In this research the environmental effects related to the position of a redox moiety with the electrochemical double layer were studied. This project was made possible with the synthesis of a series of lengths of ferrocene derived alkanethiols, a series of lengths of ferrocene derived norbornylogous bridges and a series of lengths of anthraquinone derived norbornylogous bridges. The series of ferrocene derived alkanethiols were used to study the effect of gradually varying the polarity of the self-assembled monolayers (SAMs) surface on the standard electron transfer rate constant and formal potential. This was achieved by varying the portion of hydroxyl to methyl terminated alkanethiol diluent in the SAM preparation step. It was found that the formal potential increased with a decreasing proportion of hydroxyl terminated diluent and increasing length of the diluent. For pure hydroxyl terminated diluent the formal potential was relatively independent of length. It was found that the rate constant increased for short alkane chain lengths with decreasing proportion of hydroxyl terminated diluent. However, it decreased in magnitude with long alkane chain lengths for low proportions of hydroxyl terminated diluent. The norbornylogous bridges were shown to stand proud above the diluent with a similar tilt angle as the alkanethiol diluent. The ferrocene derived norbornylogous bridges showed hydroxyl terminated monolayers had a slower rate constant then methyl terminated diluents independent of length and that it is highly probable that an alkane bridged redox moiety is located very close to the surface of the monolayer. SAMs were created with the ferrocene of the ferrocene derived norbornylogous bridges located at various heights above the monolayers surface. This was done by using various lengths of hydroxyl terminated diluent. It was found that the rate constant and the formal potential decreased with height above the surface. Interfacial potential distribution was used to account for this and to estimate a ??true?? formal potential. The anthraquinone derived norbornylogous bridges were tested at various pH values and heights above the surface. It was found that an accurate estimate for the electron transfer mechanism can not be made for surface bound species due to the effects of interfacial potential distribution. They demonstrated a novel technique for estimating the point of zero charge of the electrode.

This dissertation describes the effective encapsulation of redox active compounds inside deep-cavity cavitands: Gibb's octaacid40 and Rebek's 41 tetracarboxylate cavitand. Gibb's octaacid is a water-soluble, deep-cavity cavitand that forms well-characterized dimeric molecular capsules around hydrophobic guests. Both 1H NMR spectroscopic and voltammetric experiments clearly reveal that ferrocene plays the role of hydrophobic guest effectively. Ferrocene derivatives (ferrocenylmethyltrimethylammonium (FcNMe3+), ferrocenemethanol (FcOH), and ferrocene carboxylic acid (FcCOOH)) were also found to form inclusion complexes with octaacid cavitand however, in this case 1:1 (host to guest) ratio complexes are formed. This is in strong contrast with the dimeric capsule formed around ferrocene. Under the surveyed experimental conditions encapsulated ferrocene is electrochemically silent. We have also found that the negative charges around this dimeric molecular capsule play a very important role. For instance, hydrophobic cations, such as viologens,60 bind to the outer surface of the capsule. This opened a possibility of mediated electron transfer reactions between molecules bound inside the octaacid capsule and tightly attached to its outer surface in purely synthetic system. The cationic ferrocene derivative, ferrocenylmethyltrimethylammonium (FcNMe3+), was used as a mediator since its electrochemical potential range makes it suitable as a mediator molecule. In fact, our data clearly support that FcNMe3+ mediates electron transfer between encapsulated ferrocene and the electrode surface. Ferrocene, its derivatives (FcNMe3+ and FcOH), and cobaltocenium (Cob+) also form 1:1 inclusion complexes with Rebek's tetracarboxylate cavitand, which surprisingly are all voltammetrically silent. The formation of these inclusion complexes seems to be driven by hydrophobic interactions between the host and the guest. The lack of voltammetric response observed in this work is a very intriguing finding.

