Active metal template synthesis of rotaxanes, catenanes and knots

The use of a chemical template to control the spatial arrangement of reactants revolutionized the synthesis of mechanically interlocked molecules. The recently developed ‘active metal template’ strategy, in which transition metal ions act as both the template to guide interlocking and as the catalyst for the covalent bond forming reaction that captures the interlocked structure, has several advantages in comparison with traditional ‘passive template’ approaches. In contrast with passive template approaches the active template strategy is more efficient, completing the assembly of the interlocked structure in one step instead of two and in some cases requiring only a substoichiometric amount of metal template. In addition, fewer permanent recognition sites are required and in certain cases the active template reaction can shed light on mechanistic details of related metalcatalyzed processes and act as a conduit for reaction discovery. This Thesis will discuss the expansion of this new methodology in two main directions: firstly, exploration of new active metal template reactions, specifically the application of a novel Ni catalyzed sp3–sp3 C–C bond forming reaction, and secondly, the application of previously developed active template reactions to the synthesis of agrochemical-based [2]rotaxanes and other architectures, macrobicyclic [3]rotaxanes, [2]catenanes and a trefoil knot

Tunable solid-state fluorescent materials for supramolecular encryption

Tunable solid-state fluorescent materials are ideal for applications in security printing technologies. A document possesses a high level of security if its encrypted information can be authenticated without being decoded, while also being resistant to counterfeiting. Herein, we describe a heterorotaxane with tunable solid-state fluorescent emissions enabled through reversible manipulation of its aggregation by supramolecular encapsulation. The dynamic nature of this fluorescent material is based on a complex set of equilibria, whose fluorescence output depends non-linearly on the chemical inputs and the composition of the paper. By applying this system in fluorescent security inks, the information encoded in polychromic images can be protected in such a way that it is close to impossible to reverse engineer, as well as being easy to verify. This system constitutes a unique application of responsive complex equilibria in the form of a cryptographic algorithm that protects valuable information printed using tunable solid-state fluorescent materials

Influence of Constitution and Charge on Radical Pairing Interactions in Tris-radical Tricationic Complexes

The results of a systematic investigation of trisradical tricationic complexes formed between cyclobis(paraquat-p-phenylene) bisradical dicationic (CBPQT2(•+)) rings and a series of 18 dumbbells, containing centrally located 4,4′-bipyridinium radical cationic (BIPY•+) units within oligomethylene chains terminated for the most part by charged 3,5-dimethylpyridinium (PY+) and/or neutral 3,5-dimethylphenyl (PH) groups, are reported. The complexes were obtained by treating equimolar amounts of the CBPQT4+ ring and the dumbbells containing BIPY2+ units with zinc dust in acetonitrile (MeCN) solutions. Whereas UV-VIS-NIR spectra revealed absorption bands centered on ca. 1100 nm with quite different intensities for the 1:1 complexes depending on the constitutions and charges on the dumbbells, titration experiments show that the association constants (Ka) for complex formation vary over a wide range from Ka values of 800 M^(-1) for the weakest to 180000 M^(-1) for the strongest. While Coulombic repulsions emanating from PY+ groups located at the ends of some of the dumbbells undoubtedly contribute to the destabilization of the trisradical tricationic complexes, solid-state superstructures support the contention that those dumbbells with neutral PH groups at the ends of flexible and appropriately constituted links to the BIPY•+ units stand to gain some additional stabilization from C‒H···π interactions between the CBPQT2(•+) rings and the PH termini on the dumbbells. The findings reported in this full paper demonstrate how structural changes implemented remotely from the BIPY•+ units influence their noncovalent bonding interactions with CBPQT2(•+) rings. Different secondary effects (Coulombic repulsions versus C‒H···π interactions) are uncovered and their contributions to both binding strengths associated with trisradical interactions and the kinetics of associations and dissociations are discussed at some length and are supported by extensive DFT calculations at the M06-D3 level. A fundamental understanding of molecular recognition in radical complexes has relevance when it comes to the design and synthesis of non-equilibrium systems

Suppressing Dimer Formation by Increasing Conformational Freedom in Multi-Carbazole Thermally Activated Delayed Fluorescence Emitters

