No description available.

This project was designed to investigate the possibility of producing alignment layers for liquid crystal devices by cross-linking thin films containing anisotropic polymer bound chromophores via irradiation with polarised ultra violet light. Photocross-linkable polymers find use in microelectronics, liquid crystal displays, printing and UV curable lacquers and inks; so there is an increasing incentive for the development of new varieties of photopolymers in general. The synthesis and characterisation of two new photopolymers that are suitable as potential alignment layers for liquid crystal devices are reported in this thesis. The first polymer contains the anthracene chromophore attached via a spacer unit to a methacrylate backbone and the second used a similarly attached aryl azide group. Copolymers of the new monomers with methyl methacrylate were investigated to establish reactivity ratios in order to understand composition drift during polymerisation.

No description available.

Electrogenerated chemiluminescence (ECL) studies were performed on several interesting compounds. A series of BODIPY derivatives was examined to understand the structural effects on the electrochemical, spectroscopic, and ECL behavior. Stable electrochemistry and high fluorescence in the green to the red regions were observed. PB, MCPB, DCPB and PM580 produced intense ECL, strong enough to be seen with the naked eye in a lighted room. Unlike MCPB and DCPB, PB produced the multiple ECL peaks. Totally blocked BODIPY compound showed the improvement of fluorescence and ECL quantum yield due to the stability of radicals. Strong signal of EPR data during the oxidative electrolysis was obtained by simultaneous electrochemical-electron paramagnetic resonance technique with home-made cell. Several new antrhacene derivatives such as a variety of 2- and 4-fold anthracene-functionalized tetraarylbimesityls and a series of 9-naphthylanthracene based dimer and trimer were studied. They showed one wave on the oxidation and reduction because of a sequence, two or more electron transfers during the annihilation of the radical ions. Depended on the structure, some of them exhibited excimer formation on ECL spectra. Azide-BTA compound which consists of two triphenylamine and 2,1,3-benzothiadiazole groups at the ends bridged by a fluorene moiety was synthesized and examined. The compound is a newly synthesized D-A-[pi]-A-D molecule which had reversibility upon electrochemical oxidation and reduction, and also showed intense red fluorescence and stable red ECL emission. Using a simple reprecipitation method, well-dispersed and spherical organic nanoparticles of Azide-BTA and 9-naphthylanthracene based dimer were prepared in an aqueous solution. Controlling the preparation condition, the size of nanoparticles can be minimized to 15 nm. Especially we prepared the organic nanoparticles of 9-naphthylanthracene based dimer dispersed in organic solvent, MeCN, one of the preferred solvents for electrochemical studies and ECL. / text

2 v. : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Physical and Inorganic Chemistry, University of Adelaide, 1974

Thesis (Ph.D.) -- Dept. of Physical and Inorganic Chemistry, University of Adelaide, 1974.

No description available.

xx, 361 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Highly conjugated carbon-rich molecules have attracted interest in recent years due to unique electronic, optical and materials properties. Carbon networks based upon the phenylacetylene subunit are increasingly recognized as building blocks for a host of sensing and electronics components due to the rigidity and linearity of carbon-carbon triple bonds. Further extending this motif into a macrocycle, generating a dehydrobenzoannulene (DBA), also confers planarity, increasing the à -conjugation and giving rise to enhanced materials behavior. Functionalization of arylacetylenes and DBAs with electron donating and accepting groups manipulates the energetics such that finely-tuned optoetectronic properties can be devised for customized applications, including fluorescent sensor arrays, organic light-emitting diodes, and nonlinear optical materials. Fundamental structure-property relationship studies into certain physical modifications of molecular architecture effects on the photophysics, intramolecular charge transfer (ICT), or complexation properties are of importance in the rational design of the next generation of organic electronics. Chapter I provides a review of recent advances in the field of annulene chemistry. It is organized by cycle type, size, and application within each category. Chapter II describes syntheses and ion responses of an array of donor/acceptor-functionalized arylacetylenes. The independent manipulation of frontier molecular orbital (FMO) energy levels is discussed in relation to a fluorescent switching phenomenon. Chapter III expands this effect to include [15]DBAs. The consequences of incorporating protonatable donor/acceptor groups into a macrocycle, as well as placement of the acceptor nitrogen are examined, and comparison of calculations to experimental results imply generation of transient ICT species with induced FMO localizations. Chapter IV describes the syntheses of acyclic tetrakis(phenylethynyl)benzene (TPEB) and [14]- and [15]DBA systems utilizing fluorinated acceptor groups. Comparisons between these inductive acceptors and earlier resonance acceptors are made, and imply greater stability and processing potential for optoelectronic applications. Chapter V describes a series of bis[18]DBAs functionalized with dibutylamino groups as donors and nitro groups as acceptors. The effects of 2-donor/2-acceptor versus 4-donor/4-acceptor motifs are explored, and trends are identified in the systematic adjustment of the optical band gap that will have important implications for the design of two-photon absorbing materials. This dissertation includes my previously published and co-authored material. / Adviser: Michael M. Haley

