Ln(III)-cored complexes based on 2-thenoyltrifluoroacetone ligand for near infrared emission: Energy transfer pathway and transient absorption behavior

Lanthanide(III)-cored complexes based on 2-thenoyltrifluoroacetone (TTA) ligand for near infrared (NIR) emission have been developed to investigate the energy transfer pathway from the antenna ligand to the Ln³⁺ ion. Their photophysical studies indicate the sensitization of Ln³⁺ luminescence by energy transfer through the excited triplet state of β-diketone ligand. Nanosecond (ns) transient absorption behavior of Ln³⁺-[TTA]₃(terpy) complexes at room temperature is explored. The triplet-triplet absorption spectrum for Gd³⁺-[TTA]₃(terpy) is observed under degassed condition, whereas it is hardly observed in Er³⁺-[TTA]₃(terpy) complex. The sensitizing process in Er³⁺-[TTA]₃(terpy), through the triplet state of TTA ligand to Er³⁺ ion, is also independent on the presence of oxygen. It indicates that the energy transfer rate through the excited triplet state of β-diketone ligand to Er³⁺ ion occurs approximately faster than that of the oxygen quenching rate.     

Synthesis and luminescence properties of lanthanide(III) chelates with polyacid derivatives of thienyl-substituted terpyridine analogues

Two new polyacid derivative ligands of thienyl-substituted terpyridine analogues, N,N,N¹,N¹-[4′-(2?-thienyl)-2,2′:6′,2″-terpyridine-6,6″-diyl]bis(methylenenitrilo) tetrakis(acetic acid) (TTTA) and N,N,N¹,N¹-[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-(2″-thienyl)pyridine] tetrakis(acetic acid) (BTTA), were synthesized, and the luminescence properties of their Eu³⁺ and Tb³⁺ chelates were investigated. The Eu³⁺chelates of the two ligands are strongly luminescent having luminescence quantum yields of 0.150 (TTTA-Eu³⁺) and 0.114 (BTTA-Eu³⁺), and lifetimes of 1.284 ms (TTTA-Eu³⁺) and 1.352 ms (BTTA-Eu³⁺), whereas their Tb³⁺ chelates are weakly luminescent. The TTTA-Eu³⁺ chelate was used for streptavidin (SA) labeling, and the labeled SA was used for time-resolved fluoroimmunoassay of insulin in human sera. The method gives the detection limits of 33 pg ml⁻¹.     

Chemical tuning of high-spin complexes based on 3- and 4-hydroxy-pentadentate-Fe (III) complex-units investigated by Mössbauer spectroscopy

The pentadentate ligands 3-OH-⁵L?=?[N,N′-Bis(1,3-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] and 4-OH-⁵L?=?[N,N′-Bis(1,4-dihydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] has been prepared by a Schiff base condensation between 1,7-diamino-4-azaheptane and the dihydroxybenzaldehyde. Complexation with Fe(III) yields high-spin (S?=?5/2) complexes of [Fe^III(3-OH-⁵L)Cl] and [Fe^III(4-OH-⁵L)Cl]. These precursors were combined with [M(CN) _x ] ^y? (M?=?W(IV), Mo(IV), Ru(II), Co(III)) and heptanuclear and nonanuclear clusters of [M{(CN-Fe^III(3-OH-⁵L)} _x ]Cl _y and [M{(CN-Fe^III(4-OH-⁵L)} _x ]Cl _y resulted. Such starshaped hepta- and nonanuclear compounds are high-spin systems at room temperature. On cooling to 10 K some of the iron(III) centers switch to a second high-spin state as proven by Mössbauer spectra, i.e. multiple electronic transitions. Parts of the compounds perform a high-spin to high-spin transition.     

