This thesis describes the host-guest chemistry between cucurbit[7]uril (CB[7]) and various guests that contain isoquinoline groups, including tacrine, papaverine, N-methyl papaverinium, N-methyl laudanosinium, 6,7-dimethoxy-1,2,3,4,-tetrahydroisoquinoline, N, N-dimethyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolinium, α,α'-bis(isoquinolinium)-p-xylene and a series of 1,n-bis(isoquinolinium) alkane dications (Isq(CH2)nIsq2+, where n = 2, 4-6, 8-10 and 12). The stoichiometries and strengths of the host-guest interactions were studied using UV-visible and 1H NMR spectroscopy and high-resolution electrospray ionization mass spectrometry. A focus of this thesis is an investigation of the effects of varying the chemical structure within a series of isoquinoline-based guest on the strength of the binding affinity . The 1H NMR spectra indicates that CB[7] prefers the saturated ring of tacrine as opposed to the aromatic ring, resulting in a binding constant of (2.7 ± 0.25) x 104 M-1. The N-methylations of papaverine and 6,7-dimethoxy-1,2,3,4,-tetrahydroisoquinoline increased their respective binding constants from those of the protonated forms and changed the nature of the interaction of the guest with CB[7]. . With the series of 1,n-bis(isoquinolinium)-alkane dications, the mode of binding to CB[7] depends on the number of carbons in the polymethylene chain that bridges the two isoquinolinium groups. When the bridge is less than six carbons, CB[7] binds sequentially on the isoquinolinium groups to form 1:1 and 2:1 host-guest complexes. If the polymethylene chain length is between six and ten carbons, or is replaced with a p-xylyl group, the first CB[7] will bind over the central bridge, resulting in both of the polar portals forming ion-dipole interactions with both positively charged nitrogens. A second CB[7] binds to a terminal isoquinolinium group, which forces the original bound CB[7] to relocate to the other isoquinolinium group. When the polymethylene bridges contains twelve carbons, two CB[7] binds sequentially to the isoquinolinium groups, as observed with the shortest polymethylene bridges. With this series of guest, the binding constant is the largest when the bridge is two carbons long. This is due to the two isoquinolinium groups being in close proximity to each other, allowing CB[7] to interact with both nitrogens while still binding around the isoquinoline group. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-30 10:02:47.285

archives@tulane.edu / A recent development in the field of DNA nanotechnology is the use of synthetic moieties that are tethered to DNA to construct functional nanostructures for a wide range of applications. Due to the unique properties such as molecular recognition, self-assembly, biocompatibility and water solubility, a large number of these modified DNA-based structures were developed for application in biomedical fields. One intriguing goal of the studies is to regulate protein activities with the DNA-based nano-switches. Conceptually mimicking an allosteric protein, a well-designed DNA-based switch can recognize a biomarker from the biological environment, and then undergo a major conformational change, leading to a switch between ON and OFF states for protein activity modulation. This dissertation starts with a background on DNA Supramolecular Chemistry and also provides examples of the current mechanisms and strategies to control protein activities using DNA-based structures. The use of host-guest chemistry in conjugation with DNA systems is also discussed in this first chapter. Then, the development of two novel DNA-based transducers are described in the following chapters. The first transducer is based on a cucurbit[7]uril-DNA conjugate, which is capable of responding to an ATP input to release a carbonic anhydrase II (CA-II) inhibitor for protein activity regulation. The third chapter details an aptamer V7t1/DNA-small molecule chimera duplex that targets the CA-IX protein after recognizing a vascular endothelial growth factor (VEGF) trigger, thus raising the possibility of rewiring the HIF-1α signaling pathway. / 1 / Xiao Zhou

