Using The Intervalence Charge Transfer Band In Mixed Valence Mixed Protonated Metal Dithiolene Complexes To Follow Ground State Proton Coupled Electron Transfer

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Using the Intervalence Charge Transfer Band in Mixed Valence Mixed Protonated Metal Dithiolene Complexes to Follow Ground State Proton-coupled Electron Transfer

Author : Steven Kennedy
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (959 download)

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Book Synopsis Using the Intervalence Charge Transfer Band in Mixed Valence Mixed Protonated Metal Dithiolene Complexes to Follow Ground State Proton-coupled Electron Transfer by : Steven Kennedy

Download or read book Using the Intervalence Charge Transfer Band in Mixed Valence Mixed Protonated Metal Dithiolene Complexes to Follow Ground State Proton-coupled Electron Transfer written by Steven Kennedy and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton-coupled electron transfer (PCET) is an important phenomenon for controlling charge mobility in chemistry and biology because it allows the simultaneous movement of a proton and electron with a lower energy barrier than otherwise possible. Much work has been done on PCET systems, particularly for excited state processes in which charge mobility can be easily followed using pump-probe methods. However, while excited state PCET is utilized for the initial step of many solar energy-driven processes, including photosynthesis, ground state PCET is critical for all subsequent processes, including regeneration of solar cells. Homogeneous ground state PCET systems are of particular interest for this regeneration, but no convenient method exists for measuring parameters governing such reactions. Our work is directed toward understanding homogeneous ground state PCET reactions as probed using solution-phase steady-state methods.In order to establish a probe for these homogeneous ground state PCET reactions, we design self-exchange model systems for PCET in analogy to classical electron transfer. With our first model system, [Ni(2,3-pyrazinedithiol)2], we demonstrate that protonation of a mixed valence species, generating a mixed valence mixed protonated (MVMP) state, results in severe reduction of the electronic coupling intimately connected with electron transfer kinetics. This ligand-based mixed valence molecule can be asymmetrically protonated, rendering the MVMP state. We characterize the structural, electronic, vibrational, and magnetic properties of this complex in five different states, including the mixed valence and MVMP states, and then analyze the intervalence charge transfer (IVCT) band to demonstrate a five-fold reduction in electronic coupling upon protonation. We conclude that the reduction in electronic coupling is a result of the asymmetry of the electronic orbitals of the redox sites that results from the asymmetric protonation. As a result, the IVCT band is established as a probe for interrogating the electronic coupling in the MVMP state, which reflects the change in the PCET potential energy landscape as a result of protonation. This conclusion suggests that many systems designed to link electron and proton transfer will also exhibit a decrease in electronic coupling upon protonation as the strength of the interaction between redox and protonation sites is increased.After having established the MVMP state as a useful model system to study homogeneous ground state PCET, we explored structural modifications to control the communication between electron transfer and protonation sites. These studies allow for a more fine-tuned response to protonation in a series of metal dithiolene complexes when moving from the mixed valence to the MVMP state. We investigate the effect of changing the bridge between ligands simply by changing the metal center. In this study, we find nearly five-fold decreases in electronic coupling for both Ni and Pt, while, for the Pd complex, the electronic coupling is reduced to the point that the IVCT band is no longer observable. We ascribe the reduction in electronic coupling to charge pinning induced by asymmetric protonation. The more severe reduction in coupling for the Pd complex is a result of greater energetic mismatch between ligand and metal orbitals, reflected in the smaller electronic coupling for the pure mixed valence state. This work demonstrates that the bridging metal center can be used to tune the electronic coupling in both the mixed valence and MVMP states, as well as the magnitude of change of the electronic coupling that accompanies changes in protonation state.In addition, we explore 2,3-quinoxalinedithiol and 2,3-pyridinedithiol ligands, which are structurally altered versions of the above dithiolene ligands in which the aromatic rings are extended and the number of ring nitrogen atoms is reduced, respectively. With these complexes, we find that these modifications cause changes in the electronic coupling both in the mixed valence and MVMP states, and the degree of response to protonation, generating the MVMP state, is controlled as well. For [Ni(2,3-quinoxalinedithiol)2], the only complex with the 2,3-quinoxalinedithiol ligand that reversibly generated its MVMP state, the IVCT band, and hence the electronic coupling, disappeared upon protonation. This disappearance of electronic coupling resulted from additional electron density being placed on the ligands and not being channeled into ligand-ligand electronic coupling through the metal center. The complex [Ni(2,3-pyridinedithiol)2] retained its IVCT band in the MVMP state, but with less electronic coupling than in the 2,3-pyrazinedithiol analogue. This lower value of electronic coupling is a result of higher energy ligand orbitals that overlap with the metal orbitals to a lesser extent.Lastly, we explore the [Au(2,3-pyrazinedithiol)2] complex, which is appealing for the non-innocent character of its ligands. We report its synthesis and characterization, along with electrochemistry and spectrophotometric response to acid titration. This molecule did not exhibit generation of its singly oxidized mixed valence species, so it does not permit direct comparison to the mixed valence species of the other metal dithiolene compounds in this study.Ultimately, our investigations of these metal dithiolene MVMP model systems allow for more informed control over PCET self-exchange transformations, as interrogated through their IVCT bands. The IVCT band is established as a probe for monitoring the effect of asymmetric protonation upon electronic coupling, seeking to extend classical electron transfer model systems into the domain of PCET. The interdependence of asymmetric protonation and electron transfer will allow for better control over PCET charge mobility through structural modifications, which will allow for more rational design of systems that undergo ground state PCET in device applications.

