Complexation of radionuclide ~(152+154)Eu(Ⅲ) with alumina-bound fulvic acid studied by batch and time-resolved laser fluorescence spectroscopy

To contribute to the understanding of Eu(Ⅲ)interaction properties on hydrous alumina particles in the absence and presence of fulvic acid(FA),the complexation properties of Eu(Ⅲ)with hydrous alumina,FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy(TRLFS)techniques.The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(Ⅲ).Eu(Ⅲ)is adsorbed onto alumina particles as outer-sphere surface complexes of≡(Al-O)-Eu·(OH)·7H_2O and≡(Al-O)-Eu·6H_2O at low pH values,and as inner-sphere surface complexes as≡(Al-O)_2-Eu~+·4H_2O at high pH.In FA solution,Eu(Ⅲ)forms complexes with FA as(COO)_2Eu~+(H_2O)_x and the hydration water number in the first coordination sphere decreases with pH increasing.The formation of≡COO-Eu-(O-Al≡)·4H_2O is observed on FA-alumina hybrids,suggesting the formation of strong inner-sphere surface complexes in the presence of FA.The surface complexes are also characterized by their emission spectra[the ratio of emission intensities of~5D_0→~7F_1(λ=594nm)and~5D_0→~7F_2(λ=619nm)transitions]and their fluorescence lifetime.The findings is important to understand the contribution of FA in the complexation properties of Eu(Ⅲ)on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(Ⅲ),or its analogue trivalent lanthanide and actinide ions in natural environment.     

Complexation of hypocrellins and bivalent metals and one-electron reduction of the complexes with electron donor

The complexation of HA (or HB) with bivalent metals was examined by UV-Vis andNMR spectroscopy, and all of the complexes obtained have a metal-ligand ratio of 1:1.Thephotoinduced reduction of the complexes of HA-Zn~(2+) and HA Mg2+ (or HB-Zn~(2+), HB-Mg2+)in the presence of 1-benzyl-1,4-dihydro-nicotinamide as the electron donor was investigated byUV-Vis and ESR spectroscopy. The studies demonstrated that illumination of the complexes ofHA(HB)-Zn~(2+) and HA(HB)-Mg~(2+) led to the accumulation of the chelated semiquinone radicalanions.     

Indirect Flow Injection Chemiluminescence Method for the Determination of Tetracycfines Using Cu（]I） as a Probe Ion

This paper reported an indirect flow injection chemiluminescence （FI-CL） method for the determination of the drugs tetracycline （TC）, chlortetracycline （CTC） and oxytetracycline（OTC） using Cu（ Ⅱ ） as a probe ion. The CL reaction was induced on-line and after injection of the sample the negative peaks appeared as a result of complexation. The method was applied to the determination of TCs in pharmaceuticals and human urine with recoveries in the range95-105%.     

Studies of the Intramolecular Aromatic-ring Stacking Interactions in the Ternary Platinum（Ⅱ） Complexes

The stability constants of some ternary mixed-ligand complexes, Pt (Phen)(CA) , where Phen-1,10-phenanthroline and CA^-=carboxylate, were determined by means of potentiometric pH titration in aqueous solutions (I=0. 1mol/L, KNO3; 25℃), and the stability of them was compared with that of the corresponding binary complexes. It was revealed that the ternary complexes containing phenylalkane carboxylates ligands (PCA-) are much more stable than those formed with formate and acetate. The results indicate that there exist the intramolecular aromatic-ring interactions between the phenanthroline ring of Phen and the phenyl moiety of ligand PCA- in the ternary mixed-ligand Pt(Phen) (PCA)^- complexes. The extent of the stacking interactions, which depends on the number of methylene groups between the phenyl moieties and the coordinated phenylalkane carboxylate groups, was calculated. The best-fitted stack was obtained for the complexes with 2-phenylacetate and 3-phenylpropionate as the ligands.     