This thesis describes the use of electrospray mass spectrometry, 1H NMR, and UV-visible spectroscopy, along with molecular modeling studies, to characterize the host-guest complexes that are formed between the cucurbit[7]uril (CB[7]) host molecule and a series of cationic alkylammonium (benzethonium), biguanidinium (metformin, phenformin, chlorhexidine and alexidine), amidinium (berenil, pentamidine, and 4-hydroxy- and 4-aminobenzamidines), and flavylium (4’- and 6-methoxyflavylium and 6,4’-dimethoxyflavylium) guests in aqueous solution. The stoichiometries and binding strengths of the CB[7] host-guest complexes with these series of drug and dye molecules were determined, and have been rationalized in terms of the specific ion-dipole interactions and hydrophobic effects involved. The potential uses of CB[7] as a slow-release drug delivery agent and molecular stabilizing agent are indicated from kinetic and spectroscopic studies on the reactivities of the host-guest complexes. CB[7] forms 1:1 and 2:1 host-guest complexes with the benzethonium cation by sequential binding to the hydrophilic benzyldimethylammonium group and the hydrophobic 2,4,4-trimethylpentyl group, respectively. The binding strength at the former site is consistent with data for other CB[7]-benzylammonium guests, while the strength of binding of the neutral hydrophobic group results from efficient packing within the inner CB[7] cavity. Each of the biguanidinium guests was shown to form strong 1:1 host-guest complexes with CB[7]. Metformin proved to be small enough to form 1:2 host-guest complexes at low concentrations of CB[7], while chlorhexidine and alexidine were shown to be large enough to form sequential 2:1 and 3:1 host-guest complexes with CB[7]. UV-visible pH titrations showed that CB[7] binds more strongly to mono-protonated metformin than the di-protonated form of this guest. Both pentamidine and berenil formed tightly bound complexes with CB[7], indicating that this host could potentially act as carrier for these drug molecules. CB[7] catalyzes the acid decomposition of berenil and each of the decomposition products, 4-hydroxy- and 4-aminobenzamidinium, bind to CB[7] with increases in their pKa values in the presence of CB[7]. The three flavylium dyes, with cationic oxonium centers, were shown to complex strongly with CB[7], resulting in a stabilization of the flavylium cation, with respect to the ring-opened 2-hydroxychalcones in neutral solutions. / Thesis (Master, Chemistry) -- Queen's University, 2012-09-15 00:02:15.516

This thesis deals primarily with supramolecular chemistry based on cucurbit[n]uril (CB[n], n = 7 and 8) host molecules. The research has been focused on the synthesis and characterization of host-guest complexes CB[n] with aromatic guest molecules, and the study of the effects of the host-guest complexation on the chemical reactivity and spectroscopic properties of the included guests, such as their photoreactivity and their UV-visible absorption and emission properties, in aqueous solution. The [4+4] photodimerization of protonated 2-aminopyridine (APH+) occurs stereoselectively to give the anti-trans product as the result of a preferred orientation of two APH+ guests in the cavity of CB[7]. The CB[7] host inhibits photohydration in the course of the photoisomerizations of protonated trans-1,2-bis(4-pyridyl)ethylene and trans-1,2-bis(1-methyl-4-pyridinium)ethylene by including the (4-pyridyl)ethylene portion of the guest, while this is not observed with trans-1,2-bis(1-hexyl-4-pyridinium)ethylene, as preferential inclusion of the hexyl groups leaves the vinyl group vulnerable to photohydration. Very strong CB[7] complexation of (E)-1-ferrocenyl-2-(1-methyl-4-pyridinium)ethylene completely inhibits the (E)→(Z) photoisomerization process. The H/D exchange rates and acidities of the C(2)-proton of cationic imidazolium and thiazolium (including thiamine and thiamine phosphates) carbon acids are decreased upon their complexation with CB[7]. Inclusion of protonated aromatic amines (and aromatic alcohols) in the cavity CB[7] significantly decreases their ground and excited state acidities, such that the emission is switched from the neutral amine to the protonated amine excited state, resulting in changes in the color of fluorescence. The fluorescence of acridizinium cations can be switched off by the formation of 2:1 complexes with CB[8] and then switched back on again by the addition of CB[7] or a competing guest molecule. The stabilization of the deep blue color of the 4,4’-bis(dimethylamino)diphenyl carbonium ion, upon complexation of the corresponding carbinol with CB[7], results from a complexation-induced shift in the carbinol/carbonium ion equilibrium. A dramatic purple to blue color change in pinacyanol chloride upon addition of CB[7] is due to a partial breakup of dye aggregates, upon the interactions of the dye with the host molecule. The CB[n] complexation-induced emission and/or absorption color switch have the potential to be employed in molecular switches and in chemical sensing. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-08-07 09:21:06.553