Dynamics of Electron Transfer at the Localized-to-delocalized Transition of Mixed Valency

Author : Starla Demorest Glover
Publisher :
ISBN 13 : 9781124703428
Total Pages : 175 pages
Book Rating : 4.7/5 (34 download)

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Book Synopsis Dynamics of Electron Transfer at the Localized-to-delocalized Transition of Mixed Valency by : Starla Demorest Glover

Download or read book Dynamics of Electron Transfer at the Localized-to-delocalized Transition of Mixed Valency written by Starla Demorest Glover and published by . This book was released on 2011 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigations into the dynamics of picosecond electron transfer in a series of mixed valence systems of the type [Ru3([mu]3-O)(OAc)6(py)(CO)-([mu]2-BL)- Ru3([mu]3-O)(OAc)6(py)(CO)]−1, where BL = 1,4-pyrazine or 4,4'-bipyridine and py = 4-dimethylaminopyridine, pyridine, or 4-cyanopyridine are described. Solvent and temperature dependence into the rate of ground state intramolecular electron transfer is probed by infrared analysis of [nu](CO) bandshapes where simulated rate constants yield to rates ranging from 4 E 11 to 3 E 12 s-1. Correlations between rate constants and solvent properties including solvent reorganization energy, optical and static dielectric constants, microscopic solvent polarity, viscosity, principal rotational moments of inertia, and solvent dipolar relaxation times, have been examined. Correlations revealed a marked lack of dependence on electron transfer rates with respect to solvent thermodynamic parameters, and a strong dependence on solvent dynamic parameters. This is consistent with electron transfers having very low activation barriers that approach zero. Temperature dependent studies revealed electron transfer rates accelerated as the freezing points of solvent solutions were approached with a sharp increase in the rate of electron transfer upon freezing. This has been attributed to a localized-to-delocalized transition in these mixed valence ions at the solvent phase transition. This non-Arrhenius behavior is explained in terms of decoupling the slower solvent motions involved in the frequency factor, [nu]N, which weights faster vibrational promoter modes that increase the value of [nu]N. Solvent and temperature dependence of optically induced intramolecular electron transfer is probed by analysis of intervalence charge transfer bands in NIR spectra. The application of a semi-classical three-state model for mixed valency best describes the electronic spectra wherein is the appearance of two intervalence bands; a band which has metal-to-metal-charge-transfer character and another having metal-to-ligand-charge-transfer character. This three-state model fully captures the observed spectroscopic behavior where the MBCT transition increases in energy and the MMCT band decreases in energy as electronic communication increases through the series of mixed valence ions. The solvent and temperature dependence of the MBCT and MMCT electronic transitions is found to persist as coalescence of infrared vibrational spectra suggest ground state delocalization on the vibrational timescale. The solvent and temperature dependence of the MBCT and MMCT electronic transitions defines the mixed valence complexes as lying at the borderline of delocalization. Fine tuning the electronic coupling in the series of dimers has allowed for the resolution of a full Class II, early Class II/III, late Class II/III to Class III systems and the influence of solvent dynamics in each regime. These investigations have prompted the redefinition of borderline Class II/III mixed valency to account for outer sphere (solvent) contributions to electron transfer; in nearly delocalized systems, solvent dynamics localized otherwise delocalized electronic ground states. Further, studies explore the origins and dynamics behind spectral coalescence of vibrational [nu] (CO) bandshapes in [Ru3([mu]3-O)(OAc)6(py)(CO)-([mu]2-BL)- Ru3([mu]3-O)(OAc)6(py)(CO)]−1 systems and a picosecond isomerization in square pyramidal Ru(S2C4F6)(P(C6H5)3)2(CO) system.

