Luminescence enhancement of terbium(III) perchlorate by 2,2′‐dipyridyl on bis(benzylsulfinyl)methane complex and luminescence mechanism

A novel ternary complex, Tb₂L₄·L′·(ClO₄)₆·8H₂O, has been synthesized using bis(benzylsulfinyl)methane as the first ligand L and 2,2′‐dipyridyl as the second ligand L′. The ternary complex was characterized by element analysis, molar conductivity, coordination titration analysis, infrared, thermogravimetric‐differential scanning calorimetric and ultraviolet spectra. The results indicated that the composition of the complex was Tb₂L₄·L′·(ClO₄)₆·8H₂O (L = C₆H₅CH₂SOCH₂SOCH₂C₆H₅; L′ = Dipy). Fourier transform infrared results revealed that the perchlorate group was bonded with the Tb(III) ion by the oxygen atom, and the coordination was bidentate. The fluorescent spectra illustrated that the complex displayed characteristic fluorescence in the solid state. After the introduction of the second ligand, 2,2‐dipyridyl, the relative emission intensity and fluorescence lifetime of the ternary complex Tb₂L₄·L′·(ClO₄)₆·8H₂O were enhanced compared to the binary complex TbL_2.5(ClO₄)₃·3H₂O. This indicated that the presence of both organic ligand bis(benzylsulfinyl)methane and the second ligand 2,2‐dipyridyl could sensitize the fluorescence intensity of Tb(III) ion, and introduction of the 2,2‐dipyridyl group resulted in an enhancement of the fluorescence of the Tb(III) ternary rare earth complex. The strongest characteristic fluorescence emission intensity of the ternary complex was 9.36 times that of the binary complex. The phosphorescence spectra and fluorescence lifetime of the complex were also measured. Copyright © 2014 John Wiley & Sons, Ltd.     

Fluorescence enhancement of europium (III) perchlorate by 1,10‐phenanthroline on the 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone complex and luminescence mechanism

A novel ligand, 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone was synthesized using a new method and its two europium (Eu) (III) complexes were synthesized. The compounds were characterized by elemental analysis, coordination titration analysis, molar conductivity, infrared, thermo gravimetric analyzer‐differential scanning calorimetry (TGA‐DSC), ¹H NMR and UV spectra. The composition was suggested as EuL₅ · (ClO₄)₃ · 2H₂O and EuL₄ · phen(ClO₄)₃ · 2H₂O (L = C₁₀H₇COCH₂SOC₆H₅). The fluorescence spectra showed that the Eu(III) displayed strong characteristic metal‐centered fluorescence in the solid state. The ternary rare earth complex showed stronger fluorescence intensity than the binary rare earth complex in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 1.49 times as strong as that of the binary system. The phosphorescence spectra were also discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,characterization and luminescence of europium perchlorate with MABA‐Si complex and coating structure SiO2@Eu(MABA‐Si) luminescence nanoparticles

This article reports a novel category of coating structure SiO₂@Eu(MABA‐Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O was synthesized using HOOCC₆H₄N(CONH(CH₂)₃Si(OCH₂CH₃)₃)₂ (MABA‐Si) and was used as a ligand. Furthermore, the as‐prepared silica NPs were successfully coated with the ‐Si(OCH₂CH₃)₃ group of MABA‐Si to form Si–O–Si chemical bonds by means of the hydrolyzation of MABA‐Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O. Coating structure SiO₂@Eu(MABA‐Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core‐SiO₂ particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA‐Si) was ~20 nm. In the binary complex Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O, the fluorescence spectra illustrated that the energy of the ligand MABA‐Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO₂@Eu(MABA‐Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core‐SiO₂ spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained.     

Studies on the synthesis,characterization, human serum albumin binding and biological activity of single chain surfactant–cobalt(III) complexes

