The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl]-N,N-diethylbenzenamine are reported. The employment of microwaves in the preparation of 1 decreased the reaction time from 48 to 2 hours compared to the conventional reflux method. Stoichiometry variations allows for selective preparation of either a mononuclear, 1, or binuclear, fac-[Re2Cl2(CO)6], 2, complex. The photophysical properties of 1 were analyzed finding that it possesses significant luminescence rigidochromism. The steady state photoluminescence emission spectra of 1 in solution shift from 550 nm in frozen media to 610 nm when the matrix becomes fluid. Moreover, a very sensitive emission spectral analysis of 0.1 K temperatures steps shows a smooth transition through the glass transition temperature of the solvent host. Furthermore, synthetic modifications to L have attained a family of ambipolar compounds that have tunable photophysical, thermophysical and other material properties that render them promising candidates for potential applications in organic electronics and/or sensors - either as is or for their future complexes with various transition metals and lanthanides.

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The development of new charge transport materials for use in phosphorescent organic light-emitting diodes (OLEDs) remains an important area of research. In this thesis, several examples of carbazole-containing norbornene-based side-chain polymers were synthesized and studied. In addition, several examples of ambipolar transport moieties were produced by combining hole- (carbazole) and electron- (oxadiazole or triazole) transport groups and examined as both small molecules and as norbornene-based side-chain polymers. UV-visible absorption, fluorescence spectroscopy, cyclic voltammetry, and other methods were used to evaluate the properties of the charge transport materials for use as hole- and/or host layers. It was found that side-functionalization produced polymers with photophysical and electrochemical properties corresponding to the charge transport side groups attached. In addition, several crosslinkable hole-transporting materials (copolymer or small molecule-based) incorporating either benzocyclobutenes, trifluorovinyl ethers, oxetanes, or bis(styrene)s were developed. Thin-films of the crosslinkable materials were shown to be readily insolubilized by thermal treatment permitting the deposition of a subsequent layer from solution onto the crosslinked layer. OLEDs fabricated using several of these materials produced efficient devices. Overall, it was shown that side-chain functionalization can be used to afford solution-processable charge transport polymers where the properties are determined mainly by the side group attached. As such, this approach could be extended to additional examples of charge transport moieties.

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This thesis aims to provide a detailed understanding of side-chain functionalized polymers as emissive materials for OLEDs. The syntheses and photophysical properties of these solution-processable materials as well as the effects of metal types, polymer backbones, chain lengths, spacer types and lengths, host types, and concentrations of the metal complexes on the emission properties and device performance will be dicussed. The polymers were functionalized with host materials along with the metal complexes to enhance the charge transport and to obtain energy transfer from the host to the complex. The physical and photophysical properties of the polymers were tuned by changing the backbone and the metal complex. Poly(norbornene)s, poly(cyclooctene)s, and poly(styrene)s were studied. The differences in the glass transition temperatures and PDIs of the polymers indicated that device performances might be affected by the polymer type due to the differences in the processability of the polymers. In addition to the backbone, it was found that device performance is dependent on various parameters such as molecular weight, metal loading, spacer type, and spacer length. In each case, it was found that the polymer backbone does not interfere with the basic photopysical properties of the metal complexes. The two main classes of metal complexes studied in this thesis are metalloquinolates and iridium complexes. It was shown that the emission properties of poly(cyclooctene)s containing 8-hydroxyquinolines in their side-chains could be altered by simply changing the metal. Green- and near IR-emitting polymers were synthesized by employing aluminum and ytterbium, respectively. On the other hand, for the iridium complexes, changes in color were achieved by varying the ligands. Iridium containing polymers with emission spectra that span the entire visible spectrum were synthesized by employing the appropriate ligands. It was demonstrated that OLEDs with high efficiencies can be fabricated by using these polymers as the emissive layer.

Thesis (M.S.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.

