• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 239
  • 56
  • 54
  • 35
  • 13
  • 8
  • 5
  • 5
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 541
  • 541
  • 108
  • 90
  • 90
  • 90
  • 87
  • 76
  • 60
  • 60
  • 59
  • 55
  • 53
  • 53
  • 49
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Supramolecular chemistry of phthalocyanines. / CUHK electronic theses & dissertations collection

January 2007 (has links)
At the end of this thesis, selected 1H NMR spectra and crystallographic data are given as an Appendix. / Chapter 1 presents an overview of supramolecular chemistry and the general properties of phthalocyanines, focusing on the self-assembly of mixed porphyrin and phthalocyanine systems. / Chapter 2 describes the complexation of bis(pyridinolato) silicon(IV) phthalocyanines to several cobalt(II) porphyrins. As shown by absorption spectroscopy, both 1:1 and 1:2 molecular assemblies can be obtained depending on the relative amount of the two components and the position of the pyridyl ligand. The axially bound 1:1 phthalocyanine-porphyrin arrays have also been isolated and characterized spectroscopically. / Chapter 3 reports an extension of this work. Two novel phthalocyanines with 3 or 4 pyridyl axial substituents have been synthesized. These compounds bind to meso-tetraphenyl zinc porphyrin to form the corresponding tetrakis- and pentakis-mixed tetrapyrrole systems. / Chapter 4 discusses the preparation of several covalently-linked phthalocyanine-cyclodextrin conjugates. These compounds can form inclusion complexes with sulfonated porphyrin in water providing a new strategy to construct mixed phthalocyanine and porphyrin systems. / Chapter 5 reports the interactions of two octacarboxy phthalocyanines with beta-cyclodextrin. Through the formation of inclusion complexes, the latter serves as a disstacking agent reducing the aggregation tendency of these phthalocyanines. This supramolecular approach could be an effective way to generate hydrophilic and non-aggregated phthalocyanines, improving their photosensitising properties in aqueous media. / This thesis reports our investigation on the supramolecular chemistry of phthalocyanines. The first part of the thesis describes the self-assembly of mixed porphyrin and phthalocyanine systems through axial coordination. The second part complexes between phthalocyanines and reports the formation of some novel inclusion phthalocyanine-cyclodextrin conjugates and porphyrins, beta-cyclodextrin. / Leng, Xuebing. / "March 2007." / Adviser: Dennis K. P. Ng. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5946. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.
22

A Novel Series of Viologen-Containing Dendrimers

Bhattacharya, Papri 01 January 2008 (has links)
This dissertation investigates the synthesis, characterization and electrochemical properties of viologen-containing dendrimers. Additionally, the self-assembled system of resorcinarenes was investigated with paramagnetic guests using EPR and 1H NMR techniques. Chapter one is a brief introduction to the dendrimers and describes its evolution, structural features, synthetic methods and emerging applications to various fields of research such as catalysis, material science, drug delivery and medicine. Chapter two describes the synthesis, characterization and electrochemical properties of a new series of dendrimers. These dendrimers have a viologen unit at the core surrounded by Newkome and Fr¨¦chet dendrons. The potentials of two consecutive one-electron reductions of the viologen core were determined by cyclic voltammetry. The electrochemistry of viologen unit showed a distinct and obvious trend. Newkome and Frechet dendrons having different functional groups as repeating units has opposite effect on the half-wave potentials. The overall effect of these two dendrons is reflected by the corresponding reduction potentials. The redox site encapsulation by the Frechet and Newkome dendrons is indicated by the attenuation in heterogeneous electron transfer rate constants. Chapter three describes the probing of self-assembled capsule of resorcinarenes with 4-amino tempo and 4-trimethyl-ammonium tempo derivative. EPR spectroscopy and 1H NMR spectroscopy were used to investigate the nature of complexations involved in these systems. We observed a subsequent change in their spectroscopic parameters. Careful investigation of rotational correlation times and NMR line-widths at half height revealed that 4-trimethyl-ammonium tempo has stronger binding affinity with these capsules compared to 4-amino tempo due to favorable cation -pi interactions.
23

The influence of anion-pi interactions between multi-atomic anions and pi-acidic ring systems on the self-assembly of coordination compounds