The interaction of surfactant–cobalt(III) complexes [Co(bpy)(dien)TA](ClO₄)₃ · 3H₂O (1) and [Co(dien)(phen)TA](ClO₄)₃ · 4H₂O (2), where bpy = 2,2′‐bipyridine, dien = diethylenetriamine, phen = 1,10‐phenanthroline and TA = tetradecylamine with human serum albumin (HSA) under physiological conditions was analyzed using steady state, synchronous, 3D fluorescence, UV/visabsorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of HSA through a static mechanism. The binding constant (K_b) and number of binding‐sites (n) were obtained at different temperatures. The corresponding thermodynamic parameters (?G°, ?H° and ?S°) and E_a were also obtained. According to Förster's non‐radiation energy transfer theory, the binding distance (r) between the complexes and HSA were calculated. The results of synchronous and 3D fluorescence spectroscopy indicate that the binding process has changed considerably the polarity around the fluorophores, along with changes in the conformation of the protein. The antimicrobial and anticancer activities of the complexes were tested and the results show that the complexes have good activities against pathogenic microorganisms and cancer cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Fluorescence enhancement of rare earth Tb(III) by Tm(III) in benzyl benzoylmethyl sulphoxide complexes

A series of rare earth complexes [(Tb_xTm_y)L₅(ClO₄)₂](ClO₄)·3H₂O (x:y = 1.000:0.000, 0.999:0.001, 0.995:0.005, 0.990:0.010, 0.950:0.050, 0.900:0.100, 0.800:0.200, 0.700:0.300; L = C₆H₅CH₂SOCH₂COC₆H₅) (Tb(III) luminescence ion; Tm(III) doped inert ion) were synthesized and characterized by elemental analysis, infrared spectra (IR) and ¹H‐NMR. The photophysical properties of these complexes were studied in detail using ultraviolet absorption spectra, fluorescent spectra and lifetimes. The fluorescence spectra of complexes indicated that the fluorescence emission intensity was significantly enhanced by Tm(III). The complexes showed the best luminescence properties when the mole ratio Tb(III):Tm(III) was 0.990:0.010. The fluorescence intensity could be increased to 390%. Additionally, phosphorescence spectra and the luminescence mechanisms are discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of two novel lanthanide (III) complexes of acetophenonylcarboxymethyl sulphoxide

A novel ligand containing multiple coordinating groups (sulfinyl, carboxyl and carbonyl groups), acetophenonylcarboxymethyl sulphoxide, was synthesized. Its corresponding two lanthanide (III) binary complexes were synthesized and characterized by element analysis, molar conductivity, FT‐IR, TG‐DTA and UV spectroscopy. Results showed that the composition of these complexes was REL₃L^‐ (ClO₄)₂·3H₂O (RE = Eu (III), Tb (III); L = C₆H₅COCH₂SOCH₂COOH; L^‐ = C₆H₅COCH₂SOCH₂COO^‐). FT‐IR results indicated that acetophenonylcarboxymethyl sulphoxide was bonded with an RE (III) ion by an oxygen atom of the sulfinyl and carboxyl groups and not by an oxygen atom of the carbonyl group due to high steric hinderance. Fluorescent spectra showed that the Tb (III) complex had excellent luminescence as a result of a transfer of energy from the ligand to the excitation state energy level (⁵D₄) of Tb (III). The Eu (III) complex displayed weak luminescence, attributed to low energy transfer efficiency between the triplet state energy level of its ligand and the excited state (⁵D₀) of Eu (III). As a result, the Tb (III) complex displayed a good antenna effect for luminescence. The fluorescence decay curves of Eu (III) and Tb (III) complexes were also measured. Copyright © 2012 John Wiley & Sons, Ltd.     

A binuclear copper(II) complex of the schiff base derived from 1,1′-(2,6-pyridyl)-bis-1,3-butanedione and 3-amino-1-propanol

The reaction of Cu(ClO₄)₂·6H₂O with the Schiff base derived from 1,1′-(2,6-pyridyl)-bis-1,3-butanedione and 3-amino-1-propanol, (H₄L²), yields the complex Cu(H₄L²)(ClO₄)₂·H₂O. The crystal structure of this complex is triclinic, R = 0.0521, 5602 reflections. The species is dimeric leading to a binuclear copper(II) complex in which the well- separated (8.93 Å intramolecular and 5.46 Å inter- molecular) copper(II) atoms are in distorted square pyramidal geometries.     

