No description available.

No description available.

In recent years, application of fluorescent conjugated polymers to sense chemical and biological analytes has received much attention owing to its technological significance. Water soluble conjugated polymers are interesting towards the developing sensors for biomolecules. In this present contribution, we describe the syntheses and characterization of a series of water soluble conjugated polymers with sulfonic acid groups in the side chain. Such anionic conjugated polymers are designed to interact with biomolecules such as cytochrome-C. All polymers are water soluble and showed strong blue emission. Significant quenching of the fluorescence from our functionalized PPP was observed upon addition of viologen derivatives or cytochrome -C. / Singapore-MIT Alliance (SMA)

The chemical fate of organophosphorus pesticides is influenced by several factors, one being the chemistry of their aquatic environment. Dissolved metal ions have been shown in several instances to promote the hydrolysis of organophosphorus pesticides, with various reasons forwarded as to the intimate mechanism of metal ion promoted hydrolysis. Several postulates have suggested metal ion co-ordination of Lewis sites to be an important factor in promoting the reaction. In view of this, the study herein reports on the promoted hydrolysis of diazinon at various pH’s in the presence of several metal ions including Hg2+, Cu2+, Cd2+ and Ag+. The observed 1H and 31P NMR data indicated complexation of Cu2+ and Ag+ with diazinon through the formation of a six-membered ring (chelate), via co-ordination at both nitrogen and sulfur Lewis base sites. In contrast, NMR results with Hg2+ indicated Hg2+ ion promoted hydrolysis of diazinon through co-ordination at sulfur alone, possibly through stronger binding to the altered transition state than the reactant state. Another possibility would entail lowering of the pKa of H2O on metal complexation, thus facilitating nucleophilic attack. Electrospray ionization mass spectrometry (ESI-MS) substantiated the proposed metal ion complexation. In the case of Cu2+ and Ag+, complexation between diazinon and metal ions was observed at given m/z ratios, while subsequent MS/MS analysis of the complexed ions revealed co-ordination at both S and N sites by Cu2+ and Ag+. No complexation between diazinon and Hg2+ was observed in ESI-MS; however Hg2+ was shown to complex the hydrolytic product O,O diethyl phosphorothioic acid, presumably through sulfur. Hydrolysis of diazinon was studied at several pH’s at 22oC in the presence of Hg2+, Cu2+, Cd2+ and Ag+, by following spectrophotometrically the appearance of 2-isopropyl-6-methylpyrimidin-4-ol. Kinetic data showed Hg2+, Cu2+ and Ag+ to be extremely effective in neutral-to-mildly acidic conditions, with a reduced effect in the presence of Cd2+. Smaller rate enhancements were also observed at slightly lower pH of 4.0. Possible factors include; 1) Competing acid hydrolysis involving protonation at one heterocyclic N of diazinon (N-3). 2) The dominant nature of the HgCl2 species at pH 4.0. 3) Metal speciation. / Thesis (Master, Chemistry) -- Queen's University, 2008-01-31 13:47:24.044

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Following an introoduction on calixarene chemistry and their metal-ion complexes including some of their applications, the aims of the work are described. Thus, the first part of this thesis concerns the detemination of the standard enthalpies of solution, sH°, of new lithium and sodiimi 1:1 electrolytes based on eth p=tert-butycalix[4]arene tetraethanoate containing various anions in acetonitrile at 298.15 K. Using these data in conjunction with previously reported sH° values for the free metal-ion salts and the ligand and standard enthalpies of complexation, cH°H° of allcali-metal cations (Li+ and Na+) and the calix[4]arene ester in the same solvent, standard enthalpies of coordination, coordH° referred to the process in which the reactants and the product are in the solid stated were calculated. The anion effect on the coordination process was determined. The second part of this thesis is related to an investigation on the solution properties of pyridinocalix[4]arenes and their metal-ion complexes. Transfer Gibbs energies of geometrical isomers of pyridinocalix[4]arenes from acetonitrile to various solvents reflect that these ligands undergo selective solvation in the various solvents but these cannot be correlated with any single solvent property. The complexing ability of 5,11,17,23 - tetra - tert - butyl[25,26,27,28 - tetrakis (2-pyridyhnethyl) oxy]- calix[4]arene for metal cations was investigated by a variety of techniques. Thus 1H NMR studies were performed to obtain information about the active sites of the ligand in its interaction with metal cations. Conductance measurements were used to establish the composition of the metal-ion complexes in dipolar aprotic media. Potentiometric and calorimetric measurements were performed to derive the thermodynamics associated with the complexation process in acetonitrile and benzonitrile. Based on stability constant data, two metal-ion complexes were isolated. The crystal structure of the sodium and acetonitrile complex of 5,11,17,23- tetra- tert- butyl[25,26,27,28 - tetrakis (2-pyiidylmethyl)oxy] calix[4] arene solved by X-ray diffraction studies shows three different complexes in the lattice, two sited on a fourfold axis and a third one on a twofold axis where all ligands exhibit a 'cone' conformation and the sodium ion is encapsulated in their hydrophilic pockets with their hydrophobic cavities filled with an acetonitrile molecule. The crystal structure of the 1:1 monoacetonitrile and silver complex of the 2-pyridyl derivative with the perchlorate ion as the counter ion shows the macrocycle sited on a fourfold symmetry axis. The presence of acetonitrile in the hydrophobic cavity of the ligand is also found. The silver cation is encapsulated in the hydrophilic cavity through the ethereal oxygens and the pyridinic nitrogens. Conclusions and suggestions for furthur research in this area are given.

