Action of chelators on solid iron in phosphate-containing aqueous solutions

To study the effect of strong iron-ligands on steel corrosion, mild steel electrodes were immersed in solutions containing 20 mM phosphate buffer (pH=7.2) and between 0.01 mM and 1 M of either the iron(II)-chelators 2,2^′-bipyridine or FerroZine, or the iron(III)-chelators citrate or acetylacetonate. Resulting surface reactions were investigated by quantifying the electrochemical potential (E), the electrochemical polarization resistance (R_p), the corrosion current (I_corr) and the release of iron into solution. The surface was further analyzed by scanning electron microscopy (SEM/SEM-EDAX) and atomic force microscopy. Concentrations of 0.1 mM of any of the chelators led to slight, temporary changes in E, I_corr and R_p. Concentrations of 10 mM resulted in characteristic changes of E, which were the same for all chelators and in the precipitation of FePO₄ in the case of citrate and acetylacetonate, or vivianite [Fe₃(PO₄)₂ · 8H₂O] in the case of bipyridine and FerroZine. Concentrations of 1 mM of both iron(III)-chelators led to a temporary drop of E similar to that found with 0.1 mM chelator. With iron(II)-chelators, E dropped to about −500 mV before oscillating for several days. The amplitudes of the oscillations were up to 200 mV with periods of 30 and 20-25 min for bipyridine and FerroZine, respectively.     

The synthesis of tetrahedral bipyridyl metallo-octupoles with large second- and third-order nonlinear optical properties

Two new 4,4′-bis(donor)-6,6′-diphenyl- 2,2′-bipyridine ligands and their corresponding D_2d (Cu^I, Ag^I, Zn^II) octupolar metal complexes were synthesized, and their linear and nonlinear optical properties were investigated. A single crystal X-ray structure was also determined for the bis[4,4′-bis(diethylaminostyryl)-6,6′-diphenyl-bipyridine]copper(I) complex, which revealed a distorded pseudo-tetrahedral geometry. Molecular second-order nonlinear optical properties were determined for the complexes using the Harmonic Light Scatterring technique at 1.91 μm. These metallo-chromophores display large first hyperpolarizabilities β_1.91 in the range of 211-340 × 10⁻³⁰ esu, which increase with the Lewis acidity of the metal ion. The two-photon absorption properties of the bipyridyl ligands and related complexes were determined using either the two-photon emission method for fluorescent compounds or the open aperture Z-scan technique for non emissive ones. The complexes display red-shifted two-photon absorption bands compared to their metal-ion free chromophores, as well as a large increase of the maximum two-photon absorption cross-sections.     

A phenylcarbazole functionalized ruthenium dye for efficient dye-sensitized solar cells

A new heteroleptic Ru(II) complex of [Ru(Hcpip)(Hdcbpy)(NCS)₂]⁻·[N(C₄H₉)₄]⁺·H₂O {where Hcpip = 2-(4-(9H-carbazol-9-yl)phenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline, Hdcbpy = 4-carboxylic acid-4′-carboxylate-2,2′-bipyridine} has been synthesized and demonstrated to function as an efficient sensitizer for nanocrystalline TiO₂-based dye-sensitized solar cell (DSSC). The DSSC based on this Ru(II) complex showed a short-circuit photocurrent density of 19.2 mA cm⁻², an open-circuit photovoltage of 630 mV, a fill factor of 57.7%, corresponding to an overall light to electricity conversion efficiency of 6.98% under simulated solar light irradiation at 100 mW cm⁻². This efficiency value is 2.81- and 1.08-fold efficiency values of 2.48% and 6.47% observed for carbazole-free parent complex [Ru(Hpip)(Hdcbpy)(NCS)₂]⁻·[N(C₄H₉)₄]⁺·H₂O {where Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline}- and cis-bis(isothiocyanato)bis(4,4′-dicarboxylic acid-2,2′-bipyridine)ruthenium(II) N3-based solar cells respectively, under identical experimental conditions. The molecular structures and electronic properties of the Ru(II) complexes were also investigated by means of density functional theory calculations in an effort to understand the device performance observed.     

Optical and electron-deficient properties of poly[2,7-(9,9-dihexylfluorene)-Co-Bi-pyridine]: A combined experimental and theoretical study

A series of well-defined poly[2,7-(9,9-dihexylfluorenyl)-co-bipyridinyl] [F-(BPY)_x] with varied BPY (bipyridine) unit contents from 0 to 50% were synthesized using palladium(0) catalyzed Suzuki cross-coupling reactions, and well characterized using ¹H NMR, IR, and GPC. Their photophysical and electrochemical properties were investigated. These copolymers showed pure blue photoluminescence (440 nm) in dilute solutions with the fluorescence quantum yield >0.6. Electron-affinity potentials (LUMO levels) of these polymers estimated from cyclic voltammetry were significantly decreased with the increase of BPY content in the polymer backbone, and a level of 2.43 eV for alternating BPY-fluorene polymer (50% BPY) was achieved, making them good candidates for electron injection and transport materials in EL devices. A further great decrease in LUMO level up to 2.99 eV was found when Zn²⁺ was chelated into polymers. The experimental observations were supported by the quantum chemical calculations on these polymers, which provided the proof for the intuitive notion of an intramolecular charge transfer band in polymer chain.     