Efficient singlet-singlet (SSET) and triplet-triplet (TTET) energy transfer between fluorenyl and either phenylbenzoyl or naphthyl chromophores in enantiomerically pure dipeptides occur via through-space intramolecular dipole-induced dipole (Förster-SSET) and electron exchange (Dexter-TTET) mechanisms as demonstrated by, UV-visible absorption, fluorescence, phosphorescence and laser flash photolysis measurements. Unprotected, optically pure 3-(2-fluorenyl)-L-alanine (8, Fla) and its C- and N-protected derivatives were synthesized using a modified Sorensen procedure, and were subsequently used for solution-phase synthesis of the dipeptides (9, Bpa-Fla and 10,Npa-Fla) and solid-phase synthesis of a 15-residue peptide (7). UV absorption spectra of the dipeptides indicate that the chromophores do not interact electronically in the ground state nor do their photophysical characteristics change when incorporated into the peptides. Dipeptide bichromophore fluorescence and phosphorescence results show efficient SSET (kSSET > 109 s-1) and TTET (kTTET > 104 s-1). Fluorescence and phosphorescence spectra produced by excitation at donor absorbance wavelengths show complete energy transfer in 9 and efficient energy transfer in 10. Donor-acceptor separation (transfer separation distance) was calculated from the spectral overlap of the donor fluorescence spectrum and the acceptor UV absorption spectrum using the Förster equation for energy transfer. With the spectral overlap value, assumed orientation of the chromophores in the dipeptide and the fluorescence quantum yield of the donor, a "critical" Förster transfer distance was calculated for the two dipeptides (9, 10) to be 14.6 Ã… and 15.1 Ã…, respectively. The actual distance calculated from dipeptide fluorescence spectra, using an assumed Förster distance was 9.1 Ã… and 8.7 Ã…, respectively. HyperChem MM3 modeling of the two dipeptides yielded an average inter-chromophore separation of 11 ±3 Ã…, comparable to the experimental values. Laser flash photolysis of the two dipeptides revealed near complete TTET. The spectral analysis of each dipeptide showed essentially 100% acceptor triplet present, although the donor in each case absorbed all or most of the incident light.

<p>This thesis is divided into four parts with organic chromophores for dye sensitized solar cells as the common feature and an introduction with general concepts of the dye sensitized solar cells.</p><p>The first part of the thesis describes the development of an efficient organic chromophore for dye sensitized solar cells. The chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. During this work a strategy to obtain an efficient sensitizer was developed. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.</p><p>The second part describes the contributions to the HOMO and LUMO energy levels when alternating the linker moiety. By varying the linker the HOMO and LUMO energy levels was indeed shifted. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.</p><p>The third part describes the investigation of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths. The HOMO and LUMO energy level tuning was once again successfully shifted. The poor electronic coupling of the acceptor group to the semiconductor surface proved to be a problem for the overall efficiency of the solar cell, however.</p><p>The fourth part describes the contributions from different donor groups to the HOMO and LUMO energy levels and has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.1 % was achieved.</p>