Schottel, Brandi Lee 15 May 2009 (has links)
Anion-π interactions, weak attractions between anions and π-acidic ring systems, have become an important topic in supramolecular chemistry within the past five years. Although a variety of computational studies have been undertaken by several groups to investigate the nature of these interactions, no comprehensive experimental investigations had been performed until the completion of the work described herein. The results presented in this dissertation indicate that anion-π interactions involving large complex anions are controlling elements in self-assembly reactions with cations that involve π-acidic ring systems. Syntheses performed with the ligand 3-6-bis(2’-pyridyl)-1,2,4,5-tetrazine, or bptz, with M(II) first row transition metal salts (M = Mn, Fe, Ni, Cu, and Zn), produced self-assembled complexes that varied in shape and M:ligand ratio based on the presence of particular anions. Through a series of solution and structural studies, it was determined that the cationic polygons are templated by the size and shape of the specific anions during self-assembly. A close inspection of the bptz complexes in the solid state indicated that the anions were participating in anion-π interactions with the π-acidic central tetrazine ring of the ligand. To show that these anion-π interactions were indeed important, reactions of bptz ligand as well with 3,6-bis(2’-pyridyl)-1,2-pyridazine (bppn) with Ag(I) salts were performed to compare the effect that specific anions had on self-assembly interactions between similar ligands with different π-acidities. The results indicate that the Ag(I) complexes that included the π-acidic tetrazine ring are strongly influenced by the anion presence, while those complexes that were synthesized with the similarly shaped, but electroneutral bppn ligand only relied on the anions for charge-balance. To better understand the anion-π interactions in the obtained bptz complexes, a computational study was performed on systems with the polyatomic anions [BF4]- and [PF6]- interacting with simple heteroaromatic rings of varying degrees of π-acidity. Based on the final optimized complex geometries and Atoms in Molecules (AIM) critical point analyses, it was determined that anion-π interactions involving multiatomic anions interact with π-systems in different orientations based on the symmetry of the ring system in the complex.
24

Investigations of supramolecular and catalytic properties of PP1 dendrimers

Holley, Aaron K. January 2003 (has links)
Thesis (M.S)--Marshall University, 2003. / Title from document title page. Document formatted into pages; contains x, 74 p. including illustrations. Includes bibliographical references (p. 65-67).
25

Design and synthesis of artificial receptors for selective and differential sensing

Zhang, Tianzhi, 1973- 29 August 2008 (has links)
This dissertation consists of four chapters. The first chapter provides an in-depth background of synthetic receptors for recognitions of phosphorylated molecules. This chapter covers synthetic receptors developed within the last two decades, and it focuses on the diverse functionalities and detection techniques involved in the receptor design. Chapter 2 discusses the synthesis and employment of a metalated receptor for the selective recognition of organic phosphates and phospho-amino acids, and describes a receptor with a pseudo tetrahedral cavity, which was found to be selective to phosphate, was synthesized utilizing a new and efficient synthetic route. UV-Vis titrations were used to determine binding constants for various organic phosphates and phospho-amino acids. The receptor:Cu(II) complex was found to differentiate the degree and size of phosphate substitutions. Chapter 3 describes the synthesis and application of a type of differential receptors for the recognition of phosphorylated tri-peptides from regular tri-peptides. The tri-peptide couples described in this chapter were part of sequences in protein Filamentous R-synuclein, which was discovered to have a close relation to Parkinson's disease. Extensive Ser129 phosphorylation was observed in diseased brains. Both solid phase and solution phase differential receptors were obtained in the investigations of peptide differentiation. A series of screening methods were applied to narrow down the system combinations. Linear discrimant analysis (LDA) statistical analysis generated a large spatial separation among six tripeptides. Chapter 4 describes the synthesis of a boronic acid based receptor for carboxy and phospho sugars recognition. Due to the large affinity to gluconic acid, which is the only product of enzyme catalyzed glucose oxidation, this receptor was successfully applied in determination of glucose concentration in human serum.
26

Construction and application of new supramolecular architectures using subcomponent self-assembly

Riddell, Imogen Anne January 2013 (has links)
No description available.
27

Supramolecular chemistry of naphthalenediimides

Ponnuswamy, Nandhini January 2012 (has links)
No description available.
28

Porphyrin-based multicomponent supramolecular assemblies

Alemán-García, Miguel Angel January 2012 (has links)
No description available.
29

Dynamic supramolecular assemblies on cucurbit[8]uril 'handcuff' surfaces

Tian, Feng January 2012 (has links)
No description available.
30

The application of naphthalenediimides in supramolecular chemistry

Tambara, Koujiro January 2013 (has links)
No description available.

Page generated in 0.0818 seconds