Synthesis and Characterization of Porous Metal Phosphonates

This dissertation focuses on the challenge of developing porous metal arylphosphonates with both high crystallinity and functional porosity by using different synthetic approaches. Metal phosphonates are an extensive class of materials based upon extended inorganic-organic architectures such as chains, layers and three-dimensional networks. Metal phosphonates generally favor extended inorganic architectures leading to pillared materials with no porosity. We found that the use of template molecules, type of ligand and choice of metal ions could be used to deviate from the pillared structure. Many of these structures had interesting properties that were explored. The results can be divided into three areas: We developed non-pillared monovalent metal phosphonates by investigating both the role of water and template molecules in the solvothermal synthesis. The role of water in solvothermal reactions was found to have a profound influence on the structure of monovalent metal phosphonates and the structures could be tailored from zero/one-dimensional to two-dimensional. Non-pillared structures could be synthesized by using template molecules. For a zinc phosphonate, we converted a layered structure into a three-dimensional framework by using small template molecules in the solvothermal reaction. The compound exhibited reversible dehydration behavior. The change in the framework structure and guest positions was monitored during this process. Two different ligands were used in the development of porous aluminum phosphonates. One series exhibited reversible dehydration behavior, which had a dramatic influence on permanent porosity of the material. The stability of the dehydrated phase is a result of the geometry of the aluminum atom, which in some cases has coordinatively unsaturated metal sites. The second series was developed with ion exchange applications in mind therefore the pore environment was tailored to favor ion exchange processes. The most important aspect is that these compounds exhibit high selectivity for Th^(4+) ions. In total 28 new compounds were prepared, and their utility and structures clarified

Functionalization of Poly(Ethylene Oxide)-based Diblock Copolymer Vesicles

The principal goal of this research is to achieve the chemical labeling and surface modification of block copolymer vesicles (polymersomes) made from amphiphilic diblock copolymer Poly(butadiene-b-ethylene oxide) (PBd120- PEO89, MW 10400 g/mol) with the aim of developing possible drug carrier vehicles for controlled release of molecules triggered by stimuli-responsive environments. The terminal hydroxyl group of poly(ethylene oxide) (PEO), or poly(ethylene glycol) is converted into its corresponding carboxylic acid by a novel one-pot two-phase oxidation reaction. This regioselective and catalytic reaction assures the preservation of important structural characteristic of the block copolymers. Vesicles formed by a mixture of the carboxylate and unmodified block copolymer exhibit an increment in the critical aggregation concentration (CAC) value while the averaged vesicle size decreases demonstrating that the negative charges in the modified diblock copolymer disrupt the vesicle formation process. The carboxylated reactive intermediates are subsequently subjected to a covalent coupling reaction in organic solvent to replace the terminal hydroxyl of the PEO block. The obtained functionalized diblock copolymers are effectively incorporated into the vesicle bilayer. Also, surface density control in polymersomes of fluorescently modified diblock copolymers, synthesized by the amination reaction, is achieved. To demonstrate the ability of this polymersomes as carrier vehicles, a Noradrenaline functionalized vesicle is placed in closed contact with rat aortic smooth muscle cells (RASMC) using the micropipette aspiration technique. A distinctive increase in fluorescent intensity of cells is observed. It indicates that the drug molecule has been transported by the polymersome and internalized by the cell. In addition, diblock copolymers containing a disulfide moiety and a fluorophore are synthesized and studied through fluorescent microscopy. Vesicles are formed with this polymer and a decrease in fluorescent intensity is observed in the vesicle's bilayer after its exposure to a reductive environment. These results indicate that fluorophore molecules are successfully released into solution

Hydrothermal synthesis and structural characterization of ammonium ion-templated lanthanide(III) carboxylate-phosphonates

Using N (phosphonomethyl)iminodiacetic acid (H4PMIDA), as a complexing agent, two new complexes, (NH4)La(PMIDA)(H2O)•H2O, 1 and (NH4)Yb(PMIDA), 2 have been synthesized hydrothermally. In both compounds, the metal ions are trapped in a three five-membered chelate rings by the chelating PMIDA anions giving a bi-capped trigonal prism LaO8N and capped trigonal prism YbO6N geometries for 1 and 2, respectively. The structure of 1 consists of La(PMIDA)(H2O) chelating units, linked together by the phosphonate oxygen atoms O1 and O3 to form a double chain along the c-axis. The double chains are then connected together by the bridging phosphonate oxygen O2 to form a 2D layered structure with alternating 4- and 8-membered apertures.The structure of 2 consists Yb(PMIDA) chelating units, which are connected by alternating bridging carboxylate and phosphonate groups along the [010] direction forming chains with a corrugated pattern. The third phosphonate oxygen bridges the chains together along the [001] direction to build the two-dimensional layer with 4 and 6 membered apertures in the bc plane. Under excitation of 330nm, compound 2 shows a broad emission band at λmax = 460nm, This emission is essentially in the blue luminescent region, which corresponds to ligand centered fluorescence