Lithium-ion batteries (LIBs) are widely applied in a variety of applications such as mobile phones, laptop chargers, and electric vehicles. Thanks to a high energy density of about 120 to 220 Wh kg-1, LIBs are used for a long time, however, the present technology is unable to satisfy the increasing energy storage requirements. Therefore, increasing the energy density of LIBs to improve the performance is very important. Because of that the specific capacity and operation voltage of the anode and cathode materials determine the energy density, improving these two parameters is the key point. This can be achieved in two ways, one being the optimization of the electrode materials of existing LIBs, both cathode and anode, the other is the development of new battery systems to replace LIBs, potassium-ion batteries (KIBs) and sodium-ion batteries (NIBs) are examples of such new systems. In any case, the selection of the electrode materials is crucial. With a rapid development of two-dimensional (2D) materials, leading directly to an increase interest in exploring 2D materials in order to serve as possible electrode materials, based on their unique 2D structures, large conductivity, and most importantly, wide specific surface area. Among them lays graphene-like carbon-nitride materials with lightweight properties. These materials have collected spotlights in multiple fields that are concerned with energy harvesting and storage. The metallic monolayer C6N3 is a very recently discovered member in this family, which is chemically, mechanically, dynamically, and thermodynamically stable through the first-principal calculations. In this work, we investigate the monolayer C6N3 performance as a potential and promising foundation for the anode material of LIBs/NIBs/KIBs. According to our theoretical investigation, the metallic monolayer C6N3 should be an effective anode material for the LIBs/NIBs/KIBs, which combines high specific capacity and low average open-circuit voltage.

No description available.

