Pincer‐Type Platinum(II) Complexes Containing N‐Heterocyclic Carbene (NHC) Ligand: Structures,Photophysical and Anion‐Binding Properties,and Anticancer Activities

Two classes of pincer‐type Pt^II complexes containing tridentate N‐donor ligands ( 1 – 8 ) or C‐deprotonated N^C^N ligands derived from 1,3‐di(2‐pyridyl)benzene ( 10 – 13 ) and auxiliary N‐heterocyclic carbene (NHC) ligand were synthesized. [Pt(trpy)(NHC)]²⁺ complexes 1 – 5 display green phosphorescence in CH₂Cl₂ (Φ: 1.1–5.3 %; τ: 0.3–1.0 μs) at room temperature. Moderate‐to‐intense emissions are observed for 1 – 7 in glassy solutions at 77 K and for 1 – 6 in the solid state. The [Pt(N^C^N)(NHC)]⁺ complexes 10 – 13 display strong green phosphorescence with quantum yields up to 65 % in CHCl₃. The reactions of 1 with a wide variety of anions were examined in various solvents. The tridentate N‐donor ligand of 1 undergoes displacement reaction with CN^? in protic solvents. Similar displacement of the N^C^N ligand by CN^? has been observed for 10 , leading to a luminescence “switch‐off” response. The water‐soluble 7 containing anthracenyl‐functionalized NHC ligand acts as a light “switch‐on” sensor for the detection of CN^? ion with high selectivity. The in vitro cytotoxicity of the Pt^II complexes towards HeLa cells has been evaluated. Complex 12 showed high cytotoxicity with IC₅₀ value of 0.46 μM , whereas 1 – 4 and 6 – 8 are less cytotoxic. The cellular localization of the strongly luminescent complex 12 traced by using emission microscopy revealed that it mainly localizes in the cytoplasmic structures rather than in the nucleus. This complex can induce mitochondria dysfunction and subsequent cell death.     

Preliminary results of a small X-ray irradiator for equivalent dose estimation

In most established method for luminescence dating, the ratio of ⁹⁰Sr/⁹⁰Y radionuclides has been employed to provide reference laboratory doses to sample. Recently a small X-ray irradiator (Varian VF-50J) was introduced as an alternative to the traditionally used radioactive sources. Test results are presented whether the use of the small X-ray irradiator is possible in the dating technique. Aspects of the assessment of the X-ray irradiator include consideration of the measured optically stimulated luminescence signal and the relationship between X-ray tube currents and dose rates, as well as the dependence of equivalent dose for various dose rates. The test performances are assessed in relation to use with heated quartz.     

Singlet oxygen quenching by stable nitroxy radicals

The quenching mechanism of singlet oxygen luminescence at 1.27 μm by different aliphatic and aromatic nitroxy radicals has been studied. The ¹O₂ was generated in solutions of anthracene or protoporphyrin IX by excitation with a 347 nm laser flash. The luminescence quenching rate constants have been found to be about 10⁵ – 10⁶ M⁻¹ s⁻¹ for aliphatic radicals and about 10⁶ – 10⁷ M⁻¹ s⁻¹ for aromatic radicals and are weakly dependent upon the nature of the solvent. The maximum value k_q = 1.6 × 10⁷ M⁻⁷ s⁻¹ was obtained for di-tert-butyldiphenyl nitroxide which is characterized by a considerable delocalization of the unpaired electron over the molecular fragment and a lower steric screening of the

centre in comparison with other radicals. From an analysis of the experimental data it has been concluded that ¹O₂ quenching by radicals occurs exclusively via the electron exchange interaction in collision complexes.     

Mesomorphism and luminescence properties of platinum(II) complexes with tris(alkoxy)phenyl-functionalized pyridyl pyrazolate chelates

