Photoinduced Intramolecular Charge Transfer in Donor-Acceptor Biaryls and Resulting Applicational Aspects Regarding Fluorescent Probes and Solar Energy Conversion


Book Description

This study is focused on the effects of photoinduced intramolecular charge transfer (CT) in three differently twisted donor-acceptor (D-A) biphenyls. Taking into account a further pair of differently twisted D-A biaryls new universal insights into the photoinduced electronic and conformation dynamics of D-A biaryls are obtained. Furthermore, possible applications in fields of solar energy conversion and fluorescence sensing of microenvironments are demonstrated. Experimental means of stationary and time-resolved (ps to s) luminescence, transient absorption (sub-ps), polarization spectroscopy, high pressure and low temperature techniques are employed in conjunction with quantum chemical calculations. Twist angle and solvent dependent electron transfer (ET) interactions between the D and A aryl moieties are responsible for the low lying and solvatochromic intramolecular CT electron band which gains unusually high intensity through strong electronic coupling of the pure 1ET with the ground (S0) and 1La state. As regards the class of biaryl compounds, for the first time, an excited state electron transfer from the D to the A could be monitored by dual spectrally separated stimulated fluorescence bands with precursor-successor relationship on a sub-ps timescale for the D-A biphenyls. It is concluded that, in additon to the electronic interaction of 1ET with S0 and 1La, the electronic interaction with a close lying 1Lb state plays a fundamental role in the ET dynamics and the 1CT-S0 transition probability in D-A biaryls. The initial photoinduced conformational relaxation occurs towards planarity in all biaryls investigated. However, various results evidence that the highly twisted D-A biphenyl additionally performs a slow "excited state intramolecular back twist rotation" leading to a solvent polarity dependent conformational equilibrium between a more planar (CT) and a more twisted (CTR) conformer in S1(1CT). Using global analysis of the biexponential fluorescence decays as a function of temperature and pressure in medium polar solvents, the kinetics, thermodynamics, viscosity control and decomposed emission spectra associated with this adiabatic photoreaction are determined. The twist angle dependent ability of the D-A biphenyls to serve as fluorescent probes of micropolarity, changes of microviscosity or matrix order, protic solvents and pH is investigated. In particular, fluorescence sensing of pH seems to be promising.




Advances in Electron Transfer Chemistry


Book Description

Advances in Electron Transfer Chemistry, Volume 3 presents studies that discuss findings in the various aspects of electron chemistry. The book is comprised of four chapters; each chapter reviews a work that tackles an issue in electron transfer chemistry. Chapter 1 discusses the photoinduced electron transfer in flexible biaryl donor-acceptor molecules. Chapter 2 tackles light-induced electron transfer in inorganic systems in homogeneous and heterogeneous phases. The book also covers internal geometry relaxation effects on electron transfer rates of amino-centered systems. The sequential electron transfer reactions catalyzed by cytochrome p-450 enzymes are also dealt with. The text will be of great use to researchers interested in the field of electron transfer chemistry.







Photoinduced Electron Transfer: Conceptual basis


Book Description

Electron transfer reactions are of great importance to nearly every subdiscipline of chemistry. The simple transfer of a single electron has been shown repeatedly to be a common activating mode for organic, inorganic, and biological molecules, and the very ubiquity of such reactions has guaranteed that their investigation would involve the most fundamental questions of modern chemistry. The fact that photoexcitation induces enhanced redox reactivity via electron transfer also provides a convenient method for experimentally testing theoretical predictions regarding structural and energetic effects. As can be seen from the very size of this work there is a great deal known about photoinduced electron transfer reactions and the editors have tried to capture the diversity and excitement inherent in this broad field. The reader will find contributions from theorists and experimentalists, from organic and inorganic chemists, from the perspective of the synthetic and mechanistic viewpoint. Some contributions are fundamental basic research, while others clearly show practical applications of these principles.These volumes are intended to serve a joint purpose: as a reference resource and an introductory overview to the diverse research accomplished via photoexcitation of electron donor-acceptor systems. The information is organized in four parts. The first deals with the theoretical and conceptual factors which influence electron transfer. The second covers experimental methodology and medium effects. The third and fourth deal with reactivity, with most organic transformation being addressed in Part C and most inorganic reactions covered in Part D. Each part thus provides an overview of typical reactions observed for these classes of compounds. Part D also provides examples of photoinduced electron transfer in current use in important applications. There is of course a significant interdependence between the four parts. Subject, chemical, and author citation indices appear at the end of each of Parts A, B and C, and comprehensive indices are included in Part D.




Electron Transfer


Book Description

an integrated approach to electron transfer phenomena This two-part stand-alone volume in the prestigious Advances in Chemical Physics series provides the most comprehensive overview of electron transfer science today. It draws on cutting-edge research from diverse areas of chemistry, physics, and biology-covering the most recent developments in the field, and pointing to important future trends. This initial volume includes: * A historical perspective spanning five decades * A review of concepts, problems, and ideas in current research * Electron transfer in isolated molecules and in clusters * General theory, including useful algorithms * Spectra and electron transfer kinetics in bridged compounds The second volume covers solvent control, ultrafast electron transfer and coherence effects, molecular electronics, electron transfer and chemistry, and biomolecules. Electron transfer science has seen tremendous progress in recent years. Technological innovations, most notably the advent of femtosecond lasers, now permit the real-time investigation of intramolecular and intermolecular electron transfer processes on a time scale of nuclear motion. New scientific information abounds, illuminating the processes of energy acquisition, storage, and disposal in large molecules, clusters, condensed phase, and biophysical systems. Electron Transfer: From Isolated Molecules to Biomolecules is the first book devoted to the exciting work being done in nonradiative electron transfer dynamics today. This two-part edited volume emphasizes the interdisciplinary nature of the field, bringing together the contributions of pioneers in chemistry, physics, and biology. Both theoretical and experimental topics are featured. The authors describe modern approaches to the exploration of different systems, including supersonic beam techniques, femtosecond laser spectroscopy, chemical syntheses, and methods in genetic and chemical engineering. They examine applications in such areas as supersonic jets, solvents, electrodes, semi- conductors, respiratory and enzymatic protein systems, photosynthesis, and more. They also relate electron transfer and radiationless transitions theory to pertinent physical phenomena, and provide a conceptual framework for the different processes. Complete with over two hundred illustrations, Part One reviews developments in the field since its inception fifty years ago, and discusses electron transfer phenomena in both isolated molecules and in clusters. It outlines the general theory, exploring areas of the control of kinetics, structure-function relationships, fluctuations, coherence, and coupling to solvents with complex spectral density in different types of electron transfer processes. Timely, comprehensive, and authoritative, Electron Transfer: From Isolated Molecules to Biomolecules is an essential resource for physical chemists, molecular physicists, and researchers working in nonradiative dynamics today.