The last two decades have seen extensive growth in interest in metal-ion assemblies, especially for building new polynuclear exchange-coupled magnetic systems. However, the concept of designing polynuclear extended structures has still not matured to the level of retro-synthetic approach developed for the organic and pharmacological molecules. Although some progress has been made with secondary building units (SBUs) in metal-organic-frameworks (MOFs), the control seems to be just an illusion when it comes to bridging ligands such as the azide ion. When it is asserted that the azido ligand is versatile in its bridging capabilities, what is actually meant is that it would be difficult to predict or control its bridging properties, or in other words, the azido based polynuclear complexes are difficult to pre-design. However, this kind of serendipity is not always bad news for the chemists. For example, the azido ligand has been shown to mediate magnetic exchanges between paramagnetic metals in a predictable fashion (usually depending upon the bonding geometries). Therefore, it is a well-respected ligand in polynuclear assemblies of paramagnetic ions. Serendipitous assemblies offer new magnetic structures that we may not otherwise even think about synthesizing. Similarly, there are other ligands, such as alkoxido, oximato, carboxylato etc. which also behave like azide. These ligands are very important in the study of magnetic exchanges to develop an understanding of the underlying mechanisms in molecular magnetism. Serendipitous assemblies have also led to systems like single molecule magnets (SMMs), which have enriched the field with potential applications in computing and have also been used for the confirmation of the quantum magnetic properties like tunneling phenomenon, spin decoherence etc. Investigations incorporated in this thesis work led to several novel strategies for using serendipity as an advantage and build unprecedented structural topologies with interesting new molecular-magnetic properties. All the reported complexes were thoroughly analyzed through elemental analysis, spectroscopy, X-ray structure determination (both single crystal & powder diffractions) and variable temperature magnetic susceptibility measurements. In a few suitable cases, model structures obtained from the X-ray structures were also employed to study the magnetic exchange mechanisms through density functional theory (DFT) calculations and simulations. CHAPTER 1 of the thesis presents a general review on the ever-growing field of metal-ion assembly. In particular, the importance of the ‘serendipitous approach’ to build new and interesting metal-ion clusters and polyclusters is highlighted. This chapter also describes the basic concepts of exchange-based molecular magnetism as applied to the metal-ion assemblies. CHAPTER 2 describes the concept of using lower molar proportions of blocking bidentate chelating ligands in the neutral copper(II)-azido systems, which increases the number of coordination sites for the versatile azido bridges to assemble the metal-ions in higher dimensions, based on smaller cluster units. Syntheses, structures and magnetic properties of ten novel complexes are described in this chapter: [Cu3(tmen)2(N3)6]n (1), [Cu4(Me-hmpz)2(N3)8]n (2), [Cu4(men)2(N3)8]n (3), [Cu6(deen)2(N3)12]n (4), [Cu6(aem)2(N3)12]n (5), [Cu6(dmeen)2(H2O)2(N3)12]n (6), [Cu6(N,N'-dmen)2(N3)12]n (7), [Cu6(hmpz)2(N3)12]n (8), Cu5(N,N-dmen)2(N3)10]n (9), and [Cu5(N,N'-dmen)5(N3)10]n (10) [tmen = N,N,N',N'-tetramethylethylenediamine, Me-hmpz = 1-methylhomopiperazine, men = N-methylethylenediamine, deen = N,N'-diethylethylenediamine, aem = 4-(2-aminoethyl)morpholine, dmeen = N,N-dimethyl-N'-ethylethylenediamine, N,N'-dmen = N,N'-dimethylethylenediamine, hmpz = homopiperazine, N,N-dmen = N,N-dimethylethylenediamine]. Most of these complexes have simple oligonuclear basic building units (Scheme 1), such as trinuclear (1), tetranuclear (2, 3) and hexanuclear (4-8), but the overall arrangements of these cluster units in higher dimensions vary widely and serendipitously. For example, the hexanuclear complexes 4-7, although having almost identical basic structures, assemble in three- (4, 5) or two- (6, 7) dimensions with different connectivity among the basic structures. However, complex 9 is made from two different building units (Cu2 and Cu3). Complex 10, although having metal to blocking molar ratio 1:1, presents an unprecedented 1D structure for such complexes. Analysis of the magnetic susceptibility data for complexes 1-9 using theoretical exchange models for fitting is also described. Density functional theory (DFT, B3LYP) was employed to further analyze the experimental magnetic data for complexes 1, 2, 3 and 9 to better understand the magnetic exchange mechanisms in such systems. CHAPTER 3 continues with the same concepts developed in the previous chapter using multidentate neutral and anionic co-ligands. Using lower molar proportions of these multidentate ligands, seven novel complexes have been synthesized (keeping the initial metal to ligand ratio as 2:1): [Cu4(L1)2(N3)8]n (11), [Cu4(L2)2(N3)8]n (12), [Cu4(L3)2(N3)8]n (13), [Cu4(L4)2(N3)8]n (14), [Cu9(L5)4(N3)18]n (15), [Cu4(L6)2(H2O)2(N3)6] (16) and [Cu4(L7)2(N3)6]n (17) [where L1-5 are the condensation products of 2-pyridinecarboxaldehyde and 2-{2-(methylamino)ethyl}pyridine (L1), N,N-diethylethylenediamine (L2), N,N-dimethylethylenediamine (L3), N-methylethylenediamine (L4), N,N,2,2-tetramethylpropanediamine (L5); HL6 and HL7 are the condensation products of 2-hydroxy-3-methoxybenzaldehyde with N,N-diethylethylenediamine (HL6), and N-ethylethylenediamine (HL7)]. The ligand L1 is particularly interesting, as it is a hemiaminal ether (usually considered to be unstable intermediates in the reactions of aldehydes and secondary amines in alcoholic solvents), and was found to be trapped in 11. Although 11-13 have identical tetranuclear basic structures (with the rare simultaneous end-on and end-to-end bridges between two neighbouring metal-ions, Scheme 2) and extend in one-dimension. However, 13 is differently organized from the other two complexes. For 14, the bridging structure among the peripheral copper(II) ions changes to double end-on (Scheme 2), and the resulting structure extends in two dimensions. However, with L5, metal to ligand ratio is 9:4 (under similar conditions and initial molar proportions of the components) in 15, which can be seen as two different fragments: [Cu4(L5)4(N3)6]2+ and [Cu5(N3)12]2- linked alternately to give an overall 1D structure. HL6 and HL7 have one ionisable phenolic group that replaces one azido anion and generates two pockets for the metal atoms. These monoanionic ligands give tetranuclear complexes (16 and 17) with basic structures resembling (Scheme 2) to 11-14. While 17 is 1D in nature, two coordinated water molecules prevent the structure of 16 to grow and results in a discrete cluster. The variable temperature magnetic properties of these complexes were thoroughly analyzed through experimental and theoretical (DFT) studies. CHAPTER 4 reports the use of a pyridyl substituted propanediolate ligand in the assembly of two novel 1D heterometallic complexes: [Mn3Na(L)4(CH3CO2)(MeOH)2](ClO4)2∙3H2O (18) and [Mn3Na(L)4(CH3CH2CO2)(MeOH)2](ClO4)2∙2MeOH∙H2O (19) [LH2 = 2-methyl-2-(2-pyridyl)propane-1,3-diol, Scheme 3]; both featuring octahedral MnIV ions linked alternately to one trigonal prismatic MnII ion and even more interestingly to one trigonal prismatic NaI ion (Scheme 3). The complexes are essentially identical in structure and magnetic behavior, showing a weak ferromagnetic interaction among the neighboring manganese ions. DFT studies on a model complex supports the S = 11/2 ground spin state, deduced from dc and ac susceptibility measurements. CHAPTER 5 illustrates the use of a few dicarboxylates as potential bridging ligands to assemble tri- and hexanuclear MnIII-clusters. With the salicylaldoximate (salox) as the [MnIII3O(salox)3]+, triangle-generating moiety and keeping the reaction conditions (solvent, base, reaction time and crystallization process) identical, four new extended complexes that differ both in their basic and higher dimensional organizations are reported. When 1,3-phenylenediacetate (phda) is used (in EtOH), in the resulting complex [MnIII6O2(salox)6(EtOH)4(phda)]n∙(saloxH2)n∙(2H2O)n (20), a single type of MnIII6 clusters are linked by the dicarboxylate (interestingly the complex crystallizes with uncoordinated saloxH2 molecules). However, when two differently substituted isophthalate linkers (5-iodoisophthalate and 5-azidoisophthalate) are used, two almost identical complexes [MnIII6O2(salox)6(MeOH)5(5-I-isoph)]n∙(3MeOH)n (21) and [MnIII6O2(salox)6(MeOH)4(H2O)(5-N3-isoph)]n∙(4MeOH)n (22) are isolated, with two different types of Mn6 clusters (Scheme 4) linked alternately in one dimension. More interestingly, use of another substituted isophthalate (5-nitroisophthalate) produced a heteronuclear complex [MnIII3NaO(salox)3(MeOH)4(5-NO2-isoph)]n∙(MeOH)n(H2O)n (23) with only MnIII3 triangles as the basic cluster assembled in two dimensions. Temperature and field dependent dc and ac susceptibility measurements show that the complexes 20-22 behave as non-interacting single molecule magnets with ground spin state S = 4. Complex 23 is dominantly antiferromagnetic with a ground spin state S = 2. The magnetic behaviours of these complexes are also supported by theoretical calculations (DFT) on models generated from the crystal structures.