Solution and solid phase electrochemical behaviour of [Os(bpy)3]3[P2W18O62]

[Os(bpy)₃]₃[P₂W₁₈O₆₂] has been synthesised and characterised by elemental analysis, spectroscopic (UV-vis, IR spectroscopy) and electrochemical techniques. In 0.1 M Bu₄NPF₆ DMSO the complex shows a series of redox couples associated with the Os^3+/2+ and bipyridine ligands of the cationic [Os(bpy)₃]²⁺ moiety and the tungsten-oxo framework of the associated Dawson parent heteropolyanion, [P₂W₁₈O₆₂]⁶⁻. At this electrolyte concentration, the Os³⁺ redox form of the complex was seen to adsorb onto the electrode surface. When the electrolyte concentration is lowered to 0.01 M Bu₄NPF₆ in addition to the Os^3+/2+ redox couple, the redox process associated with the [P₂W₁₈O₆₂]^8−/7− couple also exhibited properties indicating surface based processes were present. Electroactive films of the complex were formed on carbon macroelectrodes by the redox switching of the transition metal within the complex. Voltammetric investigations into the film's behaviour in a range of buffer solutions (pH 2.0, 4.5 and 7.0) were performed. The films were found to possess better stability in acidic pH and the same pH dependence for the tungsten-oxo framework of the heteropolyanions as in solution. Solid state electrochemical measurements on mechanically attached microparticles of the complex were performed, with the effect of both the nature and concentration of the aqueous electrolyte on this behaviour being investigated. Upon redox switching between the Os^2+/3+ redox states, there is an associated insertion/expulsion of anions from/to the solution phase. Scanning electron micrographs of these solid state films were attained before and after redox cycling.     

Solvothermal synthesis of a novel mixed valence Cu(I)/Cu(II) complex containing sulphate, malate and 4,4-bipyridine, [CuCu2(mal)(SO4)(bpy)2 · H2O]n. Unique binding mode of the malate anion

The reaction of CuSO₄ · 5H₂O with 4,4^′-bipyridine and malic acid at 140 °C under solvothermal conditions afforded a mixed valence three-dimensional coordination polymer [Cu^ICu^II₂(mal)(SO₄)(bpy)₂ · H₂O]_n, (1). The building unit consists of a Cu²⁺-dimer in which copper centers are bridged by malate and sulphate anions. SO₄²⁻ anion further connects dimeric unit with the Cu¹⁺ center. Building units are linked by 4,4^′-bipyridine ligands to form double chains, that are interconnected into 3D network through additional sulphate bridge.     

Synthesis and X-ray crystal structure determination of monomeric cis-Pd(2,2′-bipyridine)(NO3)2

Complex cis-Pd(2,2′-bipyridine)(NO₃)₂ was synthesized by the reaction of cis-Pd(2,2′-bipyridine)Cl₂ with AgNO₃ in water and crystallized by vapor diffusion of diethyl ether into an acetonitrile solution of the complex. The crystal structure obtained shows that each of the two nitrate ligands are coordinated through oxygen atoms to the Pd(2,2′-bipyridine)²⁺ center in unidentate fashion. IR and ¹H NMR spectral data were also obtained.     

Novel phosphinoxide-bearing ligands and their photoluminescent complexes: Spectroscopic studies

Several novel phosphinoxide ligands have been prepared, based on molecular frameworks: pyridine, 2,2′-bipyridine, cavitands, cyclotriphosphazene and 1,3,5-triazine. These compounds form highly luminescent complexes with Eu(III) and Tb(III). Excellent luminescent properties were observed in case of pyridine and 2,2′-bipyridine ligands with photoluminescence quantum yields approaching 25%. Cavitand-based phosphinoxides turned out to be rather poor sensitisers for the lanthanide ion emission. Particularly long emission lifetime was observed in case of pyridine P-oxide complexes of Eu(III) and Tb(III), exceeding 3 ms.     

四苯乙烯衍生物的合成及聚集诱导发光性质

以2,2'-联吡啶(Bpy)为母体,通过Suzuki偶联反应在其5位和5'位引入了四苯乙烯(TPE)基团,设计合成了5-四苯乙烯-2,2'-联吡啶(Bpy-1TPE)和5,5'-二四苯乙烯-2,2'-联吡啶(Bpy-2TPE)两个具有聚集诱导发光(AIE)性质的荧光分子。经1HNMR、13CNMR及EA对目标产物进行了结构测试,并考察了其紫外-可见吸收、荧光发射、AIE、压致变色性以及结构与性质之间的构效关系。结果表明:相对于具有1个四苯乙烯单元的Bpy-1TPE,含2个四苯乙烯单元的Bpy-2TPE共轭体系更大且电荷呈对称分布,能隙宽度较低,其在二氯甲烷溶液中的最大发射峰由483 nm红移至490 nm。Bpy-2TPE表现出明显的AIE性质和压致变色性质,其固体样品经研磨后最大发射波长可由485 nm红移至500 nm。