From Nanoparticles to Non-Covalent Interactions

Author : Gabriele Canzi
Publisher :
ISBN 13 : 9781321011050
Total Pages : 204 pages
Book Rating : 4.0/5 (11 download)

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Book Synopsis From Nanoparticles to Non-Covalent Interactions by : Gabriele Canzi

Download or read book From Nanoparticles to Non-Covalent Interactions written by Gabriele Canzi and published by . This book was released on 2014 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the intricacies of inner sphere electron transfer has been a challenge for nearly 50 years. Since the preparation of the Creutz-Taube ion extensive research in inorganic mixed valence systems has been performed. We employ coalescence of [nu](CO) bandshapes observed in the 1-D infrared (IR) spectra of mixed valence complexes to determine rate constants of electron transfer (ET). Herein we report synthesis, characterization, and spectroscopy of Ru3O clusters bound to metallic nanoparticles, and report ET rates in the "ultrafast" regime. We observe that ET rates are faster when there is favorable electronic alignment between the Ru clusters and the Au nanoparticle. In addition, results show that ground state ET rate constants that are in the "ultrafast" regime depend on the pre-exponential term within the frequency factor, [nu]N not the activation energy as expected in a system undergoing ergodic electron transfer. We extended our knowledge of these complexes by studying ET at a semiconducting nanoparticle interface. Working in collaboration with Prof. Emily Weiss at Northwestern University, a complementary view of the parameters that govern ET in such systems has been developed by investigating ET rates between the triruthenium clusters and QDs. The photoinduced electron transfer rate from photoexcited CdSe QDs to triruthenium clusters having either a pyridine-4-carboxylic acid or a 4-mercaptopyridine linkage are reported. Results show that the intrinsic charge separation rate constant (kCS,int), is approximately seven times faster for a thiol linked cluster compared to a nicotinic acid bound cluster. Thus the charge transfer rates between colloidal quantum dots and redox-active ligands adsorbed to their surfaces can be tuned through the choice of the coordinating headgroup of the ligand. We report that exchange of electrons across hydrogen bonds can increase the strength of typically weak interactions. A thermodynamically stable mixed valence dimer is obtained upon the one electron reduction of a Ru3O cluster with a isonicotinic acid ancillary ligand. Observed intervalence charge transfer bands (IVCT) indicate significant coupling between the two Ru centers through linked by a hydrogen bonding interaction. The IVCT bands are found to be best explained by a semi-classical 3-state model, further highlighting the importance of the bridging interaction in these systems. Additionally, we report that the electronic coupling between two metal centers can be modulated by simple ancillary ligand substitution. The wavefunction overlap of two metal centers bridged by a hydrogen bond is found to be non-zero. We report a series of new Ru3O clusters with ancillary ligands capable of pi-stacking in solution upon a single electron reduction. Large splittings are observed berween the reductions in the electrochemical responses of these newly synthesized systems. The effects on the electrochemical splitting of the reduction waves by donating and withdrawing ligands on the "bridge" are compared. A crystal structure of the ground state shows no significant evidence of pi-pi interaction between clusters in solution. The major themes of this thesis are the role of electronic coupling, Hab, on long range ET in supramolecular mixed valence systems, and the importance of the bridging interaction in modulating Hab in these systems.