Structural and luminescence properties of [Ln(ODA)(phen)·4H2O] complexes (Ln=Sm and Dy, ODA=oxydiacetate, phen=1,10-phenanthroline)

Two novel complexes of Sm(III) and Dy(III) with mixed oxydiacetate (ODA) and 1,10-phenanthroline (phen) ligands were synthesized and their structure and luminescence properties were characterized. The complexes of [Ln(ODA)(phen)·4H₂O]Cl·5H₂O [Ln=Sm and Dy] crystallize in the monoclinic space group P2₁/n with Sm: a=12.3401(14) Å, b=16.821(2), c=12.6847(11) Å, β=107.939(10)°, V=2505.0(5) Å³, Z=4 and ρ=1.841 mg/m³, and with Dy: a=12.289(7) Å, b=16.805(6) Å, c=12.705(4) Å, β=108.144(18)°, V=2493.4(19) Å³, Z=4 and ρ=1.786 mg/m³. The complexes of [Sm(ODA)(phen)·4H₂O]⁺ and [Dy(ODA)(phen)·4H₂O]⁺ excited by UV light produce orange red and lightly white emissions, respectively, via the nonradiative energy transfer from phen to the metals. The quantum yield of the sensitized luminescence of [Dy(ODA)(phen)·4H₂O]⁺ (Q=19%) is much greater than that of [Sm(ODA)(phen)·4H₂O]⁺ (Q=1.4%). The luminescence decay times of the complexes were in a few microsecond range and independent of temperature.     

Kinetics and mechanism of uncatalysed and ruthenium(III) catalysed oxidation of allyl alcohol by diperiodatoargentate(III) in aqueous alkaline medium

The oxidation of allyl alcohol by diperiodatoargentate(III) (DPA) is carried out both in the absence and presence of ruthenium(III) catalyst in alkaline medium at 298 K and a constant ionic strength of 1.1 mol dm^?3 was studied spectrophotometrically. The oxidation products in both the cases were acrolein and Ag(I), identified by spectral studies. The stoichiometry is same in both the cases, that is, [AA]/[DPA] = 1:1. The reaction shows first order in [DPA] and has less than unit order dependence each in both [AA] and [Alkali] and retarding effect of [IO] in both the catalysed and uncatalysed cases. The order in [Ru(III)] is unity. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA) in both the cases. The uncatalysed reaction in alkaline medium has been shown to proceed via a MPA–allyl alcohol complex, which decomposes in a rate determining step to give the products. In catalysed reaction, it has been shown to proceed via a Ru(III)‐allyl alcohol complex, which further reacts with one molecule of MPA in a rate determining step to give the products. The reaction constants involved in the different steps of the mechanisms were calculated for both reactions. The catalytic constant (K_c) was also calculated for catalysed reaction at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed for both the cases. The thermodynamic quantities were also determined for both reactions. Copyright © 2007 John Wiley & Sons, Ltd.     

Methylene blue as a DNA probe for a comparative study of Cd, Pb and Cr ions binding to calf thymus DNA

Methylene blue (MB) was developed as a sensitive DNA probe for a comparative study of Cd²⁺, Pb²⁺ and Cr³⁺ ions binding with calf thymus DNA (ctDNA). The fluorescence intensity of the MB-ctDNA system increased dramatically when heavy metal ions (Cd²⁺, Pb²⁺ and Cr³⁺ ions) were added, which indicated that some of the bound MB molecules were released from the ctDNA base pairs. To compare the binding affinity of these three different heavy metal ions with ctDNA, the relationships between the fluorescence intensity of the MB-ctDNA-M (Metal ions) system and the concentration ratio of [M]/[DNA(p)] were investigated. The results showed that the order of the binding affinity of heavy metal ions with ctDNA had the following sequence: Cr³⁺> Cd²⁺>Pb²⁺. This order was further proved by the effects of heavy metal ions on the number of MB bound to ctDNA, the measurements of binding constants of these heavy metal ions to ctDNA, and the effects of heavy metal ions on the absorption of the MB-ctDNA system. In addition, the interaction mechanisms of Cd²⁺, Pb²⁺ and Cr³⁺ ions with ctDNA were also discussed in detail. These results indicated that their interaction mechanisms are related to the concentration ratios of heavy metal ions to DNA.     

Theoretical Calculations of Transition Probabilities and Oscillator Strengths for Sc(III) and Y(III)

利用最弱受约束电子势模型理论计算了二价钪离子和二价钇离子的能级间跃迁几率和振子强度的数值. 二价钪离子的计算结果与美国国家标准技术研究院(NIST)所给出的可接受值吻合良好. 二价钇离子的计算结果也与现有的其他理论方法的计算结果十分接近.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

Simultaneous Spectrophotometric Determination of Iron(II) and Iron(III) in Mixtures Using Di-2-pyridyl Ketone Benzoylhydrazone

