Ch1 The X-ray structural determinations of the neutral 1',2',1'",2'"-tetranaphthylmethyl- and the 1', 3', 1', 3'-tetranaphthylmethyl- biferrocenium triiodide have been determined. Our Mossbauer measurement for 1.34 and 1.35 indicate that the intramolecular electron transfer rates are quite sensitive to the environmental perturbations caused by the grinding of the sample. An interesting finding is that the Mossbauer results indicate that the unground diffusing sample of 1.34 is valence delocalized on the Mossbauer time scale above 180K. However, the ground diffusing sample of 1.34 exhibits a Mossbauer spectrum characteristic of a valence-trapped cation which remains valence-trapped electronic state at 300K. The effects of grinding of samples are also observed in the EPR and XRD measurements. Ch2 A great deal of research has concentrated on long range electron and energy transport in transition metal- based system and conducting polymer. We have synthesis a new bis-terpyridine bridging ligand (2.40) which the spacer is biferrocene moiety. Incorporating of the Ruthenium (II) subunits via redox-active spacer group promote to construction polynuclear transition metal complexes (i.e. multicomponent system). Cyclic voltammetric analysis indicated that there are Fe-Fe electronic coupling in the bridging ligand, and the degree of Fe-Ru electronic coupling is weak. In addition to dominant UV absorption near 240 and 280 nm from terpyridinyl and MLCT absorption from Ru to terpyridine around 480 nm, the complexes containing ferrocene or biferrocene as endgroup exhibit an unusual absorption band around 560 nm which is due to a feccocene moiety to terpyridine MLCT transition.

Palladium is one of the most common and versatile transition metals used in modern organometallic chemistry. The chemistry of palladium in its 0, +II, and +IV oxidation states is well-known; by comparison, the chemistry of palladium in its +III oxidation state is in its infancy. The work in this thesis involves the study of previously unknown Pd(III) complexes, including applications in materials chemistry and catalysis. / Chemistry and Chemical Biology

<p></p><p> My thesis work revolves around the ability to modify the 1,4,8,11-tetraazacyclotetradecane (cyclam) framework in order tune the electronic properties of resulting metal complexes towards real life applications. A huge direction for science and engineering is the pursuit of Moore’s Law, to constantly miniaturize electronic processes while improving their performance. With the physical limits of copper wiring being reached on nanoscale levels, alternative resources must be utilized. Naturally, the absolute limit of wiring would be on the single molecular scale. It is this idea that Chapters 1-3 are founded upon. Moving forward, I deemed three key concepts are important for success of this project: (1) the ability for modification of the molecule to be incorporated into existing technologies, (2) redox stability of the molecular complexes to allow multiple charges to pass through without losing integrity, and (3) the ability to function as a wire and allow current to pass through. Requirement (1) has been proven possible in previous work on cyclam, however (2) and (3) were yet to be shown for any cobalt tetraazamacrocyclic complex until this work.</p><p> Chapter 1 covers my first successful exploration into modification of the cylcam ligand in order to obtain favorable electronic properties. Cobalt complexes utilizing the MPC ligand (5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) show stability upon reduction, whereas the cyclam analogues did not. In fact, [Co(MPC)(C₂Ph)₂]⁺ was the first cobalt based tetraazamacrocyclic alkynyl complex to show such redox stability without the use of heavily electron withdrawing axial ligands. It was found that this improvement of redox stability is a result of the weakened equatorial ligand field caused by the steric bulk of the phenyl substituents of the cyclam framework. This in turn led to improved axial ligand bonding and hence greater stability. This work shows the Co^III(MPC) framework can satisfy requirement (2).</p><p> Based on the results of Chapter 1, Chapter 2 realizes the idea that with improved axial ligand bond strengths in Co^III(MPC) complexes, the possibility for electronic delocalization between cobalt and the axial ligand performing as the wire is opened. A series of dinuclear Co^III(MPC) complexes, with cobalt centers linked through a butadiyndiyl bridge, were prepared. With each cobalt being identical, theoretically each should behave electrochemically similar and reduction of the complex should be a single two electron event. It is however shown that this two electron event was, in fact, split into two single electron events. The source of this result is the delocalization of the first added electron between both cobalt centers, effectively making two half-reduced metals. Therefore, the ability for Co^III(MPC) complexes to satisfy requirement (3) has been proven.</p><p> Chapter 3 expands on the results shown in Chapters 1 and 2. Where Chapter 2 showed delocalization of an electron between cobalt centers, Chapter 3 shows delocalization of a hole through cobalt between ethynylferrocene ligands. With this, all three requirements are met and the ability as Co(MPC) to function as a wire has been proven for both oxidation and reduction, both between cobalt and through cobalt.</p><p> </p><p> Chapter 4 takes a new direction, however applies the same basic principle as the previous three in modifying the cyclam ligand to achieve desired properties. Where application in electronic devices are made stable by use of the bulky MPC ligand, application towards catalysis requires an open catalytic site and weak enough axial coordination to allow the substrate to leave once reduced. Through the alkyl substitution of the cyclam ligand in Ni^II(CTMC) (5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradecane) in place of the MPC ligand, electronically donating properties of the macrocycle were maintained while opening the axial catalytic site. In this work, it was shown that reduction in steric bulk of the ligand from phenyl to ethyl to methyl, while maintaining electron donating properties, improved catalytic efficiency and all complexes were superior to Ni^II(cyclam).</p><p></p>

