Six-, seven- and eight-coordinated Cd(II) ions with N-heterocyclic multicarboxylic acids

Two novel cadmium complexes [Cd₃(pta)₂(H₂O)₄]_n (1) (H₃pta = 2,4,6-pyridinetricarboxylic acid) and {[Cd(H₂pza)(H₂O)₂] · 2H₂O}_n (2) (H₄pza = 2,3,5,6-pyrazinetetracarboxylic acid) were synthesized. In both complexes, Cd(II) ions show three different coordination numbers of six and seven in 1 and eight in 2, respectively. Complex 1 displays a three-dimensional network structure and 2 shows a one-dimensional chain structure. The one-dimensional chains in 2 are vertical or parallel to each other and form a three-dimensional network structure by hydrogen bonds. In addition, 1 emits intense fluorescence on excitation of 342 nm.     

Equilibrium and kinetic studies of chromium ions adsorption on Co (II)-based phosphonate metal organic frameworks

Chromium is present in wastewaters resulted from a lot of industrial processes such as electroplating, dye, cement, leather tanning, and paint. Its presence at values higher than maximum admitted value of 0.05 mg/L can affect the human health and the environment. Therefore, it is essential to remove chromium from wastewaters before discharge. In this study, the adsorption potential of three types of Co (II)-based phosphonate metal organic frameworks, obtained by the reaction of CoSO₄.7H₂O with phosphonoacetic acid (CP), N,N-bis(phosphonomethyl)glycine (Gly), or vinyl phosphonic acid (VP) in hydrothermal conditions, has been investigated. The study involves batch types experiments investigating the effects of the solution pH, solid:liquid ratio, initial concentration of Cr(VI), and contact time upon the adsorption efficiency of the studied materials. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich were applied to adsorption equilibrium data to find the best among these models. The kinetics of adsorption was found to follow the pseudo-second-order model. It was found that the adsorption efficiency of the studied materials in the removal process of Cr(VI) ions from aqueous solutions is in the following order: Co-CP<Co-Gly< Co-VP.     

Four-, six- and eight-coordinated lead(II) complexes with amine- or amide-type tripodal ligands

Three novel lead(II) complexes, [Pb(L¹)](ClO₄)₂ (1) (L¹ = tris(2-benzylaminoethyl)amine), [Pb(L²)₂](ClO₄)₂ (2) (L² = tris(4-phenyl-3-aza-2-oxobutyl)amine) and [Pb₂(L³)₂](ClO₄)₄ (3) (L³ = tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) were synthesized and structurally characterized. All three complexes show different stoichiometries as well as coordination numbers of four in 1, eight in 2 and six in 3, respectively. Complex 1 displays a typical tripodal-type 1:1 (M:L) structure and 2 shows a sandwich-type 1:2 structure. The octa-dentate lead(II) ion in 2 is at the center of a dicapped trigonal prism. Complex 3 is revealed as a unique dinuclear 2:2 complex, in which two hexa-dentate lead(II) ions are linked by two carbonyl μ–O atoms forming a Pb₂(μ–O)₂ parallelogram-type moiety.     

A neutral 2D nanosized molecular square grid: the first vanadium(II)coordination polymer of norfloxacin

The hydrothermal reaction of norfloxacin (H-Norf) with NH₄VO₃ yields an unprecedented neutral nanosized molecular square grid containing a direct coordinate bond between quinololine drug and V(II), V(Norf)₂·2H₂O 1, which is characterized by single X-ray determination and IR spectrum as well as TGA.     