A method for simultaneous spectrophotometric determination of total iron, iron(II) and iron(III) in mixtures containing other metal ions has been described. The method is based on the complexation of iron with di-2-pyridyl ketone benzoylhydrazone (DPKBH) in 50% (v/v) ethanolic solution. Iron(II) complex with DPKBH exhibits two absorption maxima at 360 and 650 nm. meanwhile iron(II1) complex with DPKBH exhibits only one maximum at 360nm. Iron(II) and iron(III) complexes with DPKBH have similar behaviour at 360nm. Iron forms 1:2 complexes with the reagent. Beer's laws are obeyed over the ranges 0.1–2 μgml-1 and 0.4–5 μgrn1-l for iron(II) complexes at 360 and 650nm respectively. Iron(III) showed results similar to those obtained for iron(II) at 360nm. The effect of pH, effect of excess reagent. the stability of complexes. and the tolerance limit of many metal ions have been reported. The method is applied to the determination of total iron, iron(I1). and iron(II1) in synthetic solutions.     

Thermal transitions and degradative processes in Fe(III)-tetracarboxyphthalocyanine-grafted poly(N-vinylcarbazole)

The introduction of 2,9,16,23-tetracarboxy-Fe(III)phthalocyanine [Fe(III)tcPc] units onto fractions of poly(N-vinylcarbazole) (PVK) by Friedel-Crafts reaction leads to amorphous PVK-based grafted compounds that show major interchain distances by the wide-angle x-ray scattering (WAXS) technique. Glass transition temperatures of the products are lower than the main glass transition temperature of PVK and are attributed to local movements of the voluminous added groups. Dynamic thermogravimetric experiments show decarboxylation processes within the 250°C-500°C range and little weight loss. The large remaining residue, up to 70% of the sample at 800°C, is suggested to be the consequence of successive cross-linking reactions. The Fourier transform infrared (FTIR) spectrum of the residue is similar to that of the grafted sample before degradation.     

Sonochemical synthesis of a new nano-structures bismuth(III) supramolecular compound: New precursor for the preparation of bismuth(III) oxide nano-rods and bismuth(III) iodide nano-wires

A new nanostructured Bi(III) supramolecular compound, {[Bi₂(4,4′-Hbipy)_1.678(4,4′-Hbipy)_0.322(μ-I)₂I_5.678] (4,4′-bipy)} (1), 4,4′-bipy = 4,4′-bipyridine} was synthesized by a sonochemical method. The nano-structure of 1 was investigated using scanning electron microscopy, powder X-ray powder diffraction (XRD), IR spectroscopy and elemental analysis, and the crystal structure of compound 1 was determined by single-crystal X-ray diffraction. The thermal stability of bulk compound 1 and of nano sized particles was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Bi₂O₃ and BiI₃ nano-structures were obtained by calcinations of nano-structures of compound 1 at 400 °C under air and nitrogen atmospheres, respectively.     

铽配合物——蒙脱土新型复合发光材料的插层组装、表征和发光性能

合成了铽的配合物[TbL] (ClO₄)₃(L: 2, 2, 2', 2'-四[N-苯基-N-苄基(乙酰胺)-2-氧甲基]丁醚), 通过离子交换反应将配离子[TbL]³⁺插层组装到蒙脱土(MMT)层板间, 制备出了新型复合发光材料 [TbL]³⁺-MMT．用元素分析、X射线衍射、傅氏变换红外光谱和紫外-可见光谱对材料进行了表征, 对其荧光性质进行了研究．结果表明, 复合发光材料保持了蒙脱土良好的层柱结构特征和[TbL]³⁺离子的笼状结构特征, [TbL]³⁺离子以单层形式分布于蒙脱土层板间．在紫外光激发下, 复合发光材料发出较强的绿色荧光, 其发射光谱与相应配合物的发射光谱相似．与相应纯配合物比较, 复合发光材料单位质量Tb³⁺的相对荧光强度、荧光单色性和光稳定性有显著改善, 其激发波长向可见光区发生明显位移, 说明插层组装对相应配合物的激发波长有一定的调制作用.     