A series of new mesomorphic platinum(II) complexes 1 – 4 bearing pyridyl pyrazolate chelates are reported herein. In this approach, pyridyl azolate ligands have been strategically functionalized with tris(alkoxy)phenyl groups with various alkyl chain lengths. As a result, they are ascribed to a class of luminescent metallomesogens that possess distinctive morphological properties, such as their intermolecular packing arrangement and their associated photophysical behavior. In CH₂Cl₂, independent of the applied concentration in the range 10^?6–10^?3 M , all Pt^II complexes exhibit bright phosphorescence centered at around 520 nm, which is characteristic for monomeric Pt^II complexes. In stark contrast, the single‐crystal X‐ray structure determination of [Pt(C4pz)₂] ( 1 ) shows the formation of a dimeric aggregate with a notable Pt???Pt contact of 3.258 Å. Upon heating, all Pt^II complexes 1 – 4 melted to form columnar suprastructures, for which similar intracolumnar Pt???Pt distances of approx. 3.4–3.5 Å are observed within an exceptionally wide temperature range (>250 °C), according to the powder XRD data. Upon casting into a neat thin film at RT, the luminescence of 1 – 4 is dominated by a red emission that spans 630–660 nm, which originates from the one‐dimensional, chainlike structure with Pt–Pt interaction in the ground state. Taking complex 4 as a representative, the emission intensity and wavelength were significantly decreased and blueshifted, respectively, on heating from RT to 250 °C. Further heating to liquefy the sample alters the red emission back to the green phosphorescence of the monomer. The results highlight the pivotal role of tris(alkoxy)phenyl groups in the structural versus luminescence behavior of these Pt^II complexes.     

Luminescence of Europium(III) Chelates with 4-(Arylethynyl)pyridines as Ligands

Some Spectral properties and luminescence intensities of Eu^III chelates with 4-(arylethynyl)pyridine-2,6-dicarboxylic acids 1 – 15 and 2,2′,2″,2′″-{[4-(arylethynyl)pyrridine-2,6-diyl]bis(methylenenitrilo)} tetrakis(acetic acids) 16 – 26 were measured both in H₂O and EtOH solutions for the purpose of developing suitable labels to be used in time-resolved luminescence-based bioaffinity assays (Tables 1 and 2). The substitution at the Ar group has a significant effect upon the observed luminescence intensities, excitation wavelengths, and decay constants of the complexes, Moreover, the changes in the environment cause great variation in those properties of certain Eu^III chelates.     

Syntheses,Structures, Magnetic Properties,and NIR Emission Properties of a Series of Novel 1, 2, 4, 5‐Cyclohexanetetracarboxylate‐bridged Lanthanide Complexes with 3D Framework Structures

Solvothermal combination of trivalent lanthanide metal precursors with 1, 2, 4, 5‐cyclohexanetetracarboxylic acid (L) ligand has afforded the preparation of a family of eight new coordination polymers [Ln₄(L)₃(H₂O)₁₀] · 7H₂O (Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) ( 1 – 8 ). Structural analyses reveal that the 1, 2, 4, 5‐cyclohexanetetracarboxylic acid ligand with e,a,a,e (L^I) conformation displays a μ₄‐(κ³O, O, O⁵)(κ²O²,O²)(κ²O⁴,O⁴)‐bridging mode to generate 3D frameworks of complexes 1 – 8 and the α‐Po topology with the short Schläfli symbol {4¹².6³} could be observed in complexes 1 – 8 . The near‐infrared luminescence properties were studied, and the results have shown that the Ho^III, Er^III, and Yb^III complexes emit typical near‐infrared luminescence in the solid‐state. Variable‐temperature magnetic susceptibility measurements of complexes 2 – 7 have shown that complex 2 (Gd) shows the ferromagnetic coupling between magnetic centers, whereas the complexes 3 – 7 show the antiferromagnetic coupling between magnetic centers. Additionally, the thermogravimetric analyses were discussed.     

Circularly polarized luminescence induced by excimer based on pyrene-modified binaphthol

A new chiral bromobinaphthol-pyrene compound was developed to achieve a green circularly polarized luminescence (CPL) from its excimer with a dissymmetry factor (|g_lum|) value of 4.3 × 10⁻³ and a high quantum yield Φ_{F, solid} up to 55.9%, while no CPL signals could be observed for the blue luminescence from unimolecule. Meanwhile, reversal CPL signals can be observed from both concentrated solution and solid     

