Polynuclear Complexes of Lanthanide Elements and Silver-Exploratory Synthesis and Property Investigation

Abstract

Polynuclear lanthanide complexes have attracted increasing interest in coordination and materials chemistry as they generally possess aesthetically pleasing molecular structures and display interesting properties possibly for useful chemical and materials applications. The work described herein concerned with the exploratory synthesis, structural characterization, and property investigation of a number of polynuclear lanthanide and silver complexes with selected organic ligands. Details of this thesis work are summarized in the following chapters: Chapter 1 offers a background of the research, with an emphasis on lanthanide-containing compounds and polynuclear silver complexes. Synthetic methodologies, novel structural characteristics, and interesting physical properties toward possible applications are surveyed in order to convey the justification of this thesis work. Chapter 2 describes the design and synthesis, structural characterization of a series of dinuclear lanthanide complexes with 1-(2-pyridylazo)-2-naphthol. The photophysical properties of these complexes pertinent to optical-limiting applications are evaluated. Chapter 3 details the halide-templated assembly of dodecanuclear and pentadecanuclear lanthanide hydroxide complexes featuring histidine as supporting ligand via the ligand-controlled hydrolysis. Salient structural features of these complexes are discussed. Chapter 4 reports the synthesis, structural characterization, and spectroscopic studies of the giant polynuclear lanthanide complexes containing a 60-metal cluster core when threonine was used as the supporting ligand. Carbonate has been identified as a novel anionic template in these clusters. These Ln60 cluster complexes feature a sodalite cage structure with 24 vertex-sharing cubane-like [Ln₄(μ₃-OH) ₄]⁸⁺ units. Their magnetic and optical properties are measured and discussed. Chapter 5 describes the unexpected discovery of a polynuclear silver complex with histidine, first isolated from the reaction of a halide-containing polynuclear lanthanide hydroxide complex and then rationally prepared by using silver nitrate and histidine. A series of analogous silver complexes with other amino acids have subsequently prepared and structurally characterized. Chapter 6 details two silver-amino acid helicates composed of individual helical coordination polymers. Optically pure helicates were obtained by using enantiomerically pure amino acids. While silver-glutamate possesses a double-helical structure, silver-aspartate displays an unprecedented six-strand helical structure. Chapter 7 summarizes the results presented in Chapters 2-6 and elaborates on some future research directions toward which each of these projects may be heading.