Fluorescence methods are being used increasingly in biochemical, medical, and chemical research. This is because of the inherent sensitivity of this technique. and the favorable time scale of the phenomenon of fluorescence. 8 Fluorescence emission occurs about 10- sec (10 nsec) after light absorp tion. During this period of time a wide range of molecular processes can occur, and these can effect the spectral characteristics of the fluorescent compound. This combination of sensitivity and a favorable time scale allows fluorescence methods to be generally useful for studies of proteins and membranes and their interactions with other macromolecules. This book describes the fundamental aspects of fluorescence. and the biochemical applications of this methodology. Each chapter starts with the -theoreticalbasis of each phenomenon of fluorescence, followed by examples which illustrate the use of the phenomenon in the study of biochemical problems. The book contains numerous figures. It is felt that such graphical presentations contribute to pleasurable reading and increased understand ing. Separate chapters are devoted to fluorescence polarization, lifetimes, quenching, energy transfer, solvent effects, and excited state reactions. To enhance the usefulness of this work as a textbook, problems are included which illustrate the concepts described in each chapter. Furthermore, a separate chapter is devoted to the instrumentation used in fluorescence spectroscopy. This chapter will be especially valuable for those perform ing or contemplating fluorescence measurements. Such measurements are easily compromised by failure to consider a number of simple principles."

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Principles of fluorescence spectroscopy

Thermally activated delayed fluorescence (TADF) emitters, which produce light by harvesting both singlet and triplet excitons without noble metals, are emerging as next-generation organic electroluminescent materials. In the past few years, there have been rapid advances in molecular design criteria, our understanding of the photophysics underlying TADF and the applications of TADF materials as emitters in organic light-emitting diodes (OLEDs). This topic is set to remain at the forefront of research in optoelectronic organic materials for the foreseeable future. In this Review, we focus on state-of-the-art materials design and understanding of the photophysical processes, which are being leveraged to optimize the performance of OLED devices. Notably, we also appraise dendritic and polymeric TADF emitters — macromolecular materials that offer the potential advantages of low cost, solution processable and large-area OLED fabrication. Thermally activated delayed fluorescence (TADF) emitters are promising electroluminescent materials for next-generation organic light-emitting diodes (OLEDs). In this Review, the molecular design, photophysical characteristics and OLEDs composed of small-molecule, dendritic and polymeric TADF emitters are discussed.

All-organic thermally activated delayed fluorescence materials for organic light-emitting diodes

Electron Transfer Past and Future (R Marcus) Electron Transfer Reactions in Solution: A Historical Perspective (N Sutin) Electron Transfer--From Isolated Molecules to Biomolecules (M Bixon & J Jortner) Charge Transfer in Bichromophoric Molecules in the Gas Phase (D Levy) Long--Range Charge Separation in Solvent--Free Donor--Bridge--Acceptor Systems (B Wegewijs & J Verhoeven) Electron Transfer and Charge Separation in Clusters (C Dessent, et al) Control of Electron Transfer Kinetics: Models for Medium Reorganization and Donor--Acceptor Coupling (M Newton) Theories of Structure--Function Relationships for Bridge--Mediated Electron Transfer Reactions (S Skourtis & D Beratan) Fluctuations and Coherence in Long--Range and Multicenter Electron Transfer (G Iversen, et al) Lanczos Algorithm for Electron Transfer Rates in Solvents with Complex Spectral Densities (A Okada, et al) Spectroscopic Determination of Electron Transfer Barriers and Rate Constants (K Omberg, et al) Photoinduced Electron Transfer Within Donor--Spacer--Acceptor Molecular Assemblies Studied by Time--Resolved Microwave Conductivity (J Warman, et al) From Close Contact to Long--Range Intramolecular Electron Transfer (J Verhoeven) Photoinduced Electron Transfers Through sigma Bonds in Solution (N--C Yang, et al) Indexes

Electron transfer : from isolated molecules to biomolecules

Theoretical models that have been proposed and applied to proton transfer reactions are reviewed in this work. Simple models, like the Eigen model, Marcus theory and the intersecting state model, are applied to excited-state intermolecular proton transfers. The kinetics and thermodynamics of proton transfers occuring in the singlet states of aromatic molecules with OH, NH3+, NH2 and CO substituents are reviewed.

Excited-state proton transfer reactions I. Fundamentals and intermolecular reactions

Publisher Summary This chapter focuses on the electron transfer reactions in organic chemistry. The simplest elementary act in homogeneous solution chemistry is the exchange of an electron between two chemical entities. No bonds need to be formed or broken in the process, and if the two species are identical, except for a difference in oxidation state, no net chemical change takes place. Such self-exchange reactions constitute the basis of theoretical treatments of electron transfer. A more complex and chemically interesting situation is the electron-transfer reaction between two species of different chemical composition. In electron-transfer theory, it is an important postulate that electrons are transferred one by one, which does not mix well with the two-electron centered electronic theory of organic molecules. Organic electron transfers rarely occur as isolated steps because of the high chemical reactivity of odd-electron species. Processes involving one or several electron-transfer steps are not likely to preserve the stereochemical integrity of the reactants. With the present upsurge of research studies frequently invoking organic electron-transfer steps in mechanistic discussions, there is a great need of a theoretical background applicable to organic species and compatible with the language of physical organic chemistry.

Electron transfer reactions in organic chemistry

Fluorescence yields of azulene derivatives

Mesure du spectre de fluorescence de AlClTPP, ZnTPP et CdTPP dans l'acetonitrile a 296 K et determination du rendement quantique. Les vitesses des transitions radiatives a partir du second etat excite (S 2 ) ont ete calculees a l'aide de l'equation de Strickler-Berg. Interpretation des transitions non radiatives a partir de (S 2 ) (TPP=tetraphenylporphyrine)

S2 .fwdarw. S0 fluorescence of some metallotetraphenylporphyrins

Rate constants for quenching of several triplets by ferrocene have been determined in ethanol. Most triplets have been found to be deactivated by ferrocene, yielding no observable transient absorption. The rate constant increases with increasing triplet energy in the range 8000–17000 cm−1. The quenching mechanism has been discussed, the lowest triplet level of ferrocene being estimated to be 15000±1000 cm−1.

Hiroshi Kokubun

Papers

Fluorescence yields of azulene derivatives

S2 .fwdarw. S0 fluorescence of some metallotetraphenylporphyrins

A Study of Quenching of Triplets by Ferrocene

Relaxation mechanism of excited acridine in nonreactive solvents

Nonradiative relaxation processes of the higher excited triplet states of anthracenes studied by a double excitation method