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

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.

El auto-ensamblaje donde debido a la interacción con el disolvente moléculas de un compuesto anfifílico se asocian espontáneamente es un proceso general que puede servir para la preparación de entidades supramoleculares de gran tamaño con aplicación en la preparación de materiales tanto dispersos en fase liquida como sólidos insolubles. Por otra parte la asociación supramolecular puede ocurrir también entre moléculas diferentes y cuando una de ellas es una cápsula molecular esta puede albergar en su interior una molécula de tamaño inferior al de su abertura. Los CB[n] son oligómeros cíclicos de unidades de glicol uril unidas por puentes metileno que definen una cavidad en forma de calabaza hueca que permite alojar en su interior moléculas de colorantes fluorescentes. En la presente tesis doctoral se ha desarrollado una matriz de sensores para sales de amonio cuaternarias, ?-aminoácidos y ácido ?-hidroxibutírico. De la misma manera los CBs pueden también formar complejos con acetanilidas conteniendo grupos aminopropil. En la presente tesis doctoral se va a sacar ventaja del auto-ensamblaje de líquidos iónicos con estructura de imidazolio simétrico sustituído con dos grupos ?-alquenilo para formar liposomas. Otro tema de interés será establecer como el proceso de auto-ensamblaje influye en la asociación supramolecular entre líquidos iónicos con estructura de imidazolio y cucurbituriles. Por último el ensamblaje entre iones inorgánicos y biopolímeros naturales se empleará para pre-organizar los precursores inorgánicos de manera que cuando estos sufran polimerización el biopolímero actúe como agente plantilla controlando el tamaño de las partículas inorgánicas formadas. El objetivo general de la presente tesis doctoral es estudiar procesos de agregación que ocurren de manera espontánea en el seno de disoluciones acuosas y que dan lugar a la formación de complejos supramoleculares huésped-hospedador o a la formación de entidades supramoleculares de tipo liposomas. / Buaki Sogo, M. (2012). APLICACIÓN DE FENÓMENOS DE AUTO-ENSAMBLAJE Y ASOCIACIÓN SUPRAMOLECULAR CON CUCURBIT[n]URIL PARA EL DESARROLLO DE MATRICES DE SENSORES Y MATERIALES FUNCIONALES [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17830

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This thesis describes the host-guest chemistry between Cucurbit[7]uril (CB[7]) and CB[8] and a series of guests including bispyridinium cations, phenols and  napthalenes. These guests are bound to ruthenium polypyridine complexes or ruthenium based water oxidation catalysts (WOCs). The investigations are based upon utilizing the covalently linked photosensitizer and the electronic effects and chemical processes are investigated. / QC 20100927

Supramolecular interactions are of great importance in the fabrication of new functional materials. In particular, colloidal assembly via supramolecular pathway has contributed to numerous innovations in material chemistry, on account of its specific, directional and dynamic non-covalent interactions. By taking advantage of the non-covalent supramolecular interactions, tailored complementary colloidal building blocks which are normally incompatible with each other could be integrated interdependently, forming novel hybrid materials with emerging properties. This thesis mainly focuses on the design, preparation and characterization of novel colloidal assemblies based on cucurbit[n]urils host-guest interactions, including hybrid ‘raspberry-like’ colloids, catalytic polymeric nanocomposites, advanced structured colloids, and supramolecular polymer colloidal hydrogel.

Making use of the non-covalent bond to make materials is of great interest in many fields of research. This PhD thesis describes a variety of highly interdisciplinary research undertaken at the interface between chemistry, materials science, physics and engineering. Chapter 1 is an introductory chapter into the core concepts underlying this thesis. Supramolecular chemistry as a broad research field is briefly reviewed, followed by a focus on host-guest chemistry. The macrocyclic cucurbit[n]urils (CB[n]s) in particular are highlighted with a discussion on their recent applications since their discovery. Emulsions and their controlled generation with microfluidic techniques are then reviewed, as they have been used as templates for self-assembly processes throughout this thesis. A study into the synthesis of extended polymer networks composed entirely from small molecules held together by non-covalent interactions is described in Chapter 2. These highly dynamic and responsive supramolecular polymer networks have not yet been constructed with CB[n] host-guest chemistry. The ability of the larger CB[8] macrocycle to encapsulate multiple guest molecules in a stepwise fashion was taken advantage on in designing the synthesis of branching monomers. The monomers had two (A$_2$) or three (B$_3$) terminal guest moieties for CB[8], which upon combination formed branching supramolecular polymers that were multi-stimuli responsive. However, the polymers precipitated from solution at high concentrations rather than form a cross-linked network, due to competing intra-chain cyclisation and the limited water solubility of CB[8]. By confining these polymers to microfluidic droplets, directed assembly to the liquid-liquid interface could drive polymerisation to form an interfacial cross-linked gel that was both elastic and self-healing. Chapter 3 follows on from these results, describing attempts into constructing hyperbranched supramolecular polymers from an AB$_2$ guest molecule and CB[8] that would form globular polymers. Intramolecular complexation dominated with the guest molecules synthesised (A and B complexing within the molecule), evidenced by a variety of characterisation. Compared to previous works that relied on linear molecules to form a folded conformation for intramolecular complexes, these molecules were pre-organised with a unique cooperative complexation pathway. The stimuli-responsiveness of the complexes was probed, and the formation of self-sorting mixtures was demonstrated with multiple CB[n] and additional guest molecules. Controlling the self-assembly of semi-conducting nanocrystals with CB[7] is detailed in Chapter 4, a process that typically requires harsh conditions or extensive time-scales. Semi-conducting nanocrystals could be assembled instantaneously from water into extended networks that were highly porous with excess CB[7], retaining their nanoscale properties. Limiting quantities of CB[7] could then form nanoscale aggregates that remained in solution. Confinement of these assemblies within microfluidic droplets allowed the synthesis of dense microparticles, that retained their shape after re-dispersal in water. By simply including metallic nanocrystals as a minor component, mixed aggregates could be synthesised analogously. Finally, Chapter 5 draws overall conclusions from the results of this thesis, looking broadly at the potential for future prospects in these areas of research.