Polymeric Structure and Solid ~(31)P, ~(113)Cd NMR Spectra of Cadmium(II) Dialkyldithiophosphate (Alkyl = n-butyl and i-butyl)

Owing to the particular affinity toward metal ion and changeable dentation, dialkyldithiophosphates are commonly used ligands in preparation of the transition metal complexes with variable structures1. For instances relevant to this work, the IIB metal complexes defined crystallographically so far have provided the examples as follows2-12 (Scheme 1). Scheme 1 The frameworks of IIB metal complexes of dialkyldithiophosphate MMMMMMMMMM a b c d …     

TERNARY COMPLEXES OF Cu(ATP)AND HETEROAROMATIC N BASE-ISOQUINOLINE AND BENZIMIDAZOLE:STABILITY CONSTANT AND STACKING EFFECT

The stability constants of the binary complexes ofCu~(2+) with isoquinoline and benzimidazole as well as the ternarycomplexes of Cu(ATP)with the same ligands have been measuredin aqueous solution spectrophotometrically and a strongstacking interaction between the heteroaromatic ring of theligands and the purine moiety of ATP has been found.The factof this stacking interaction is much stronger than that in thesystems of Cu(ATP)with pyridine and imidazole shows thatthe stacking interaction increases with the size of theheteroaromatic ring of the ligands.     

Spectroscopic Characterization of Mo-Co-S and Mo-Fe-S Complexes-derived Catalysts for Desulfurization and Denitrification

The characteristic studies, by means of LR, UV-Vis and XPS spectroscopies, of the preparation process of Mo-Co-S and Mo-Fe-S catalysts for HDS and HDN, derived from (NH4)2MoS4-CoCl2 and (NH4)2MoS4-FeCl2 complexes supported on γ-Al2O3, respectively, indicate that the catalytically essential moiety on the surface of the catalysts is dominantly some sulfido-bimetallic species with such a structural unit (M' =Co or Fe), and both Co and Fe, served as promoters, can donate electrons to Mo probably via bridging-S. The nature of active-sites and the mechanism of promotion are discussed according to the results.     

Studies on Cobalt-Carbon Cluster——Svntnesis of α-Naphthyl α-Thienyl and Substituted-Phonyl Phenylacetyene Dicobalt Hexacarbonyls

12 new diarylacet ylenedicobal t hexacarbonyl complexes were synthesized by complexation reaction of a-naphthyl,a-thienyl or sub-stituted-phenyl phenylacetylene with Co2CO)8 and N-acetylation ofp-aminophenyl phenylacetylenedicobalt hexacarbonyl.The structures of all the complexes were characterized by elemental analysis,IR and H NMR spectroscopy.Making a comparison between the N-acetylation of p-aminophenyl phenylacetylenedicobalt hexacarbonyl and that of aniline under comparable conditions,we found that the clustercore PhC2Co2(CO)6 para to an amino group attached to aromatic ring does not obviously affect the nucleophilicity of aniline.     

Synthesis of New Ruthenium（Ⅱ）Bipyridyl Complexes and Studies on Their Photophysical and Photoelectrochemical Properties

Two new mixed-ligand ruthenium(Ⅱ） complexes,Ru(dcbpy)-(LL)NCS)2[where dcbpy=4,4‘-dicarboxyl-2,2‘‘-bipyridine,LL=4,4‘-bis(N-methyl-anilinomethyl)-2,2‘‘-bipyridine(2)],were synthesized,and the tphotophysical properties of these complexes were studied.The metal-to-ligand charge transfer (MLCT) transitions of these complexes exhibited solvatochromic effect due to the existence of NCS ligands.The MLCT energies also strongly depend on the pH values of the solutions because of protonation and deprotonation of the carboxyl groups.The pKa values of the ground state,4.0 for 1 and 3.8 for 2,were obtained from the titration curves.The photoelectrochemical properties of 1 and 2 as sensitizers in sandwich-type solar cells have been studied.Complex 1 exhibited better photoelectrochemical behavior than complex 2 as expected.It was proved that the design of mixed-ligand complex by introducing electron donating group in one of the ligands should be a promising approach.     