The electron transport through a molecular wire under the influence of an external laser field is studied using a reduced density matrix formalism. The full system is partitioned into the relevant part, i.e. the wire, electron reservoirs and a phonon bath. An earlier second-order perturbation theory approach of Meier and Tannor for bosonic environments which employs a numerical decomposition of the spectral density is used to describe the coupling to the phonon bath and is extended to deal with the electron transfer between the reservoirs and the molecular wire. Furthermore, from the resulting time-nonlocal (TNL) scheme a time-local (TL) approach can be determined. Both are employed to propagate the reduced density operator in time for an arbitrary time-dependent system Hamiltonian which incorporates the laser field non-perturbatively. Within the TL formulation, one can extract a current operator for the open quantum system. This enables a more general formulation of the problem which is necessary to employ an optimal control algorithm for open quantum systems in order to compute optimal control fields for time-distributed target states, e.g. current patterns. Thus, we take a fundamental step towards optimal control in molecular electronics. Numerical examples of the population dynamics, laser controlled current, TNL vs. TL and optimal control fields are presented to demonstrate the diverse applicability of the derived formalism.

Reactive ion scattering spectrometry (RISS) utilizing low energy (tens of eV) polyatomic ions was employed to characterize self-assembled monolayers (SAMs) on gold. The terminal composition of halogenated SAMs, chemisorption motifs of disulfide and diselenide SAMs, and electron transfer properties of molecular wire containing SAMs were interrogated to develop the versatility of RISS as an analytical surface characterization technique.Novel halogen terminated SAMs were examined for their ability to convert translational to vibrational energy of colliding projectile ions. A general increasing energy deposition trend correlated with increasing terminal mass with the exception of the iodine functionality. Increased amounts of surface abstractions and sputtering from C12I suggest competitive ion-surface interactions account for less than predicted energy deposition results. Mixed films of CH2Br and CH3 terminal groups elucidated interfacial surface crowding discerned by energy deposition results.Thiol and disulfide based SAMs were shown by RISS comparisons to be dissimilar in structure. Terminal orientation, however, was the same based on ion-surface reactions, disproving the proposed dimer model of disulfide SAMs. Ion-surface reactions and electron transfer properties of disulfide surfaces suggested greater percentages of c(4x2) superlattice structure than in thiol SAMs. Based on increased hydrogen reactivity, decreased methyl reactivity, and increased energy deposition results, diselenide based SAMs were more disordered than S-Au based SAMs. Electron transfer results monitored through total ion currents (TIC) showed Se-Au contacts are more conductive than S-Au attachments.Molecular wire candidates whose electron transfer capabilities are difficult to characterize by traditional techniques were characterized by RISS after being doped into matrix SAMs. Electron transfer properties were dependent on the isolating SAM matrix, dipole moments of the wires, and the potential applied to the surface. Changes in surface voltage dictated molecular wire geometry and electron transfer. Wires were annealed into preferential geometries by colliding ions, but did not operate as switches.While not related to the advancement of RISS, structural elucidation of the pharmaceutical carvidioliol was investigated by collision-induced dissociation, surface-induced dissociation, sustained off-resonance irradiation, and sustained off-resonance irradiation-resonant excitation and through gas-phase hydrogen/deuterium exchange. This molecule fragmented easily by all methods and demonstrated the chemical specificity of gas-phase hydrogen/deuterium exchange experiments.

No description available.

The literature surrounding organic small-molecule donor-acceptor systems is summarised for a range of optoelectronic applications (OLEDs, OPVs, OFETs etc.). There is a focus on the key building blocks: 1,3,4-oxadiazole (OXD), diphenylamine (DPA), carbazole (Cbz) and fluorene (F). The incorporation of such moieties into various donor-acceptor systems is discussed with further reference to selected alternative organic donor and acceptor systems. The syntheses of novel bipolar molecules based on a donor-spacer-acceptor (DPA/Cbz-F-OXD) structure and the incorporation of these molecules into single-layer OLEDs is presented. It is demonstrated how the emission colour can be tuned from green to deep blue by systematic manipulation of the structure. A significant result is that high efficiency accompanied with pure, deep blue emission in single-layer OLEDs can be achieved with this structural motif. The incorporation of these materials as part of a simple two-component blend to produce white OLEDs is presented and the modification of the materials to improve electron-transport properties is discussed. The synthesis of DPA-bridge-OXD wire systems is presented with the use of oligo-p-phenyleneethynylene units as a bridge of varying length to investigate the effect on charge transfer between the donor and acceptor. Photophysical studies demonstrate the change in absorption, emission and fluorescence lifetimes as the length scale of the molecules is altered. The synthesis of a series of planarised and twisted DPA-bridge-OXD systems based upon phenylene linkers is discussed. Finally, a series of DPA-F-OXD-anchor molecules is presented for incorporation into DSSC devices. The synthesis of these materials is described and the suitability of various anchoring groups for DSSCs is analysed through photophysical and device studies.