Extraction of metal ions with non-fluorous bipyridine derivatives as chelating ligands in supercritical carbon dioxide

Three new non-fluorous bipyridine derivatives, bis(2-(2-butoxyethoxy)ethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 1), bis(2-(2-ethoxyethoxy)ethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 2), and bis(2-butoxyethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 3), were synthesized as chelating ligands to remove metal ions from solid matrix into supercritical CO₂ (scCO₂). These produced compounds 1-3 showed considerable solubilities in scCO₂ (8.0 g/l, 4.8 g/l, 7.8 g/l for ligands 1-3 at 313 K, respectively) and the tested solubility data were then calculated and correlated with semiempirical model at different pressures and temperatures, which showed satisfactory agreement with each other and the average absolute relative deviation were in the range of 0.1-28.3%. The effects of pressure, temperature, time, and ligand to metal ratio (5:1 to 75:1) on the extraction efficiency of metal ions were also systematically investigated. The extraction efficiency was 100% for Ni²⁺ and 95.9% for Cu²⁺ in scCO₂ with the system of ligand 1, ultrapure water, and perfluoro-1-octanesulfonic acid tetraethylammonium salt (PFOAT) under the optimized conditions (25 MPa, 313 K, 90 min, and ligand to metal ratio of 10). Although all ligands exhibited good efficiency for Ni²⁺ (>85%) and Cu²⁺ (>70%) extraction, the extraction of mixed metal ions indicated that the bipyridine derivatives had low selectivity. Finally, the detailed calculation results exhibited that the extraction constants (K_ex) of the metal ions increased with the increase of the extraction efficiency in the same extraction system for each same metal ion.     

含膦氧配体的稀土配合物对Mannich反应的催化作用

在研究稀土金属氯化物对Mannich反应的催化作用基础上,进一步研究了部分稀土氯化物与单膦氧配体、三苯氧膦(Ph_3PO)以及两种双膦酸酯、四异丙基亚甲基双磷酸酯{(~iPrO)_2P(O)CH_2P(O)(~iPrO)_2=L]}及双二苯基膦氧甲烷{[Ph_2P(O)CH_2P(O)Ph_2]=dppmO_2}所形成的配合物对Mannich反应的催化作用。结果发现,膦氧配体与稀土氯化物的配合物的催化能力比相应的氯化物低,但GdCl_3和TmCl_3与L(物质的量比1:1)结合时所形成的配合物的催化能力没有下降。     

Circular dichroism enhancement by the coordination of different metal ions with a pair of chiral tripodal ligands

The coordination of metal ions with a pair of chiral tripodal ligands (R or S)-2-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenoxy)-N-(1-phenylethyl)acetamide (R- or S-L) results in the circular dichroism (CD) enhancement distinctly, giving fingerprint information among different metals. Specifically, the CD signals show more obvious magnification upon coordination with Ln^3 + compared with Zn^2 + and other metals. Structural analyses show that in Eu-complex (1), the Eu^3 + metal center is surrounded in a 10-coordinating geometry and the ligand takes fan-like configuration, while in Zn-complex (2), Zn^2 + is surrounded in a 7-coordinating geometry and the ligand takes pincer-like configuration. These differences in the coordination structure as well as intramolecular packing effects are responsible for the variation in CD signal responses of different metal-coordinated systems.     

Sensing metal ions with two new azomethine–thiophene pincer ligands (NSN): Fluorescence and MALDI-TOF-MS applications

The two new pincer azomethine–thiophene ligands (N,NE′,N,NE′)-N,N′-(thiophene-2,5-diylbis(methan-1-yl-1-ylidene))bis(naphathalen-2-ylmethanamine) (L1) and (E)-(4,6-dihydropyren-1-yl)-N-((5-((E)-(pyren-1-ylmethylimino)ethyl)thiophen-2-yl)methylene)methanamine (L2), their absorption, fluorescence and MALDI-TOF-MS spectroscopic studies are described. The two systems synthesised combine the emissive probes pyrene and naphthyl with the good chelating properties of a tridentate SN₂ donor-set from a thiophene Schiff-base ligand. Both ligands gave analytically pure solid complexes with Ni(II) and Pd(II) salts. The bichromophoric pyrene derivative L2 presents two emission bands in solution, one corresponding to the monomer species and a red-shifted band attributable to the intramolecular excimer. Ni(II) and Pd(II) complexation affects the conformation in solution, increasing the monomer emission at the expense of the excimer band; this effect could be explored in metal ion sensing. System L1 behaves as a non emissive probe. In situ complexation reactions followed by MALDI-TOF-MS spectrometry without matrix support have also been performed; these experiments show that L1 could be a potential chemosensor for Ni(II) and Pd(II).     

