Luminescent Langmuir-Blodgett film of a new amphiphilic Eu β-diketonate

This work reports on the synthesis and characterization of the ligand 3-hexadecylpentane-2,4-dione (Hhdacac) and its Eu³⁺ complexes Eu(hdacac)₆·2H₂O, Eu(hdacac)₆·phen and Eu(hdacac)₆·tta, where phen and tta denote 1,10-phenanthroline and thenoyltrifluoroacetone, respectively. These new compounds present long carbon chains and their expected miscibility into non-polar ambients is confirmed by the emission spectra of Eu(hdacac)₆·tta in hexane. Moreover, the amphiphilic properties of Eu(hdacac)₆ complexes allow the obtainment of thin luminescent films by the Langmuir-Blodgett technique. In both cases (solids and films), the typical antenna effect of β-diketonates is observed. The alluring characteristics of these compounds raise great interest in many fields of Materials Science, like photo- and electro-luminescent materials (mainly thin “organic” films), metal catalysts or probes in non-polar solutions, and Langmuir-Blodgett films of several compositions. For the characterization of these products, nuclear magnetic resonance spectroscopy (¹H NMR), thermogravimetric analysis, elementary analyses (C, H), scanning electron microscopy (energy dispersive X-ray spectroscopy), absorption (UV-vis/FT-IR) and photoluminescence spectroscopies were used.     

Catalytic Chemosensing Assay for Selective Detection of Methyl Parathion Organophosphate Pesticide

Herein, a catalytic chemosensing assay (CCA), based on a bimetallic complex, [Ru^II(bpy)₂(CN)₂]₂(Cu^II)₂ (bpy=2,2′-bipyridine), is described. This complex integrates a task-specific catalyst (Cu^I-catalyst) and a signaling unit ([Ru^II(bpy)₂(CN)₂]) to specifically hydrolyze methyl parathion, a highly toxic organophosphate (OP) pesticide. The bimetallic complex catalyzed the hydrolysis of the phosphate ester to generate o,o-dimethyl thiophosphate (DTP) anion and 4-nitrophenolate. Intrinsically, 4-nitrophenolate absorbed UV/Vis light at λ_max=400 nm, creating the first level of the chemosensing signal. DTP interacted with the original complex to displace the chromophore, [Ru^II(bpy)₂(CN)₂], which was monitored by spectrofluorometry; this was classified as the second level of chemosensing signal. By integrating both spectroscopic and spectrofluorometric signals with a simple AND logic gate, only methyl parathion was able to provide a positive response. Other aromatic and aliphatic OP pesticides (diazinon, fenthion, meviphos, terbufos, and phosalone) and 4-nitrophenyl acetate provided negative responses. Furthermore, owing to the metal-catalyzed hydrolysis of methyl parathion, the CCA system led to the detoxification of the pesticide. The CCA system also demonstrated its catalytic chemosensing properties in the detection of methyl parathion in real samples, including tap water, river water, and underground water.     

Selective non-chromatographic determination of tributyltin in sediments using EDTA and diphenylcarbazone as masking agent

Two analytical procedures based on the generation of volatile tributyltin derivatives, their separation by headspace solid-phase microextraction (HS SPME) and subsequent determination using plasma optical emission spectrometry (OES) have been developed for the selective determination of trace tributyltin (TBT) in the presence of other butyltins and inorganic tin in sediments without the use of chromatography. A microwave-assisted leaching of tin compounds from the sediment using 25%_v/v acetic acid is applied for sample pretreatment. The first method takes advantage of TBT chloride releasing from the lecheate after adding 3 M hydrochloric acid, and subsequent separation of the analyte by HS SPME using Carboxen-poly(dimethylsiloxane) (CAR/PDMS). The second method involves the use of masking agents, namely ethylenediaminetetraacetic acid (EDTA) and diphenylcarbazone (DFC), which form stable chelates with monobutyltin (MBT) and dibutyltin (DBT), respectively, followed by the ethylation of tributyltin at pH 5 using sodium tetraethylborate (NaBEt4) solution. The final concentration of NaBEt4 is 0.05%_w/v. The parameters affecting the TBT derivatisation and separation by HS SPME have been optimised including the selection of SPME fibre coating (PDMS, CAR/PDMS), the amount of masking agents and NaBEt4 added, sorption time (2–40 min) and sorption temperature (25–60°C). Higher sensitivity and robustness are attained with the method involving ethylation derivatisation, leading to the limit of detection (LOD) of 3 ng L^?1. The selective release of TBT is observed from aqueous solutions, where the concentrations of MBT and DBT were in 2–50-fold excess to TBT. The SPME-TD-MIP-OES methods have been validated against several certified reference materials (CRMs), including SOPH-1 marine sediment, PACS-2 marine sediment and BCR 646 freshwater sediment.     