Photoinduced Mixed-valency and Delocalization Dynamics in Strongly Coupled Multinuclear Ruthenium Complexes

Author : Jane Susan Henderson
Publisher :
ISBN 13 : 9781321848304
Total Pages : 10 pages
Book Rating : 4.8/5 (483 download)

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Book Synopsis Photoinduced Mixed-valency and Delocalization Dynamics in Strongly Coupled Multinuclear Ruthenium Complexes by : Jane Susan Henderson

Download or read book Photoinduced Mixed-valency and Delocalization Dynamics in Strongly Coupled Multinuclear Ruthenium Complexes written by Jane Susan Henderson and published by . This book was released on 2015 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-valence dimers of the type Ru3(O)(OAc)6(CO)L-BL-Ru3(O)(OAc)6(CO)L (BL = bridging ligand and L = a pyridyl ligand) form strongly coupled systems in their [Ru3III,III,II-BL- Ru3III,II,II]- state, observed by intervalence charge transfer (IVCT) bands in the near-IR. Ancillary ligand substitution has been shown to control bimolecular electron transfer rates from electronically excited zinc tetraphenylporphyrin (ZnTPP); quenching constants, kq, for 3ZnTPP* are 3.0 × 109, 1.5 × 109, and 1.1 × 109 M−1 s−1 for BL = pyrazine (pz), L = 4-cyanopyridine (cpy), pyridine (py), or 4-dimethylaminopyridine (dmap), respectively. The preparation, electrochemistry, and spectroscopic characterization of three new species, Ru3(O)(OAc)6(CO)(ZnTPPpy)-pz-Ru3(O)(OAc)6(CO)L, where ZnTPPpy = zinc(II) 5-(4-pyridyl)- 10,15,20-triphenylporphyin and L = dmap, py or cpy, are reported. Observation of IVCT band growth under continual photolysis ([lambda]exc = 568 nm) confirms a phototriggered intramolecular electron transfer from Zn porphyrin to the Ru3O donor-bridge-acceptor dimer, resulting in a strongly coupled mixed-valence species. Femtosecond transient absorption spectroscopy was implemented to follow photoinduced electron transfer reactions in the series of asymmetric porphyrin-coordinated dyads. Excitation of the porphyrin subunit resulted in electron transfer to the Ru3O dimer with a time constant [tau] ≈ 0.6 ps. The intramolecular electron transfer was confirmed by excitation of the Ru3O MLCT, which resulted in the formation of a vibrationally unrelaxed porphyrin ground state. Under both excitation experiments, the back electron transfer was extremely fast ([tau]CR

Spectroscopic Investigation of Ground State Charge Transfer in Organic Mixed-valence and Charge-transfer Systems

Author : Angela Bischof
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (951 download)

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Book Synopsis Spectroscopic Investigation of Ground State Charge Transfer in Organic Mixed-valence and Charge-transfer Systems by : Angela Bischof

Download or read book Spectroscopic Investigation of Ground State Charge Transfer in Organic Mixed-valence and Charge-transfer Systems written by Angela Bischof and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron transfer processes are widespread in chemistry, and form the basis of photosynthetic systems and molecular electronic devices. However, studying electron transfer processes in these systems directly can be difficult. In order to understand the fundamental processes in these systems, charge transfer (CT) and mixed-valence (MV) compounds have been used extensively as model systems to study the basics of electron transfer reactions under various conditions. This dissertation uses steady-state spectroscopic analyses to determine how structure affects electronic coupling and charge delocalization in several MV and CT systems that are of interest for understanding the fundamental processes that occur in organic devices. In Chapter 2, we find that the introduction of an ethylene bridging ligand between two bis(alkoxy)benzene redox sites increases the intramolecular electronic coupling when compared to the system in which the redox active sites are directly connected, despite an increase in distance. We quantify the increase in coupling as a function of both distance and steric effects. Chapter 3 focuses on the systematic investigation of how van der Waals forces control the electronic coupling in non-covalently bound organic mixed-valence naphthalene diimide dimers, and we find that, in general, as the van der Waals forces in the intermolecular complex increase so does the electronic coupling. Chapter 4 focuses on the analysis of the CT band in donor-acceptor charge-transfer liquid crystals (DACLCs) and uses resonance Raman spectroscopy to investigate the phase-dependence of the charge transfer transition and the vibrational modes that are associated with this transition. Overall, this dissertation contributes to the fundamental understanding of how structure impacts charge transfer in organic MV and CT systems.

