and multinuclear NMR (¹H,¹³C,²⁰⁵Tl). The molecular structures of [TlCl₂(pic)(Hpic)]·0.5H₂O (1), [TlCl₂(nic)(Hnic)] (2), [TlCl(inic)₂]·0.6C₂H₅OH (3) and [TlCl(3hpic)₂(h3hpic)] (4) are determined by single-crystal X-ray diffraction. A distorted octahedral TlCl₂N₂O₂ core containing the O,N-chelating ligands is achieved in the monomeric complex 1. The coordination polyhedron in compounds 2–4 is pentagonal bipyramidal, i.e. TlCl₂NO₄ in 2, and TlClN₂O₄ in 3 and 4, respectively. O,O′,N-Bridging ligands result in a polymer chain for 2 and a three-dimensional polymeric association in 3, while compound 4 is monomeric (O, N-and O,O-chelating ligands).     

Hydrothermal synthesis and characterization of two new arsenic–vanadate compounds with the same cluster anion [As8V14O42(H2O)]4−

Two new arsenic–vanadate compounds [Co(C₄H₁₃N₃)₂]₂[As₈V₁₄O₄₂(H₂O)]?·?3.5H₂O (1) and (C₂N₂H₉)₂(C₂N₂H₁₀)[As₈V₁₄O₄₂(H₂O)]?·?2.33H₂O (2) have been hydrothermally synthesized and characterized by X-ray single crystal diffraction, IR spectra and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic space group P ₂(1)/c, a?=?24.649(9)?Å, b?=?13.364(5)?Å, c?=?22.463(8)?Å, β?=?104.008(5)°, V?=?7180(5)?ų, Z?=?4, R ₁?=?0.0787, and wR ₂?=?0.1859. Compound 2 crystallizes in rhombohedral system with space group R3c, a?=?b?=?c?=?22.2405(5)?Å, α?=?β?=?γ?=?110.4030(10)°, V?=?8163.4(3)?ų, Z?=?6, R ₁?=?0.0341 and wR ₂?=?0.0941. The structural analyses show that both compounds have the same discrete cluster anion [As₈V₁₄O₄₂(H₂O)]^4?. Moreover, in 1, the polyanions are connected through van der Waals forces to generate soft channels that are filled by [Co(C₄H₁₃N₃)₂]²⁺ cations and water. In 2, water and organic molecules link cluster anions to create the supramolecular assembly through hydrogen bonding.     

Synthesis and characterization of nickel(II) complexes with three potentially hexadentate Schiff-base ligands and polyamines: X-ray crystal structure determination of one nickel(II) complex

Three new potentially hexadentate N₄O₂ Schiff-base ligands (H₂L¹, H₂L² and H₂L³) were prepared from the reaction of the polyamines N,N′-bis(2-aminophenyl)-1,2-ethanediamine (L¹), N,N′-bis(2-aminophenyl)-1,3-propanediamine (L²) and N,N′-bis(2-aminophenyl)-1,4-butanediamine (L³), respectively with salicylaldehyde. Reaction of the Schiff bases with Ni(II) salts in the presence of N(Et)₃ gave the neutral complexes [NiL⁴], [NiL⁵] and [NiL⁶]. Ni(II) complexes of the polyamines were also prepared. One of complexes [Ni(L¹)(MeCN)₂](ClO₄)₂·MeCN has been characterized through X-ray diffraction methods.     

Synthesis and characterization of Cu(II) complexes of tetradentate and tridentate symmetrical Schiff base ligands involving <Emphasis Type="Italic">o</Emphasis>-phenelenediamine,salicylaldehyde and diacetylmonoxime

A mononuclear complex [CuL] (1), a binuclear complex [Cu₂LCl₂(H₂O)] (2), a trinuclear complex [Cu₃L₂](ClO₄)₂ (3) involving o-phenylenediamine and salicylaldehyde and another binuclear complex of a tridentate ligand (H₂L¹) [Cu₂L₂¹](CH₃COO)₂ (4) involving o-phenylenediamine and diacetylmonoxime have been synthesized, where H₂L = N,N′-o-phenylenebis(salicylideneimine) and H₂L¹ = 3-(2-aminophenylimino)butan-2-one oxime. All the complexes have been characterized by elemental analyses, spectral and magnetic studies. The binuclear complex (2) was characterized structurally where the two Cu(II) centers are connected via an oxygen-bridged arrangement.     

