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Author: Abdulkadir Kocak Publisher: ISBN: Category : Ligands Languages : en Pages : 196
Book Description
Non-covalent interactions between metal ions and ligands such as water and methane have been extensively studied due to their biological and industrial importance. Gas phase studies can reveal the fundamental nature of these metal-ligand interactions. Photofragment spectroscopy is a powerful technique to investigate bond strengths, dissociation dynamics, molecular geometry and clustering and can be applied to electronic and vibrational spectroscopy. Using a home built apparatus, which combines ion production via laser ablation, separation via time-of-flight (TOF) mass spectrometry, laser excitation, and TOF fragment mass analysis, we have obtained electronic spectra of Co+(H2O) and vibrational spectra of M+(CH4)n (M=Co, Ni, Cu, Ag; n=1-4 or 1-6). The experimental techniques, apparatus, data acquisition and analysis employed throughout this thesis are described and explained in chapters 1 and 2. Chapter 3 discusses the electronic spectra of Co+(H2O), Co+(HOD) and Co+(D2O), measured from 13500 cm-1 to 18400 cm-1 using photodissociation spectroscopy. Transitions to four excited electronic states, with vibrational and partially resolved rotational structure are observed. The Co+-(H2O) binding energy is determined from the dissociation onset. The experiments and supporting calculations provide detailed information such as the electronic configuration of excited electronic states, how the Co+ electronic state affects the Co+-H2O bond strength, and how binding to Co+ changes the geometry of water. Chapter 4 discusses measurement and analysis of vibrational spectra of M+(CH4)m(Ar)3-m and M+(CH4)n (M=Co, Ni; m=1,2; n=3,4) in the C-H stretching region (2500-3100 cm-1). Interaction with the metal leads to large red shifts in the C-H stretches for proximate hydrogens. The extent of this shift is sensitive to the methane coordination (h2 vs. h3) and to the metal-methane distance. The structures of the complexes are determined by comparing measured spectra with those calculated for candidate structures. All complexes show h2 methane coordination and the d orbital occupancy determines which structures are preferred. Chapter 5 extends these studies to M+(CH4)n (M=Cu, Ag; n=1-6). Clusters have h2 methane coordination and prefer symmetrical structures due to the d10 spherical electronic configuration of M+. Clusters with n>4 also show features from second shell ligands. Chapter 6 discusses extending this work to metal cluster ion -methane interactions.
Author: Abdulkadir Kocak Publisher: ISBN: Category : Ligands Languages : en Pages : 196
Book Description
Non-covalent interactions between metal ions and ligands such as water and methane have been extensively studied due to their biological and industrial importance. Gas phase studies can reveal the fundamental nature of these metal-ligand interactions. Photofragment spectroscopy is a powerful technique to investigate bond strengths, dissociation dynamics, molecular geometry and clustering and can be applied to electronic and vibrational spectroscopy. Using a home built apparatus, which combines ion production via laser ablation, separation via time-of-flight (TOF) mass spectrometry, laser excitation, and TOF fragment mass analysis, we have obtained electronic spectra of Co+(H2O) and vibrational spectra of M+(CH4)n (M=Co, Ni, Cu, Ag; n=1-4 or 1-6). The experimental techniques, apparatus, data acquisition and analysis employed throughout this thesis are described and explained in chapters 1 and 2. Chapter 3 discusses the electronic spectra of Co+(H2O), Co+(HOD) and Co+(D2O), measured from 13500 cm-1 to 18400 cm-1 using photodissociation spectroscopy. Transitions to four excited electronic states, with vibrational and partially resolved rotational structure are observed. The Co+-(H2O) binding energy is determined from the dissociation onset. The experiments and supporting calculations provide detailed information such as the electronic configuration of excited electronic states, how the Co+ electronic state affects the Co+-H2O bond strength, and how binding to Co+ changes the geometry of water. Chapter 4 discusses measurement and analysis of vibrational spectra of M+(CH4)m(Ar)3-m and M+(CH4)n (M=Co, Ni; m=1,2; n=3,4) in the C-H stretching region (2500-3100 cm-1). Interaction with the metal leads to large red shifts in the C-H stretches for proximate hydrogens. The extent of this shift is sensitive to the methane coordination (h2 vs. h3) and to the metal-methane distance. The structures of the complexes are determined by comparing measured spectra with those calculated for candidate structures. All complexes show h2 methane coordination and the d orbital occupancy determines which structures are preferred. Chapter 5 extends these studies to M+(CH4)n (M=Cu, Ag; n=1-6). Clusters have h2 methane coordination and prefer symmetrical structures due to the d10 spherical electronic configuration of M+. Clusters with n>4 also show features from second shell ligands. Chapter 6 discusses extending this work to metal cluster ion -methane interactions.