Electron Transfer and Delocalization in Mixed-valence Complexes

Author : Casey Hughes Londergan
Publisher :
ISBN 13 :
Total Pages : 320 pages
Book Rating : 4.:/5 (318 download)

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Book Synopsis Electron Transfer and Delocalization in Mixed-valence Complexes by : Casey Hughes Londergan

Download or read book Electron Transfer and Delocalization in Mixed-valence Complexes written by Casey Hughes Londergan and published by . This book was released on 2003 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Building Model Systems to Understand Proton-Coupled Electron Transfer in Heme

Author : Christina J. Hanson
Publisher :
ISBN 13 :
Total Pages : 111 pages
Book Rating : 4.:/5 (846 download)

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Book Synopsis Building Model Systems to Understand Proton-Coupled Electron Transfer in Heme by : Christina J. Hanson

Download or read book Building Model Systems to Understand Proton-Coupled Electron Transfer in Heme written by Christina J. Hanson and published by . This book was released on 2013 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton-Coupled Electron Transfer (PCET) is an important mechanistic motif in chemistry, which allows for efficient charge transport in many biological systems. We seek to understand how the proton and electron motions are coupled in a bidirectional system allowing for individual turning of the kinetics and thermodynamics. The target of interest is a biomimedic heme system allowing for a detailed mechanistic study of the formation of the oxidation states of heme, of particular interest the highly reactive Fe(IV)=O species. The bidirectional model is prepared using a hangman porphyrin with an axially coordinated to the metal center, and the electron transfer event is triggered by excitation of the porphyrin. The synthesis of this motif is discussed as well as initial studies into the binding of a coordinated electron acceptor to the metal center. In the future, the excited state of the acceptor will be used to trigger the electron transfer portion of the PCET event. To understand the signatures of different electron acceptors and binding to the metal center, a redox inactive zinc porphyrin is used as a model to allow for longer excited state lifetimes and well known transient signatures. Three diimide acceptors have been coordinated through a pyridine ring to the metal center of the porphyrin, and electron transfer was triggered both by excitation of the porphyrin and the acceptor. Lifetimes of the charge separated state were determined using picoseconds and nanosecond transient absorption. The acceptors are then coordinated to a symmetrical iron porphyrin in an attempt to understand the behavior of charge separation in the more complicated open d shell system. Spectroscopic data of both systems is shown.

Charge Transfer in Multiple Site Chemical Systems

Author : T. J. Meyer
Publisher :
ISBN 13 :
Total Pages : 18 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis Charge Transfer in Multiple Site Chemical Systems by : T. J. Meyer

Download or read book Charge Transfer in Multiple Site Chemical Systems written by T. J. Meyer and published by . This book was released on 1985 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report covers work done by the author in both mixed-valence dimers and metallopolymers. Concerning the dimers, crystal structures of related monomers were obtained to judge the adequacy of classical approximations in calculating inner-sphere vibrational trapping. A series of homometallic and heterometallic dimers were prepared and a relationship between redox asymmetry and intervalence transfer absorption band energy was found. Electronic structure was observed in the intervalence transfer absorption band of an OS(II)-Os(III) mixed-valence dimer, owing to the presence of well-separated spin orbit states in Os(III). Other dimers were prepared to study the transitions between various states within the dimers. Both metal to metal and ligand to ligand electron transfer was seen in optically prepared mixed-valence dimers. Concerning the polymers, redox-site incorporation into poly-vinylpyridine, P-chlorosulfonated polystyrene and oxidatively electro-polymerized films were studied. Characterization and stability of these films as well as comparison to monomeric analogues was accomplished. Practical application of the metallopolymers include their use as a chromophore in a photoelectrochemical cell and as a catalyst for the oxidation of C1- to C12.

