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Investigation Of Ligand Centered Mixed Valency And Optical Electron Transfer In Rhenium Based Supramolecular Coordination Compounds
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Book Synopsis Investigation of Ligand-centered Mixed Valency and Optical Electron Transfer in Rhenium Based Supramolecular Coordination Compounds by : Peter Henry Dinolfo
Download or read book Investigation of Ligand-centered Mixed Valency and Optical Electron Transfer in Rhenium Based Supramolecular Coordination Compounds written by Peter Henry Dinolfo and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary focus of this thesis is the examination of intramolecular electron transfer processes in mixed valence compounds. Rhenium based supramolecular coordination chemistry has been used create a number of highly symmetrical structures that contain cofacially arranged, redox active ligands. When reduced by an odd number of electrons, the molecules belong to an unusual class of mixed valence compounds where the ligands are the degenerate redox centers, i.e. Ligand-Centered Mixed Valency. Inter-ligand electronic communication in these systems is controlled by direct donor/acceptor orbital overlap rather than by superexchange through the molecular framework. As shown by X-ray crystallography and semiempirical modeling, the spectroscopically determined electronic coupling strengths are consistent with geometrical configurational differences between the cofacial ligand pairs. In a number of cases, electroabsorbance (Stark) spectroscopy has been employed to directly evaluate the adiabatic charge transfer distances. Depending the geometrical arrangement of the redox active ligand pairs, the degree of electronic communication can be tuned from non-interacting (Robin-Day Class I), to fully delocalized (Class III).
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2005 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mixed-Valence Systems by : Yuwu Zhong
Download or read book Mixed-Valence Systems written by Yuwu Zhong and published by John Wiley & Sons. This book was released on 2023-05-30 with total page 517 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Valence Systems Comprehensive overview on the advanced development of mixed-valence chemistry Mixed-Valence Systems: Fundamentals, Synthesis, Electron Transfer, and Applications covers all topics related to the theory and experimental results of mixed-valence systems, including the design, synthesis, and applications of mixed-valence compounds containing inorganic, organometallic and organic redox-active centers. The text also covers the recent advances in mixed-valence chemistry, including the development of new mixed-valence systems, transition of mixed valency, better understanding of the spectral characteristics of intervalence charge transfer, and controllable electron transfer related to molecular electronics. In Mixed-Valence Systems, readers can expect to find detailed information on sample topics such as: Characterization and evaluation of mixed-valence systems, electron paramagnetic resonance spectroscopy, and electrochemical methods Optical analysis, important issues in mixed-valence chemistry, transition of mixed valency from localized to delocalized, and solvent control of electron transfer Theoretical background, potential energy surfaces from classical two-state model, and quantum description of the potential energy surfaces Reorganization energies, electronic coupling matrix element and the transition moments, generalized Mulliken–Hush theory, and analysis of the band shape of intervalence charge transfer Strengthening the relationship of mixed-valence electron transfer and molecular electronics, Mixed-Valence Systems is of immense value to researchers and professionals working in the field of electron transfer, molecular electronics, and optoelectronics.
Book Synopsis Journal by : American Chemical Society
Download or read book Journal written by American Chemical Society and published by . This book was released on 2004 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Optical and Luminescence Studies of Rhenium(i) Diimine Alkynyl Complexes and Their Utilization As Building Blocks for the Assembly of Multinuclear and Mixed-Metal Complexes by : CHAN-FUNG. LAM