Luminescence of Cr3+ in natural and calcined diaspore

The luminescence of Cr³⁺ in natural and calcined diaspore is applied to probe structural properties of the phases. Steady-state luminescence spectra of the natural diaspore [a-AlO(OH)] are typical of 2E→4A2 transitions of Cr³⁺ luminescence centers (R-lines) substituting for Al³⁺ in six-fold coordination. The dehydroxylated phase of the diaspore is characterized by a low degree of crystallinity. This phase is not detectable by XRD and Raman spectroscopy up to 900°C. The time-resolved luminescence spectra of the diaspore treated at 900°C showed two variations: the first is an R-line of Cr3+ luminescence in octahedral sites with a strong crystal field in a very disordered environment, and the second is a broad band of Cr³⁺ luminescence in weaker crystal field sites. The crystalline phase of corundum [a-Al₂O₃] is detected by XRD and Raman spectroscopy after treating the diaspore at 1000°C and above (up to 1300°C). The lines in the spectrum of the diaspore treated at this temperature are typical of Cr³⁺ luminescence centers (R-lines) in Cr-corundum (ruby) structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Three Distinct Silver(I) Coordination Polymers: Bridging‐­Ligand Directed Syntheses,Crystal Structures,Luminescence, and Nitrobenzene Sensing Properties

Three distinct Ag^I‐DMAP [DMAP = 4‐(dimethylamino)pyridine] coordination polymers [Ag₂I₂(DMAP)₂]_n ( 1 ), [Ag₂(CN)₂(DMAP)_2.5 · DMAP]_n ( 2 ), and [Ag(SCN)(DMAP)]_n ( 3 ) were constructed by monatomic I^–, diatomic CN^–, and triatomic SCN^– bridges, respectively. 1 – 3 were determined by FT‐IR spectroscopy, elemental analyses, TGA, powder and single‐crystal X‐ray diffraction. 1 exhibits a 1D wavelike chain structure, sustained by 3‐connected I^– bridges, whereas 2 shows a unique 1D single‐ and double‐strand alternating chain, supported by 3‐connected CN^– bridges. Compound 3 has a 2D 3‐connected network architecture, fabricated by 3‐connected SCN^– bridges, and exhibits a (4 · 8²) topology. The luminescence and nitrobenzene sensing properties of 1 – 3 were explored in 2‐propanol suspensions, which revealed that compounds 1 – 3 exhibit DMAP originated luminescence emissions and are highly sensitive for nitrobenzene detection.     

Bright Luminescence by Combining Chiral [2.2]Paracyclophane with a Boron–Nitrogen-Doped Polyaromatic Hydrocarbon Building Block

Novel BN-doped compounds based on chiral, tetrasubstituted [2.2]paracyclophane and NBN-benzo[f,g]tetracene were synthesized by Sonogashira–Hagihara coupling. Conjugated ethynyl linkers allow electronic communication between the π-electron systems through-bond, whereas through-space interactions are provided by strong π–π overlap between the pairs of NBN-building blocks. Excellent optical and chiroptical properties in racemic and enantiopure conditions were measured, with molar absorption coefficients up to ϵ=2.04×10⁵ M⁻¹ cm⁻¹, fluorescence quantum yields up to Φ_PL=0.70, and intense, mirror-image electronic circular dichroism and circularly polarized luminescence signals of the magnitude of 10⁻³ for the absorption and luminescence dissymmetry factors. Computed g_lum,calcd. values match the experimental ones. Electroanalytical data show both oxidation and reduction of the ethynyl-linked tetra-NBN-substituted paracyclophane, with an overlap of two redox processes for oxidation leading to a diradical dication.     

Preparation and characterization of loess sediment for use as a reference material in the annual radiation dose determination for luminescence dating

Loess sediment was prepared and characterized with well-established K, Th and U contents, and corresponding ⁴⁰K, ²³²Th and ^235,238U activities, intended for use as a reference material in the annual radiation dose determination for luminescence dating. To this purpose, loess was collected in Volkegem, Belgium, and — after drying, pulverizing and homogenizing — characterized via k ₀-INAA and HPGe gamma-ray spectrometry. This led to 12 kg material with a grain size below 50 μm, with established K, Th and U homogeneity, with the ²³²Th and ²³⁸U decay series proven to be in equilibrium, and with the following K, Th and U reference data: K = 16.5±1.5 g·kg⁻¹ (⁴⁰K = 497±45 Bq·kg⁻¹); Th = 10.4±0.6 mg·kg⁻¹ (²³²Th = 42.2±2.5 Bq·kg⁻¹); U = 2.79±0.12 mg·kg⁻¹ (²³⁸U = 34.5±1.5 Bq·kg⁻¹; ²³⁵U = 1.59±0.09 Bq·kg⁻¹; ^235+238U = 36.1±1.7 Bq·kg⁻¹). These data were confirmed via comparison with the results from NaI(Tl) field gamma-ray spectrometry, thick-source ZnS alpha-counting and thick-source GM beta-counting (after converting all data to Gy·ka⁻¹). The reference material is available (as aliquots up to 200 g) from the Ghent Luminescence Laboratory to all interested luminescence dating laboratories upon motivated request.     