Correlations in 11B NMR spectra of dihalo derivatives of bis(1,2-dicarbollyl)cobalt(III)

In the ¹¹B NMR spectra of dihalo derivatives of bis(dicarbollyl)cobalt(III), we have identified a correlation between the ¹¹B NMR chemical shifts of substituted boron atoms and boron atoms found in other positions on the carborane skeleton. We have observed an increased shielding effect for fluorine atoms (compared with other halogens), manifested in an upfield shift of the ¹¹B NMR signals for antipodal and trans boron atoms. For the fluorine-containing compound Bu₄N⁺ [8,8′-F₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻, we propose the following sequence of electron density transfer: B(8) → {B(6) and B(10)} → B(4, 7). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 547–549 (cont.), July–August, 2006.     

Trigonally-compressed octahedral geometry of hexaamminecobalt(III) complex cation in aqueous solution investigated from the electronic spectra

Electronic spectra of hexaamminecobalt(III) complex cation in aqueous solution were analyzed to obtain spectral components. Subsequently, based on the spectral components, the coordination geometry around the cobalt(III) ion was investigated, using the reverse angular overlap model method. The result indicates that the geometry is a trigonally compressed octahedron with the polar angle of 57.9?±?1.0° under D_3d symmetry, where the polar angle is the angle between the trigonal axis and the Co–N bond. From this angle, the top and side N–Co–N bond angles are calculated as 94.4° and 85.6°, respectively. The density functional theory computation supported this trigonally compressed structure in aqueous solution.     

Synthesis, Characterization, Antioxidant Activity and DNA-Binding Studies of Three Rare Earth (III) Complexes with 1-(4-Aminoantipyrine)-3-tosylurea Ligand

1-(4-Aminoantipyrine)-3-tosylurea (H₂L) and its three lanthanide (III) complexes, M(H₂L)₃ 3NO₃ [where M = Nd(III), Sm(III) and Eu(III)], have been synthesized and characterized. In addition, the DNA-binding properties of the three complexes have been investigated by UV–vis (ultraviolet and visible) absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, cyclic voltammetry, and viscosity measurements. Results suggest that the three complexes bind to DNA via a groove binding mode. Furthermore, the antioxidant activity (superoxide and hydroxyl radical) of the metal complexes was determined by using spectrophotometer methods in vitro. These complexes were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. Absorption spectra of the complex 3 inTris-HCl buffer upon addition of calf-thymus DNA. [complex]=1×10^-5 M, [DNA]=(0-1) ×10^-5 M. Arrow shows the absorbance changing upon increasing DNA concentrations. Inset: plots of [DNA]/(ε_a – ε_f) versus [DNA] for the titration of DNA with the complex.     

Synthesis and utilization of chitin-humic acid hybrid as sorbent for Cr(III)

New types of hybrid material have been synthesized by using four different methods of immobilization of humic acid (HA) on chitin. The most stable hybrid material toward the change of medium acidity was then utilized as sorbent for Cr(III).The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, using the recommended procedure of International Humic Substances Society (IHSS), while the chitin was isolated from crab shell waste through deproteination using 3.5% (w/v) NaOH and followed by removal of inorganic impurities using 1 M HCl. The four methods of immobilization of HA on chitin were (i) Method A: chitin powder (4 g) was gently poured into the stirred solution of 0.4 g HA in 40 mL of 0.01 M NaOH. After overnight stirring, the solid was separated, washed with water, and dried in oven at 70 °C. (ii) Method B: gelatinous chitin (40 g) in 250 mL of 0.5 M HCl was reacted with HA (4 g) in 500 mL of 0.5 M NaOH and aged for 24 h. The product was washed with water and dried. (iii) Method C: HA powder (0.5 g) was mixed with the stirred gel of chitin (2.5 g) in 60 mL of CaCl₂ saturated methanol and the mixture was then washed with the mixed solution of 25 mL of 2 M sodium citrate and ethylene glycol 1:1. The solid was separated, washed with water, and dried. (iv) Method D: the solution of HA (0.056 g) in 10 mL of 0.01 M NaOH was reacted with the gel of chitin (0.2 g) in 10 mL of CaCl₂ saturated methanol. After 24 h stirring, the solid was separated from the reaction medium, washed with the mixed solution of 2 M sodium citrate and ethylene glycol 1:1, and followed by washing with water and drying. Parameters investigated in this study consisted of the stability test of the immobilized HA, as well as the rate constant (k₁), capacity (b), and energy (E) of sorption as well as the rate constant of desorption (k₋₁). The k₁ and k₋₁ were determined according to a kinetic model of first order sorption reaching equilibrium, while the b and E were determined according to the Langmuir isotherm model.Compared to HA, Methods, A, C, and D; Method B produced the most stable immobilization of HA on chitin. The hybrid material (Chitin-HA) synthesized through Method B was stable in the acidity range that equivalent to pH 2.0-11.0. At the acidity giving maximum sorption, i.e. pH 5, the presence of immobilized HA on the Chitin-HA enhanced more than three times the k₁ and k₋₁, i.e. from 0.057 min⁻¹ and 8.51 × 10⁻⁴ (min⁻¹) (mol/L) for chitin to 0.183 min⁻¹ and 3.27 × 10⁻³ (min⁻¹) (mol/L) for the Chitin-HA. On the contrary, the presence of HA on Chitin-HA only gave small increase on b and small decrease on E. The values of b and E for Cr(III) on chitin were 1.45 × 10⁻² mol/g and 23.12 kJ/mol, respectively, while those on Chitin-HA were 1.78 × 10⁻² mol/g and 19.95 kJ/mol, respectively.     