Title: Spectroscopic Study of Singlet Oxygen in Cells and Model Systems Author: Marek Scholz Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. Roman Dědic, Ph.D., KChFO Abstract: Singlet oxygen (1O2), the first excited state of molecular oxygen, plays many important roles in nature and technology. The work is aimed at development of novel methods for monitoring of 1O2 in cells and other biological samples. Two main ap- proaches were employed: direct detection of the very weak near-infrared phospho- rescence of 1O2, and detection of Singlet Oxygen-Feedback Delayed Fluorescence (SOFDF), which is the emission from the photosensitizer induced by energy transfer from 1O2. The first part of the thesis introduces the basic concepts of photophysics and photochemistry of 1O2: its generation, deactivation, applications, and overview of detection methods. The second part presents the experimental results. Wide-field mi- crospectroscopic detection of 1O2 phosphorescence enabled us to acquire 1O2-based images and near-infrared spectra from single cells incubated with photosensitizers. However, the direct detection suffers from the inherently very low phosphorescence quantum yield. It is shown that SOFDF may overcome this problem and become a promising alternative tool for studies of 1O2 and...

Developing organic light-emitting diodes (OLEDs) as the next generation display devices is not only of industrial interest, but also a scientific challenge in and of itself that requires multi-disciplinary efforts to make the technology successful. Thermally activated delayed fluorescence (TADF) is a recent breakthrough in OLED technology whose prime value is to enable purely organic emitters to recruit the dark triplet excitons in the device, thus avoiding expensive and toxic rare metal based emitters. This thesis is centred on TADF and contains work in three major areas. Firstly, novel ionic TADF emitters were designed for use in light-emitting electrochemical cells (LEECs), which is an alternative electroluminescent device technology to OLEDs, with a much simplified fabrication procedure and architecture. The vast majority of these ionic emitters are based on reported TADF scaffolds where the donors were tethered with an imidazolium hexafluorophosphate group to obtain the ionic character required for LEEC devices (TL and BTL series, Chapter 2). On the other hand, TADF emitters with a carboxylate group were also designed which act as both acceptor and intrinsic charged functionality for LEEC applications (CTL series, Chapter 2). Secondly, attempts were made to create novel TADF molecular scaffolds in order to enrich the current library of TADF emitters. Research efforts were focused on polyaromatic moieties such as anthracene (An series, Chapter 4) and fluoranthene (FA series, Chapter 4) that are seldom reported in TADF literature. In addition, TADF emitters with phosphine oxide as the acceptor group have also been studied (PO series, Chapter 5). Lastly, structure-property relationship studies of TADF emitters were undertaken as a function of tuning of donor and acceptor functionalities using both theoretical and experimental approaches in order to gain more insight for designing desirable TADF emitters (Chapter 3).

abstract: Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of an OLED are emissive molecules that generate light in response to electrical stimulation. Ideal emitters are efficient, compatible with existing materials, long lived, and produce light predominantly at useful wavelengths. Developing an understanding of the photophysical processes that dictate the luminescent properties of emissive materials is vital to their continued development. Chapter 1 and Chapter 2 provide an introduction to the topics presented and the laboratory methods used to explore them. Chapter 3 discusses a series of tridentate platinum complexes. A synthetic method utilizing microwave irradiation was explored, as well as a study of the effects ligand structure had on the excited state properties. Results and techniques developed in this endeavor were used as a foundation for the work undertaken in later chapters. Chapter 4 introduces a series of tetradentate platinum complexes that share a phenoxy-pyridyl (popy) motif. The new molecular design improved efficiency through increased rigidity and modification of the excited state properties. This class of platinum complexes were markedly more efficient than those presented in Chapter 3, and devices employing a green emitting complex of the series achieved nearly 100% electron-to-photon conversion efficiency in an OLED device. Chapter 5 adapts the ligand structure developed in Chapter 4 to palladium. The resulting complexes exceed reported efficiencies of palladium complexes by an order of magnitude. This chapter also provides the first report of a palladium complex as an emitter in an OLED device. Chapter 6 discusses the continuation of development efforts to include carbazolyl components in the ligand. These complexes possess interesting luminescent properties including ultra-narrow emission and metal assisted delayed fluorescence (MADF) emission. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2014