Mononuclear and dinuclear complexes of dibenzoeilatin: synthesis, structure, and electrochemical and photophysical properties

This work describes a study of Ru(II) and Os(II) polypyridyl complexes of the symmetrical, fused-aromatic bridging ligand dibenzoeilatin (1). The synthesis, purification, and structural characterization by NMR of the mononuclear complexes [Ru(bpy)(2)(dbneil)](2+) (2), [Ru(tmbpy)(2)(dbneil)](2+) (3), and [Os(bpy)(2)(dbneil)](2+) (4), the homodinuclear complexes [[Ru(bpy)(2)](2)[micro-dbneil]](4+) (5), [[Ru(tmbpy)(2)](2)[micro-dbneil]](4+) (6), and [[Os(bpy)(2)](2)[micro-dbneil]](4+) (7), and the heterodinuclear complex [[Ru(bpy)(2)][micro-dbneil][Os(bpy)(2)]](4+) (8) are described, along with the crystal structures of 4, 6, and 7. Absorption spectra of the mononuclear complexes feature a low-lying MLCT band around 600 nm. The coordination of a second metal fragment results in a dramatic red shift of the MLCT band to beyond 700 nm. Cyclic and square wave voltammograms of the mononuclear complexes exhibit one reversible metal-based oxidation, as well as several ligand-based reduction waves. The first two reductions, attributed to reduction of the dibenzoeilatin ligand, are substantially anodically shifted compared to [M(bpy)(3)](2+) (M = Ru, Os), consistent with the low-lying pi orbital of dibenzoeilatin. The dinuclear complexes exhibit two reversible, well-resolved, metal-centered oxidation waves, despite the chemical equivalence of the two metal centers, indicating a significant metal-metal interaction mediated by the conjugated dibenzoeilatin ligand. Luminescence spectra, quantum yield, and lifetime measurements at room temperature in argon-purged acetonitrile have shown that the complexes exhibit (3)MLCT emission, which occurs in the IR-region between 950 and 1300 nm. The heterodinuclear complex 8 exhibits luminescence only from the Ru-based fragment, the intensity of which is less than 1% of that observed in the corresponding homodinuclear complex 5; no emission from the Os-based unit is observed, and an intramolecular quenching constant of k(q) > or = 3 x10(9) s(-)(1) is evaluated. The nature of the quenching process is briefly discussed.     

Mononuclear Cu(II) complexes of novel salicylidene Schiff bases: synthesis and mesogenic properties

Two new Schiff base ligands 1 and 2 (where 1 = 4-(2-hydroxybenzilidenamino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate, 2 = 4-(4-(decyloxy)-2-hydroxybenziliden amino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate) and their copper (Cu)(II) complexes have been synthesised and characterised. The derivatives were fully characterised structurally, and their mesomorphic behaviour was investigated by polarised optical microscopyand differential scanning calorimetry. The structure of Cu(II) complex having 1 as ligand (3) was determined by X-ray diffraction. The Schiff base ligands exhibit enantiotropic nematic phases, the Cu(II) complex 4 shows monotropic nematic phase behaviour, while compound 3 does not show mesomorphism.     

Direct electrochemical synthesis of anionic complexes of thallium halides

Conclusion Using a platinum cathode and thallium anode, electrolysis of solutions containing halogens results in the formation of anionic complexes of univalent and trivalent thallium depending on the nature of the halogen and electrolyte.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1106–1108, May, 1987.     

Mononuclear iron(III)macrocyclic complexes derived from 4-methyl-2,6-di(formyl/benzoyl)phenol and diamines: synthesis,spectral speciation and electrochemical behaviour

Two series of macrocyclic iron(III) complexes of stoichiometry [Fe(L)Cl₂]Cl (1, 2) have been synthesised and characterised. Compounds belonging to series 1 are derived from 4-methyl-2,6-diformylphenol and diamines (H₂L), and those of 2 from 4-methyl-2,6-dibenzoylphenol and diamines. All the brown complexes have been characterised by physicochemical techniques. The mass, infrared, electronic, ESR and Mössbauer spectroscopies, magnetic susceptibility data, molar conductance, X-ray diffraction and cyclic voltammetric studies provide unambiguous evidence that 1 and 2 are high-spin iron(III) complexes in which the metal has an octahedral geometry. The Mössbauer data are consistent with high-spin iron(III) and substantial covalency in the Fe(III)–ligand bonds. Cyclic voltammetric studies in DMSO of the mononuclear iron(III) complexes show that they undergo quasi-reversible reduction with E_1/2 approximately −0.74 V versus SCE.     