Intervalence Transfer in Mixed-valence Complexes of Ruthenium and Iron

Author : Michael Jay Powers
Publisher :
ISBN 13 :
Total Pages : 398 pages
Book Rating : 4.:/5 (42 download)

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Book Synopsis Intervalence Transfer in Mixed-valence Complexes of Ruthenium and Iron by : Michael Jay Powers

Download or read book Intervalence Transfer in Mixed-valence Complexes of Ruthenium and Iron written by Michael Jay Powers and published by . This book was released on 1977 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Intervalence Electron Transfer in Mixed-valence Compounds

Author : Bruce Conrad Bunker
Publisher :
ISBN 13 :
Total Pages : 416 pages
Book Rating : 4.:/5 (563 download)

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Book Synopsis Intervalence Electron Transfer in Mixed-valence Compounds by : Bruce Conrad Bunker

Download or read book Intervalence Electron Transfer in Mixed-valence Compounds written by Bruce Conrad Bunker and published by . This book was released on 1979 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Proton-Coupled Electron Transfer at Nickel Pincer Complexes

Author : Felix Schneck
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (112 download)

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Book Synopsis Proton-Coupled Electron Transfer at Nickel Pincer Complexes by : Felix Schneck

Download or read book Proton-Coupled Electron Transfer at Nickel Pincer Complexes written by Felix Schneck and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of metal coordination on carbon-centered proton-coupled electron transfer processes is an attractive field of research. Reported literature is limited to thermodynamic investigations and substrate oxidation using C-H bond formation at metal complexes is not reported. Comparison of organic HAT processes with related processes in coordination compounds suggests similar linear free energy relationships for N-H and O-H bond dissociation/formation. This thesis reports the synthesis of nickel pincer complexes containing a C-basic site and their redox and protonation reactivity. Oxid...

Modeling the Reactivity of Proton Coupled Electron Transfer at the Surface of Heterogeneous Metal Oxide Materials Through the Use of Polyoxometalate Clusters

Download Modeling the Reactivity of Proton Coupled Electron Transfer at the Surface of Heterogeneous Metal Oxide Materials Through the Use of Polyoxometalate Clusters PDF Online Free

Author : Alex A. Fertig
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)

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Book Synopsis Modeling the Reactivity of Proton Coupled Electron Transfer at the Surface of Heterogeneous Metal Oxide Materials Through the Use of Polyoxometalate Clusters by : Alex A. Fertig

Download or read book Modeling the Reactivity of Proton Coupled Electron Transfer at the Surface of Heterogeneous Metal Oxide Materials Through the Use of Polyoxometalate Clusters written by Alex A. Fertig and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Charge transfer reactions are a crucial component to many biologically and technologically relevant processes. It has been shown that these reactions typically occur in the presence of charge compensating cations, such as protons, in a process commonly referred to as proton coupled electron transfer (PCET). The energetic benefits of performing charge transfer reactions through PCET has inspired a significant amount of research into understanding the foundation aspects of these reactions, and in particular, the study of PCET at heterogeneous metal oxides materials has resulted in substantial advancement toward processes such as catalysis and energy storage and transformations. However, challenges in mechanistic analysis of these reactions have resulted in researchers turning to alternative methods to study the ability for metal oxide compounds to perform PCET. One promising class of compounds are polyoxometalate clusters, where the ability to synthetize atomically precises structures allows these compounds to act as analogous for their extended state congeners. This work will focus on exploiting the advantages of utilizing polyoxometalates to further our understanding of PCET at the surface of metal oxide materials. Chapter 2 begins by establishing the ability to quantify the thermochemical parameters required for the transfer of both protons and electrons at polyoxovanadate-alkoxide clusters through multiple methods. Additionally, this chapter explores the correlation between the thermodynamic driving force for PCET and the overall rate of the charge transfer process through the Marcus cross relation. Chapter 3 provides a follow-up analysis of further reduced versions of the polyoxovanadate cluster, where in addition to quantification of the strength of surface bound hydroxide ligands, these clusters are applied toward the activation of small molecules, such as O2, in order to from both hydrogen peroxide and water. Chapter 4 analyzes the physicochemical consequences of modification of the surface chemistry of polyoxometalate cluster through organic functionalization. Additionally, this work begins to analyze the impact electronic communication at the metal oxide core imparts on the ability for PCET to occur. Chapter 5 continues my investigation into surface reactivity at metal oxide clusters by limiting reactivity toward H-atom transfer to terminal oxide ligands at the surface of the cluster. By localizing the active site to a V=O site, formation of an oxygen atom deficient species is formed as a result of hydrogenation of the oxygen, and evolving H2O as a result. Overall, the study of PCET at polyoxometalates provides invaluable insight into the surface localized reactivity at extended state metal oxide materials and will aid in the advancement in the design of efficient heterogeneous catalysts"--Pages xii-xiii.