Synthesis,characterization and luminescent properties of europium complexes with 2,4,6‐tris‐(2‐pyridyl)‐s‐triazine as highly efficient sensitizers

Using 2,4,6‐tris‐(2‐pyridyl)‐s‐triazine (TPTZ) as a neutral ligand, and p‐hydroxybenzoic acid, terephthalic acid and nitrate as anion ligands, five novel europium complexes have been synthesized. These complexes were characterized using elemental analysis, rare earth coordination titrations, UV/vis absorption spectroscopy and infrared spectroscopy. Luminescence spectra, luminescence lifetime and quantum efficiency were investigated and the mechanism discussed in depth. The results show that the complexes have excellent emission intensities, long emission lifetimes and high quantum efficiencies. The superior luminescent properties of the complexes may be because the triplet energy level of the ligands matches well with the lowest excitation state energy level of Eu³⁺. Moreover, changing the ratio of the ligands and metal ions leads to different luminescent properties. Among the complexes, Eu₂(TPTZ)₂(C₈H₄O₄)(NO₃)₄(C₂H₅OH)·H₂O shows the strongest luminescence intensity, longest emission lifetime and highest quantum efficiency. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescent properties of Eu(TTA)3·3H2O nanocrystallines

Nanocrystallines of rare earth complex, Eu(TTA)₃·3H₂O, were synthesized by the chemical precipitation method and were characterized by elemental analysis, ultraviolet visible absorption spectroscopy (UV–vis), infrared spectroscopy (IR), differential thermal analysis–thermogravimetry (TG‐DTA), X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The size of the nanocrystallines was tunable by selecting the proper buffer system, which was used to control the pH of the solution. A small polydispersity in particle size ranging from 70 to 250 nm was obtained when ammonia was used. The nanocrystallines showed the characteristic fluorescence of europium ions and energy transfer from the organic ligand to central ions was observed by fluorescence excitation and emission spectroscopy. These nanoparticles of rare earth complexes have potential application in luminescent materials due to their excellent fluorescence properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis,crystal structure and fluorescence properties of terbium complexes with phenoxyacetic acid and 2,4,6‐tris‐(2‐pyridyl)‐s–triazine

Two complexes of Tb³⁺, Gd³⁺/Tb³⁺ and one heteronuclear crystal Gd³⁺/Tb³⁺ with phenoxyacetic acid (HPOA) and 2,4,6‐tris‐(2‐pyridyl)‐s–triazine (TPTZ) have been synthesized. Elemental analysis, rare earth coordination titration, inductively coupled plasma atomic emission spectrometry (ICP‐AES) and thermogravimetric analysis‐differential scanning calorimetry (TG‐DSC) analysis show that the two complexes are Tb₂(POA)₆(TPTZ)₂·6H₂O and TbGd(POA)₆(TPTZ)₂·6H₂O, respectively. The crystal structure of TbGd(POA)₆(TPTZ)₂·2CH₃OH was determined using single‐crystal X‐ray diffraction. The monocrystal belongs to the triclinic system with the P‐1 space group. In particular, each metal ion is coordinately bonded to three nitrogen atoms of one TPTZ and seven oxygen atoms of three phenoxyacetic ions. Furthermore, there exist two coordinate forms between C₆H₅OCH₂COO^– and the metal ions in the crystal. One is a chelating bidentate, the other is chelating and bridge coordinating. Fluorescence determination shows that the two complexes possess strong fluorescence emissions. Furthermore, the fluorescence intensity of the Gd³⁺/Tb³⁺ complex is much stronger than that of the undoped complex, which may result from a decrease in the concentration quench of Tb³⁺ ions, and intramolecular energy transfer from the ligands coordinated with Gd³⁺ ions to Tb³⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

Reduction of Escherichia coli O157:H7 on radish seeds by sequential application of aqueous chlorine dioxide and dry‐heat treatment

Aims: To assess the effectiveness of sequential treatments of radish seeds with aqueous chlorine dioxide (ClO₂) and dry heat in reducing the number of Escherichia coli O157:H7. Methods and Results: Radish seeds containing E. coli O157:H7 at 5·5 log CFU g^?1 were treated with 500 μg ml^?1 ClO₂ for 5 min and subsequently heated at 60°C and 23% relative humidity for up to 48 h. Escherichia coli O157:H7 decreased by more than 4·8 log CFU g^?1 after 12 h dry‐heat treatment. The pathogen was inactivated after 48 h dry‐heat treatment, but the germination rate of treated seeds was substantially reduced from 91·2 ± 5·0% to 68·7 ± 12·3%. Conclusions: Escherichia coli O157:H7 on radish seeds can be effectively reduced by sequential treatments with ClO₂ and dry heat. To eliminate E. coli O157:H7 on radish seeds without decreasing the germination rate, partial drying of seeds at ambient temperature before dry‐heat treatment should be investigated, and conditions for drying and dry‐heat treatment should be optimized. Significance and Impact of the study: This study showed that sequential treatment with ClO₂ and dry‐heat was effective in inactivating large numbers of E. coli O157:H7 on radish seeds. These findings will be useful when developing sanitizing strategies for seeds without compromising germination rates.     