STRUCTURE AND CATALYTIC ACTIVITY OF RHODIUM COMPLEX COORDINATED ON 2-VINYLPYRIDINE-METHYL ACRYLATE COPOLYMER FOR THE CARBONYLATION OF METHANOL

A series of rhodium complexes coordinated on the hybrid ligand. 2-vinylpyridine-methyl acrylate copolymers, as catalyst for the carbonylation of methanol were synthesized by the reaction of the copolymers with tetracarbonyldichlorodirhodium. These complexes were in general very reactive in carbonylation of methanol to form acetic acid and methyl acetate without other by-product. The XPS studies of the complexes showed that the binding energies of Nls(399.1-399.4 eV) and that of Ols(532.5-532.9 eV) were higher than that of the copolymer ligand (Nls 398.1-398.3 eV and Ols 532.2-532.3 eV), indicating the fromation of N→Rh and O→Rh coordination bonds. The IR spectra of complexes showed that the appearance of two absorption peaks of terminal carbonyl at 1990-2100 cm~(-1), characteristic of the cis-dicarbonyl rhodium moiety. These XPS and IR studies confirm the formation of cis-dicarbonylrhodium complex with the active centers(A) and (B) as shown in the text. The increase of activity of the complex in the c     

Quantum-chemical and correlation study of deprotonation and complexation of 1-amino-4-hydroxyanthraquinone

Existing views on the deprotonation and complexation of 1-amino-4-hydroxyanthraquinone are wrong. This compound, its anions, and complexes with metals are not individual substances, but they form a dynamic equilibrium mixture of keto-enol (keto-oxide) and amino-imine tautomers. Different samples of the same compound differ by the tautomeric composition, the respective information is contained in their electron absorption spectra. In weak alkaline solutions the deprotonation occurs exclusively at the hydroxy group. Most typical structure of 1-amino-4-hydroxyanthraquinone anions is 1,10-quinoid, its metal complexes have 9,10-and 1,10-quinoid structures. The ground states of molecules are more responsible for the tautomeric transformations than the excited states. Quantum-chemical calculations of tautomeric anthraquinones by semiempirical PPP methods are more reliable than modern ab initio calculations.     

Prediction of pKa values of nido-carboranes by density functional theory methods

A great parallel exists between metal complexes of cyclopentadienyl and arene ligands on one side and metal complexes of the nido derivatives of the icosahedral o-carborane clusters. With few exceptions, the metal complexation in the cluster can be viewed as the substitution of one or more bridging hydrogen atoms by the metal. Therefore, a necessary requirement for the complexation is the deprotonation of the nido cluster to generate a coordination site for that metal. The reaction to remove these protons, which most probably is one of the most commonly done processes in boron and metallaborane chemistry, is barely known, and no quantitative data are available on the magnitude of their pKa values. With the purpose of determining the acidity of nido-carboranes, a procedure to calculate the pKa values of nido boron clusters is presented in this paper for the first time. To this objective, some nido clusters have been selected and their geometry and NMR-spectroscopic properties have been studied, giving a good correlation between the theoretical and experimental data in both geometry distances and 11B NMR spectroscopy. Of notice is the result that proves that the singular carbon atom in the thermodynamic isomer of [C2B10H13]- is definitely part of the cluster and that its connection with the C2B3 face would be better defined by adding additional interactions with the two boron atoms nearest to the second cluster carbon. The pKa values of the nido species have been calculated by correlating experimental pK(a) values and calculated reaction Gibbs energies DeltaG(s). Some pKa values of importance are -4.6 and +13.5 for 7,8-[C2B9H13] (1) and 7,8-[C2B9H12]- (2), respectively.     

Aqueous solution study of Cu(II) and Ni(II) complexes of macrocyclic oxa- and thia-containing trans-dioxo-tetraamines