As cucurbiturilas são moléculas versáteis empregadas em diversos ramos da química, essas gaiolas moleculares formam uma família de homólogos oriundos da condensação da glicolurila e do formaldeído em meio ácido. As aplicações se estendem para campos como catálise, fotoquímica, sínteses orgânica e inorgânica, química de materiais e supramolecular. Particularmente a cucurbit[6]urila, comumente chamada apenas de CB[6], uma molécula bastante simétrica, têm em seus opérculos, sítios propícios à coordenação, especialmente com espécies pequenas e pouco polarizáveis. Aproveitando o caráter dos portais, foi possível sintetizar um complexo inédito, com um sítio catalítico proveniente de íons vanadila, VO2+, ligados às extremidades do cavitando. O acesso ao centro catalítico desta molécula, seria determinado pela captura do substrato no interior do macrociclo, limitado pelo volume do substrato e pelas relações de solvofobicidade, pois a cavidade possui um caráter hidrofóbico. A estrutura desse complexo ainda não foi completamente elucidada, pois não foi possível obter um cristal único e determiná-la através de difração de raios-x. As técnicas de caracterização no estado sólido empregadas indicaram que esse novo complexo teria o seu centro metálico provavelmente numa configuração piramidal de base retangular, isso é evidenciado pelas medidas espectroscópicas que remetem a uma simetria C2V. Foram feitas tentativas de coordenação mono e binuclear, mas algumas técnicas apontam para a formação apenas da espécie mononuclear. Os primeiros testes catalíticos, em condições brandas para a conversão de hidrocarbonetos apresentaram bons resultados frente a substratos lineares e inatividade frente a substratos cíclicos mais volumosos. Os resultados obtidos nos levam a crer que as reações de oxidação de alcanos, com estas espécies, se dão pelo interior da cavidade, ao longo do orbital dz2 do íon (V=O)2+, e não pela parte superior através do átomo de oxigênio ligado ao vanádio. / Cucurbiturils are versatile molecules used in several branches of chemistry. These molecular cages form a family of homologues from the condensation of glycoluril and formaldehyde in acidic medium. Their applications range from catalysis, photochemistry, organic and inorganic synthesis, materials and supramolecular chemistry. Particularly cucurbit[6]uril, or simply CB[6], is a very symmetrical molecule, which posesses coordination points on its portals, especially with hard acids. Due to this characteristic, it was possible to synthesize a new complex, with a vanadyl, VO2+, catalytic center bonded to the extremity of the cavitand. The access to the catalytic center of this molecule should be determined by the entrance of the substrate inside the macrocycle, which is limited by its volume and by solvophobicity, because the cavity is strongly hydrophobic. The structure of this new complex could not be completely solved yet, because it was impossible to obtain a single crystal for X-rays diffraction analysis. The solid state characterization techniques indicated that this new complex has its metallic center in a rectangular-base pyramid configuration. This was shown by the spectroscopic evidences which point to a d1 ion in a C2V symmetry. Attempts were made to synthesize both mono and binuclear species, but all the techniques we have used have demonstrated that only the former one was obtained. The first catalytic tests for hydrocarbons convertion in mild conditions have shown good results towards for linear substrates and no activity at all towards more volumous cyclic molecules. The results we have obtained indicate that the alkane oxidation reactions with these complexes occur inside the cavity along the (V=O)2+ ion dz2 orbital , and not on its superior moiety on the vanadyl oxygen atom.