Preparation and properties of anionic transition metal complexes containing triheterocarbenium ions

Summary Thermally stable anionic tetracarbonylcobalt complexes containing triheterocarbenium ions, [Co(CO)₄]^–[cation]⁺, have been synthesized by the ion exchange reaction of [Co(CO)₄]^–PPN⁺ with the corresponding carbenium ions. Similar molybdenum complexes containing cyclopentadienyl and carbonyl ligands were also prepared. The complexes were characterized by elemental analyses and by i.r. and n.m.r. spectroscopies. The ionic structures of the complexes are confirmed on the basis of their large electric conductivities.     

Structure and properties of complexes of polycationic brushes with anionic liposomes

The adsorption of anionic lipid vesicles (liposomes) on the surfaces of colloidal particles containing grafted polycationic chains (cationic brushes) is studied. The stability of liposome-brush complexes in aqueous salt solutions increases with the content of anionic lipid in the liposomal membrane; complexes with liposomes containing 20 and 30 mol% anionic lipids do not dissociate into individual components in a 1.2 M NaCl solution. The integrity of the brush-bound liposomes is preserved. The developed approach can be used to obtain nanosized carriers for biologically active compounds.     

ATRP synthesis and association properties of thermoresponsive anionic block copolymers

Thermosensitive anionic block copolymers of sodium 2‐acrylamido‐2‐methylpropanesulfonate (AMPS) and N‐isopropylacrylamide (NIPAAM) with different block lengths were prepared by atom transfer radical polymerization (ATRP). Controlled polymerization was achieved by using ethyl 2‐chloropropionate (ECP) as initiator and CuCl/CuCl₂/tris(2‐dimethylaminoethyl)amine (Me₆TREN) catalytic system in DMF:water 50:50 (v/v) mixtures at 20 °C. Blocks lengths ranging from 36 to 98 repeating units were obtained. The association properties in aqueous solutions at different NaCl ionic strengths were studied as a function of temperature and polymer concentration by dynamic light scattering, fluorescence spectroscopy, and energy‐filtered transmission electron microscopy. The block copolymers with a higher pNIPAAM/pAMPS ratio formed spherical core‐shell type micelles independently of the ionic strength. The block copolymers with lower pNIPAAM/pAMPS ratio formed core‐shell type micelles at high ionic strength. Larger particles were observed at low ionic strength, which could be due to the formation of vesicles or compound micelles/micellar clusters. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4830–4842, 2008     

The direct electrochemical synthesis of anionic organodihalocadmate(II) complexes

The tetra-n-propylammonium salts of RCdX₂^? anions (R = CH₃, C₂H₅, C₄H₉, CF₃, C₆H₅, C₆F₅; X = Cl, Br, I) have been prepared by the electrochemical oxidation of cadmium metal. The element forms the sacrificial anode of a cell in which the solution phase is a methanol/benzene mixture containing (C₃H₇)₄NX and RX. Gram quantities of product were obtained by room temperature electrolysis for ca. 5 h.     