Intramolecular Electron Transfer in Mixed-valence Triarylamines

Author : Kelly Lancaster
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (642 download)

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Book Synopsis Intramolecular Electron Transfer in Mixed-valence Triarylamines by : Kelly Lancaster

Download or read book Intramolecular Electron Transfer in Mixed-valence Triarylamines written by Kelly Lancaster and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-valence compounds are of interest as model systems for the study of electron transfer reactions. The intramolecular electron transfer processes and patterns of charge delocalization in such compounds depend on the interplay between the electronic (V) and the vibronic (L) coupling. One can obtain both parameters from a Hush analysis of the intervalence band that arises upon optical intramolecular electron transfer if the band is intense and well-separated from other bands. This is quite often the case for mixed-valence triarylamines. As such, both Hush analysis and simulation of the intervalence band are widely used to classify these compounds as charge localized (class-II) or delocalized (class-III). Yet one must estimate the diabatic electron transfer distance (R) to calculate V in the Hush formalism. For mixed-valence triarylamines, R is commonly taken as the N-N distance; we show this to be a poor approximation in many cases. The activation barrier to thermal intramolecular electron transfer in a class-II mixed-valence compound is also related to the parameters V and L. Thus, if one can capture the rate of thermal electron transfer at multiple temperatures, then two experimental methods exist by which to extract the microscopic parameters. One technique that is widely used for organic mixed-valence compounds is variable-temperature electron spin resonance (ESR) spectroscopy. But this method is only rarely used to determine thermal electron transfer rates in mixed-valence triarylamines, as the electron transfer in most of the class-II compounds with distinct intervalence bands is too fast to observe on the ESR timescale. We show, for the first time, that one can use ESR spectroscopy to measure thermal electron transfer rates in such compounds. Simulation of ESR spectra based on density functional theory calculation and comparison with optical data also uncover the nature (i.e., adiabatic or nonadiabatic) of the electron transfer process.

Experimental and Theoretical Studies of Electron Transfer and Mixed Valence Systems

Author : Gerald Michael Sando
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (549 download)

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Book Synopsis Experimental and Theoretical Studies of Electron Transfer and Mixed Valence Systems by : Gerald Michael Sando

Download or read book Experimental and Theoretical Studies of Electron Transfer and Mixed Valence Systems written by Gerald Michael Sando and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes several experimental and theoretical studies in the general areas of electron transfer and mixed valency. Experimentally, we have used resonance Raman combined with time dependent spectral modeling to study a possible mixed valence system to determine the nature of the excited state of the molecule. In addition, nanosecond transient absorption was used to study a model of dye sensitized solar cells to help clarify the mechanism of back electron transfer. On the theoretical side, a sum over states formalism was used for predicting rates, absorption spectra, and emission spectra for electron transfer reactions as a function of vibrational mode mixing, revealing a large increase in rate for deeply inverted reactions when the Duschinsky effect is included. An application of the theory to a series of organometallic molecules, the Co(CO)4 and V(CO)6 anion/radical systems, is also discussed. In addition, density functional theory is applied to a related radical pair, [Co(Cp)|V(CO)6], and the importance of these results in analyzing previous experimental ultrafast electron transfer results is discussed. Classical spectral simulations of absorption and Stark spectroscopy of mixed valence systems were also performed, suggesting a breakdown of the Liptay assumptions as the Class II/III limit is approached.