As cucurbiturilas são moléculas versáteis empregadas em diversos ramos da química, essas gaiolas moleculares formam uma família de homólogos oriundos da condensação da glicolurila e do formaldeído em meio ácido. As aplicações se estendem para campos como catálise, fotoquímica, sínteses orgânica e inorgânica, química de materiais e supramolecular. Particularmente a cucurbit[6]urila, comumente chamada apenas de CB[6], uma molécula bastante simétrica, têm em seus opérculos, sítios propícios à coordenação, especialmente com espécies pequenas e pouco polarizáveis. Aproveitando o caráter dos portais, foi possível sintetizar um complexo inédito, com um sítio catalítico proveniente de íons vanadila, VO2+, ligados às extremidades do cavitando. O acesso ao centro catalítico desta molécula, seria determinado pela captura do substrato no interior do macrociclo, limitado pelo volume do substrato e pelas relações de solvofobicidade, pois a cavidade possui um caráter hidrofóbico. A estrutura desse complexo ainda não foi completamente elucidada, pois não foi possível obter um cristal único e determiná-la através de difração de raios-x. As técnicas de caracterização no estado sólido empregadas indicaram que esse novo complexo teria o seu centro metálico provavelmente numa configuração piramidal de base retangular, isso é evidenciado pelas medidas espectroscópicas que remetem a uma simetria C2V. Foram feitas tentativas de coordenação mono e binuclear, mas algumas técnicas apontam para a formação apenas da espécie mononuclear. Os primeiros testes catalíticos, em condições brandas para a conversão de hidrocarbonetos apresentaram bons resultados frente a substratos lineares e inatividade frente a substratos cíclicos mais volumosos. Os resultados obtidos nos levam a crer que as reações de oxidação de alcanos, com estas espécies, se dão pelo interior da cavidade, ao longo do orbital dz2 do íon (V=O)2+, e não pela parte superior através do átomo de oxigênio ligado ao vanádio. / Cucurbiturils are versatile molecules used in several branches of chemistry. These molecular cages form a family of homologues from the condensation of glycoluril and formaldehyde in acidic medium. Their applications range from catalysis, photochemistry, organic and inorganic synthesis, materials and supramolecular chemistry. Particularly cucurbit[6]uril, or simply CB[6], is a very symmetrical molecule, which posesses coordination points on its portals, especially with hard acids. Due to this characteristic, it was possible to synthesize a new complex, with a vanadyl, VO2+, catalytic center bonded to the extremity of the cavitand. The access to the catalytic center of this molecule should be determined by the entrance of the substrate inside the macrocycle, which is limited by its volume and by solvophobicity, because the cavity is strongly hydrophobic. The structure of this new complex could not be completely solved yet, because it was impossible to obtain a single crystal for X-rays diffraction analysis. The solid state characterization techniques indicated that this new complex has its metallic center in a rectangular-base pyramid configuration. This was shown by the spectroscopic evidences which point to a d1 ion in a C2V symmetry. Attempts were made to synthesize both mono and binuclear species, but all the techniques we have used have demonstrated that only the former one was obtained. The first catalytic tests for hydrocarbons convertion in mild conditions have shown good results towards for linear substrates and no activity at all towards more volumous cyclic molecules. The results we have obtained indicate that the alkane oxidation reactions with these complexes occur inside the cavity along the (V=O)2+ ion dz2 orbital , and not on its superior moiety on the vanadyl oxygen atom.