Dye-sensitized solar cells (DSCs) convert sunlight to electricity at a low cost. In the DSC, a dye anchored to a mesoporous TiO2 semiconductor is responsible for capturing the sunlight. The resulting excited dye injects an electron into the conduction band of the TiO2 and is in turn regenerated by a redox mediator, normally iodide/triiodide, in a surrounding electrolyte. The success of the iodide/triiodide redox couple is mainly attributed to its slow interception of electrons at the TiO2 surface, which suppresses recombination losses in the DSC. One of the main limitations with the iodide/triiodide redox couple is, however, the large driving force needed for regeneration, which minimizes the open circuit voltage and thus the energy conversion efficiency. In this thesis, alternative redox couples to the iodide/triiodide redox couple have been investigated. These redox couples include the one-electron transition metal complexes, ferrocene and cobalt polypyridine complexes. The use of one-electron redox couples in the DSC has previously been shown to lead to poor photovoltaic performances, because of increased recombination. Cobalt redox couples were here found to give surprisingly high efficiencies in combination with the triphenylamine-based organic dye, D35. The success of the D35 dye, in combination with cobalt redox couples, was mainly attributed to the introduction of steric alkoxy chains on the dye, which supress recombination losses. By introducing steric substituents on the dye, rather than on the redox couple, mass transport limitations could in addition be avoided, which previously has been suggested to limit the performance of cobalt complexes in the DSC. The result of this study formed the basis for the world record efficiency of DSCs of 12.3 % using cobalt redox couples. Interfacial electron-transfer processes in cobalt-based DSCs were investigated to gain information of advantages and limitations using cobalt redox couples in the DSC. The redox potentials of cobalt redox couples are easily tuned by changing the coordination sphere of the complexes, and regeneration and recombination kinetics were systematically investigated by increasing the redox potential of the cobalt complexes. Our hope is that this thesis can be a guideline for future design of new redox systems in DSCs.

The de novo design of peptides is a central area of research in chemical biology. Although it is now possible to design helical peptide structures from first principle, designing â-sheets remains a challenge. Significant advances in this area have been made by using molecular scaffolds, which stabilize â-sheets through intramolecular H-bonding involving the scaffold or which direct supramolecular assembly of the conjugate. In my thesis, I have made use of novel strategies, using ferrocene (Fc) as a central scaffold for controlling the secondary structure of peptides. This approach has been highly successful. Four major new strategies are introduced and described in this thesis: <p>a) Cyclization of Fc-peptide conjugates of the type Fc[CO-Xxx-CSA]2 (Xxx = Gly, Ala, Val, Leu) and Fc[CO-Gly-Xxx-CSA]2 (Xxx = Val, Ile; CSA = cysteamine) leads to the clean formation of novel cyclic bioorganometallic conjugates, which exhibit strong intramolecular hydrogen bonding interactions that restrict the mobility of the podand peptide chains. In the latter system, this intermolecular hydrogen bonding interaction was exploited for the design of a novel â-barrel-like structure. For Fc[CO-Gly-Val-CSA]2 and Fc[CO-Gly-Ile-CSA]2 discrete cyclic supramolecular assemblies were formed in which the individual molecules assemble along the rims of the molecules, resulting in the formation of tubular peptide superstructures that possess a central cavity and are filled with water molecules. <p>b) Prior to my work, work by Hirao and Metzler-Nolte clearly showed that the two podand peptide chains in Fc-peptide conjugates are pointing away from each other. This would indicate that extended â-sheets cannot be formed by simply extending the podand peptide chains. In my work, I clearly demonstrate that, in contrast to earlier results, it is possible to use the Fc scaffold to stabilize â-sheet-like interactions in longer peptide chains. Two systems are described in this thesis Fc[CO-Gly-Val-Cys(Bz)-OMe]2 and Fc[CO-Gly-Ile-Cys(Bz)-OMe]2. In both the cases, amino acids are employed that have a high propensity for â-sheet formation. Both Fc-peptide conjugates exhibit strong interstrand hydrogen bonding, resembling that found in â-sheets.<p>c) In this work, I have demonstrated the use of ferrocene amino acid (Fca) to control the structure in peptides. In contrast to previous work by Metzler-Nolte, my work is largely focusing on the design of a repetitive Fca-peptide motif. It is proposed that this repetition will enable strong interactions between the peptide portions of the conjugate, resulting in the formation of an extended structure. To this effect, a series of Fca-conjugates of the type Boc-[Fca-Ala]n-OMe (n = 1-4) was synthesized and fully characterized. All systems display the expected interaction between the Ala residues having a 12-membered hydrogen bonded ring. Such a structural motif resembles that found in naturally occurring â-helical structures of the spike-region of some viral proteins. <p>d) I have also demonstrated the use of a novel Fc-derivative, Fc[NH-Boc]2, to control the structure of podand amino acid chains. Fc-diamine was synthesized by the convenient carbazide route giving this useful scaffold in high yield. This material was converted into its peptide conjugate and the resulting conjugate displays the elusive 14-membered hydrogen bonding ring. <p>Thus, in my work, I have provided a new complementary tool for peptide design that will undoubtedly find applications for the design of de novo proteins in the near future.