Co(II)-Mediated and microwave assisted coupling between 2,6-diaminopyridine and nitriles. A new synthetic route to N-(6-aminopyridin-2-yl)carboximidamides

The Chinese-lantern-type Co₂(O₂CBu^t)₄{2,6-(NH₂)₂C₅H₃ N}₂ complex reacts with RCN (R = Me or Prⁿ) under microwave irradiation (MWI) to give the mononuclear amidine complexes Co(O₂CBu^t)₂{H₂N(C₅H₃ N)NHC(R)=NH} (R = Me (4a) or Prⁿ (4c)). Under microwave irradiation, the addition of 2,6-diaminopyridine to acetonitrile in the presence of the pivalate complexes Co₂(μ₂-OH₂)(O₂CBu^t)₄(HO₂CBu^t)₄ (1) or [Co(OH)_n(O₂CBu^t)_2−n ]_x (2) afforded complex 4a in higher yield compared to the corresponding reaction performed earlier without MWI. The use of MWI makes it possible to perform analogous reactions with nitriles RCN (R = Et, Prⁿ, or Ph) giving rise to complexes 4b—d, respectively. Compounds 4a—d were characterized by elemental analysis and IR spectroscopy. The structure of complex 4c was established by X-ray diffraction. Amidines H₂N(C₅H₃N)NHC(R)=NH, which formed in the coordination sphere of cobalt(II), were isolated in the free state from methanolic solutions of complexes 4a—d under the action of Na₂S and were characterized by electrospray mass spectrometry and ¹H and ¹³C{¹H} NMR spectroscopy. The reactions of 2-aminopyridine with both complexes 1 and 2 in acetonitrile under microwave irradiation produced the Co(O₂CBu^t)₂(H₂NC₅H₄N)₂ complex. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–42, January, 2006.     

Structure,DNA-binding interaction and antitumour activity of two novel complexes coordinated by tridentate 1,3-bis(benzimidazol-2-yl)-2-oxapropane ligand

Two novel DNA-intercalating complexes, [Cd(hipa)(bbiop)] _n (1) and [Ni(ada)(bbiop)] _n ·2H₂O (2) with hipa, ada and potentially tridentate ligand bbiop (bbiop, 1,3-bis(benzimidazol-2-yl)-2-oxa-propane; hipa, 5-hydroxyisophthalate; ada, aniline-N,N-diacetate), have been synthesised under hydrothermal methods and structurally characterised by single crystal X-ray diffraction analysis, elemental analysis, UV–vis spectrum and fluorescent spectrum. The bbiop ligand exists as chelating-tridentate μ₁-(η₃–N₁, N₂, O₆) coordination fashion. In addition, their in vitro cytotoxicities towards four selected tumour cell lines have been evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Complex 1 exhibits the most dramatic inhibitory effect on MG-63, and its inhibition rate is higher than that of its free ligands, H₂bbiop and hipa, indicating significantly enhanced effect after forming complex. On the basis of the combination of UV–vis absorption and fluorescence titrations, complex 1 can interact with the base pairs of double-helical DNA via an intercalative mode with intrinsic binding constant, K _b, of 4.62 × 10⁷, presenting the high DNA-binding affinity.     

Synthesis,crystal structures,photoluminescence, electrochemistry and DFT study of aluminium(III) and gallium(III) complexes containing a novel tetradentate Schiff base ligand

Single crystals of the aluminium and gallium complexes of 6,6′‐{(1E,1′E)‐[1,2‐phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2‐methoxyphenol), namely diaqua(6,6′‐{(1E,1′E)‐[1,2‐phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2‐methoxyphenolato)‐κ⁴O¹,N,N′,O^1′)aluminium(III) nitrate ethanol monosolvate, [Al(C₂₂H₁₈N₂O₄)(H₂O)₂]NO₃·C₂H₅OH, 1 , and diaqua(6,6′‐{(1E,1′E)‐[1,2‐phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2‐methoxyphenolato)‐κ⁴O¹,N,N′,O^1′)gallium(III) nitrate ethanol monosolvate, [Ga(C₂₂H₁₈N₂O₄)(H₂O)₂]NO₃·C₂H₅OH, 2 , were obtained after successful synthesis in ethanol. Both complexes crystallized in the triclinic space group P, with two molecules in the asymmetric unit. In both structures, in one of the independent molecules the tetradentate ligand is almost planar while in the other independent molecule the ligand shows significant distortions from planarity, as illustrated by the largest distance from the plane constructed through the central metal atom and the O,N,N′,O′‐coordinating atoms of the ligand in 1 of 1.155 (3) Å and a distance of 1.1707 (3) Å in 2 . The possible reason for this is that there are various strong π‐interactions in the structures. This was confirmed by density functional theory (DFT) calculations, as were the other crystallographic data. DFT was also used to predict the outcome of cyclic voltammetry experiments. Ligand oxidation is more stabilized in the gallium complex. Solid‐state photoluminescence gave an 80 nm red‐shifted spectrum for the gallium complex, whereas the aluminium complex maintains the ligand curve with a smaller red shift of 40 nm.     