The host-guest chemistry between cucurbit[7]uril (CB[7]) and cationic organic guests of medicinal and biological interest are described in this thesis. In the first part, three cationic steroidal neuromuscular blockers (SNMBs) were studied, along with guests that model their monocationic N-alkyl-N-methylheterocyclic (morpholinium, pyrrolidinium and piperidinium) terminal groups of the SNMBs, and dicationic guests in which the two N-methylheterocyclic rings are linked by a decamethylene chain, modelling a variety of NMBs. Other cationic drugs related to acetylcholine processes in neuromuscular blockage were also studied. In the second part, the amino acids lysine, and its mono-, di- and trimethylated and acetylated Nε derivatives, and arginine, and mono- and (symmetric and asymmetric) dimethylarginine, were investigated as guests, along with analogs of arginine. The nature and strength of the complexation between CB[7] and these guests in aqueous solution were determined by 1H NMR spectroscopy and ESI mass spectrometry. The CB[7] showed high binding affinity (KCB[7] = 106-109 M-1) towards the N-alkyl-N-methylheterocyclic cations with a trend of piperidinium > pyrrolidinium > morpholinium, which reflects the relative hydrophobicities of the guests. The CB[7] forms 1:1 and 2:1 host-guest complexes with dicationic model guests, with the CB[7] initially encapsulating the decamethylene chain. The second CB[7] binds to a terminal site, resulting in electrostatic repulsions with the first CB[7], which are resolved by the translocation of the first CB[7] to the opposite terminal site. This 2:1 binding mode is also observed with CB[7] and the SNMBs, and the trend in KCB[7] with these SNMB terminal sites is comparable to that observed for the monocationic model guests. The other cationic drugs also form stable host-guest complexes with CB[7], and the binding constants displayed dependences on the size, charge, and hydrophobicity of the guests. The CB[7] exhibits significant selectivity towards different lysine and arginine derivatives, which can be related to the relative hydrophobicity afforded by the methyl substituents and the positioning of the guest within the CB[7] cavity. The 3500-fold selectivity for Nε,Nε,Nε-trimethyllysine over lysine by CB[7] is the highest observed for a synthetic macrocyclic receptor, while a modest selectivity of symmetrical over asymmetrical dimethylarginine by CB[7] is observed. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-09-26 14:33:40.063

Cucurbit[8]uril (CB[8]) has attracted great interest in the cucurbit[n]uril (CB[\textit{n}]) family on account of its capability to simultaneously accommodate two guests inside its cavity, to form strong yet dynamic ternary complexes. Owing to the photo-induced \textit{trans} to \textit{cis} isomerisation property, azobenzene (Azo) derivatives have been widely employed in several host-guest systems, leading to various light-responsive materials. This thesis focuses on CB[8]-based ternary complexes, especially those involving Azo derivatives. These systems can be exploited as a platform to hierarchically fabricate supramolecular constructs, including crystalline structures and composite materials. Specifically, novel morphology-controlled (1D needle-like, 2D sheet-like) crystals have been prepared by adjusting the assembly of Azo-CB[8] complexes, which can be further developed to oriented macroscopic free-standing crystalline pillars grown from a glass surface. Next, a composite micelle-nanoparticle complex has been prepared utilising Azo-CB[8] assemblies, which demonstrates $\sim$90$\%$ efficiency in surfactant recycling. Finally, an organic CB[8]-mediated hydrogel reinforced by inorganic nanowires has been prepared. This hybrid structure shows increased stiffness due to various supramolecular interactions. Chapter 1 gives a brief introduction to CB[\textit{n}] host-guest chemistry with emphasis on CB[\textit{n}]-based crystalline structures and CB[8] ternary complexes. Recent progress of Azo-based host-guest chemistry is then reviewed. In addition, shape-controlled crystals formed \textit{via} supramolecular interactions are discussed at the end of the chapter. Chapter 2 focuses on the crystalline structure of the 1:2 homoternary complex formed between CB[8] and a methyl orange (MO) guest, which is the fastest CB[8]-based crystallisation to date. As a commonly used pH indicator, MO possesses an azobenzene moiety with both an electronically positive amino group and an anionic sulfonate group. At low pH values, formation of the homoternary complex 2MO@CB[8] occurs, serving as a 'tectonic' building block, which rapidly stacks into a herringbone arrangement. The intermolecular and intercomplex interactions inside 2MO@CB[8] crystals are discussed, whereby the CB[8] macrocycle orients the electrostatic charges on MO guests resulting in the repulsive interactions being shielded; this in turn leads to fast electrostatically-driven crystal growth. The 2MO@CB[8] system provides a promising approach for designing ultrarapid crystallisation systems derived from CB[\textit{n}] host-guest complexes. Moreover, the host-guest chemistry