Download or read book Synthesis, Optical and Luminescence Studies of Rhenium(i) Diimine Alkynyl Complexes and Their Utilization As Building Blocks for the Assembly of Multinuclear and Mixed-Metal Complexes written by CHAN-FUNG. LAM and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Synthesis, Optical and Luminescence Studies of Rhenium(I) Diimine Alkynyl Complexes and Their Utilization as Building Blocks for the Assembly of Multinuclear and Mixed-metal Complexes" by Chan-fung, Lam, 林親鳳, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled SYNTHESIS, OPTICAL AND LUMINESCENCE STUDIES OF RHENIUM(I) DIIMINE ALKYNYL COMPLEXES AND THEIR UTILIZATION AS BUILDING BLOCKS FOR THE ASSEMBLY OF MULTINUCLEAR AND MIXED-METAL COMPLEXES submitted by LAM Chan Fung for the degree of Doctor of Philosophy at The University of Hong Kong in July 2005 A series of mononuclear rhenium(I) diimine complexes with hyperbranched or functional alkynyl ligands, [C H -1,3-(HC C C H C C) -5-{Re(CO) (N N)(C C 6 3 6 4 2 3 t C H C C)}] (N N = bpy, Bu bpy) and [Re(CO) (N N)(C C C C R)] (R = C H I-p, 6 4 2 3 6 4 C H C C SiMe -p, CHC C H-p, C H OSiMe Bu-p, CHOH-p) have been 6 4 3 6 4 6 4 2 6 4 synthesized. The X-ray crystal structures of [CH-1,3-(HCCCHCC)-5-{Re(CO)(Bubpy)(CCCHCC)}] and 63 64 2 32 64 [Re(CO)(Bubpy)(CCCCCHCCH-p)] have been presented. By employing 32 64 [Re(CO) (N N)(C C C C C H I-p)] as a precursor, a series of dinuclear rhenium(I) 3 6 4 alkynyl complexes with extended conjugation, [Re(CO) (N N)(C CC C C H C C 3 6 4 t (C H ) C C C H C CC C)Re(CO) (N N)] [n = 0, 1; N N = Bu bpy, (CF ) bpy], 6 4 n 6 4 3 2 3 2 have been prepared. Additionally, a series of symmetrical and unsymmetrical trinuclear rhenium(I) alkynyl complexes, [C H -1,3,5-{Re(CO) (N N)(C C C C 6 3 3 t t C H C C)} ] [N N = Bu bpy, (CF ) bpy] and [C H -1,3-{Re(CO) (Bu bpy)(C C 6 4 3 2 3 2 6 3 3 2 C C C H C C C H C C)} -5-{Re(CO) ( Bu bpy)(C C C H C C)}], have also 6 4 6 4 2 3 2 6 4 been synthesized. The lowest-lying excited states of these complexes were 3 3 tentatively assigned as admixture of MLCT[d (Re) *(N N)], LLCT[ (C C R) 3 *(N N)] and IL[ (C C R) *(C C R)] origin. Besides, a series of luminescent heterometallic rhenium(I) palladium(II) t complexes, trans-[Pd(PEt ) Cl{(C C Ar C C)Re(CO) (N N)}] (N N = bpy, Bu bpy; 3 2 3 2 Ar = C H S, C H ) and trans-[Pd(PEt ) {(C C C H C C)Re(CO) ( Bu bpy)} ], have 4 2 6 4 3 2 6 4 3 2 2 been synthesized. The X-ray crystal structures of t trans-[Pd(PEt)Cl{(CCCHCC)Re(CO)(N N)}] (N N = bpy, Bu bpy) have been 32 64 3 2 determined. Their emission was attributed to MLCT[d (Re) *(N N)] 3 phosphorescence mixed with LLCT[ (C C R) *(N N)] character. A lower emission energy for the hetero-bimetallic complex was observed upon coordination of the electron-rich palladium(II) moiety into the rhenium(I) alkynyl system. However, replacement of the remaining chloro group on the palladium centre with an additional rhenium(I) alkynyl moiety resulted in a higher energy emission for the hetero-trimetallic complex. A series of luminescent heterometallic rhenium(I) platinum(II) phosphine complexes, [{Re(CO)(NN)(CCCHCC)}Pt(PP)] [PP = dppe, depe, 3 6 4 2 t cis-(PEt), trans-(PEt ); N N = Bu bpy, (CF ) bpy], have been synthesized. The 32 3 2 2 3 2 X-ray crystal structure of [{Re(CO){(CF)bpy}(C C CH C C)}Pt(dppe)] has 3 3 2 6 4 2 been determined. The emission was ascribed as derived from states of a [d (Re) 3 3 *(N N)] MLCT origin that mixed with LLCT[ (C C R) *(N N)] character; or alternatively, as an excited state of a [ {C C C H C C Pt(P P)} *(N N)] 6 4 metalloligand-to-ligand charge transfer character. Another new class of luminescent heterometallic rhenium(I)platinum(II) polypyridine alkynyl complexes, t [Re
Book Synopsis Directory of Graduate Research by : American Chemical Society. Committee on Professional Training
Download or read book Directory of Graduate Research written by American Chemical Society. Committee on Professional Training and published by . This book was released on 2005 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
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.
