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.

Despite an ever growing number of reports concerning the anion-π interaction, controversy surrounding the nature of these weak supramolecular interactions continues. In an effort to further explore the nature and properties of anion-π interactions, experimental and computational methods were employed to study their occurrence in inorganic, organic and biological systems. As part of ongoing research in the Dunbar group on the topic of anion-π based supramolecular interactions, the ligand 3,6-bis(2′-pyrimidyl)-1,2,4,5-tetrazine (bmtz) was synthesized and reacted with [Cu(NCMe)4][BF4] to form the octanuclear complex [Cu8(bmtz)6][BF6]6·6MeCN. Crystallographic evidence indicates an in situ reduction of two of the complexed bmtz ligands to radical anions. A second blue compound has also been observed in this reaction, and recent work has resulted in a direct synthesis of this compound. Preliminary results indicate that this second compound contains Cu(II) centers, as expected. Further work is necessary to identify the second blue compound. In an effort to explore the fundamental question of whether or not anion-π interactions can occur between complex anions and olefins a series of Density Functional Theory and ab initio computations have been preformed for the tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane, 7,7,8,8-tetracyano-1,2,4,5-tetrafluoroquinodimethane and octacyanoquinodimethane molecules with the anions tetrafluoroborate and hexaflurophosphate. These optimizations indicate favorable interactions for all cases and are further supported by critical point analysis, performed using the Atoms in Molecules theory, and Natural Bond Orbitals analysis. DFT and NBO computations were also employed to explore the simultaneous anion-π and π-type charge transfer interactions observed between 1,4,5,8,9,12-hexaazatriphenylene-hexacarbonitrile and the chloride, bromide and iodide anions, as observed previously by the Dunbar group. Computations involving chloride and bromide anions are in full agreement with the previously reported spectroscopic and crystallographic evidence. Finally, the question of whether or not anion-π interactions occur in proteins was investigated by searching the Protein Data Bank for interactions between chloride or iodide anion and the aromatic moieties of the phenylalanine, tyrosine and tryptophan residues. Computer scripts were specifically written for this search and revealed promising interactions between chloride anions and all three amino acids. Procedural and statistical considerations preclude these examples from being definitive.

Differential scanning calorimetry (DSC), atomic force microscopy (AFM), 1H nuclear magnetic resonance (NMR), one-and two-dimensional fourier transform infrared spectroscopes (FTIR), size exclusion chromatography (SEC), dynamic light scattering (DLS), viscosity analyses have been used to investigate the miscibility behavior, specific interactions and supramolecular structures of poly(vinylbenzyl thymine-co-butyl methacrylate) (PVBT-co-PBMA, T-PBMA) blending with poly(vinylbenzyl adenine-co-styrene) (PVBA-co-PS, A-PS) through multiple hydrogen bonding complex upon varying the vinylbenzyl thymine and vinylbenzyl adenine contents in DNA-like copolymers. We describe FTIR and 1H NMR spectra reveal that hydrogen bonding between VBA and VBT exclusively. In addition, viscosity measurement, SEC, and DLS provide the formation of supramolecular network structure in this binary blend system. A miscibility window exists when the vinylbenzyl thymine and vinylbenzyl adenine fraction in the copolymer is greater than 11 mol% in the A-PS/T-PBMA blend system, as predicted using the Painter¡VColeman association model.

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).

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.

No description available.

No description available.

No description available.

No description available.

No description available.