Intervalence Electron Transfer in Bicobaltocene Cations: Comparison with Biferrocenes

Author : George E. McManis
Publisher :
ISBN 13 :
Total Pages : 15 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis Intervalence Electron Transfer in Bicobaltocene Cations: Comparison with Biferrocenes by : George E. McManis

Download or read book Intervalence Electron Transfer in Bicobaltocene Cations: Comparison with Biferrocenes written by George E. McManis and published by . This book was released on 1988 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The near-infrared absorption parameters for bicobaltocene monocation, (Cp2Co)2+, evaluated in several solvents, are compared with corresponding data for biferrocene cation, (Cp2Fe)2+, in order to ascertain the consequence of metal substitution upon the degree of redox-site electronic coupling. From the markedly (ca. 5 fold) larger intervalence band intensities, narrower bandwidths, and milder solvent dependence of the band energy observed for the former system, the degree of Co(III)-Co(II) electronic coupling is deduced to be substantially greater than for Fe(III)-Fe(II). A similar conclusion is reached from a comparison of near-infrared spectra for bis(fulvalene)-dicobalt and -diiron monocations. These differences are also reflected in more negative comproportionation free energies for the cobalt mixed-valence analogs, as derived from electrochemical data. These findings are consistent with orbital symmetry considerations, since electron transfer for the Co(III)-Co(II) system is expected to involve a ligand-centered 4e1g orbital, as compared with strongly metal-localized 4e2 or 8a1g orbitals that are apparently utilized in the Fe(III)-Fe(II) metallocene case. Keywords: Mixed valence compounds, Donor acceptor orbital overlap, Electronic coupling, Biferrocene, Bicobaltocene.

Bioinorganic Photochemistry

Author : Grazyna Stochel
Publisher : John Wiley & Sons
ISBN 13 : 9781405193276
Total Pages : 398 pages
Book Rating : 4.1/5 (932 download)

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Book Synopsis Bioinorganic Photochemistry by : Grazyna Stochel

Download or read book Bioinorganic Photochemistry written by Grazyna Stochel and published by John Wiley & Sons. This book was released on 2009-06-10 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioinorganic photochemistry is a rapidly evolving field integrating inorganic photochemistry with biological, medical and environmental sciences. The interactions of light with inorganic species in natural systems, and the applications in artificial systems of medical or environmental importance, form the basis of this challenging inter-disciplinary research area. Bioinorganic Photochemistry provides a comprehensive overview of the concepts and reactions fundamental to the field, illustrating important applications in biological, medical and environmental sciences. Topics covered include: Cosmic and environmental photochemistry Photochemistry of biologically relevant nanoassemblies Molecular aspects of photosynthesis Photoinduced electron transfer in biosystems Modern therapeutic strategies in photomedicine The book concludes with an outlook for the future of environmental protection, discussing emerging techniques in the field of pollution abatement, and the potential for bioinorganic photochemistry as a pathway to developing cheap, environmentally friendly sources of energy. Written as an authoritative guide for researchers involved in the development of bioinorganic photochemical processes, Bioinorganic Photochemistry is also accessible to scientists new to the field, and will be a key reference source for advanced courses in inorganic, and bioinorganic chemistry.

Mixed-Valence Compounds

Author : D.B. Brown
Publisher : Springer Science & Business Media
ISBN 13 : 9400990766
Total Pages : 517 pages
Book Rating : 4.4/5 (9 download)

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Book Synopsis Mixed-Valence Compounds by : D.B. Brown

Download or read book Mixed-Valence Compounds written by D.B. Brown and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 517 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been a decade since two seminal reviews demonstrated that mixed-valence compounds share many unique and fascinating features. The insight pro vided by those early works has promoted a great deal of both experimental and theoretical study. As a result of extensive efforts, our understanding of the bonding and properties of mixed-valence compounds has advanced substantially. There has been no compre hensive treatment of mixed-valence compounds since 1967, and the meeting convened at Oxford in September, 1979, provided a unique opportunity to examine the subject and its many ramifications. Mixed-valence compounds play an important role in many fields. Although the major impact of the subject has been in chemistry, its importance has become increasingly clear in solid state physics, geology, and biology. Extensive interest and effort in the field of molecular metals has demonstrated that mixed-valency is a prerequisite for high elec trical conductivity. The intense colors of many minerals have been shown to be due to mixed-valency, and the electron-transfer properties of certain mixed-valence metalloproteins are important in biological processes. Experts from all of these areas participated in this meeting, and the truly interdisciplinary nature of the subject made it a unique learning experience for all in attendance.