Author: Christopher Copeland Publisher: ISBN: Category : Languages : en Pages :
Book Description
The study of the non-covalent interactions between metals ions and ligands such as water and methane are key to understanding many processes including solvation, homogeneous catalysis and metals in biology. Similarly, the study of interactions between transition metal ions and cluster ions with hydrocarbons is of great importance in the understanding of C-H activation reactions which are involved in generation of fuels. Gas-phase metal complexes are good models for understanding the intrinsic interactions between the metal and the ligand. Understanding the mechanisms behind these interactions can be done by characterizing the structure and bonding in the molecular reactants, products, and intermediates. This characterization is made possible by combining experimental spectroscopy with computational studies to provide insight into molecular geometries and binding characteristics of ions. In this work, we explore two non-covalent interactions involved in solvation and catalysis by studying entrance-channel complexes of the reactions of transition metal ions with water and methane respectively. The motivations, techniques, apparatus, data acquisition and analysis methods are discussed in Chapters 1 and 2. Chapter 3 discusses the electronic spectroscopy of the 7B1 and 7B2 excited states of Mn+(H2O) and Mn+(D2O) measured using photodissociation spectroscopy. Progressions in the Mn+-H2O stretch are observed in both excited states, with the in-plane-bend also observed in the first excited state of Mn+(H2O), and the out-of-plane bend observed in the second excited state of both Mn+(H2O) and Mn+(D2O). Partially resolved rotational structure in the first excited state is analyzed. Chapter 4 discusses the vibrational spectroscopy of Fex+(CH4)n. Vibrational spectra are measured for Fe2+(CH4)n (n=1-3), Fe3+(CH4)n (n=1-3), and Fe4+(CH4)4 in the C-H stretching region (2650-3100 cm−1) using photofragment spectroscopy, monitoring loss of CH4. All spectra are dominated by an intense peak around 2800 cm−1, due to the symmetric C-H stretch. Density functional theory calculations are used to identify possible structures and geometries and to predict the spectra. Chapter 5 identifies possible extensions of the Chapter 3 and 4 studies to new first, second, and third-row transition metal-water and metal-methane complexes, as well as complexes of metal cluster ions with water and methane. Lastly, Chapter 5 describes alterations to the instrument.
Author: Pavel Hobza Publisher: Royal Society of Chemistry ISBN: 1847558534 Category : Science Languages : en Pages : 239
Book Description
Co-authored by an experimentalist (Klaus M3ller-Dethlefs ) and theoretician (Pavel Hobza), the aim of this book is to provide a general introduction into the science behind non-covalent interactions and molecular complexes using some important experimental and theoretical methods and approaches.