Effects of the interaction between Na2Wo4‐6‐benzylaminopurine anionic chelate and rhodamine 6G on the resonance Rayleigh scattering and fluorescence spectra and their analytical applications

In pH 4.99‐6.06 Britton‐Robinson (BR) buffer medium, 6‐benzylaminopurine (6‐BA) reacted with Na₂WO₄ to form 1:1 anionic chelate (6‐BA·WO₄)^2‐, which further reacted with rhodamine 6G to form ternary ion complexes at room temperature. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) with a maximum RRS wavelength of 316 nm. Meanwhile, the fluorescence of the solution was quenched and excitation (λ_ex) and emission (λ_em) wavelengths of the fluorescence were 290 and 559 nm, respectively. Intensities of RRS enhancing (ΔI_RRS) and fluorescence quenching (ΔI_F) were directly proportional to concentrations of 6‐BA. As a result, RRS and fluorescence quenching for determination of trace amounts of 6‐BA were developed. Under optimal conditions, linear ranges and detection limits of the two methods were 0.05‐15.00 µg/mL and 8.2 ng/mL (RRS), 0.50‐15.00 µg/mL and 17.0 ng/mL, respectively. It was found that the RRS method was superior to fluorescence quenching. The influence of these methods were investigated and results showed that RRS had good selectivity. RRS was applied to determine 6‐BA in vegetable samples with satisfactory results. Furthermore, the reaction mechanisms of the ternary ion‐association system are discussed. In addition, the polarization experiment revealed that the resonance light scattering (RLS) peak of Na₂WO₄‐6‐BA‐R6G consisted mainly of depolarized resonance fluorescence and resonance scattering. It was speculated that light emission fluorescence energy (E_L) transformed into resonance light scattering energy (E_RLS), which was a key reason for enhancement of RRS. Copyright © 2012 John Wiley & Sons, Ltd.     

Chromogenic and fluorescent ‘turn‐on’ chemodosimeter for fluoride based on a F–‐triggered cascade reaction

We developed a new chromogenic and fluorescent ‘turn‐on’ chemodosimeter 1 based on a F^–‐triggered cascade reaction. This system displayed significant changes in UV/vis absorption and fluorescence emission intensities selectively for F^– over other anions in a mixture of CH₃CN/H₂O (95 : 5, v/v) and in acetonitrile. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,structure, and biological active evaluation of a new cyclic tetranuclear copper(II) complex bridged both by oxamido and carboxylate groups

A new tetracopper(II) complex bridged both by oxamido and carboxylato groups, namely [Cu₄(dmaepox)₂(bpy)₂](NO₃)₂·2H₂O, where H₃dmaepox and bpy represent N‐benzoato‐N′‐ (3‐methylaminopropyl)oxamide and 2,2′‐bipyridine, was synthesized, and its structure reveals the presence of a centrosymmetric cyclic tetracopper(II) cation assembled by a pair of cis‐dmaepox^3–‐ bridged dicopper(II) units through the carboxylato groups, in which the endo‐ and exo‐copper(II) ions bridged by the oxamido group have a square‐planar and a square‐pyramidal coordination geometries, respectively. The aromatic packing interactions assemble the complex molecules to a two‐dimensional supramolecular structure. The reactivity toward DNA and protein bovine serum albumin (BSA) indicates that the complex can interact with herring sperm DNA through the intercalation mode and the binding affinity is dominated by the hydrophobicity and chelate ring arrangement around copper(II) ions and quenches the intrinsic fluorescence of BSA via a static process. The cytotoxicity of the complex shows selective cancer cell antiproliferative activity.     