Mononuclear and dinuclear complexes of isoeilatin

This work describes the synthesis and characterization of mononuclear and dinuclear Ru(II) and Os(II) complexes based on the symmetrical bridging ligand isoeilatin (1). The crystal structure of 1.[HCl]2 consists of layers of tightly pi-stacked molecules of the biprotonated isoeilatin. The mononuclear complexes [Ru(bpy)2(ieil)]2+ (2(2+)) and [Os(bpy)2(ieil)]2+ (3(2+)) form discrete dimers in solution held together by face-selective pi-stacking interactions via the isoeilatin ligand. Coordination of a second metal fragment does not hinder the pi-stacking completely, as demonstrated by the concentration dependence of the 1H NMR spectra of the dinuclear complexes [{Ru(bpy)2}2{mu-ieil}]4+ (4(4+)), [{Os(bpy)2}2{mu-ieil}]4+ (5(4+)), and [{Ru(bpy)2}{mu-ieil}{Os(bpy)2}]4+ (6(4+)) and supported by the solid-state structure of meso-4.[Cl]4. The bridging isoeilatin ligand conserves its planarity even upon coordination of a second metal fragment, as demonstrated in the solid-state structures of meso-4.[Cl]4, meso-4.[PF6]4, and meso-5.[PF6]4. All of the dinuclear complexes exhibit a preference (3/2-3/1) for the formation of the heterochiral as opposed to the homochiral diastereoisomer. Absorption spectra of the mononuclear complexes feature a low-lying dpi(M) --> pi*iel MLCT band around 600 nm that shifts to beyond 700 nm upon coordination of a second metal fragment. Cyclic and square-wave voltammetry measurements of the complexes exhibit two isoeilatin-based reduction waves that are substantially anodically shifted compared to [M(bpy)3]2+ (M = Ru, Os). Luminescence spectra, quantum yields, and lifetime measurements at room temperature and at 77 K demonstrate that the complexes exhibit 3MLCT emission that occurs in the IR region between 950 and 1300 nm. Both the electrochemical and photophysical data are consistent with the low-lying pi orbital of the isoeilatin ligand. The dinuclear complexes exhibit two reversible, well-resolved, metal-centered oxidation waves, despite the chemical equivalence of the two metal centers, indicating a significant metal-metal interaction mediated by the bridging isoeilatin ligand.     

Mononuclear gold(I) acetylide complexes with urea group: synthesis, characterization, photophysics, and anion sensing properties

A series of mononuclear gold(I) acetylide complexes with urea moiety, R'(3)PAuC≡CC(6)H(4)-4-NHC(O)NHC(6)H(4)-4-R (R' = cyclohexyl, R = NO(2) (2a), CF(3) (2b), Cl (2c), H (2d), CH(3) (2e), (t)Bu (2f), OCH(3) (2g); R' = phenyl, R = NO(2) (3a), OCH(3) (3b); R' = 4-methoxyphenyl, R = H (4a), OCH(3) (4b)), have been synthesized and characterized. The crystal structures of Ph(3)PAuC≡CC(6)H(4)-4-NHC(O)NHC(6)H(4)-4-NO(2) (3a) and (4-CH(3)OC(6)H(4))(3)PAuC≡CC(6)H(4)-4-NHC(O)NHC(6)H(5) (4a) have been determined by X-ray diffraction. Complexes 2a-2g, 3b, and 4a-4b show intense luminescence both in the solid state and in degassed THF solution at 298 K. Anion binding properties of complexes 2a-2g, 3a-3b, and 4a-4b have been studied by UV-vis and (1)H NMR titration experiments. In general, the log K values of 2a-2g with the same anion in THF depend on the substituent R on the acetylide ligand of 2a-2g: R = NO(2) (2a) > CF(3) (2b) ≥ Cl (2c) > H (2d) > CH(3) (2e) ≈ (t)Bu (2f) ≥ OCH(3) (2g). Complex 2a with NO(2) group shows the dramatic color change toward F(-) in DMSO, which provides an access of naked eye detection of F(-).     

Mononuclear and binuclear wirelike ruthenium(II) complexes with oligo-diethynyl-thiophene bridged back-to-back terpyridine ligands: synthesis and electrochemical and photophysical properties