Four macrocyclic trans-dioxo-tetraamines containing sulphur or oxygen as additional donors have been prepared: 1-oxa-3,14-dioxo-4,7,10,13-tetraazacyclopentadecane, 1-thia-3,14-dioxo-4,7,10,13-tetraazacyclopentadecane, 1-oxa-3,16-dioxo-4,8,11,15-tetraazacycloheptadecane and 1-thia-3,16-dioxo-4,8,11,15-tetraazacycloheptadecane. Their protonation as well as their metal binding properties with Cu²⁺ and Ni²⁺ have been determined at 25°C in 0.10 mol dm⁻³ KNO₃. The complexation process was investigated by potentiometric, calorimetric and UV/VIS-spectroscopic titrations. IR-spectroscopy was used to establish the involvement of the amido groups in the coordination. Oxidation of the complexes to the trivalent state of the metal ion was also investigated by cyclic voltammetry. Metal ion complexation promotes the deprotonation of the amide nitrogens, resulting in a neutral complex with four nitrogen donors and a MLH_-2 stoichiometry at pH 8. Additional complexes with stoichiometry ML and MLH_-1 were needed to describe the complexation in the pH range 2–11. Their stability constants were calculated. The presence of oxygen or sulphur donors as well as ring enlargement influence the complexation properties. The electronic spectra indicate rather distorted tetragonal coordination geometries for the Cu(II)-complexes. The Ni(II)-complexes are all square–planar with the exception of an equilibrium between a square–planar and an octahedral form for NiL¹H₋₂. All complexes are easily but irreversibly oxidized to the trivalent state of the metal ion.     

Complexes of DOTA-bisphosphonate conjugates: probes for determination of adsorption capacity and affinity constants of hydroxyapatite

The adsorption on hydroxyapatite of three conjugates of a bisphosphonate and a macrocycle having C1, C2, and C3 spacers and their terbium complexes was studied by the radiotracer method using 160Tb as the label. The radiotracer-containing complex of the conjugate with the C3 spacer was used as a probe for the determination of the adsorption parameters of other bisphosphonates that lack a DOTA unit. A physicochemical model describing the competitive adsorption was successfully applied in the fitting of the obtained data. The maximum adsorption capacity of bisphosphonates containing bulky substituents is determined mainly by their size. For bisphosphonates having no DOTA moiety, the maximum adsorption capacity is determined by the electrostatic repulsion between negatively charged bisphosphonate groups. Compounds with a hydroxy or amino group attached to the alpha-carbon atom show higher affinities. Macrocyclic compounds containing a short spacer between the different bisphosphonic acid groups and the macrocyclic unit exhibit high affinities, indicating a synergic effect of the bisphosphonic and the macrocyclic groups during adsorption. The competition method described uses a well-characterized complex and allows a simple evaluation of the adsorption behavior of bisphosphonates. The application of the macrocycle-bisphosphonate conjugates allows easy radiolabeling via complexation of a suitable metal isotope.     

Catalysis of diribonucleoside monophosphate cleavage by water soluble copper(II) complexes of calix[4]arene based nitrogen ligands

Calix[4]arenes functionalized at the 1,2-, 1,3-, and 1,2,3-positions of the upper rim with [12]ane-N(3) ligating units were synthesized, and their bi- and trimetallic zinc(II) and copper(II) complexes were investigated as catalysts in the cleavage of phosphodiesters as RNA models. The results of comparative kinetic studies using monometallic controls indicate that the subunits of all of the zinc(II) complexes and of the 1,3-distal bimetallic copper(II) complex 7-Cu(2) act as essentially independent monometallic catalysts. The lack of cooperation between metal ions in the above complexes is in marked contrast with the behavior of the 1,2-vicinal bimetallic copper(II) complex 6-Cu(2), which exhibits high catalytic efficiency and high levels of cooperation between metal ions in the cleavage of HPNP and of diribonucleoside monophosphates NpN'. A third ligated metal ion at the upper rim does not enhance the catalytic efficiency, which excludes the simultaneous cooperation in the catalysis of the three metal ions in 8-Cu(3). Rate accelerations relative to the background brought about by 6-Cu(2) and 8-Cu(3) (1.0 mM catalyst, water solution, pH 7.0, 50 degrees C) are on the order of 10(4)-fold, largely independent of the nucleobase structure, with the exception of the cleavage of diribonucleoside monophosphates in which the nucleobase N is uracil, namely UpU and UpG, for which rate enhancements rise to 10(5)-fold. The rationale for the observed selectivity is discussed in terms of deprotonation of the uracil moiety under the reaction conditions and complexation of the resulting anion with one of the copper(II) centers.     