Functional Hydride Transfer by a Thiolate‐Containing Model of Mono‐Iron Hydrogenase featuring an Anthracene Scaffold

We report the synthesis, X‐ray structure and functional biomimetic activity of a model complex of mono‐iron hydrogenase (Hmd). To achieve the desired biomimetic fac‐CNS(thiolate) ligation motif, an anthracene framework is used to provide the requisite donors in a single chelate. A bulky aryl thiolate (ortho dimethylphenyl) is included to achieve mononuclearity. In addition to exhibiting structural (X‐ray) and spectroscopic (NMR, IR) similarity to the enzyme, the complex is competent for H₂ activation (heterolysis) and hydride transfer to a model substrate—mimicking the functional behavior of the enzyme in a biomimetic CNS coordination sphere for the first time.     

[Cd<Subscript>5</Subscript>(OH)(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>][CH<Subscript>3</Subscript>CO<Subscript>2</Subscript>]<Subscript>9</Subscript>, a cadmium hydroxy-acetate compound with a layered network

[Cd₅(OH)(H₂O)₃][CH₃CO₂]₉ crystallizes in the triclinic system, with the space group P , a = 10.897(3) Å, b = 11.035(5) Å, c = 16.061(12) Å, = 96.83(7), = 95.31(8), = 118.22(6) and z = 2. Its structure has been determined using 9497 unique single crystal data. The final refinements let the agreement factors R₁ and wR₂(F²) converge to reach the respective values of 0.0548 and 0.0986. R₁ = 0.0338 for the 7264 unique data with I > 2(I). [Cd₅(OH)(H₂O)₃][CH₃CO₂]₉ is a cadmium hydroxide acetate compound with a bi-dimensional structure in which hydrogen bonds insure cohesion between layers stacked along the [1 10] direction. The inorganic network is built up of layers constituted of CdO₆ octahedra and CdO₇ pentagonal bi-pyramids sharing edge or corner.     

Synthesis and crystal structures of quadruply carboxylate-bridged dimeric lanthanide(III) complexes of betaine

Three dimeric lanthanide(III) complexes, [Eu₂(bet)₈(H₂O)₄](CIO₄)₆ (1), [Tb₂(bet)₈(H₂O)₄](ClO₄)₆ (2), and [Eu₂(bet)₄(H₂O)₈] Cl₆·6H₂O (3) (bet = Me₃N⁺CH₂COO^–, trimethyl-aminoacetate), have been prepared and structurally characterized by X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P2₁/c, with a = 11.7807(8), b = 27.757(5), c = 11.7980(8) Å, = 99.500(4)°, V = 3805.1(8) ų, and Z = 2. Complex 2 is isomorphous to complex 1, crystallizing in the monoclinic space group P2₁/c, with a = 11.7769(14), b = 27.725(3), c = 11.795(5) Å, = 99.668(14)°, V = 3797(2) ų, and Z = 2. Complex 3 crystallizes in the orthorhombic space group Pbca, with a = 12.5664(8), b = 17.8645(9), c = 22.2573(8) Å, V = 4996.6(4) ų and Z = 4. Both complexes 1 and 2 comprise quadruply carboxylate-O,O-bridged [M₂(bet)₄]⁶⁺ dimeric cores (M = Eu, Tb), and each metal ion is further coordinated by two terminal aqua ligands and two monodentate bet carboxylates to form a distorted square-antiprismatic coordination geometry. Complex 3 also has a [Eu₂(bet)₄]⁶⁺ core, in which two bet ligands act in the ¹:¹:₂ bridging fashion, and the other two bet ligands in the less common ²:¹:₂ bridging fashion, namely bridging-chelate mode. Each europium(III) ion in complex 3 is further coordinated by four water molecules to complete a monocapped square antiprism.     

Detection of electrophoretically separated cytochromes P450 by element-labelled monoclonal antibodies via laser ablation inductively coupled plasma mass spectrometry