No description available.

L’objectif de ces travaux est la synthèse molécules destinées à la formation de fils moléculaires par auto-assemblage. La reconnaissance sélective d’un noyau imidazole par une porphyrine de zinc à anse phénanthroline est utilisée comme outil pour l’assemblage. Plusieurs variations structurales ont été apportées aux blocs d’assemblage de manière à explorer différentes possibilités de contrôle sur la formation des fils moléculaires. Sont présentés dans ce document, les synthèses des molécules, ainsi qu’une partie des études réalisées pour interpréter la nature des assemblages formés à la fois en solution, mais également sur des surfaces. La microscopie à force atomique a mis en évidence des espèces linéaires régulières auto-assemblées dont la formation est assistée par la surface. / The selective recognition of imidazole by a phenanthroline-strapped zinc porphyrin was used as a tool for the self-assembly of molecular wires. Several structural variations on the building blocks were explored as a way to control the formation of the molecular wires. This thesis presents the synthesis of the molecules investigated and studies of the assemblies formed in solution and on surfaces. Self-assembled linear species, whose formation was assisted by the surface, were observed by atomic force microscopy.

In case of charge-transfer complex of TTF:TCNQ lot of work had previously been done on single crystals and thin films to study various interesting properties including phase transitions which were attributed to Peierls instability. But as seen from the review of molecular wires it is clear that apart from synthesis of TTF:TCNQ in molecular wire form, not much was known about the behavior of these wires at low temperatures. There were some open questions listed below, which we tried to address in the thesis Can nanowires of TTF:TCNQ be grown across prefabricated electrodes which are separated by gaps < 1 μm. Can the nanowires grown in such smaller gaps, show Peierls transition, which is the signature of quasi one dimensional conduction. As the size and length of the grown wires are small it was expected that they will have less staking disorder as compared to the thin films. What will be conduction mechanism at low temperatures in such single/few nanowire samples. If the nanowires show Peierls transition and CDW formation at low temperatures, can nonlinear conduction be seen due to motion of CDW, if so how well do they compare with the reported results for TTF:TCNQ single crystals. In case of Cu:TCNQ it can be noted from the above review that even though much advances have been made on synthesizing good quality Cu:TCNQ films and incorporating them in novel device structures, there has been much controversy regarding conduction mechanism. There were many conflicting results in literature regarding switching in these devices. In this thesis work we wanted to address the feasibility of switching in Cu:TCNQ under reduced size of top electrodes and also address few other issues like To grow Cu:TCNQ nanowires by using vapor phase evaporation method Can resistive switching be induced in Cu:TCNQ by using a local probe STM tip (Pt-Rh) operated in high vacuum. Since the measurement will be done in high vacuum what will be the effect of environment (absence of oxygen, water vapor) on reproducibility of resistive switching. Will localized switching depend on the top electrode material. This has been probed by coating different metals on the C-AFM tip and using them as top electrode in conducting mode. With what contact force will we get reproducible resistive switching. Can a device structure be made with an array of top electrode in the form of metal dots (< 10 μm) and study switching using C-AFM. This thesis is divided into seven main chapters and two appendix chapters, which are listed below: In the present chapter 1, a detailed overview and literature survey of charge-transfer complexes TTF:TCNQ and Cu:TCNQ which were relevant to our present study was presented. This was followed by our motivation in undertaking the present work. In chapter 2 the various experimental techniques developed during the course of the thesis work such as e-beam lithography, design of the vacuum chamber for deposition of organic molecules, design of ultra high vacuum scanning tunneling microscope (UHV-STM chamber along with the STM head, modification of conducting AFM for obtaining the switching data have been described. In chapter 3 we describe the preparation of TTF:TCNQ molecular wires across prefabricated electrodes and different measurements done on the samples. In particular the observation Peierls transition in the grown nanowires of TTF:TCNQ and the nonlinear conduction mechanism involved at low temperatures will be discussed in detail. In chapter 4 we describe the preparation of Cu:TCNQ nanowires on Cu substrate using vapor phase technique. Resistive switching measurements done on the Cu:TCNQ nanowires in high vacuum with Pt-Rh tip as top electrode will be discussed in detail. In chapter 5 we describe the resistive switching measurements performed on Cu:TCNQ nanowires with different metal coated C-AFM tips as well as FIB deposited platinum dots as top electrodes. In chapter 6 we make a few comments about possible switching mechanism involved, when STM tip, C-AFM induced as well as platinum coated dots were used as top electrodes. In chapter 7 we conclude this thesis by summarizing the main results. Also we point out the scope for future work that can be based upon the results presented in this work. In Appendix A a brief review of self assembled monolayer (SAM) of alkane thiols is presented followed by details about experiments done for insitu study of growth of SAMs of decanethiol and octadecanethiol on silver substrates using ellipsometry and force-displacement spectroscopy. In Appendix B a brief description of work done to grow isolated nanowires of Cu:TCNQ, between two metal electrodes in planar geometry and in anodic alumina membranes is given.