Author: Muhammad Affawn Ashraf Publisher: ISBN: Category : Languages : en Pages :
Book Description
Understanding the non-covalent interaction between metals and small ligands such as methane and ammonia is of key importance because of their industrial and biological applications. However, these interactions are difficult to study and quantify in the bulk phase due to the interaction with neighboring molecules or atoms. Gas phase spectroscopy of mass-selected clusters is a powerful technique that overcomes this challenge by allowing clusters with known composition to be studied in the gas phase. In this thesis, we investigate the interaction between three types of small molecular ligands with metal and metal cluster ions, and answer questions about their geometries and bonding by employing photofragment spectroscopy and density functional theory (DFT). The vibrational spectra of Fe2+ (CH4)n (n=1-3) are dominated by a single intense peak about 100 cm−1 redshifted from the bare methane C-H stretch suggesting that the interaction is similar among the clusters. Comparison with calculations carried out using DFT methods indicate that the observed spectra are due to octet complexes with [eta]3 hydrogen coordination between methane ligands and the Fe atoms and that the observed peak is due to the symmetric C-H stretch. Understanding the geometry of these complexes reveals the increased extent of covalency in bonding responsible for selective reactivity as the size of the metal core increases. Vibrational spectra of Alx+(C2H6)n (x=1,2; n=1-3) have distinct complex features, and are very different from spectra of typical methane ligated metal ion complexes. The spectra show that the most intense peak is ~200 cm−1 red shifted from the bare ethane C-H stretches, enough to exhibit Fermi resonance between the bends and the stretches. Comparison with spectra of Al+(C2H6)1−6 reveals larger red shifts for the ethane complexes, indicating that ethane interacts more strongly with Alx+ than methane. We find that scaled harmonics using dispersion corrected DFT methods do not successfully predict the spectra, and we employ dressed local mode Hamiltonian method to predict the observed spectra and identify possible isomers. These results suggest that more rigorous DFT models are needed to predict metal-ion hydrocarbon ligand interaction. Calculations in best agreement with the observed spectra predict that ethane ligands tend to bind the same side of the Alx+ indicating dispersion interaction among the ligands, and that geometries are favored where the metal core is interacting with hydrogens from both methyl groups in the ethane. These findings are crucial in understanding how C-H bond strength and the size of hydrocarbon affect bonding in metal-ion hydrocarbon complexes. The electronic spectrum of the Cr+(NH3) complex measured via loss of NH3 ligand exhibits spin orbit splitting suggesting a transition from the ground 6A1 state to the excited 6E ([pi]) state. The spectrum shows a thermodynamic onset of photodissociation at 14850 cm−1 providing a precise upper limit on the binding energy. Comparison with the A ← X transition in Cr+ reveals that the excited Cr+(NH3) binds roughly 3000 cm−1 less strongly than the ground state Cr+(NH3).
Author: N. Russo Publisher: Springer Science & Business Media ISBN: 940100191X Category : Science Languages : en Pages : 595
Book Description
In September 2002, a NATO-ASI was held in Cetraro (CS), Italy on the theme of "Metal-Ligand Interactions in Molecular-, Nano-, Micro-, and Macro-systems in Complex Environments". This event has followed the previous ones held in the same place in 1991, 1994 and 1998. In the present and the previous schools a broad interdisciplinary cross-section of experimental and theoretical researchers, interested in a better understanding of metal-ligand interactions from different viewpoints, was linked together to exchange experience, to review the state-of-the-art, to indicate new techniques and methods, to explore new fields and perspectives. Particular emphasis was given to the problems related with the crossing from molecular systems to nano-, macro-and micro-scale materials and to the effects of the environment on the properties of the molecular systems. The school was organized around lectures and special research seminares given by leading experts in the following fields: • metal clusters • inorganic complexes and materials • surface phenomena • adsorption and catalysis • organic and bio-inorganic systems • ab initio theory • density functional theory • classical and quantum dynamics This volume contains the formal lectures and selected contributed papers and describes the main aspects and problems tackled during the 12 days of the event.
Author: A. Pullman Publisher: Springer Science & Business Media ISBN: 9401763925 Category : Science Languages : en Pages : 397
Book Description
The 9th Jerusalem Symposium was dedicated to the memory of Professor Ernst David Bergmann. An imposing and deeply moving memorial session, chaired by Professor Ephraim Katzir, the President of the State of IsƯ rael and a close friend of Professor Bergmann preceded the Symposium itself. During this session, Professor Bergmann's personality, scienƯ tific achievements and contributions to the development of his country were described and praised, besides President Katzir, by Professor A. Dvoretzky, President of the Israel Academy of Sciences and Humanities, Professor D. Ginsburg, Dean of the Israel Institute of Technology in Haifa and the author of these lines. May I just quote short extracts from these speeches. President Katzir: "As we open this ninth in the series of symposia initiated in 1967, it is difficult for me as, I am sure, for many of Ernst Bergmann's friends, co-workers and students, to be here without him. He was not only a great scientist and a beloved teacher, he was one of the most important founders of science in this country. To him we owe many institutes and the establishment here of many branches of science." Professor Dvoretzky: "Ernst Bergmann's greatness did not stem from one component overshadowing all the others. It was a multifaceted greatƯ ness consisting of the harmonious co~lescing of seemingly contrasting entities into a wonderful unity "
Author: Christoph A. Schalley Publisher: John Wiley & Sons ISBN: 0470131152 Category : Science Languages : en Pages : 593
Book Description
Details the many benefits of applying mass spectrometry to supramolecular chemistry Except as a method for the most basic measurements, mass spectrometry (MS) has long been considered incompatible with supramolecular chemistry. Yet, with today's methods, the disconnect between these two fields is not warranted. Mass Spectrometry and Gas-Phase Chemistry of Non-Covalent Complexes provides a convincing look at how modern MS techniques offer supramolecular chemists a powerful investigatory toolset. Bringing the two fields together in an interdisciplinary manner, this reference details the many different topics associated with the study of non-covalent complexes in the gas phase. The text begins with brief introductions to supramolecular chemistry and such relevant mass spectrometric methods as ionization techniques, analyzers, and tandem MS experiments. The coverage continues with: How the analyte's transition into the gas phase changes covalent bonding How limitations and pitfalls in analytical methods may produce data misinterpretations Artificial supramolecular aggregates and their examination Biomolecules, their complexes, and their examination After the general remarks making up the first section of the book, the following sections describe specific experimental procedures and are illustrated with numerous examples and short tutorials. Detailed citations end each chapter. Mass spectrometrists, supramolecular chemists, students in these fields, and interested readers from other disciplines involving the study of non-covalent bonds will all value Mass Spectrometry and Gas-Phase Chemistry of Non-Covalent Complexes as an innovative and practical resource.
Author: Jean-Pierre Schermann Publisher: Elsevier ISBN: 0080558224 Category : Science Languages : en Pages : 499
Book Description
Spectroscopy and Modeling of Biomolecular Building Blocks presents an overview of recent advances in the intertwining of the following research fields: photon and electron spectroscopy, quantum chemistry, modelling and mass-spectrometry. The coupling of these disciplines offers a new point of view to the understanding of isolated elementary building blocks of biomolecules and their assemblies. It allows the unambiguous separation between intrinsic properties of biomolecular systems and those induced by the presence of their environment. The first chapters provide background in modelling (I), frequency-resolved spectroscopy using microwave, infrared and UV photons, time-resolved spectroscopy in the femtosecond domain and energy-resolved electron spectroscopy (II) and production of gas-phase neutral and ionic biomolecular species, mass-spectrometry, ion mobility and BIRD techniques (III). Chapter IV is devoted to case studies of gas-phase experimental investigations coupled to quantum or classical calculations. The topics are structural studies of nucleobases and oligonucleotides, peptides and proteins, sugars; neuromolecules; non-covalent complexes; chiral systems, interactions of low-energy electrons with biomolecules in the radiation chemistry context and very large gas-phase biomolecular systems. The fifth chapter concerns the link between gas-phase and liquid-phase. Different treatments of solvation are illustrated through examples pointing out the influence of progressive addition of water molecules upon properties of nucleobases, peptides, sugars and neuromolecules. Offer a new perspective to the understanding of isolated elementary building blocks of bio molecules Includes case studies of experimental investigations coupled to quantum or classical calculations
Author: Abdulkadir Kocak
Author: Abdulkadir Kocak
Author: Christopher Copeland
Author: Pavel Hobza
Author: Muhammad Affawn Ashraf
Author: N. Russo
Author: Azam Rahimi
Author: A. Pullman
Author: Christoph A. Schalley
Author: Jean-Pierre Schermann
Author: John Steven Loring