In the present work, in order to evaluate the seriousness of environmental pollution caused by antibiotics abuse, and by industrial and agricultural pollutants, different strains of Pseudomonas aeruginosa were collected from industrial area, abandoned metal hardware factory, fishery pool, vegetable garden and fruit farm, river mud, and different origins of water bodies in southern Taiwan. The organisms were analyzed for their drug resistance against a variety of antibiotics and agricultural pesticides. They were also analyzed for endurance toward heavy metal ions including mercury, cadmium, arsenic and chromium ions. As the data indicated that, in terms of their resistance to clinical frequently used antibiotics, about 40% of the Pseudomonas aeruginosa isolates of the environment have developed resistance against Cefoperazone, about 20% showed resistance against Tobramycin, and only about 4% revealed resistance against Imipenem and Ceftazidime. As to heavy metal ion resistance, about 27% of the environmental Pseudomonas aeruginosa strains demonstrated resistance against mercury ion, and about 10% exhibited resistance against arsenic ions, whereas no resistance was observed toward chromium ions. In terms of resistance to agricultural pesticides, about 36% environmental isolates demonstrated resistance against Paraquat, but none of the tested Pseudomonas aeruginosa show resistance toward Cartap and Methomyl. To sum up the findings, so far only minor portion of Pseudomonas aeruginosa acquired drug resistance, therefore, immediate measure is required to prevent the spreading of drug-resistant Pseudomonas aeruginosa . It is suggested that all the physicians and pharmacists to prescribe antibiotics should be more careful and responsible manner. Meanwhile, it would also call on the restrained usage of pesticides and antibiotics in the livestock and aquatic product industry, and strengthening pollution control in the industrial sector.