between CB[8] and a variety of Azo derivatives with different functional groups is discussed, demonstrating the influence of guest structures on their crystalline behaviours. Chapter 3 further explores the mechanism of 2MO@CB[8] crystallisation through a series of experimental and computational methods. Control over the crystal shape, length and growth rate can be achieved in a facile manner whilst maintaining the same (internal) unit cell. Therefore, the properties of the macro-scale crystals can be tuned at the molecular level through adjusting the assembly of 2MO@CB[8] building blocks. For example, tuning the ionic strength of the solution enables a second growth dimension, yielding 2D crystals with sheet-like and more complex morphologies. Furthermore, our understanding of oriented electrostatics provided by the homoternary tecton can then be exploited to prepare oriented macroscopic free-standing crystalline pillars grown from a glass surface at room temperature. Next, CB[8] ternary complexes have been employed as 'bridges' to link (organic) soft and (inorganic) hard materials together, resulting in composite materials. In chapter 4, a micelle-nanoparticle complex (\textbf{MNC}) structure has been assembled \textit{via} host-guest interactions between Azo-functionalised, cargo-loaded micelles and magnetic SiO$_2$ nanoparticles (NPs) functionalised with CB[8] catenanes. Owing to the photo-responsive and magnetic properties, \textbf{MNCs} can be exploited to recycle detergents (micelles) from aqueous solution. This is followed by the controlled release of the encapsulated hydrophobic molecules inside the micelle cavity. In this process, both the micelles and NPs can be recycled efficiently. The novel \textbf{MNC} structure provides a promising approach to recycle versatile drug carriers through host-guest chemistry. Chapter 5 introduces a CB[8]-based hydrogel in which inorganic nanowires (NWs) are employed to enhance the gel stiffness. The supramolecular hydrogel is comprised of methylviologen-functionalised poly(vinyl alcohol) (PVA-MV), hydroxyethyl cellulose with naphthyl moieties (HEC-Np) and CB[8]. The gel structure is effectively enhanced by the framework supporting effects of CePO$_4$ NWs and additional hydrogen bonding interactions between NWs and PVA-MV/HEC-Np polymers. The high aspect ratio NWs serve as a 'skeleton' for the network, providing extra physical crosslinks. This results in a single continuous phase hybrid supramolecular network with improved strength, showcasing a general approach to reinforce soft materials. Finally, this thesis closes with a summary and perspective chapter, concluding the present work and highlighting an insight towards future work. Utilising CB[8] ternary complexes, various supramolecular constructs can be prepared through hierarchical self-assemblies, leading to a wide variety of composite systems and functional materials in the future.

This dissertation investigates the preparation and electrochemical studies on a series of novel redox active hybrid dendrimers. The author also describes cucurbit[8]uril (CB8) mediated dendrimer self-assembly and their size selection by applying external electrochemical stimulus. In addition to this, a series of redox active, carboxylic acid terminated dendrimers were deposited onto indium tin oxide (ITO) surfaces. The surface interactions between the dendrimers and the metal oxides were characterized by electrochemical, spectroscopic, and atomic force microscopic methods. Additionally, the author describes molecular recognition behavior studies between several redox active guests and cucurbit[7]uril (CB7) in non-aqueous media. Furthermore, the author also describes the preparation and electronic communication studies on a series of bisferrocenylamino triazine derivatives. Three chapters of this dissertation deal with dendrimer applications in several different topics. A general introduction to dendrimers is given in Chapter I, including a short history, dendrimer structural features, synthetic methodologies, and also including their general applications on several different topics. Chapter II describes the preparation and characterization of a series of novel redox active hybrid dendrimers. These dendrimers consist of a ferrocenylamino nucleus and two series of popular dendrons (Fréchet and Newkome type). Interestingly, the microenvironment surrounding the redox residues is finely adjustable by varying the size of these two types of dendrons. Chapter III describes the molecular recognition studies with selected redox active guests and the macrocyclic host CB7 in non-aqueous media. The extremely strong host-guest interaction between CB7 and ferrocenylmethyl-trimethylammonium (FA) in aqueous media experiences a substantial thermodynamic stability loss when transferred to non-aqueous media. In stark contrast to this, the binding behavior between CB7 and the dicationic guest methyl viologen (MV) exhibits less sensitivity to environmental variation. Furthermore, the electrochemical studies were performed under non-aqueous media. In general, host CB7 encapsulation of these redox active guests in non-aqueous media