An Interlocked Figure-of-Eight Molecular Shuttle

Here is reported the synthesis and characterization of an interlocked figure-of-eight rotaxane molecular shuttle from a dibenzo-24-crown-8 (DB24C8) derivative. This latter bears two molecular chains, whose extremities are able to react together by click chemistry. One of the two substituting chain holds an ammonium function aimed at driving the self-entanglement through the complexation of the DB24C8 moiety. In the targeted figure-of-eight rotaxane, shuttling of the DB24C8 along the threaded axle from the best ammonium station to the weaker binding site triazolium was performed through deprotonation or deprotonation-then-carbamoylation of the ammonium. This way, two discrete co-conformational states were obtained, in which the folding and size of the two loops could be changed.     

Sequence selective recognition in the minor groove of dsDNA by pyrrole,imidazole-substituted bis-benzimidazole conjugates

A series of pyrrole, imidazole-substituted bis-benzimidazole conjugates, Py-Py-Im-gamma-biBenz, Py-Py-gamma-biBenz, Py-Im-gamma-biBenz, and Im-Py-gamma-biBenz (1-4), were prepared in an attempt to target dsDNA sequences possessing both A/T and G/C bps. The dsDNA interactions and sequence specificity of the conjugates have been characterized via spectrofluorometric titrations and thermal melting studies. All conjugates form 1:1 complexes with dsDNA at subnanomolar concentrations. The Im moiety selectively recognizes a G/C bp embedded in the A/T-rich binding site. This represents the first clear example of sequence selective recognition in a 1:1 motif.(1) The equilibrium association constant (K(1)) for complexation of a specific nine-bp dsDNA site, 5'-gcggTATGAAATTcgacg-3', by conjugate 1 is approximately 2.6 x 10(9) M(-1). Displacement of the G/C position or G/C-->A/T substitution within the nine-bp site decreases the K(1) by approximately 8-fold, whereas two continuous G/C bps decrease the K(1) by approximately 50-fold magnitude. The K(1) values for seven-bp dsDNA, 5'-gcggtaTGAAATTcgacg-3' and 5'-gcggtaCAAAATTcgacg-3', binding sites by conjugates Py-Im-gamma-biBenz (3) and Im-Py-gamma-biBenz (4) are approximately 2.3 x 10(9) and approximately 1.2 x 10(9) M(-1), respectively. However, the conjugates with no Im moiety, Py-Py-gamma-biBenz (2) and Py-Py-Py-gamma-biBenz (5 and 6), are specific for seven- to nine-bp A/T-rich sites and single A/T-->G/C bp substitution within the binding site decreases the K(1) values by 1-2 orders of magnitude.     

钐、铕-四环素类抗生素络合物荧光性能的研究及其在荧光分析中的应用

本文探讨了钐、铕-四环素、强力霉素、土霉素、金霉素络合物的荧光性能及利用该体系以荧光分析光度法测定痕量钐和铕的可能性与最佳测定条件.结果表明:在高碱度条件下(pH12～1.0mol/L NaOH),以四环素体系的稳定性、灵敏性最好,钐和铕的检测限分别为38.2和0.09ng/mL.     

Synthetic,Spectroscopic, and Biological Aspects of Triorganosilicon(IV) Complexes of Tridentate Schiff Bases

Abstract

Hexacoordinated organosilicon complexes of type R₃Si(L) (R = ethyl, butyl, phenyl; HL = ligand, obtained by the condensation of 4-aminoantipyrine with 2-hydroxyacetophenone, 2-hydroxybenzophenone, 2-hydroxybenzaldehyde, and 2-hydroxynapthaldehyde) have been synthesized and characterized by elemental analysis, molar conductance, and spectroscopic studies (IR, ¹H, ¹³C, and ²⁹Si NMR). The spectroscopic studies indicated that the ligands acted as tridentate coordinating through azomethine nitrogen, carbonyl oxygen, and oxygen of hydroxyl after deprotonation to the central silicon atom. The ligands and their organosilicon complexes have been evaluated for antimicrobial activities against fungi (Aspergillus niger and Candida albicans), and against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), and Gram-negative bacteria (Escherichia coli). The aim of the present work is to synthesize novel eco-friendly fungicides and bactericides and to study the effect of the biological activity of ligands on the complexation with organosilicon moiety. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Surface‐Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation.