Conformational Analysis Of Molecules In Excited States
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Conformational Analysis Of Molecules In Excited States
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Author : Jacek Waluk
language : en
Publisher: John Wiley & Sons
Release Date : 2000-06-13
Conformational Analysis Of Molecules In Excited States written by Jacek Waluk and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000-06-13 with Science categories.
A unique look at some of the hottest topics in photophysics and photochemistry today The study of molecules in excited states has exploded over the past decade, providing new insights into conformational changes in organic molecules and opening up research opportunities for scientists and professionals in chemistry, physics, biology, medicine, and materials engineering. Using conformational analysis as a unifying concept, this important new work provides readers with a cohesive and cutting-edge overview of this fascinating and challenging field. From conformational changes accompanying photoinduced electron transfer to elementary photophysical and photochemical processes in living systems, the most representative and challenging topics are carefully gleaned from the vast literature, highlighting major conceptual problems along with the relevant experimental techniques. Authoritative, detailed contributions from both experimentalists and theoreticians include coverage of: * Conformational changes in intramolecular excited state electron transfer * Conformational aspects of excited state proton transfer * The novel topic of solute-solvent friction in chemical reactions * Mechanisms and structural aspects of exciplex formations * Conformational aspects of organic photochemistry * Calculations of excited state conformational properties
Structures And Conformations Of Non Rigid Molecules
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Author : J. Laane
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Structures And Conformations Of Non Rigid Molecules written by J. Laane and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
From the beginnings of modern chemistry, molecular structure has been a lively area of research and speculation. For more than half a century spectroscopy and other methods have been available to characterize the structures and shapes of molecules, particularly those that are rigid. However, most molecules are at least to some degree non-rigid and this non-rigidity plays an important role in such diverse areas as biological activity, energy transfer, and chemical reactivity. In addition, the large-amplitude vibrations present in non-rigid molecules give rise to unusual low-energy vibrational level patterns which have a dramatic effect on the thermodynamic properties of these systems. Only in recent years has a coherent picture of the energetics and dynamics of the conformational changes inherent in non-rigid (and semi-rigid) molecules begun to emerge. Advances have been made in a number of different experimental areas: vibrational (infrared and Raman) spectroscopy, rotational (microwave) spectroscopy, electron diffraction, and, most recently, laser techniques probing both the ground and excited electronic states. Theoretically, the proliferation of powerful computers coupled with scientific insight has allowed both empirical and ab initio methods to increase our understanding of the forces responsible for the structures and energies of non-rigid systems. The development of theory (group theoretical methods and potential energy surfaces) to understand the unique characteristics of the spectra of these floppy molecules has also been necessary to reach our present level of understanding. The thirty chapters in this volume contributed by the key speakers at the Workshop are divided over the various areas. Both vibrational and rotational spectroscopy have been effective at determining the potential energy surfaces for non-rigid molecules, often in a complementary manner. Recent laser fluorescence work has extended these types of studies to electronic excited states. Electronic diffraction methods provide radial distribution functions from which both molecular structures and compositions of conformational mixtures can be found. Ab initio calculations have progressed substantially over the past few years, and, when carried out at a sufficiently high level, can accurately reproduce (or predict ahead of time) experimental findings. Much of the controversy of the ARW related to the question of when an ab initio is reliable. Since the computer programs are readily available, many poor calculations have been carried out. However, excellent results can be obtained from computations when properly done. A similar situation exists for experimental analyses. The complexities of non-rigid molecules are many, but major strides have been taken to understand their structures and conformational processes.
Conformational Analysis Of Some Small Non Rigid Molecules
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Author : Michael Brian Kelly
language : en
Publisher:
Release Date : 1989
Conformational Analysis Of Some Small Non Rigid Molecules written by Michael Brian Kelly and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Molecular structure categories.
Excited States
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Author : Edward C. Lim
language : en
Publisher: Elsevier
Release Date : 2013-10-22
Excited States written by Edward C. Lim and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-22 with Science categories.
Excited States, Volume 7 is a collection of papers that discusses the excited states of molecules. The first paper reviews the rotational involvement in intra-molecular in vibrational redistribution. This paper analyzes the vibrational Hamiltonian as to its efficacy in detecting the manifestations of intra-molecular state-mixing in time-resolved and time-averaged spectroscopic measurements. The next paper examines the temporal behavior of intra-molecular vibration-rotation energy transfer (IVRET) and the effects of IVRET on collision, reaction, and the decomposition processes. This paper also describes how IVRET can decrease the anisotropy of the angular distribution of photo dissociating molecules that takes longer than the rotational period of disassociation. The third paper explains rotations and electronic decay by focusing on nonresonant light scattering, which is explained in the theory of radiationless transitions, when the exciting light source is included. The last paper shows how sub-Doppler techniques adapted from atomic physics can measure accurately dense rotational triplet structure and singlet-triplet couplings in high vibrational triplet levels. This book will prove helpful for researchers whose work involves physical chemistry or molecular chemistry and physicists involved in atomic or solid-state physics.
Conformational Analysis Of Flexible Molecules Using Steady State Fluorescence Energy Transfer
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Author : David Allen DeGoey
language : en
Publisher:
Release Date : 1994
Conformational Analysis Of Flexible Molecules Using Steady State Fluorescence Energy Transfer written by David Allen DeGoey and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with Conformational analysis categories.
Efficient Conformational Analysis Of Small Molecules
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Author : Ken David Yamaguchi
language : en
Publisher:
Release Date : 2001
Efficient Conformational Analysis Of Small Molecules written by Ken David Yamaguchi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Excited States V5
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Author : Edward Lim
language : en
Publisher: Elsevier
Release Date : 2012-12-02
Excited States V5 written by Edward Lim and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-02 with Science categories.
Excited States, Volume 5 consists of three concise and detailed chapters. These chapters cover the topics of excited-state potential surfaces of polyatomic molecules; vibronic spectroscopy of benzene; and quantum statistical mechanical (QSM) theory for molecular relaxation processes. Chapter 1 discusses excited-state potential surfaces with focus on ab initio calculations. Simple methods of computational schemes are also presented in this chapter. Chapter 2 reviews the excited electronic states of benzene. This chapter also includes the basic theory of benzene electronic excitations and the various types of spectroscopy (absorption, vibrational Raman, and electron-impact). Lastly, Chapter 3 presents a unified QSM theory, phenomenological theory of irreversible thermodynamics, and kinetics. The focus of QSM theory is on the nonlinear domain and is used to construct a nonlinear theory for the relaxation of excited molecules that are electric, vibrating, and rotating. This volume is a good reference for students and researchers studying in the field of chemistry and physics.
Conformational Analysis
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Author : G Chiurdoglu
language : en
Publisher: Elsevier
Release Date : 2012-12-02
Conformational Analysis written by G Chiurdoglu and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-02 with Science categories.
Conformational Analysis: Scope and Present Limitations contains the proceedings of the Brussels International Symposium on Conformational Analysis held in Brussels, Belgium, in September 1969. The papers focus on the theoretical aspects and applications of conformational analysis, such as those concerning the aliphatic and especially the cyclic series. Topics covered include the geometry of five-membered rings; conformational transmission in steroids; conformational aspects of N-quaternization; and applications of nuclear magnetic resonance spectrometry in conformational studies of cyclohexane derivatives. This book is comprised of 20 chapters and begins with a discussion on the conformational aspects of some five-membered ring compounds based mainly on observed (diffraction methods) and calculated torsional angles. The reader is then introduced to nuclear magnetic resonance studies of the conformations and conformational barriers in cyclic molecules; conformational studies of six-membered heterocycles; conformational transmission in steroids; and solvolytic cyclizations involving double bonds. The remaining chapters explore the conformational analysis of methylcyclohexane, cyclohexane systems, and carbonium ions; conformations of membrane-active cyclodepsipeptides; energetics of isomeric transition states and competitive reaction pathways in conformational analysis; and conformational aspects of the reaction of the 1-methylcyclodecane-l,6-diols with acid. This monograph will be of interest to organic chemists.
Conformational Analysis
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Author : Ernest L. Eliel
language : en
Publisher:
Release Date : 1967
Conformational Analysis written by Ernest L. Eliel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1967 with categories.
Conformational Analysis Of Molecules By Nmr Spectroscopy Using Vicinal 13c 13c Coupling Constants
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Author :
language : en
Publisher:
Release Date : 1996
Conformational Analysis Of Molecules By Nmr Spectroscopy Using Vicinal 13c 13c Coupling Constants written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
A series of one hundred and nine rigid and flexible molecules (dibenzofurans, biphenyls, fluorenes, fluorenones and diphenyl ethers) with a range of substituents have been studied with a view to obtaining conformational data from vicinal 13C-,13C coupling constants. The molecules were characterized primarily by nuclear magnetic resonance spectroscopy (proton, carbon-13, fluorine-19, nitrogen-15, heteronuclear (13C-1H)correlation spectroscopy, DEPT-90/DEPT-135, NOE spectroscopy). Finally, the INADEQUATE experiment was used to obtain 13C-13C coupling constants. Twelve novel crystal structures were obtained from the study, and conformations obtained for biphenyls and diphenyl ethers compared with conformational studies by other methods, indicating that the lowest energy conformations can be retained in both solid and solution states, provided that other factors, (e.g. crystal packing forces) are not dominant.Comparison of our data, using state-of-the-art techniques for assignments, with previous theoretical predictions of conformations from carbon chemical shifts proved unsatisfactory. Attempts to use vicinal carbon coupling constants to obtain a dihedral angle dependence were unsuccessful. For rigid molecules, vicinal coupling constants could not be assigned with confidence and the dihedral angle dependent contribution could not be quantified because of the multifactorial nature of these couplings. Previous literature strongly suggests that these coupling constants do not exhibit a dihedral angle dependence. Previous literature has also shown that the vicinal coupling constants required in the present study for the conformational analysis of biphenyls do not exhibit a dihedral angle dependence. The dihedral angle dependent contributions from vicinal coupling constants in certain diphenyl ethers were completely eclipsed by additional "through-space" coupling. The results of a molecular mechanics study showed that it was not possible to obtain conformer distributions for biphenyls or diphenyl ethers. Therefore, Karplus-type equations for these molecules could not be formulated. This work represents one of the most comprehensive and diverse NMR analyses of dibenzofurans, diphenyl ethers and biphenyls, and makes a significant contribution to the carbon coupling constant data currently available.