induces different electrochemical behavior compared to that of aqueous media. For instance, the cyclic voltammetric response of CB7 encapsulated FA in DMSO exhibit substantial cathodic potential shift, which is opposite to the behavior in aqueous media. Chapter IV describes CB8 mediated dendrimer self-assembly. A new series of pi-donor containing Newkome type dendrimers were synthesized. These pi-donor containing dendrimers are found to form stable ternary charge transfer complexes with another series of pi-acceptor (viologen) containing dendrimers. Furthermore, one electron reduction of the viologen residue disrupts the charge transfer complexes and leads to the assembly of viologen radical cation dimmers. And, thus, may result in substantial size selection between these two types of dendrimer assemblies. Chapter V describes the exploration of a series of redox active dendrimers bearing multiple carboxylic acids as surface anchoring groups to attach onto the optical transparent semiconductor material ITO coated glass surfaces. The dendrimer derivatized ITO slides were further prepared as working electrodes, and the subsequent electrochemical studies revealed that these dendrimers strongly adsorb onto ITO surfaces. Especially, the ITO electrodes treated with the second generation dendrimer exhibit rather stable electrochemical behavior. The surface coverages of ITO electrodes treated with dendrimers were estimated by current integration. Atomic force microscopic studies provided insights on surface topographical variation before and after the dendrimer deposition. Infrared spectroscopic studies further revealed the chemical interactions between dendrimer carboxylic acid groups and the metal oxide surfaces. Chapter VI describes the preparation of a series of triazine based bisferrocenylamino derivatives. Variable 1H-NMR and 13C-NMR spectroscopic studies clearly indicate that these bisferrocenylamino triazine derivatives exhibit rotamerization phenomena. And, the rotamer coalescence temperatures are mediated by the third substituent group. The X-ray crystallographic analyses disclose the partial double bond character between the amino nitrogen and the triazine carbon, which reveal the structural proof behind the rotamerization phenomena. Furthermore, electrochemical experiments are performed under two sets of experimental conditions. No electronic communication is observed when using the traditional tetrabultylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. In stark contrast to this, electronic communication between the bisferrocenyl residues is observed when using tetrabultylammonium tetrakis(pentafluorophenyl)borate (TBAB(C6F5)4) as supporting electrolyte. Surprisingly, the electronic communication strength can be mediated by a third substituent group. Computational studies provide insights into the molecular geometry and electronic structure of the mixed valence species. By combining the supporting electrolyte dependant electronic communication behavior, near-IR spectroscopic studies and the computational results, we conclude that, the electronic communication between the bisferrocenyl residues in these investigated triazine derivatives occurs through space metal-metal interactions.

Although most vegetables are grown using conventional tillage (CT) practices, no-tillage (NT) is becoming more prominent in vegetable production due to growers gaining more understanding of the economic and ecological benefits associated with the NT production system. Nitrogen (N) fertility management in NT systems is important to maximize yield productivity, but there is little available information on N fertilizer recommendations for vegetable crops grown in this production system. Therefore, two field studies were conducted at a grower location in southern Illinois to determine the effect of N application rates in NT zucchini squash and cucumber production following the herbicide burn-down of a wheat cover crop in early spring. Results indicated that the maximum total squash fruit yield was achieved when 30 to 120 lb N/acre was sidedress applied [or a range of 125 to 210 lb total N (pre-plant, soil, and applied N)/acre]. Although squash plant growth was maximized when 180 lb N/acre was sidedressed (or a range of 264 to 273 lb total N/acre), the overall yield was less compared to the 30 to 120 lb N/acre rates. Cucumber results indicated that maximum total fruit yield was achieved again at 30 to 120 lb N/acre sidedress rates (or a total N rate range of 114 to 208 lb/acre). Cucumber plant growth was maximized at a sidedress application of 120 to 180 lb N/acre, although yield decreased at the 180 lb N/acre sidedress rate (or 260 to 270 lb total N/acre). It appears that if cucurbit vegetables have high amounts of N available in the soil through over application of N fertilizer, the excess N will be used for plant vegetative growth rather than for fruit production. These studies indicated that when too much N is applied in both NT cucumbers and zucchini squash, these high N rates will stimulate vegetative growth (as indicated by high plant vigor and leaf chlorophyll content) while reducing fruit yields.