The syntheses, structural features, electrochemical behavior, absorption spectra, and photophysical properties of five mononuclear complexes [(terpy)Ru(terpy-DEDBT(n)-terpy)](2+), RuT(n), and five binuclear complexes [(terpy)Ru(terpy-DEDBT(n)-terpy)Ru(terpy)](4+), RuT(n)Ru, are reported, where n varies from 1 to 5 so that the metal-metal distance is estimated to be 42 A for the largest binuclear complex, RuT(5)Ru (terpy is 2,2':6',2"-terpyridine and DEDBT is 2,5-diethynyl-3,4-dibutylthiophene). The metal-centered oxidation potentials for the mononuclear and binuclear species are slightly more positive than for the reference [Ru(terpy)(2)](2+) complex, owing to the withdrawing nature of the back-to-back terpyridine ligands incorporating the repeat diethynyl-thiophene units. Comparison of the reduction potentials for the mononuclear and binuclear complexes reveals that the reduction steps are localized either at the terpy fragments of the T(n) ligands or at the terpy peripheral ligands. The spectroscopic results (absorption spectra at room temperature, luminescence spectra and lifetimes at room temperature and at 77 K) in acetonitrile solvent are consistent with the establishment of electronic delocalization within the oligomeric diethynyl-thiophene fragments (DEDBT(n)) of the T(n) ligands; however, the results also indicate that the terpy units of these ligands and the DEDBT(n)fragments are not strongly coupled. Both at room temperature and at 77 K, the (3)metal-to-ligand charge-transfer luminescence of RuT(n) and RuT(n)Ru complexes is strongly depressed in the larger species with respect to what happens for n < or = 2 (where the luminescence quantum yield is phi approximately 10(-4)); this is discussed in terms of the possible intervention of triplet levels localized at the oligothiophene DEDBT(n)(fragments.     

Structure and properties of complexes formed by cationic polymers and anionic cholesterol-containing liposomes

The adsorption of the synthetic polycation poly(N-ethyl-4-vinylpyridinium bromide) on the surface of three-component lipid vesicles (liposomes) formed from a mixture of anionic cardiolipin, electroneutral egg lecithin, and nonionic cholesterol is studied via laser microelectropheresis, dynamic light scattering, conductometry, fluorescence spectroscopy, and UV spectroscopy. The incorporation of cholesterol into the liposomal membrane increases its microviscosity; however, the membrane remains liquid-crystalline. Simultaneously, an increase in the fraction of cholesterol causes the formation of defects in liposome membranes during their binding with poly(N-ethyl-4-vinylpyridium bromide) and makes complexation irreversible. The results of this study are of interest for predicting the behavior of polyelectrolytes and biologically active structures formed on their basis on the surface of cells and the reaction of the cellular membrane to the adsorbed polymer.     

Control of magnetic spin states by various mixed anionic ligands in trinickel complexes: synthesis, crystal structures and physical properties

This study provides an opportunity to control the magnetic spin of nickel atoms using various mixed anionic ligands. A series of linear trinickel complexes supported by two kinds of ligands, oligo-alpha-pyridylamido and sulfonyl amido/amido, were synthesized and their structures were determined by X-ray diffraction. The three nickel atoms of [Ni(3)(Lpts)(2)(dpa)(2)] (dpa(-) = dipyridylamido, Lpts(2-) = N,N'-bis(p-toluenesulfonyl)pyridyldiamido) display short Ni-N ( approximately 1.90 Angstrom) bond distances, which are consistent with a low spin state of Ni(II) ions, and exhibit spin states of (0, 0, 0) for the three Ni(II) ions. One of the terminal Ni(II) ions of [Ni(3)(Lms)(2)(dpa)(2)(H(2)O)] (Lms(2-) = N,N'-bis(4-methylsulfonyl)-pyridyldiamido) and [Ni(3)(Lpts)(2)(pepteaH(2))] (pepteaH(2)(2-) = pentapyridyldiamidodiamine) bonded with an axial ligand exhibits a square pyramidal (NiN(4)X) geometry with long Ni-N bond distances ( approximately 2.10 Angstrom) which are consistent with a high spin Ni(II) configuration. The spin states of these trinickel complexes are (1, 0, 0). Complexes interchanged by the removal or addition of an axial water molecule. The structural features of are comparable with those of . Both the terminal Ni(II) ions in [Ni(3)(LAc)(2)(dpa)(2)] (Lac(2-) = N,N'-biacetyl-pyridyldiamido) are in square pyramidal geometry and exhibit high spin. The spin states of the nickel ions in are (1, 0, 1), and the two terminal nickel ions exhibit antiferromagnetic interactions. The molecular structure of [Ni(3)(Lpts)(2)(dpa)(2)](BF(4)), which was obtained by the one-electron oxidation is similar to those of the neutral analogue , except for the presence of a counter anion to compensate for the positive charge on the Ni(3) core. All of the Ni-Ni bond lengths of are slightly shorter (ca. 0.05 Angstrom) than those in the neutral analogues. This is attributed to the formation of partial Ni-Ni bonding.     