Numerous structurally and enzymatically similar cytochromes P450 (CYPs) are involved in the metabolism of xenobiotics and are present in different amounts and with different enzyme profiles in human tissues and cells. Analysis of their adaptively regulated and individually variable patterns is a peculiar analytical challenge. We developed a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) based method for concomitant detection and semiquantitative determination of electrophoretically separated and blotted CYPs. The first results are given here for the two enzymes CYP1A1 and CYP2E1. Specific monoclonal antibodies directed against the enzymes were differentially labelled with europium via a covalently linked chelator and with iodine, respectively. Analysis of the modified antibodies shows that both europium and iodine are coupled to the heavy and the light chains of the antibodies. Also, the antibodies maintained their antigen-binding properties after labelling as demonstrated by LA-ICP-MS-analysed immunoblots. The method allowed us to detect specifically and concomitantly both CYP enzymes in complex biological samples, i.e. microsomes of rat liver and minipig duodenum, which are characterized by different levels and proportions of the two CYP enzymes. A strong CYP1A1 signal is found in liver microsomes of 3-methylcholanthrene-treated rats, while it is (nearly) absent in liver microsomes of rats treated with isonocotinic acid hydrazide (isoniazid). The constitutively expressed CYP2E1 is found in microsomes of both treatment groups. Duodenal microsomes of minipigs orally exposed to polycyclic aromatic hydrocarbons show a clear CYP1A1 signal. Low levels of CYP2E1 can also be detected in these microsomes. The LA-ICP-MS method allows concomitant determination of CYPs, thereby exhibiting sensitivity similar to that of conventional chemoluminescence detection via peroxidase-labelled secondary antibodies. The latter method allows readout of a single CYP protein in a 1D separation. Although the results presented here are only for labelling by use of the elements iodine and europium, the same strategy can be applied also for other lanthanide elements in combination with chelating compounds, so LA-ICP-MS of western blots offers a new capability to be applied for highly multiplexed CYP determinations via labelled antibodies.     

The effect of replacement of Sr by Ca on the structural and luminescence properties of the red-emitting Sr2Si5N8:Eu LED conversion phosphor

The influence of the replacement of Sr by Ca on structural and luminescence properties of Eu²⁺-doped Sr₂Si₅N₈ is reported. The Rietveld refinement of the powder X-ray diffraction data shows that the Ca²⁺ ion preferentially occupies the larger Sr site in Sr₂Si₅N₈:Eu²⁺. Although the excitation spectrum is hardly modified, the position of the emission band of Eu²⁺ can be tailored through partial replacement of Sr by Ca in Sr₂Si₅N₈:Eu²⁺, resulting in red-emission shifting from 620 to 643 nm. Furthermore, (Sr, Ca)₂Si₅N₈:Eu²⁺ shows high potential as a conversion phosphor for white-light LED applications due to similar absorption, conversion efficiency and thermal quenching behaviour for 465 nm excitation after the introduction of the Ca ion.     

Crystal and molecular structures of the Rh[(C2H5O)2PS2]3 and Co[(C6H5O)2PS2]3 chelate compounds

The crystal structures of the Rh[(EtO)₂PS₂]₃ (I) and Co[(PhO)₂PS₂]₃ (II) chelate compounds were determined from X-ray diffraction (XRD) data (CAD-4 diffractometer, MoK _β radiation, 1193 F _hkl , R = 0.0516 for I and 513 F _hkl , R = 0.0305 for II). Crystals I are monoclinic: a = 14.233(3) Å, b = 13.570(3) Å, c = 14.272(3) Å; β = 90.66(3)°, V = 2756.3(10) ų, Z = 4, ρ_calc = 1.587 g/cm³, space group C2/c. Crystals II are trigonal: a = 15.149(2) Å, c = 30.306(6) Å; V = 6023.2(16) ų, Z = 6, ρ_calc = 1.493 g/cm³, space group R3ˉ. Structures I and II consist of discrete mononuclear molecules. The coordination polyhedra of the M atoms (M = Rh, Co) are distorted octahedra formed by six sulfur atoms of three cyclic bidentate (RO)₂ PS₂⁻ ligands. Original Russian Text Copyright ? 2008 by R. F. Klevtsova, L. A. Glinskaya, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 2, pp. 330–334, March–April, 2008.     

Synthesis and photophysical properties of novel organic–inorganic hybrid materials covalently linked to a europium complex

A novel sol–gel derived hybrid material (classed as Eu-DBM-Si) covalently grafted with Eu(DBM-OH)₃·2H₂O (where DBM-OH = o-hydroxydibenzoylmethane) was prepared through the primary β-diketone ligand DBM-OH. All the synthesized ligands were characterized by ¹H NMR, elemental analyses and Fourier transform infrared spectra (FTIR). The resultant Eu-DBM-Si material exhibited good transparent and homogenous property. Compared to the Eu-DBM hybrid prepared by physically doped silicon dioxide with Eu(DBM-OH)₃·2H₂O, the Eu-DBM-Si hybrid presented more efficient ligand-to-Eu³⁺ energy transfer and a significant improvement in the measured emission quantum yield. Furthermore, the photophysical properties of these hybrid materials, such as the photoluminescence (PL) spectra, PL intensities, symmetry properties, lifetime decays, and Judd-Ofelt parameters were also investigated in detail.