Reusable Amperometric Immunosensor for the Determination of Cortisol

Abstract

A novel reusable amperometric immunosensor was developed for the determination of cortisol by co-immobilizing horseradish peroxidase (POD) and cortisol-antibody on a chemically activated affinity membrane which is mounted over the tip of an oxygen electrode. The enzymatic electrocatalytic current response to the respective substrate is inhibited by the association of the antigen to the co-immobilized antibody. The sensor can be regenerated to facilitate several assays by washing with dilute hydrochloric acid solution. The advantages of the sensor include rapid-response, simple analysis methodology and high selectivity. The calibration curve for cortisol is linear in the concentration range of 1 × 10^?7 – 1 × 10^?5M. The optimal conditions of immobilization and pH have been studied. The inhibition of enzymatic activity was confirmed by luminescence measurement utilizing the luminol- H₂O₂-POD system.     

Excited state decay of tetrahalomanganese(ii) complexes

The excitation and emission spectra and decay times of several MnX^2-₄ (X = Cl^?, Br^?, 1^?) complexes of various tetraalkylammonium, -phosphonium, and -arsonium salts have been measured for the pure solids at 298°K and 77°K. High luminescence quantum yields (0.3-1.0) reveal that lifetimes fairly accurately reflect radiative decay rates. An impressive correlation exists between the lifetime, τ, of the ⁴T₁ (G) →⁶ A₁ emission and the ligand, X: for X = Cl^?, τ = 1.2 - 3,5 x 10^?3 sec; X = Br^?, τ = 0.35 - 0.43 X 10^?3 sec; X =l^?, τ = 0.036 – 0.055 X 10^?3 sec. We attribute this decreasing lifetime largely to the enhanced spin-orbital coupling associated with the heavier halide. We find that direct population of high energy charge-transfer (CT) states gives smaller emission yields than excitations in the ligand-field (LF) region.     

Fluorescent Optosensor for Humidity Measurements in Air

A fiber‐optic sensor for relative‐humidity (RH) monitoring in environmental samples is described based on the adiabatic photoreaction that produces an intramolecular charge‐transfer excited state, which is the basis of the sensor response. The sensitive membranes are obtained immobilizing a highly fluorescent dye, 4‐[2‐(pyrazin‐2‐yl)‐1,3‐oxazol‐5‐yl]benzenamine (pzoxba; formerly called appzox), in hydroxypropylcellulose (HPC). The composition of the sensing films was optimized to a final ratio pzoxba/HPC of 1.8⋅10⁻⁵ mol g⁻¹ with a 100‐μm membrane thickness. The optode response spans from 1.68 to 100% RH, with a detection limit of 0.56% (Table 2). Typical response times (t₉₀) to 0 – 100% relative humidity are 1 – 2 min, the relative standard deviation for repeated measurements being 0.77 – 1.8%. The optode is insensitive to typical organic vapor interferents of commercial capacitive sensors (see Table 3) as well as to molecular oxygen, an important quencher of other luminescence‐based optical sensors. The proposed optode was successfully applied and validated for continuous monitoring of the relative humidity level in environmental samples.     

Rapid Determination of Minocycline in Pharmaceutical Formulations and Human Urine/Serum Samples Based on the Minocycline-Europium-Sodium Dodecylbenzene Sulfonate Luminescence System

Abstract

A new luminescence method based on the minocycline (MNC)-europium (Eu³⁺)-sodium dodecylbenzene sulfonate (SDBS) system was developed for the determination of MNC. SDBS formed a ternary complex with MNC-Eu³⁺ and significantly enhanced the luminescence intensity of Eu³⁺. The enhanced luminescence intensity showed a good linear relationship with the concentration of MNC over the range of 4.0 × 10^?7 ～ 1.0 × 10^?5 mol L^?1 with a detection limit of 2.0 × 10^?8 mol L^?1. This method is rapid and sensitive, and has been successfully applied for the determination of MNC in capsules and human urine/serum samples. The luminescence mechanism is also studied.     