Allyl complexes of scandium: synthesis and structure of neutral, cationic and anionic derivatives

Neutral, cationic and anionic allyl compounds of scandium contain highly fluxional allyl ligands in solution, whilst in the solid state both η(1)- and η(3)-binding modes are detected.     

Chromatographic study of anionic complexes

Summary The diffusion of tartrate complexes of Cu²⁺, Co²⁺, Ni²⁺ and Cd²⁺ through filter paper strips has been examined using 50% and 60% ethanol as solvents. The R_f values are higher when 50% ethanol is used. When 50% ethanol is used, it is noted in the case of Cu²⁺, Co²⁺ and Ni²⁺ that the R_f values decrease with the addition of tartrate in the beginning. Then the value increases and finally becomes constant. In case of Cd²⁺ the R_f value decreases by the addition of tartrate. In 60% ethanol the R_f value does not change by small additions of tartrate but decreases with higher concentration of the complexing agent. In case of Cd²⁺ the R_f value becomes zero by increasing the concentration of tartrate.Part I: See Z. analyt. Chem. 159, 332 (1957/58).     

Chromatographic study of anionic complexes

Summary In this paper the variation of diffusion, through filter paper strips by the ascending method, of citrate complexes of Cu²⁺, Ni²⁺, Co²⁺ and Fe³⁺ has been studied using 50%, 55% and 60% ethanol as solvents. The R_f value is found to be less with higher concentrations of ethanol used. It has been noted that with 50% ethanol the R_f value increases with the addition of citrate and finally tends to become constant with high concentrations of citrate ions. In 55% ethanol the R_f value becomes constant at a later stage. In 60% ethanol it is noted that the R_f value does not change with small additions of citrate, but on increasing its concentration the R_f value begins to diminish.Part II see Z. analyt. Chem. 165, 81 (1959).     

Chromatographic study of anionic complexes

Summary In this paper the variation of diffusion, through a filter paper strip by the ascending method, of cuprioxalate complex has been studied. Various mixtures of Cu+^2üC₂O ₄ ^2– ions have been investigated. It has been noted that till there is a precipitation, the R_f values tend to decrease and finally reach nearly to zero, when the oxalate precipitates completely. With redissolution of the precipitate to form the complex anion, R_f values increase again to a maximum and then have a slight tendency to diminish. No tailing occurs in the chromatograms in cases where the copper has passed into the anion.     

Chromatographic study of anionic complexes

Summary In this paper we have reported our results on the attempted separation of copper(II), nickel(II), cobalt(II) and iron(III) in mixtures by filter paper strip chromatography, using aqueous ethanol as solvent. The effect of the presence of varying concentrations of citrate ion as a complexing agent in the mixtures has been studied. The complexing agent has been added in the metal solution, and not in the solvent as usually done by previous workers.     

Mononuclear copper(II) complexes of bis-triazole-based macrocyclic Schiff base hydrazones: direct synthesis,EPR studies,magnetic and thermal properties

Mononuclear copper(II) complexes of 1,2,4-triazole-based Schiff base macrocyclic hydrazones, III and IV, have been reported. The prepared amorphous complexes have been characterized by spectroscopic methods, electron spray ionization mass spectrometry, and elemental analysis data. Electrochemical studies of the complexes in DMSO show only one quasi-reversible reduction wave at +0.43 V (ΔE = 70 mV) and +0.42 V (ΔE = 310 mV) for III and IV, respectively, which is assigned to the Cu(II) → Cu(I) reduction process. Temperature dependence of magnetic susceptibilities of III and IV has been measured within an interval of 2–290 K. The values of χ_M at 290 K are 1.72 × 10^?3 cm³ mol^?1 and 1.71 × 10^?3 for III and IV, respectively, which increases continuously upon cooling to 2 K. EPR spectra of III and IV in frozen DMSO and DMF were also reported. The trend g_|| > g⊥ > g_e suggests the presence of an unpaired electron in the d_x2?y2 orbital of the Cu(II) in both complexes. Furthermore, spectral and antimicrobial properties of the prepared complexes were also investigated.