Ideal emitters for organic light-emitting diodes (OLEDs) are capable of efficiently harvesting non-emissive triplet states, have high colour stabilities, and possess high photoluminescence quantum yields (PLQYs). Maintaining colour stability and PLQY is particularly challenging for multi-carbazole thermally activated delayed fluorescence (TADF) materials that form persistent dimers due to intermolecular interactions of their extended aromatic systems (with altered electronic states). Addressing this challenge, three new emitters are presented, which demonstrate that, somewhat counterintuitively, sterically uncrowded acceptor units can suppress these undesirable interactions. They do so by allowing the surrounding carbazole donors to be arranged with lower dihedral angles, which in turn limits their availability for dimerization. A new pyrazine-centered emitter 4CzPyz is contrasted directly with the cyanopyridine and terephthalonitrile analogues, 4CzCNPy and 4CzTPN respectively. The pyrazine derivative demonstrates enhanced colour stability in the solid-state compared to the cyanopyridine and terephthalonitrile acceptors, which we assign to its absence of intermolecular face-to-face aromatic interactions. This suppression of dimer formation is shared by two cyanopyrazine emitters 2Cz2CNPyz and 3CzCNPyz, each of which feature reduced steric pressure and flatter Cz-Pyz dihedral angles than non-heterocyclic analogues. Flatter dihedral angles consequently lead to C–H bonds of the Cz donors extending outwards at angles that prevent the stacking required for dimerization. This expanded understanding of dimer formation in TADF materials will guide future efforts to maintain colour stability in higher performance TADF materials by curbing the prevalence of face-to-face aromatic interactions

Complement in the pathogenesis of Alzheimer's disease

The emergence of complement as an important player in normal brain development and pathological remodelling has come as a major surprise to most scientists working in neuroscience and almost all those working in complement. That a system, evolved to protect the host against infection, should have these unanticipated roles has forced a rethink about what complement might be doing in the brain in health and disease, where it is coming from, and whether we can, or indeed should, manipulate complement in the brain to improve function or restore homeostasis. Complement has been implicated in diverse neurological and neuropsychiatric diseases well reviewed elsewhere, from depression through epilepsy to demyelination and dementia, in most complement drives inflammation to exacerbate the disease. Here, I will focus on just one disease, the most common cause of dementia, Alzheimer’s disease. I will briefly review the current understanding of what complement does in the normal brain, noting, in particular, the many gaps in understanding, then describe how complement may influence the genesis and progression of pathology in Alzheimer’s disease. Finally, I will discuss the problems and pitfalls of therapeutic inhibition of complement in the Alzheimer brain

The International Companion to Scottish Poetry

A range of leading international scholars provide the reader with a comprehensive and innovative investigation of the extraordinary richness and diversity of Scotland\u2019s poetry. Addressing Languages and Chronologies, Poetic Forms, and Topics and Themes, this International Companion covers the entire subject from from the early Middle Ages to the modern day, and explores the connections, influences and interrelations between English, Gaelic, Latin, Old Norse and Scots verse. CONTENTS Series Editors\u2019 Preface Introduction (Carla Sassi) Part 1: Languages and Chronologies Early Celtic Poetry (to 1500) (Thomas Owen Clancy) Scots poetry in the Fourteenth and Fifteenth Centuries (R. D. S. Jack) Poetry in Latin (Roger Green) Poetry in the Languages and Dialects of Northern Scotland (Roberta Frank, Brian Smith) The Sixteenth and Seventeenth Centuries (S\uecm Innes, Alessandra Petrina) The Eighteenth Century (Ronald Black, Gerard Carruthers) The Nineteenth Century (Ian Duncan, Sheila Kidd) The Poetry of Modernity (1870\u20131950) (Emma Dymock, Scott Lyall) Contemporary Poetry (1950\u2013) (Attila D\uf3sa, Michelle Macleod) Part 2: Poetic Forms The Form of Scottish Gaelic poetry (William Gillies) Scots Poetic Forms (Derrick McClure) The Ballad in Scots and English (Suzanne Gilbert) Part 3: Topics and Themes Nature, Landscape and Rural Life (Louisa Gairn) Nation and Home (Carla Sassi, Silke Stroh) Protest and Politics (Wilson McLeod, Alan Riach) Love and Erotic Poetry (Peter Mackay) Faith and Religion (Meg Bateman, James McGonigal) Scottish Poetry as World Poetry (Paul Barnaby) The Literary Environment (Robyn Marsack) Endnotes Further Reading Notes on Contributors Index