Shaping RNA structures with metal ions and metal ion complexes

The research in our laboratory focuses on the role of metal ions and their complexes in structure formation and folding of nucleic acids. Large catalytic RNAs, like group II introns and some riboswitches, as well as shorter RNAs and DNAs containing modified nucleotides for the assembly of nanodevices are examined. Abundant metal ions like Mg2+ or natural metabolites like coenzyme B12 are in the center of interest, but also other metal ions, complexes thereof and B12 derivatives are applied with the aim to understand the largely unknown and manifold non-covalent interactions with nucleic acids. We apply a multitude of techniques, including potentiometric pH titrations, NMR spectroscopy, X-ray crystallography, gel electrophoresis and single molecule FRET experiments. Here we briefly summarize each of our research topics emphasizing the interaction of coenzyme B12 and its derivatives with the btuB riboswitch of E. coli. This highly conserved sequence, found in the 5'-untranslated region (5'-UTR) of the btuB mRNA, is involved in the regulation of the btuB protein expression. After a summary on the historical discovery of such riboswitches and their mechanism of action, we shortly focus on our own contributions to understand the structural equilibrium, high affinity and selectivity of the interaction between this specific RNA sequence and the largest and most complex cellular metabolite, coenzyme B12.     

Effect of light metal ions on the sorption of heavy metal ions on natural polymers

Dried ground formaldehyde-treated peanut skins, white ash bark, and So. Wisconsin red maple bark are efficient substrates for removal of many heavy metal ions from waste streams, but possible interference by common light metal cations has never been determined. The influence of Ca²⁺, Mg²⁺, or Na⁺ on the removal of the heavy metal ions Pb²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ by the above substrates was studied in both batch and packed-column experiments. It was found that Pb²⁺ and Cu²⁺ were minimally affected by the presence of these light metal ions in solution, while the uptake of Cd²⁺ and Zn²⁺ was significantly reduced. Calcium ion produced the greatest effect of the light metals tested.     

Chelating agents and the regulation of metal ions

Up to about the early 1980s it was perhaps still possible to summarize in a review of a moderate length the development of the medicinal applications of chelation chemistry and the exploitation of such chemistry in regulating the metal ion concentrations in the body. However, in the last few years there has a great surge in the development of chelation chemistry and its usage in medicine and related areas of life sciences research. It is no longer the case that such a review primarily concentrates upon the use of chelating agents in removing toxic metals from the body but it must now cover the use of chelating agents in the imaging procedures nuclear medicine and magnetic resonance imaging (MRI), the use of chelating agents in unravelling the biochemistry of reactive oxidative species (ROS) and the control and measurement of intracellular calcium ions. It is in the recent applications that there have been the greatest developments over the last ten years.     

Interaction of metal ions with montmorillonite and vermiculite

The behaviour of montmorillonite and vermiculite toward adsorption of Cd²⁺, Pb²⁺, Zn²⁺, Mn²⁺, Cu²⁺ and Zn²⁺ was compared. In general, the uptake of metal ions on both clay minerals decreased with decreasing of pH and in the presence of ligands forming stable complexes. Metal ion retention on montmorillonite was less affected by the competition of sodium ions at high ionic strengths with respect to vermiculite. On the other hand, the total capacity of vermiculite with respect to the investigated metal ions was found to be much higher than that of montmorillonite, whereas the order of affinity of the metal ions for the two clay minerals was similar, i.e.: Pb²⁺ = Cd²⁺ < Cu²⁺ < Zn²⁺ < Mn²⁺ < Ni²⁺ for montmorillonite and Pb²⁺ < Cu²⁺ < Cd²⁺ < Zn²⁺ < Ni²⁺ < Mn²⁺ for vermiculite.The similarities and differences between the two clay minerals were also investigated by principal component analysis and hierarchical cluster analysis.The results of this study may be used to predict the uptake efficiency of these adsorbents in view of their application for the removal of metal ions from contaminated effluents. The choice of vermiculite or montmorillonite for the uptake of metal ions or other elements will depend on the composition of the effluent to be treated.     