Bismuth(III) based Metal Organic Frameworks: Luminescence,Gas Adsorption,and Antibacterial Studies

Bi^III‐MOFs 1 – 4 were prepared via solvothermal method using four organic linkers; 2‐mercapto‐3‐methyl‐4‐thiazoleacetic acid (H₂MMTA), 2,6‐naphthalenedicarboxylic acid (2,6‐NDA), 4,6‐dihydroxy‐2‐mercaptopyrimidine (H₂DMP), and 4‐mercaptobenzoic acid (H₂MBA), respectively. The resulting MOFs were structurally/morphologically characterized by UV/Vis, AAS/ICP‐MS, Fourier transform infrared spectroscopy (FT‐IR), ¹H NMR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and powder X‐ray diffraction technique. All these MOFs showed good luminescence properties exhibiting blue luminescence. N₂ gas adsorption isotherms of 1 – 4 confirmed the porosity of these frameworks. In order to evaluate the effect of metal ion upon chelation, the free organic linkers and respective MOFs were screened for their antibacterial potential against some pathogenic bacteria and appreciable activity was observed.     

Application of electrogenerated chemiluminescence of luminol to determination of traces of cobalt(II) in aqueous alkaline solution

A selective method for determination of traces of cobalt(II) in aqueous alkaline solution has been developed, based on the electrochemical generation of luminescence from luminol at a rotating ring—disc electrode. The detection limit is 10^-8 M, and the linear calibration range extends up to 3 × 10^-6 M; the r.s.d. for 2.0 × 10^-7 M cobalt is 6%. Of 21 metal ions, only chromium(III) and copper(II) interfere seriously; EDTA also interferes.     

Polypyrrole Bilayers: Charge Trapping and Application for Amperometric Ions Sensing

Bilayers composed of polypyrrole: doped by perchlorate ions (PPy(ClO₄) – anion exchanging inner layer) and by dodecyl sulfate ions (PPy(DS) – cation exchanging outer layer) are very effective charge trapping systems that are usually not observed for other bilayers comprised of polypyrrole. Chronopotentiometric experiments carried out for oxidation and reduction showed that the trapping effect in the inner layer resulted from different ion exchange properties of the component polymers, leading to a low permeability of the reduced outer layer towards anions. Estimated diffusion coefficients of Cl^? anions in the oxidized and reduced PPy(DS) are in the range of 10^?9 and lower than 10^?10 cm² s^?1, respectively. The presence of the outer layer limiting the ion transfer was found to be beneficial to improve the signal resolution in amperometric mode of ion sensing within wide KCl concentration range, from 10^?5 M up to 3 M. The influence of experimental conditions (film thickness, response time) on optimization of this novel kind of polymeric bilayer ion sensors was studied.     

双光子敏化Eu3+高效发光活细胞成像纳米生物探针

将Eu(tta)₃dpbt (dpbt: 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine; tta:thenoyltrifluoroacetonato)包埋在甲基丙烯酸甲酯-苯乙烯共聚物、正辛基三甲氧基硅及其水解缩合产物组成的杂化基质中, 制备了Eu(tta)₃dpbt 质量分数为40%的荧光纳米粒子, 其平均粒径为45 nm. 所制备的发光纳米粒子在水中分散稳定性高、光稳定性好、细胞毒性低、长波敏化Eu³⁺发光性能优良, 适宜作为生物分析的发光标记物. 所制备的发光纳米粒子的可见区激发峰位于415 nm, 激发峰尾部延展至475 nm, 其发光量子产率为0.31(λ_ex=415 nm, T=23 ℃), 最大双光子激发作用截面为5.0×10⁵ GM (λ_ex=830 nm, 1 GM=10^-50 cm⁴·s·photo^-1×particle^-1). 以转铁蛋白修饰上述发光纳米粒子表面制备的纳米生物探针被成功应用于活的HeLa肿瘤细胞的特异性标记和双光子激发Eu³⁺发光成像.     

Luminescence Determination of Europium in High-Purity Yttrium and Gadolinium Oxides

ABSTRACT

A luminescence spectrometric method was developed for the determination of ultratrace amounts of europium (down to 1×10^?10 M) in high-purity yttrium and gadolinium oxides. This is based on the enhanced luminescence of europium thenoyltrifluoroacetone (TTA)-Tri-n-octyl phosphine oxide (TOPO)-Triton X-100 in the presence of terbium. The luminescence intensity is linear with europium concentration in the range 1×10^?9 to 1×10^?6 M under the recommended conditions. The optimized procedure is successfully utilized for the determination of ultratrace amounts of europium in yttrium and gadolinum oxides.