Book Synopsis Synthesis, Characterization, and Photophysical Investigation of Some New Rhenium(I) Complexes by : David Joseph Anderson
Download or read book Synthesis, Characterization, and Photophysical Investigation of Some New Rhenium(I) Complexes written by David Joseph Anderson and published by . This book was released on 1991 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Optical Spectra and Chemical Bonding in Transition Metal Complexes by : Thomas Schönherr
Download or read book Optical Spectra and Chemical Bonding in Transition Metal Complexes written by Thomas Schönherr and published by Springer. This book was released on 2004-08-19 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Axel Christian Klixbüll Jørgensen was a “Polyhistor”,one of the very few in the highly specialized science of our time.His interests and contributions in ch- istry covered the whole Periodic Table.This statement demonstrates the breadth of his interests,however,it also sheds light on the constraints of chemistry which deals with a large, yet limited number of elements. It is not surprising that Jørgensen went beyond these limits,exploring the probable or plausible ch- istry of yet unknown elements and elementary particles such as quarks. Even chemistry itself did not place rigid limits on his mind,he was able to transfer his chemical concepts to scientific problems far beyond the normal such as in astrophysics. “Structure and Bonding” is intimately associated with the name C.K. J- gensen both as initiator and author over several decades.The appearance of a special edition in memory of this great scientist is a self-evident prolongation of his many contributions to the success of this series.
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
Book Synopsis Electronic Structure of Ruthenium Complexes with Non-Innocent Ligands by : Amit Das
Download or read book Electronic Structure of Ruthenium Complexes with Non-Innocent Ligands written by Amit Das and published by LAP Lambert Academic Publishing. This book was released on 2013 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed valency in a ligand bridged homo-polynuclear complex arises when metal centers exist in their different oxidation states. The extent of intermetallic electronic coupling in the mixed valent state of polynuclear complex varies primarily depending on the nature of bridging and ancillary ligands as well as on the metal ion. On the other hand, the use of redox active (redox non-innocent) ligands in the complex framework creates ambiguities in the assignment of valence and spin configurations of such complexes as both the metal and ligand centers can take part in electron transfer processes. In consequence precise determination of valence and spin distributions in transition metal complexes comprising of redox non-innocent ligands is considered to be a formidable challenge. Thus, this book has been focused on how to overcome such problems through the correlation of experimental and theoretical results.
Book Synopsis Spectroscopic and Electrochemical Investigation of Ligand- Bridged Rhenium (I) Complexes by : Robert Jay Yoblinski
Download or read book Spectroscopic and Electrochemical Investigation of Ligand- Bridged Rhenium (I) Complexes written by Robert Jay Yoblinski and published by . This book was released on 1993 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Ligand Tuning Effects Upon the Multielectron Reduction and Single Electron Oxidation of (Bi)pyridyl Complexes of Cis- and Trans-Dioxorhenium(V): Redox Thermodynamics, Preliminary Electrochemical Kinetics, and Charge-Transfer Absorption Spectroscopy by : M. S. Ram
Download or read book Ligand Tuning Effects Upon the Multielectron Reduction and Single Electron Oxidation of (Bi)pyridyl Complexes of Cis- and Trans-Dioxorhenium(V): Redox Thermodynamics, Preliminary Electrochemical Kinetics, and Charge-Transfer Absorption Spectroscopy written by M. S. Ram and published by . This book was released on 1991 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we report the effects of a more subtle perturbation due to changes in ligand substituents. The redox thermodynamics of a total of twenty cis and trans dioxo rhenium (V) complexes are surveyed; five of these have been subjected to more extensive pH dependent studies in order to elucidate how electron transfer is coupled to proton release and uptake. Also reported is a brief study of substituent effects upon electronic absorption spectra for the cis dioxo series. These measurements (along with resonance Raman and electrochemical studies) have been used to show that the cis spectra, in contrast to the trans, are dominated by charge-transfer transitions. Other significant findings are: (1) that the one-electron Re(VI) reduction potentials are influenced in a predictable fashion by substituent electronic effects, (2) that the two-electron Re(V) reduction potentials, surprisingly, are not affected appreciably by ligand-substituent based electron withdrawal or donation effects, and (3) that the two-electron kinetics, however, are influenced detectable by remote ligand substituents. The second and third observations are perhaps the most intriguing; they are tentatively interpreted in terms of proton demand and in terms of invisible oxidation state effects.