水泥和粉煤灰中重金属和有毒离子的溶出问题及思考

介绍了水泥材料中有害组分的溶出试验方法，试验研究了粉煤灰水泥砂试体及粉煤灰硬化体中重金属离子的溶出问题，得出了重金属离子溶出的一些规律及抑制Cr^6 溶出的方法，并提出我国水泥工业今后在这方面有必要进行的研究工作。     

重金属离子脱除技术进展

综述了脱除水中重金属离子的各类主要方法 ,侧重介绍了近年来开发的若干新技术。     

超分子配体及其金属配合物研究的新进展

介绍了新型超分子化合物的合成及应用,新型金属卟啉超分子化合物的合成,新型冠醚超分子配合物的合成及应用.     

对合成催化剂配体金属有机化合物的研究

完成了金属镁及有机化合物配置合成催化剂配体的方式,并且分析及介绍了两者的反应。金属离子在出现金属化合反应之后,能够取代有机化合物中的的氢原子。碳负离子反应是金属化合物及有机化合物能够出现化学反应,基于此特性,对此种化合物制备过程中的条件进行了分析,从而为不对称有机化学反应催化剂制备过程中提供基础。     

Colorimetric sensing of metal ions by bis(spiropyran) podands: Towards naked-eye detection of alkaline earth metal ions

In order to develop a selective and sensitive colorimetric sensor for metal ions, a series of oligoether-linked bis(spiropyran) podands were prepared and their ability to colorimetrically sense alkaline earth metal ions was investigated. UV–vis absorption and ¹H NMR spectroscopic studies showed that the podands isomerized from the colorless spiropyran form to the colored merocyanine form upon complexation with alkaline earth metal ions, whereas spectral changes were not visible in the presence of alkali metal ions. Podands of spiropyran subunits linked by a spacer of a 3-oxapentan-1,5-dioxy group, i.e. X-BSP-1 (X = MeO, tBu, iPr, H, Cl, Br), exhibited high selectivity to Ca²⁺. Introduction of an electron-donating group to the 5-position of each indoline ring of the podand gave rise to an increase in affinity to alkaline earth metal ions, enhancing the sensitivity. The absorption maximum of the colored metal–X-BSP-1 complex varied over a range of ca. 30 nm, from reddish purple to bluish purple. Clear discrimination of the Ca²⁺ complex from that of Mg²⁺ was possible using the naked eye. These results indicate the potential application of the X-BSP-1 podands as a colorimetric sensor for Ca²⁺.     

Inactivation of rice bran lipase with metal ions

The inactivation of rice bran lipase was studied in vitro and in vivo using metal ions in methanol or HCl. Lipase was extracted from rice bran in 0.1 M potassium phosphate buffer, pH 7.0 and purified by ammonium sulphate fractionation. The 25–55% ammonium sulphate fraction was subjected to DEAE-cellulose ion exchange chromatography and the fraction (F6) eluted at V_e/V_o of 14.37 was purified about 333-fold. In-vitro studies on F6 lipase showed that Fe³⁺ and Ni²⁺ completely inhibited the lipase activity at 5 × 10^?5 M concentration, while Zn²⁺ and Cu²⁺ did so at 2.5 × 10^?4 M. The results on in-vivo inactivation of rice bran lipase showed that Fe³⁺ and Ni²⁺ at 200 μg g^?1 significantly checked the release of free fatty acids (FFA) from rice bran for 6 days of storage when compared with using concentrated HCl (2%, v/w) only. The triglyceride content of oil was also maximum with Fe³⁺ and Ni²⁺ treatment at 200 μg g^?1. The present results suggest that Fe³⁺ and Ni²⁺ could be effectively used to arrest the release of FFA in rice bran and thus contribute to improving the edible quality of rice bran oil.