Excited States and Electron Transfer in Solution
Excited States and Electron Transfer in Solution

Author: Timothy Daniel Kowalczyk

Publisher:

Published: 2012

Total Pages: 185

ISBN-13:

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Our understanding of organic materials for solar energy conversion stands to benefit greatly from accurate, computationally tractable electronic structure methods for excited states. Here we apply two approaches based on density functional theory (DFT) to predict excitation energies and electron transfer parameters in organic chromophores and semiconductors in solution. First, we apply constrained DFT to characterize charge recombination in a photoexcited donor-acceptor dyad and to understand the photophysical behavior of a fluorescent sensor for aqueous zinc. Second, we discover that the delta-self-consistent-field ([Delta]SCF) approach to excited states in DFT offers accuracy comparable to that of the better-established but more indirect linear-response time-dependent DFT approach, and we offer some justification for the similarity. Finally, we investigate a spin-restricted analog of [Delta]SCF known as restricted open-shell Kohn-Sham (ROKS) theory. We resolve a known ambiguity in the formal solution of the ROKS equations for the singlet excited state by presenting a self-consistent implementation of ROKS with respect to the mixing angle between the two open shells. The excited state methods developed and applied in this work contribute to the expanding toolkit of electronic structure theory for challenging problems in the characterization and design of organic materials.

Chemical and Biological Generation of Excited States
Chemical and Biological Generation of Excited States

Author: Waldermar Adam

Publisher: Elsevier

Published: 2012-12-02

Total Pages: 401

ISBN-13: 0323152309

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Chemical and Biological Generation of Excited States discusses major aspects of chemical and biological generation of electronic excitation. This book is organized into 11 chapters that focus on both chemi- and bioenergized processes. This book first discusses some of the fundamental aspects of the description of excited state behavior in condensed media. It then examines the field of gas-phase dioxetane chemiluminescence both by itself and in relation to solution-phase studies. The presented analysis is based on statistical mechanics and supported by a very simple limiting case calculation. Chapter 4 describes the state-of-the-art of how excitation yields are determined experimentally in chemienergized processes. This is followed by a discussion on activation parameters and stability trends, focusing on solution-phase data. Chapters 6 and 7 examine solution-phase chemiluminescence resulting from high-energy electron-transfer reaction, often involving aromatic radical ions, and the mechanism of excitation step. The next chapters cover the generation of electronic excited states in bioluminescence and the evaluation of luminescent oxidation mechanisms using oxygen tracers. The chapters also explain the formation of electronically excited products in dark biological processes and the mechanism of chemiexcitation as it relates to redox metabolism. Specific examples of biological oxygenation reactions yielding luminescence are also presented. Furthermore, this book discusses the concept and applicability of chemiluminigenic probing for the quantification and differentiation of oxygenation activities in mammalian phagocytes. The concluding chapter is devoted to the possible formation of singlet oxygen in various systems and processes that mimic singlet oxygen reactions. The book intends to attract young scientists as well as established research workers to broaden the horizons of this rapidly growing and potentially very important field.

Heterogenous Photochemical Electron Transfer
Heterogenous Photochemical Electron Transfer

Author: Michael Gratzel

Publisher: CRC Press

Published: 2018-01-18

Total Pages: 170

ISBN-13: 1351081659

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The present monograph attempts to unify these diverse and exciting new developments within a common framework. First, the physical principles underlying heterogenous electron-transfer processes are outlined in a concise way and are compared to the homogeneous counterpart. This analysis includes the notion of the Fermi level in liquids and solids as well as the distribution of electronic energy levels in solids and liquids. A comparison is made between the salient kinetic features of homogeneous and heterogeneous electron transfer reactions. This establishes the basis for the subsequent treatment of the transduction of excitation energy and photo-initiated electron transfer in organized molecular assemblies, such as micelles, vesicles and monolayers. Transmembrane redox processes are critically reviewed. Particular attention is given to semiconductor electrodes and particles. This includes a discussion of quantum size effects, the nature of space charge layers as well as surface states and the dynamics of charge carrier-induced redox reactions at the semiconductor solution interface. These processes are of fundamental importance in such diverse fields as photochromism, electrochromic displays, electroreprography and photography, information storage, photocatalysis, photodegradation of paints, and solar energy conversion.

Understanding and Manipulating Excited-State Processes
Understanding and Manipulating Excited-State Processes

Author: V. Ramamurthy

Publisher: CRC Press

Published: 2001-08-21

Total Pages: 780

ISBN-13: 9780824705794

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A state-of-the-art review of original research, this book includes discussions of intramolecular photoadditoin of nucleophiles, electrophiles, and radical species to the activated aromatic ring; new methods for regio-, anantio-, and diastereoselective photooxygenations involving singlet oxygen mechanisms; and applications of microreactors for photochemical synthesis of large-ring compounds, photochemical rearrangement, photocycloaddition, and chiral photochemical synthesis. It covers the role of layered inorganic solids in the construction, characterization, and analysis of supramolecular assemblies of metal ions, molecules, metal complexes, and proteins, and more.

Hydrogen Bonding and Transfer in the Excited State
Hydrogen Bonding and Transfer in the Excited State

Author: Ke-Li Han

Publisher: John Wiley & Sons

Published: 2011-03-16

Total Pages: 1229

ISBN-13: 1119972922

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This book gives an extensive description of the state-of-the-art in research on excited-state hydrogen bonding and hydrogen transfer in recent years. Initial chapters present both the experimental and theoretical investigations on the excited-state hydrogen bonding structures and dynamics of many organic and biological chromophores. Following this, several chapters describe the influences of the excited-state hydrogen bonding on various photophysical processes and photochemical reactions, for example: hydrogen bonding effects on fluorescence emission behaviors and photoisomerization; the role of hydrogen bonding in photosynthetic water splitting; photoinduced electron transfer and solvation dynamics in room temperature ionic liquids; and hydrogen bonding barrier crossing dynamics at bio-mimicking surfaces. Finally, the book examines experimental and theoretical studies on the nature and control of excited-state hydrogen transfer in various systems. Hydrogen Bonding and Transfer in the Excited State is an essential overview of this increasingly important field of study, surveying the entire field over 2 volumes, 40 chapters and 1200 pages. It will find a place on the bookshelves of researchers in photochemistry, photobiology, photophysics, physical chemistry and chemical physics.