Book Synopsis The Effects of Electronic Delocalization in Highly Coupled Mixed Valence Systems by : Benjamin James Lear
Download or read book The Effects of Electronic Delocalization in Highly Coupled Mixed Valence Systems written by Benjamin James Lear and published by . This book was released on 2007 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: The trinuclear ruthenium cluster RuO(OAc)6L3 (where L is an ancillary ligand) is used to make a variety of mixed valence compounds in which two or more clusters are joined together by an organic bridging ligand. The magnitude of electronic coupling in the mixed valance state of these compounds is quite large and the complexes reside on the Robin-Day class II/class III borderline. The large degree of coupling in these complexes gives rise to ultrafast electron transfer whose effects are observable in the infrared (IR) spectra of these complexes. Utilizing the IR properties of the complexes we are able to arrive at thermodynamic estimates of the electronic coupling parameter (H AB) for asymmetric mixed valence compounds. These asymmetric compounds give rise to mixed valence isomers and the temperature dependence of the isomer populations is used to determine deltaH and deltaS for the electron transfer event in these complexes. The large coupling in these complexes reduces the barrier to electron transfer significantly (enabling ultrafast electron transfer). This places the rate of electron transfer under the control of the nuclear dynamics of the complex and the surrounding environment. The result is that the rate of electron transfer in these mixed valence complexes shows a strong dependence on kinetic parameters of the solvent (those that describe the movement of the nuclei of the system), but not on thermodynamic parameters of the solvent (that describe more static energetic contributions of the environment). This, in turn, leads to an unexpected temperature dependence of the electron transfer rate. It is found that the electron transfer rate dramatically increases when the solvent is frozen. This results form a decoupling of the relatively slow solvent motions from the electron transfer event allowing for the faster internal vibrational motions of the mixed valence complex to control the rate of electron transfer. The effects of the large electronic coupling in these complexes also gives rise to other surprising behaviors. The extent of the electronic coupling in the mixed valence systems is known to depend on the electron donor strength of the attached ancillary ligands. It is shown that, through supramoleuclar interactions at the ancillary ligands of these mixed valence systems, the electronic coupling may be modulated. There is a significant decrease in the resonance stabilization associated with breaking of symmetry in a mixed valence system and that this energy (together with the energy gained by restoration of symmetry) can provide substantial driving force for chemical interactions. This effect is explained in terms of both the direct stabilization of the compound through electronic coupling and in terms of resonance stabilization of the unpaired electron in the mixed valence compound. This result is then extended to molecular electronics where it is shown that changes in current effected by a chemical interaction can provide a driving force for said chemical interaction. The large magnitude of electronic coupling in these mixed valence systems is also shown to be sufficient to stabilize as the ground state what would be thought of as low-lying excited states. It is shown that an electron may transfer from a cluster to the bridging ligand and that this electron transfer gives rise to an increase in electronic coupling throughout the mixed valence state. This increase in electronic coupling is found to be sufficient to stabilize the radical state of the organic bridge. The large energy difference between uncoupled (diabatic) and coupled (adiabatic) mixed valence compounds is also exploited in order to determine whether an electron entering into the mixed valence molecule enters into a diabatic or adiabatic wavefunction. The electron transfer rate from photo-generated triplet zinc tetraphenylphorpyrin to the mixed valence compounds was observed. Comparisons of the observed electron transfer rate to the diabatic and adiabatic driving force for electron transfer are made. It is concluded that the electron enters into a diabatic wavefunciton of the mixed valence compound after which the compound evolves into the adiabatic wavefunciton. The major theme throughout this thesis is the exploitation of the huge value of electronic coupling (H AB) in order to give rise to and explain some very unique and unexpected behaviors of these mixed valence complexes.
Book Synopsis An Investigation of the Electronic Coupling in Some Dimeric Ruthenium (II) Polyridine Complexes by : Roland Ngebichie Njabon
Download or read book An Investigation of the Electronic Coupling in Some Dimeric Ruthenium (II) Polyridine Complexes written by Roland Ngebichie Njabon and published by . This book was released on 2013 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed understanding of respiration at the molecular level requires an understanding of the many electron transfer steps involved in the process. These electron transfer processes are extremely fast and are impossible to measure by simple rapid mixing techniques. In order to get around this problem, scientists have used laser flash photolysis. This technique relies on the fact that under proper conditions, a reactant can be generated by a very short laser pulse. Once generated, the course of the reaction can be monitored by various techniques capable of very rapid time response. Many applications of this methodology rely on the use of ruthenium (II) polypyridine complexes to initiate the reactions of interest. This approach has been used to study the rates of electron transfer between cytochrome c, and cytochrome b5, cytochrome peroxidase and cytochrome oxidase and the bc1 complex. The latter are key components in the respiration process. In these investigations special emphasis was placed on the design of ruthenium complexes that were efficient and compatible with the biological components. A thorough understanding of the design parameters are critical to continued success in this area. Dimeric