This work attempted to detect chemical warfare agent (CWA) simulants via electrochemistry utilizing two approaches. The first approach consisted of a ferrocene (Fc) amino acid derivative film on Au surfaces. The molecule [(BocHN)Fc(CO)CSA]2 was electrodeposited onto Au microelectrodes through a SAu bond. Once immobilized, the Fc amino acid derivative was Boc deprotected allowing for the amino group to react with the target molecule. Detection of the target simulant was monitored by cyclic voltammetry (CV) while following the formal potential of the Fc molecule, which is influenced by its immediate electronic microenvironment. Reaction with either 1 mM diethyl cyanophosphonate (DECP) or 2 chloroethyl ethyl sulfide (2 CEES), both effectively simulants for the CWAs Tabun nerve agent and blistering sulfur mustard respectively, was not observed. However, detection of 1 mM acetyl chloride was achieved by observing a potential anodic shift from 217 ± 6 mV, for the Boc deprotected form, to 388 ± 7 mV for the reacted state of the molecule. The lack of reactivity with the Fc amino acid system was hypothesized as a kinetic issue.<p> In the second approach, the electrochemistry of gas generated naked Ag nanoparticles (NPs) deposited on indium tin oxide covered glass plates is compared to bulk polycrystalline Ag. The nano specific electrochemistry of Ag NPs has been identified and includes the preferential formation of â oxides. In 100 mM KOH supporting electrolyte, disruption of â oxide formation is exploited to test for the presence of 1 mM DECP resulting in the dissolution of Ag via cyanide complexes leading to a CV signal decrease. While in 8.0 M KOH, â oxide formation is enhanced leading to testing capabilities for 1 mM 2 CEES resulting in the disappearance of the â oxide peak and the appearance of surface oxide peak during CV. Analogous electrochemistry is not observed on polycrystalline bulk Ag.