This dissertation focuses on the investigation of gas-phase characteristics of cucurbituril host-guest systems using ion mobility spectrometry (IMS) and related techniques. Collision cross-sections (CCS) of alkylammonium complexes of cucurbit[n]uril (CB[n]) are measured to understand the allosteric interactions that induce conformational changes in the complex in the presence of metal cations on one of the portals of the cucurbit[6]uril (CB[6]) host. Cationic species on one CB[6] rim sterically force longer linear alkylammonium guests out of the cucurbituril cavity during complex formation. Similarly, rigid cucurbituril-metal complexes were studied using IMS to demonstrate the effect of long-range ion-neutral interactions on the gas phase mobility of ions. The contributions of charge state and charge distribution to the ion mobility CCS measured using a drift tube ion mobility spectrometer (DTIMS) were studied. This IMS method characterization will help in the study of biomolecules and may answer some of the questions regarding CCS measurements in protein structures, that are still being debated. While most of the studies were done using an IMS system, this dissertation also includes gas phase characterization studies done using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. A novel gas-phase CCS measurement technique - cross sectional areas using Fourier transform ion cyclotron resonance mass spectrometry (CRAFTI) was attempted on bigger systems like the [cucurbit[6]uril-n-alkylammonium]+ complexes. Infrared multi-photon dissociation (IRMPD), collision induced dissociation (CID), and sustained off-resonance irradiation (SORI) studies were done on many CB[n] systems, which helped to extract useful structural information about the complexes.

The recently discovered cucurbit[n]uril are a range of macrocyclic hosts which have enormous potential in industrial, medical and academic applications. Cucurbit[n]uril have a rigid repeating structure of methylene bridged glycouril, which give cucurbit[n]uril their gourd like shape of a cavity with two carbonyl fringed portals. In this thesis the host-guest binding abilities of three cucurbit[n]uril (n = 6, 7, 8) have been examined for a range of potential guests. These guests ranged from simple alkyl amines through globular alkyl and carboranyl amines to bipyridyl systems. In total 45 guest molecules where examined. Most of the guests examined where either cationically charged, capable of hydrogen binding, contained a substantial molecular dipole, or a combination of these. Furthermore, all of the potential guests examined had some solubility in an acidified aqueous sodium sulfate solution within which the host-guest properties were examined. It was generally found that the larger guests did have selectivity for the larger hosts. However, when the host became too large weaker complexes would form and for the range of materials examined here cucurbit[7]uril was found to be the 'best' host system. In one example, p-xylene diamine, a 2:1 complex with cucurbit[8]uril was observed. While not the focus of this work a new rapid purification method was developed for the cucurbit[n]uril using different metal ions to either solubilise or precipitate the different cucurbit[n]uril. In the second part of this work these same guest molecules where used as potential templates in the synthesis of cucurbit[n]uril. Surprisingly the guests that bound strongly to an individual host did not seem to template the cucurbit[n]uril synthesis at all. Rather these strong binders inhibited the reaction such that little or no cucurbit[n]uril formed under the reaction conditions studied. However, several examples provided excellent template results. Indeed the results indicate that guests which bound with intermediate rates of exchange are the best templates and using templates under these conditions we have been able to produce cucurbit[7]uril as 46% by mass of the total cucurbit[n]uril product. This is the highest yield ever recorded for cucurbit[7]uril and it is the first example of cucurbit[7]uril being the major product of this condensation reaction. In an another example cucurbit[8]uril formed 18% of the product an increase of 150% over the standard reaction conditions. While studying both the template reactions and the host-guest binding properties of the cucurbit[n]uril a new supramolecular form, an 'inverse rotaxane' was discovered. Inverse rotaxanes are not held in place by large blocking groups, rather the molecular structure encapsulated by the cucurbit[n]uril host prevents decomplexation of the axle.