Xanthine complexes with 3d metal perchlorates

Complexes of xanthine (xnH) with 3d metal perchlorates were prepared by refluxing mixtures of ligand and metal salt in ethyl acetate-triethyl orthoformate. In all cases, partial substitution of anionic xn⁻ for ClO₄⁻ groups occurs, and the solid complexes isolated also contain invariably two neutral xnH ligands per metal ion, viz. Cr(xn)₂(xnH)₂ClO₄, Fe(xn)₂(xnH)₂ClO₄·H₂O, M(xn)(xnH)₂ClO₄·H₂O (M = Fe, Co, Ni) and M(xn)(xnH)₂ClO₄· 2H₂O (M = Mn, Zn). The new complexes are generally hexacoordinated and appear to be linear chainlike polymeric species characterized by a (-Mxn-)_n single-bridged backbone. Four terminal ligands per metal ion, including two xnH groups in all cases, complete its inner coordination sphere; the remaining two terminal ligands differ from complex to complex as follows: M = Cr³⁺ xn⁻, -OClO₃; Fe³⁺ xn⁻, H₂O; Fe²⁺, Co²⁺, Ni²⁺OClO₃, H₂O; Mn²⁺, Zn²⁺ two aqua ligands. Probable binding sites of bidentate bridging xn⁻ and unidentate terminal xnH and xn⁻ are discussed.     

Epoxide ring opening in a zinc(II) complex in water without any Lewis acid catalyst: Formation of only one diastereomer out of 2

The epoxide ring in 5,6-dihydro-5,6-epoxy-1,10-phenanthroline (L) opens up in its reaction with 4-methylaniline and 4-methoxyaniline in water in equimolar proportion at room temperature without any Lewis acid catalyst to give a monohydrate of 6-(4-methyl-phenylamino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L′·H₂O) and 6-(4-methoxyphenyl-amino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L″) respectively. Reaction time decreases from 72 to 14 h in boiling water. But the yields become less. Reaction of L with Zn(ClO₄)₂·6H₂O in methanol in 3:1 molar ratio at room temperature affords white [ZnL₃](ClO₄)₂·H₂O. The X-ray crystal structure of the acetonitrile solvate [ZnL₃](ClO₄)₂·MeCN has been determined which shows that the metal has a distorted octahedral N₆ coordination sphere. [ZnL₃](ClO₄)₂·2H₂O reacts with 4-methylaniline and 4-methoxyaniline in boiling water in 1:3 molar proportion in the absence of any Lewis acid catalyst to produce [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, respectively in 1-4 h time in somewhat low yield. In the ¹H NMR spectra of [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, only one sharp methyl signal is observed implicating that only one diastereomer out of the 2³ possibilities is formed. The same diastereomers are obtained when L′·H₂O and L″ are reacted directly with Zn(ClO₄)₂·6H₂O in tetrahydrofuran at room temperature in very good yields. Reactions of L′·H₂O and L″ with Ru(phen)₂Cl₂·2H₂O (phen = 1,10-phenanthroline) in equimolar proportion in methanol-water mixture under refluxing condition lead to the isolation of two diastereomers of [Ru(phen)₂L′](ClO₄)₂·2H₂O and [Ru(phen)₂L″](ClO₄)₂·2H₂O.     

Synthesis, crystal structures, DNA-binding properties, cytotoxic and antioxidation activities of several new ternary copper(II) complexes of N,N′-(p-xylylene)di-alanine acid and 1,10-phenanthroline

Three novel ternary copper(II) complexes, [Cu₂(phen)₂(l-PDIAla)(H₂O)₂](ClO₄)₂·2.5H₂O (1), [Cu₄(phen)₆(d,l-PDIAla)(H₂O)₂](ClO₄)₆·3H₂O (2) and [Cu₂(phen)₂(d,l-PDIAla)(H₂O)](ClO₄)₂·0.5H₂O (3) (phen = 1,10-phenanthroline, H₂PDIAla = N,N’-(p-xylylene)di-alanine acid) have been synthesized and structurally characterized by single-crystal X-ray crystallography and other structural analysis. Spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements indicate that the three compounds, especially the complex 3, strongly bind to calf-thymus DNA (CT-DNA). The intrinsic binding constants of the ternary copper(II) complexes with CT-DNA are 0.89 × 10⁵, 1.14 × 10⁵ and 1.72 × 10⁵ M⁻¹, for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the HeLa (Cervical cancer), HepG2 (hepatocarcinoma), HL-60 cells (myeloid leukemia), A-549 cells (pulmonary carcinoma) and L02 (liver cells). Investigations of antioxidation properties show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals.     

