Probing the nano-structure of ionic liquids using the nuclear overhauser effect

A methodology utilising the distance dependence of the rotating frame Overhauser effect (ROE) has been developed to investigate the existence of nano-structured domains in ionic liquids. A partition coefficient termed the domain preference integral ratio (DPIR) has been created to offer a simple perspective by which the preferential solubility of probe molecules in ionic liquids can be assessed. A model system, consisting of the first five oligomers of methyl methacrylate (MMA) has been designed to investigate the source of an 'ionic liquid effect' observed in the free radical polymerisation (FRP) of MMA conducted in ionic liquids. Investigation by rotating frame Overhauser effect spectroscopy (ROESY) and calculation of the DPIR has been used to probe the solvation environment of the model system. Furthermore, calculation of the DPIR for the reversible addition fragmentation chain transfer (RAFT) control agent cyanobenzoyl dithiobenzoate (CB DB) has led to a series of predictions of the outcome of the RAFT controlled FRP of MMA in ionic liquids. The reaction kinetics of the RAFT controlled reactions have been monitored to investigate the success of the methodology to predict the outcome of a reaction based upon the observed solvation environment of one of the reactant molecules.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Structural and optical properties of inherently chiral polythiophenes: A combined CD-electrochemistry, circularly polarized luminescence, and TD-DFT investigation

Circular dichroism (CD) and ultraviolet absorption (UV) spectra of films obtained by electrochemical polymerization of inherently chiral 2,2\u2032-bis(2,2\u2032-bithiophene-5-yl)-3,3\u2032-bithianaphthene (T4-BT2) are taken during electrochemical polarization cycles. Besides the bisignate CD features in the near UV range recorded at zero potential, new features in the visible 12near-infrared range are observed under increased applied potential. Results are interpreted with the help of static and time-dependent (TD) density functional theory (DFT) calculations, which shed light on the structural and electronic properties of neutral and charged oligomers (from monomers to tetramers) and reproduce UV and CD spectra satisfactorily. Furthermore, properties of the excited state of T4-BT2 monomers in solution are enlightened by combining circularly polarized luminescence (CPL) measurements with TD-DFT calculations

Potential‐Driven Chirality Manifestations and Impressive Enantioselectivity by Inherently Chiral Electroactive Organic Films

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral polyheterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3’-bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co-planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system

Inherently Chiral Macrocyclic Oligothiophenes: Easily Accessible Electrosensitive Cavities with Outstanding Enantioselection Performances

Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations in application derive from insolubility, scarce processability and chain-end effects. This study describes an easy access to chiral cyclic oligothiophenes constituted by 12 and 18 fully conjugated thiophene units. Chemical oxidation of an “inherently chiral” sexithiophene monomer, synthesized in two steps from commercially available materials, induces the formation of an elliptical dimer and a triangular trimer endowed with electrosensitive cavities of different tunable sizes. Combination of chirality with electroactivity makes these molecules unique in the current oligothiophenes literature. These macrocycles, which are stable and soluble in most organic solvents, show outstanding chiroptical properties, high circularly polarized luminescence effects and an exceptional enantiorecognition ability