The de novo design of peptides is a central area of research in chemical biology. Although it is now possible to design helical peptide structures from first principle, designing â-sheets remains a challenge. Significant advances in this area have been made by using molecular scaffolds, which stabilize â-sheets through intramolecular H-bonding involving the scaffold or which direct supramolecular assembly of the conjugate. In my thesis, I have made use of novel strategies, using ferrocene (Fc) as a central scaffold for controlling the secondary structure of peptides. This approach has been highly successful. Four major new strategies are introduced and described in this thesis: <p>a) Cyclization of Fc-peptide conjugates of the type Fc[CO-Xxx-CSA]2 (Xxx = Gly, Ala, Val, Leu) and Fc[CO-Gly-Xxx-CSA]2 (Xxx = Val, Ile; CSA = cysteamine) leads to the clean formation of novel cyclic bioorganometallic conjugates, which exhibit strong intramolecular hydrogen bonding interactions that restrict the mobility of the podand peptide chains. In the latter system, this intermolecular hydrogen bonding interaction was exploited for the design of a novel â-barrel-like structure. For Fc[CO-Gly-Val-CSA]2 and Fc[CO-Gly-Ile-CSA]2 discrete cyclic supramolecular assemblies were formed in which the individual molecules assemble along the rims of the molecules, resulting in the formation of tubular peptide superstructures that possess a central cavity and are filled with water molecules. <p>b) Prior to my work, work by Hirao and Metzler-Nolte clearly showed that the two podand peptide chains in Fc-peptide conjugates are pointing away from each other. This would indicate that extended â-sheets cannot be formed by simply extending the podand peptide chains. In my work, I clearly demonstrate that, in contrast to earlier results, it is possible to use the Fc scaffold to stabilize â-sheet-like interactions in longer peptide chains. Two systems are described in this thesis Fc[CO-Gly-Val-Cys(Bz)-OMe]2 and Fc[CO-Gly-Ile-Cys(Bz)-OMe]2. In both the cases, amino acids are employed that have a high propensity for â-sheet formation. Both Fc-peptide conjugates exhibit strong interstrand hydrogen bonding, resembling that found in â-sheets.<p>c) In this work, I have demonstrated the use of ferrocene amino acid (Fca) to control the structure in peptides. In contrast to previous work by Metzler-Nolte, my work is largely focusing on the design of a repetitive Fca-peptide motif. It is proposed that this repetition will enable strong interactions between the peptide portions of the conjugate, resulting in the formation of an extended structure. To this effect, a series of Fca-conjugates of the type Boc-[Fca-Ala]n-OMe (n = 1-4) was synthesized and fully characterized. All systems display the expected interaction between the Ala residues having a 12-membered hydrogen bonded ring. Such a structural motif resembles that found in naturally occurring â-helical structures of the spike-region of some viral proteins. <p>d) I have also demonstrated the use of a novel Fc-derivative, Fc[NH-Boc]2, to control the structure of podand amino acid chains. Fc-diamine was synthesized by the convenient carbazide route giving this useful scaffold in high yield. This material was converted into its peptide conjugate and the resulting conjugate displays the elusive 14-membered hydrogen bonding ring. <p>Thus, in my work, I have provided a new complementary tool for peptide design that will undoubtedly find applications for the design of de novo proteins in the near future.

This work attempted to detect chemical warfare agent (CWA) simulants via electrochemistry utilizing two approaches. The first approach consisted of a ferrocene (Fc) amino acid derivative film on Au surfaces. The molecule [(BocHN)Fc(CO)CSA]2 was electrodeposited onto Au microelectrodes through a SAu bond. Once immobilized, the Fc amino acid derivative was Boc deprotected allowing for the amino group to react with the target molecule. Detection of the target simulant was monitored by cyclic voltammetry (CV) while following the formal potential of the Fc molecule, which is influenced by its immediate electronic microenvironment. Reaction with either 1 mM diethyl cyanophosphonate (DECP) or 2 chloroethyl ethyl sulfide (2 CEES), both effectively simulants for the CWAs Tabun nerve agent and blistering sulfur mustard respectively, was not observed. However, detection of 1 mM acetyl chloride was achieved by observing a potential anodic shift from 217 ± 6 mV, for the Boc deprotected form, to 388 ± 7 mV for the reacted state of the molecule. The lack of reactivity with the Fc amino acid system was hypothesized as a kinetic issue.<p> In the second approach, the electrochemistry of gas generated naked Ag nanoparticles (NPs) deposited on indium tin oxide covered glass plates is compared to bulk polycrystalline Ag. The nano specific electrochemistry of Ag NPs has been identified and includes the preferential formation of â oxides. In 100 mM KOH supporting electrolyte, disruption of â oxide formation is exploited to test for the presence of 1 mM DECP resulting in the dissolution of Ag via cyanide complexes leading to a CV signal decrease. While in 8.0 M KOH, â oxide formation is enhanced leading to testing capabilities for 1 mM 2 CEES resulting in the disappearance of the â oxide peak and the appearance of surface oxide peak during CV. Analogous electrochemistry is not observed on polycrystalline bulk Ag.