Synthesis, characterization, and DNA binding and cleavage properties of copper(II)-tryptophanphenyl-alanine-1,10-phenanthroline/2,2'-bipyridine complexes

The mononuclear dipeptide‐based Cu^II complexes [Cu^II(trp‐phe)(phen)(H₂O)] ⋅ ClO₄ ( 1 ) and [Cu^II(trp‐phe)(bpy)(H₂O)] ⋅ ClO₄ ( 2 ) (trp‐phe=tryptophanphenylalanine, phen=1,10‐phenanthroline, bpy=2,2′‐bipyridine) were isolated, and their interaction with DNA was studied. They exhibit intercalative mode of interaction with DNA. The intercalative interaction was quantified by Stern Volmer quenching constant (K_sq=0.14 for 1 and 0.08 for 2 ). The Cu^II complexes convert supercoiled plasmid DNA into its nicked circular form hydrolytically at physiological conditions at a concentration as low as 5 μM (for 1 ) and 10 μM (for 2 ). The DNA hydrolysis rates at a complex concentration of 50 μM were determined as 1.74 h⁻¹ (R=0.985) for 1 and 0.65 h⁻¹ (R=0.965) for 2 . The rate enhancement in the range of 2.40–4.10×10⁷‐fold compared to non‐catalyzed double‐stranded DNA is significant. This was attributed to the presence of a H₂O molecule in the axial position of the Cu complexes.     

External fluorescence retention of calcein‐marked juvenile brown trout Salmo trutta raised in natural and artificial environments

The fluorescence retention and intensity of juvenile brown trout Salmo trutta marked during their first summer were monitored in a hatchery and in four natural streams. A handheld detector was used for direct examination. In the hatchery, three marking treatments (T) were compared: 3·5 min in a 0·5% calcein solution (T0·5‐3·5), 7 min in a 0·5% calcein solution (T0·5‐7) and 3·5 min in a 1% calcein solution (T1‐3·5). The fish were raised indoors for 11 months and then outdoors until 18 months. The fluorescence retention rate was 100% in all treatments at 11 months, although T1‐3·5 showed the highest mean fluorescence intensity, followed by T0·5‐7 and T0·5‐3·5. The fluorescence intensity was not correlated with the final total length (L_T) of the fish in two treatments, although it significantly decreased with increasing L_T in T1‐3·5. At 18 months, <30% of the fish were still slightly fluorescent, suggesting a negative effect of sunlight exposure. In stream studies, the fluorescence intensity did not significantly differ according to final L_T; an overall mean ± s.d . retention rate of 70·7 ± 26·6% was measured at 12 months with a decrease to 48·6 ± 24·6% at 24 months. Significant differences amongst streams and within reaches of the same stream were observed. Because of a significant positive effect of the shading index on the fluorescence intensity, the use of calcein should be restricted to streams unexposed to direct sunlight. Consequently, the marking method would be reliable for 1 year monitoring studies in shaded streams.     

Phenoxyl-copper(II) complexes: models for the active site of galactose oxidase

 The reaction of the macrocycles 1,4,7-tris (3,5-di-tert-butyl-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L¹H₃, or 1,4,7-tris(3-tert-butyl-5-methoxy-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L²H₃, with Cu(ClO₄)₂·6H₂O in methanol (in the presence of Et₃N) affords the green complexes [Cu^II(L¹H)] (1), [Cu^II(L²H)]·CH₃OH (2) and (in the presence of HClO₄) [Cu^II(L¹H₂)](ClO₄) (3) and [Cu^II(L²H₂)] (ClO₄) (4). The Cu^II ions in these complexes are five-coordinate (square-base pyramidal), and each contains a dangling, uncoordinated pendent arm (phenol). Complexes 1 and 2 contain two equatorially coordinated phenolato ligands, whereas in 3 and 4 one of these is protonated, affording a coordinated phenol. Electrochemically, these complexes can be oxidized by one electron, generating the phenoxyl-copper(II) species [Cu^II(L¹H)]^+ ·, [Cu(L²H)]^+ ·, [Cu^II(L¹H₂)]^2+ ·, and [Cu^II(L²H₂)]^2+ ·, all of which are EPR-silent. These species are excellent models for the active form of the enzyme galactose oxidase (GO). Their spectroscopic features (UV-VIS, resonance Raman) are very similar to those reported for GO and unambiguously show that the complexes are phenoxyl-copper(II) rather than phenolato-copper(III) species. Received: 10 February 1997 / Accepted: 7 April 1997