Photoinduced Electron Transfer


Book Description

Electron transfer reactions are of great importance to nearly every subdiscipline of chemistry. The simple transfer of a single electron has been shown repeatedly to be a common activating mode for organic, inorganic, and biological molecules, and the very ubiquity of such reactions has guaranteed that their investigation would involve the most fundamental questions of modern chemistry. The fact that photoexcitation induces enhanced redox reactivity via electron transfer also provides a convenient method for experimentally testing theoretical predictions regarding structural and energetic effects. As can be seen from the very size of this work there is a great deal known about photoinduced electron transfer reactions and the editors have tried to capture the diversity and excitement inherent in this broad field. The reader will find contributions from theorists and experimentalists, from organic and inorganic chemists, from the perspective of the synthetic and mechanistic viewpoint. Some contributions are fundamental basic research, while others clearly show practical applications of these principles.These volumes are intended to serve a joint purpose: as a reference resource and an introductory overview to the diverse research accomplished via photoexcitation of electron donor-acceptor systems. The information is organized in four parts. The first deals with the theoretical and conceptual factors which influence electron transfer. The second covers experimental methodology and medium effects. The third and fourth deal with reactivity, with most organic transformation being addressed in Part C and most inorganic reactions covered in Part D. Each part thus provides an overview of typical reactions observed for these classes of compounds. Part D also provides examples of photoinduced electron transfer in current use in important applications. There is of course a significant interdependence between the four parts. Subject, chemical, and author citation indices appear at the end of each of Parts A, B and C, and comprehensive indices are included in Part D.




Light Harvesting in Photosynthesis


Book Description

This landmark collective work introduces the physical, chemical, and biological principles underlying photosynthesis: light absorption, excitation energy transfer, and charge separation. It begins with an introduction to properties of various pigments, and the pigment proteins in plant, algae, and bacterial systems. It addresses the underlying physics of light harvesting and key spectroscopic methods, including data analysis. It discusses assembly of the natural system, its energy transfer properties, and regulatory mechanisms. It also addresses light-harvesting in artificial systems and the impact of photosynthesis on our environment. The chapter authors are amongst the field’s world recognized experts. Chapters are divided into five main parts, the first focused on pigments, their properties and biosynthesis, and the second section looking at photosynthetic proteins, including light harvesting in higher plants, algae, cyanobacteria, and green bacteria. The third part turns to energy transfer and electron transport, discussing modeling approaches, quantum aspects, photoinduced electron transfer, and redox potential modulation, followed by a section on experimental spectroscopy in light harvesting research. The concluding final section includes chapters on artificial photosynthesis, with topics such as use of cyanobacteria and algae for sustainable energy production. Robert Croce is Head of the Biophysics Group and full professor in biophysics of photosynthesis/energy at Vrije Universiteit, Amsterdam. Rienk van Grondelle is full professor at Vrije Universiteit, Amsterdam. Herbert van Amerongen is full professor of biophysics in the Department of Agrotechnology and Food Sciences at Wageningen University, where he is also director of the MicroSpectroscopy Research Facility. Ivo van Stokkum is associate professor in the Department of Physics and Astronomy, Faculty of Sciences, at Vrije Universiteit, Amsterdam.




Intramolecular Charge Transfer


Book Description

Bridging the gap between the multitude of advanced research articles and the knowledge newcomers to the field are looking for, this is a timely and comprehensive monograph covering the interdisciplinary topic of intramolecular charge transfer (ICT). The book not only covers the fundamentals and physico-chemical background of the ICT process, but also places a special emphasis on the latest experimental and theoretical studies that have been undertaken to understand this process and discusses key technological applications. After outlining the discovery of ICT molecules, the authors go on to discuss several important substance classes. They present the latest techniques for studying the underlying processes and show the interplay between charge transfer and the surrounding medium. Examples taken from nonlinear optics, viscosity and polarity sensors, and organic electronics testify to the vast range of applications. The result is a unique information source for experimentalists as well as theoreticians, from postgraduate students to researchers.




Factoring the Contribution of Through-space and Through-bond Interactions to Rates of Photoinduced Electron Transfer in Donor- Spacer-acceptor Molecules Using Ultrafast Transient Absorption Spectroscopy


Book Description

Contributions from through-space and through-bond interactions to the electronic coupling matrix elements for photoinduced charge separation and recombination in linked donor-spacer-acceptor molecules were studied. The molecules consisted of a 4-piperidinyl-naphthalene-1,8-dicarboximide electron donor and a N-(n-octyl)pyromellitimide electron acceptor attached to the 1,5- and 1,8-positions of either anthracene or dibenzobicyclo(2.2.2)octatriene spacers.