A simple setup miniaturization with multiple benefits for Green Chemistry in nanoparticle synthesis

The development of nanomaterials often relies on wet-chemical syntheses performed in reflux-setups using round-bottom-flasks. An alternative approach to synthesize nanomaterials is here presented that uses glass tubes designed for NMR analysis as reactors. This approach uses less solvent, uses less energy, generates less waste, provides safer conditions, is less prone to contamination and is compatible with high throughput screening. The benefits of this approach are illustrated by an in breadth study with the synthesis of gold, iridium, osmium and copper sulfide nanoparticles

Synthesis of Framework Isomer MOFs Containing Zinc and 4-Tetrazolyl Benzenecarboxylic Acid via a Structure Directing Solvothermal Approach

The solvothermal synthesis of framework isomers was carried out using the hybrid carboxylate and tetrazolate functional ligand, 4-tetrazolyl benzenecarboxylic acid (H2TBC, TBC = 4-tetrazolyl benzenecarboxylate) and zinc. H2TBC was also synthesized with the solvothermal approach, and is referred herein as structure 1. Using single-crystal X-ray diffraction, we found that the tetrazolate groups of TBC show an unusual “opposite-on” coordination mode with zinc. Three previously characterized metal-organic frameworks (MOFs) were obtained by systematically changing the solvents of the H2TBC-Zn reaction, (1) ZnTBC, 2, which has a non-porous structure; (2) Zn2(TBC)2(H2O), 3, which has an amphiphilic pore structure and (3) Zn2(TBC)2{guest}, 4, which is porous and has channels containing uncoordinated N heteroatoms. Fluorescence spectra of 4 reveal a strong blue emission mainly from the TBC ligands

Reversible Dehydration Behavior Reveals Coordinatively Unsaturated Metal Sites in Microporous Aluminum Phosphonates

Incorporation of the same ligand into three different aluminum phenylenediphosphonates (Al­(H₂O)­(O₃PC₆H₄PO₃H) (<b>1</b>), Al₄(H₂O)₂­(O₃PC₆H₄PO₃)₃ (<b>2</b>), and Al₄(H₂O)₄­(O₃PC₆H₄PO₃)_2.84­(OH)_0.64 (<b>3</b>)) was accomplished by varying the synthetic conditions. The compounds have different sorption properties; however, all exhibit reversible dehydration behavior. The structures of the hydrated and dehydrated phases were determined from powder X-ray diffraction data. Compounds <b>2</b> and <b>3</b> were found to be microporous, while compound <b>1</b> was found to be nonporous. The stability of the dehydrated phase and the resulting porosity was found to be influenced by the change in the structure upon loss of water

From small structural modifications to adjustment of structurally dependent properties: 1-methyl-3,5-bis­[(E)-2-thienyl­idene]-4-piperidone and 3,5-bis­[(E)-5-bromo-2-thienyl­idene]-1-methyl-4-piperidone

The mol­ecules of the title compounds, C16H15NOS2, (I), and C16H13Br2NOS2, (II), are E,E-isomers and consist of an extensive conjugated system, which determines their mol­ecular geometries. Compound (I) crystallizes in the monoclinic space group P21/c. It has one thio­phene ring disordered over two positions, with a minor component contribution of 0.100 (3). Compound (II) crystallizes in the noncentrosymmetric ortho­rhom­bic space group Pca21 with two independent mol­ecules in the unit cell. These mol­ecules are related by a noncrystallographic pseudo-inversion center and possess very similar geometries. The crystal packings of (I) and (II) have a topologically common structural motif, viz. stacks along the b axis, in which the mol­ecules are bound by weak C—H⋯O hydrogen bonds. The noncentrosymmetric packing of (II) is governed by attractive inter­molecular Br⋯Br and Br⋯N inter­actions, which are also responsible for the very high density of (II) (1.861 Mg m−3)