In this thesis, photocrosslinked ferrocene-based methacrylate polymers for thin-film cathodes in lithium batteries have been synthesized. Patterned thin-film electrodes of the ferrocene-based methacrylate polymers are fabricated by photocrosslinking. The structure and composition of the photocrosslinkable polymers are characterized by infrared spectra, nuclear magnetic resonances, and gel permeation chromatography. The result of quartz crystal microbalance shows that the crosslinked polymers prevent the polymers from dissolving into organic electrolytes. The cyclic voltammogram shows the photocrosslinked ferrocene-based methacrylate polymers have a redox couple. The energy capacity of the polymer for lithium batteries is about 40-50 mAh g-1 at a discharge rate of 10 C. The results show that the photocrosslinked ferrocene-based methacrylate polymers also improve the batteries.

Pyrazoles have been focus of a large number of investigations in the design and synthesis of novel biologically active agents that show remarkable medicinal activities. Although pyrazoles have been studied for over a century as an important class of heterocyclic compounds, they still continue to attract considerable attention due to the wide range of medicinal activities they possess. Recent studies have shown that combination of a ferrocenyl unit with structural features of pyrazoles can lead to products with enhanced or/and unexpected biological activity since several ferrocene derivatives have already been shown to be active against a number of tumors. As a result, we have investigated the reaction of 3-ferrocenylpropynal with hydrazinium salts. As anticipated, these reactions afforded two kinds of pyrazoles, namely 1-alkyl/aryl-5-ferrocenylpyrazoles (1,5-isomer) and 1-alkyl/aryl-3- ferrocenylpyrazoles (1,3-isomer). In most cases, 1,5-pyrazole isomers have resulted from these reactions as the single or the major product of the reactions. The structures of 1-benzyl-5-ferrocenylpyrazole, 1-phenyl-5-ferrocenyl-pyrazole and 1- (2-hydroxy-ethyl)-3-ferrocenylpyrazole were identified by X-ray single crystal analysis. The analogous reactions between 3-phenylpropynal and hydrazinium salts were also studied, which afforded 1-alkyl/aryl-5-phenylpyrazoles (1,5-isomer) and/or v 1-alkyl/aryl-3-phenylpyrazoles (1,3-isomer). The regioselectivity of the reactions is mainly governed by the nature of the substituents in hydrazine derivative.

Pyrazoles have been intensely studied in the design and synthesis of biologically active agents because they display considerable medicinal activities. Recent studies have shown that integration of a ferrocenyl unit with structural features of pyrazoles can result in the formation of the new products with enhanced or/and unexpected biological activity since several ferrocene derivatives have already been illustrated to be active against a number of tumors. Therefore, we have investigated the electrophilic cyclizations of the hydrazones to afford 5-ferrocenyl-4-((4-nitrophenyl)sulfenyl)-substituted pyrazole derivatives. First, the requisite hydrazone derivatives were synthesized by the reactions of ferrocenyl propargyl aldehydes or ketones with a series of hydrazines. Then electrophilic cyclizations of these hydrazones were investigated by treating with 4-(nitrophenyl)sulfenyl chloride as electrophile. By employing these electrophilic cyclizations, a series of 5-ferrocenyl-4-((4-nitrophenyl)sulfenyl)-1H-pyrazoles, 5-ferrocenyl-4-((4-nitrophenyl) sulfenyl)-3-methyl-1H-pyrazoles and 5-ferrocenyl-4-((4-nitrophenyl)sulfenyl)-3-phenyl-1H-pyrazoles have been synthesized in moderate to good yields.