Studies of the catalytic activity of Fe(III)(salen) complexes as epoxidation catalysts

Two new Fe(III)(salen) complexes, FeL¹ClO₄·2H₂O (1) and FeL²ClO₄ (2) [L¹ = N,N′-ethylenebis(3-formyl-5-methylsalicylaldimine) and L² = N,N′-cyclohexenebis(3-formyl-5-methylsalicylaldimine)], have been synthesized and characterized. The catalytic activity of the complexes for epoxidation of alkenes has been investigated in the presence of two terminal oxidants PhIO and NaOCl, with two solvents CH₃CN and CH₂Cl₂. As alkenes styrene and (E)-stilbene have been chosen for investigation; styrene is a better substrate than electron-rich (E)-stilbene. The study also suggests that unlike their Mn(III) counterparts, 1 and 2 are poor epoxidation catalysts; catalysis proceeds with formation of one intermediate, rather than forming more than one intermediate depending on the terminal oxidant used. Use of exogenous neutral donor ligands such as Py, PyNO and 1-MePy is effective to improve catalytic behavior.     

A mixed bridged trinuclear copper(II)–1,10‐phenanthroline complex with a linear structure

The title compound, diaqua‐1κO,3κO‐di‐μ‐hydroxido‐1:2κ²O:O,2:3κ²O:O‐di‐μ‐methacrylato‐1:2κ²O:O′,2:3κ²O:O′‐bis(1,10‐phenanthroline)‐1κ²N,N′;3κ²N,N′‐tricopper(II) dinitrate dihydrate, [Cu₃(C₄H₅O₂)₂(OH)₂(C₁₂H₈N₂)₂(H₂O)₂](NO₃)₂·2H₂O, has the central Cu atom on an inversion centre. The three Cu^II atoms are in a linear arrangement linked by methacrylate and hydroxide groups. The coordination environments of the Cu^II ions are five‐coordinated distorted square‐pyramidal for the outer Cu atoms and four‐coordinated square‐planar for the central Cu atom. All nitrate ions, hydroxide groups and water molecules are linked by hydrogen bonds, forming a linear structure. The complex exhibits ferromagnetic exchange coupling, which is helpful in elucidating magnetic interactions between copper ions and other metallic ions in heteronuclear complexes.     

Eu(C10H9N2O4)(C10H8N2O4)(H2O)3]•0.5bipy•3H2O配合物的合成、晶体结构及荧光性质

在水-乙醇混合体系中, 以2-羰基丙酸水杨酰腙(C₁₀H₁₀N₂O₄)、2,2-联吡啶(C₁₀H₈N₂, 简写bipy)与Eu(NO₃)₃•4H₂O反应, 首次培养出黄色单晶[Eu(C₁₀H₉N₂O₄)(C₁₀H₈N₂O₄)(H₂O)₃]•0.5bipy•3H₂O. 该晶体属三斜晶系, 空间群为P-1, 晶胞参数a＝0.93392(16) nm, b＝1.3100(2) nm, c＝1.3895(2) nm, α＝97.205(3)°, β＝105.411(2)°, γ＝106.364(2)°, V＝15.35(2) nm³, Z＝2, μ＝2.118 mm^－1, D_c＝1.686 Mg/m³, F(000)＝786, R＝0.0116, wR＝0.0507, GOF＝0.995. 晶体测试结果表明, 该单晶结构为铕的9配位配合物, 两个2-羰基丙酸水杨酰腙分别以负一价和负二价酮式和三个水分子同时参与配位; 每个2-羰基丙酸水杨酰腙中的羧基氧、酰胺基中的羰基氧和C＝N中的氮与Eu^3＋配位, 形成两个共边的稳定五元环, 另三个配位原子则分别来自三个水分子中的氧原子, 该配合物在空间呈扭曲的单帽四方反棱柱, 而在不对称单位中还有游离的一个2,2-联吡啶分子和三个水分子, 这些游离分子与配位分子之间存在大量分子内和分子间氢键, 整个分子在空间呈三维网状结构. 发光性能测试表明该配合物具有很好的荧光性质.