Magnetic properties of oxalate ligand based molecular materials: NBu4M(II)[Fe(III)(ox)3], Bu4=n-(C4H9)4, M=Co,Cr

The oxalate ligand bridged mixed-metal molecular compounds NBu₄Co(II)[Fe(III)(ox)₃] and NBu₄Cr(II)[Fe(III)(ox)₃] (where NBu₄⁺=tetra-n-butyl ammonium ion, ox²⁻=oxalate ion) are prepared. X-ray powder diffraction profiles are indexed in P6₃ space group to derive unit cell parameters. Their magnetic properties were studied in the temperature range of 5–300 K under different applied magnetic fields in zero-field-cooled as well as field-cooled conditions. The magnetic transition temperatures for these compounds were determined from the temperature dependence of remnant magnetization under a very low field. The compounds are ferrimagnetic in nature and exhibit a disordered structure at temperatures below the magnetic transition temperature.     

Experimental optimum design and luminescence properties of NaY(Gd)(MoO_4)_2:Er~(3+)phosphors

Three-factor orthogonal design(OD) of Er~(3+)/Gd~(3+)/T(calcination temperature) is used to optimize the luminescent intensity of Na Y(Gd)(MoO_4)_2:Er~(3+)phosphor.Firstly,the uniform design(UD) is introduced to explore the doping concentration range of Er~(3+)/Gd~(3+).Then OD and range analysis are performed based on the results of UD to obtain the primary and secondary sequence and the best combination of Er~(3+),Gd~(3+),and T within the experimental range.The optimum sample is prepared by the high temperature solid state method.Photoluminescence excitation and emission spectra of the optimum sample are detected.The intense green emissions(530 nm and 550 nm) are observed which originate from Er~(3+)~2H_(11/2)→~4I_(15/2)and~4S_(3/2)→~4I_(15/2),respectively.Thermal effect is investigated in the optimum NaY(Gd~(3+))(MoO_4)_2:Er~(3+)phosphors,and the green emission intensity decreases as temperature increases.     

氧化铟/聚(3,4-乙烯二氧噻吩)复合材料的微结构及其热电性能研究

通过化学氧化合成的方法将纳米In_2O_3复合到聚(3,4-乙烯二氧噻吩)(PEDOT)中得到In_2O_3/PEDOT复合材料.利用X射线衍射、红外光谱、电子显微镜及正电子湮没等方法对复合材料的微观结构进行了系统研究,同时对材料的热学和电学性能进行了表征.结果表明,当In_2O_3的含量在22 wt%以下时,In_2O_3能很好地分散到PEDOT基体中.热电性能测试则显示In_2O_3/PEDOT复合材料的导电率随In_2O_3含量增加明显增大.纯PEDOT的电导率仅为7.5 S/m,而含12.3 wt%In_2O_3的复合材料的电导率达到25.75 S/m.该复合材料相应的功率因子(68.8×10~(-4)μW/m·K~2)相对于纯的PEDOT(14.5×10~(-4)μW/m·K~2)提高了近4倍.另外,复合材料的热导率相对于纯PEDOT也有所降低.最终复合材料的热电优值由0.015×10~(-4)提高到了0.073×10~(-4).结果表明,In_2O_3/PEDOT复合材料的热电性能相对于纯PEDOT的热电性能得到了比较明显的提高.