ruthenium complexes at the current time appear to be among the best candidates for photochemical initiators. The photophysical properties of these complexes, however, have not yet been examined. In particular the excited-state lifetime of some of the monomers of interest appears to be comparable or even longer than the corresponding dimers. This observation is inconsistent with the single covalent bond that links the two monomeric units which would provide strong electronic coupling and rapid excited state decay. Preliminary observations suggest a very weak electronic coupling. The underlying basis of this inconsistency is important in future design endeavors and may provide useful information for the use of these complexes in other areas such as solar energy conversion. In order to investigate the magnitude of the electronic coupling, both symmetric and asymmetric ruthenium (II) dimeric complexes were synthesized. The ligands used in the synthesis of these dimers were limited to either those commercially available or those that could be easily synthesized. The symmetric ruthenium (II) bipyridine dimer ([Ru(bpy)2diphen(bpy)2](PF6)4)and ([Ru(TAP)2diphen(TAP)2](PF6)4 were synthesized through a nickel catalyzed coupling reaction . The asymmetric dimer ([Ru(bpy)2diphen(dmbpy)2](PF6)4) on the other hand was synthesized by decarbonylating [Ru(dmbpy)2(CO)2](PF6)2 with three fold of excess trimethylamine N-oxide in the presence of 2-methoxy ethanol and reacting it with [Ru(bpy)2diphen](PF6)2. Emission measurements confirmed that there is no significant difference in the excited state lifetime of the monomers and the dimers (both symmetric and asymmetric) used in this study. The result from our electrochemical studies showed that the mixed dimer complex was made up of two metal centers with different redox potentials. The symmetric dimer on the other hand has the same redox potential for each of the two metal centers and they do not interact with each other thus giving a single two electron oxidation at the same potential. Finally, our result from the emission study of the mixed dimer showed that the emission energy of the mixed dimer was equal to the average of the bpy and dmbpy dimers. From the photochemical studies, one can conclude that the mixed dimer and the symmetric dimers behaved as the monomers because there was no significant change in the excited state life time This indicates that the metal center of both the mixed dimer and the symmetric dimers are weakly coupled by the bridging ligand and there is no significant coupling between the two metal centers.
Book Synopsis Synthesis and Characterization of Rigid Supramolecular Coagulants by : Shiho Kobayashi
Download or read book Synthesis and Characterization of Rigid Supramolecular Coagulants written by Shiho Kobayashi and published by . This book was released on 2008 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: We synthesized large Ru coordination complexes that bind to carbon nanotubes, giving them enhanced functionality. By manipulating ligands on the Ru center, the size and the charge state of ruthenium coordination complexes can be controlled. Coordinating either bidentate or tridentate ligands to Ru(II) has allowed us to control the morphology of the multimetal system yet have different charge states on the overall complex. These complexes can be used to study supramolecular interactions with carbon nanotubes and with each other in solution. We can promote and control electron transfer between carbon nanotubes and Ru complexes through these interactions. Taking advantage of carbon nanotubes' good electron accepting properties and mechanical stiffness, carbon nanotubes are applicable towards photovoltaic cells. Synthetic methods and characterization of several new ruthenium complexes are discussed. These include novel + 1 and +2 ruthenium coordination complexes that are then used to make various constructs of higher order oligomers, specifically the + 1/+ 1, +1/+2 and +2/+2 dimer system.
Book Synopsis Redox-Active Ligands by : Marine Desage-El Murr
Download or read book Redox-Active Ligands written by Marine Desage-El Murr and published by John Wiley & Sons. This book was released on 2024-01-31 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Redox-Active Ligands Authoritative resource showcasing a new family of ligands that can lead to better catalysts and promising applications in organic synthesis Redox-Active Ligands gives a comprehensive overview of the unique features of redox-active ligands, describing their structure and synthesis, the characterization of their coordination complexes, and important applications in homogeneous catalysis. The work reflects the diversity of the subject by including ongoing research spanning coordination chemistry, organometallic chemistry, bioinspired catalysis, proton and electron transfer, and the ability of such ligands to interact with early and late transition metals, lanthanides, and actinides. The book is divided into three parts, devoted to introduction and concepts, applications, and case studies. After the introduction on key concepts related to the field, and the different types of ligands and complexes in which ligand-centered redox activity is commonly observed, mechanistic and computational studies are described. The second part focuses on catalytic applications of redox-active complexes, including examples from radical transformations, coordination chemistry and organic synthesis. Finally, case studies of redox-active guanidine ligands, and of lanthanides and actinides are presented. Other specific sample topics covered include: An overview of the electronic features of redox-active ligands, covering their historical perspective and biological background The versatility and mode of action of redox-active ligands, which sets them apart from more classic and tunable ligands such as phosphines or N-heterocyclic carbenes Preparation and catalytic applications of complexes of stable N-aryl radicals Metal complexes with redox-active ligands in H+/e- transfer transformations By providing up-to-date information on important concepts and applications, Redox-Active Ligands is an essential reading for researchers working in organometallic and coordination chemistry, catalysis, organic synthesis, and (bio)inorganic chemistry, as well as newcomers to the field.
