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When nonlinear optical (NLO) effects were first observed experimentally in the early 1960s, the door to a new field of research was opened. Over the last 50 years, this area has expanded rapidly, supported by applications and devices that are based on nonlinear effects. The search for small, and yet fast and highly efficient devices for, e.g., data processing, data storage, or logic gates, is ongoing. Materials with nonlinear optical properties, and in particular organometallic complexes and coordination compounds, have been found to be strong candidates in this area for a number of reasons. An overview of the results that have been published by research groups in this field over the last decade is given in the opening Chapter. Understanding the highly complex physical processes of nonlinear optics, and maximizing these effects to make practical use of them, is a challenge for theoreticians, physicists and chemists. The overlap of these fields enables us to develop models to derive strategies towards building efficient NLO materials. The focus of the present work is on two aspects of ruthenium acetylide complexes incorporating pi-conjugated systems. The first part considers the effects on NLO properties, resulting from lengthening the pi-delocalized system in unbranched octupolar (star-shaped) ruthenium acetylide complexes. Acetylide complexes of bis(bidentate)-ligated Ru have proven to provide desired physical and optical properties; the star-shaped design of the complexes allows access to mono-disperse macromolecular entities that combine large pi-conjugated systems, while incorporating the desired metal centers. In this part of the work, a number of systematically varied octupolar ruthenium acetylide complexes were synthesized and characterized. Their optical and physical properties are discussed, and their nonlinear optical properties were explored by frequency-dependent Z-scan measurements. A variety of new NLO scaling factors are suggested and were applied to NLO data, and the applicability of the new NLO scaling factors was explored. Linear, oligo(phenylethynyl)-bridged ruthenium acetylide complex analogues of the star-shaped complexes were also synthesized, in order to establish the different NLO properties of linear (dipolar) vs. star-shaped (octupolar) arrangements. The second part of this work presents a group of systematically varied mono-disperse, branched ruthenium acetylide complexes (dendrimers). The main interest was the variation of the core unit. Six first-generation organometallic dendrimers with nitrogen, boron, and phenyl cores were synthesized and characterized. The NLO properties of two nitrogen-cored zero-generation dendrimers and an analogous nitrogen-cored first-generation dendrimer were explored; comparison to analogous organic zero-, first- and second-generation dendrimers revealed a drastic enhancement of the NLO properties on incorporation of the metal centers. A number of star-shaped and dendritic mixed-metal osmium-ruthenium acetylide complexes were also synthesized. --provided by Candidate.
Metal alkynyl complexes are of interest for a variety of possible applications, one being their use as advanced nonlinear optical (NLO) materials. This Thesis describes the synthesis and characterization, along with computational studies, of group 8 metal alkynyl complexes, which may exhibit interesting NLO properties. Chapter 1 discusses the theoretical background of NLO properties. This is followed by a brief review of the research that has been conducted in the field of organometallic NLO materials. Chapter 2 focuses on the syntheses of group 8 metal acetylide complexes possessing dipolar and octupolar configurations. Syntheses of both linear and branched substitution on the aryl core of either homo- or heterometallic complexes are described here, as well as crystal structures. The physical properties of these complexes are examined using a range of measurements, including cyclic voltammetry, IR and UV-vis spectroscopy. Chapter 3 covers the computational studies of the synthesized and unsynthesized complexes in Chapter 2 using the time-dependent density functional theory (TD-DFT) method. The computed linear and nonlinear optical data allow for a better understanding of the molecular electronic structure responsible for the experimental data.
Ruthenium compounds have shown very good second order and third order behaviour. Very high non-linear optical (NLO) response is due to the extensive coordination and organometallic chemistry of ruthenium. Electron-rich d6 ruthenium (II) centres are especially well-suited for incorporation into NLO chromophores because their highly polarizable d orbitals can cause effective -electron-donating properties when coordinated to ligands with low-lying * orbitals. This work provides an understanding of the NLO properties of ruthenium complexes. All systems display large second-order NLO response. This effort may provide the guidelines to synthesize the high-performance NLO materials. The present investigation gives insight into the NLO response of ruthenium complexes and endeavors to disclose the origin of the NLO response of this family, which is interesting and important in design and synthesis of new promising NLO materials."
The field of nonlinear optics has expanded rapidly over the last 50 years as these nonlinear optical (NLO) effects are increasing utilised in devices. NLO involves the manipulation of light by as it travels through a material, which has the potential to be used in all optical data processing as well as intensity dependent imaging. These applications demand new materials with large nonlinear optical properties, of which organometallics and metal coordination complexes have a good reputation. Organometallics, especially ruthenium alkynyl complexes permit many different structural alterations which result in linear and nonlinear optical property tuning allowing for precise design of materials, however understanding of the structure-property relationships is imperative for such design. In this work, complexes with a systematically varied structure have been had their third order nonlinear optical properties analysed utilising the Z-scan technique covering a broad wavelength range; the nonlinear absorptive properties being of particular interest. Comparison of these results allows for determination of structural moieties that give high NLO response. Ruthenium alkynyl dendrimers have considerable nonlinear absorptive properties and the second part of this work covers the modification of the core structure to assess its potential for inclusion into larger systems. The level of core substitution (the number of arms branching from the core) and even the core symmetry influences the electronic properties of the molecule and therefore the nonlinear optical properties. The design limitations and synthesis of ruthenium alkynyl complexes with twelve different core substitutions is detailed and the optical and nonlinear optical properties discussed.
The aims of this work were to highlight changing trend in the nonlinear optical (NLO) behaviour of ruthenium alkynyl complexes on structure modification. Chapter 1 discusses the theoretical background of NLO properties. This is followed by a brief review on the research that has been conducted in the field of organometallic NLO materials. Chapter 2 is concerned with the synthesis of a series of ruthenium bis-alkynyl complexes varying in ligand composition by chain lengthening and/or changing the arylalkynyl para-substituted functional groups, together with their cyclic voltammetric data and linear optical data. Chapter 3 discusses the strategies for synthesizing wedges with ABC composition and their use in the syntheses of dendrimers with C3subh -symmetry. A series of alkynylruthenium dendrimers with different peripheral groups was made. The electrochemical properties of these dendrimers were assessed, and the linear optical and cubic nonlinear optical properties were studied. Chapter 4 examines the effect of the number of ruthenium centers on dendrimer NLO behaviour. Mono-ruthenium, bi-ruthenium and tri-ruthenium dendrons were synthesized and their linear optical properties studied. Chapter 5 focuses on the electronic communication between ruthenium centers in multi-ruthenium alkynyl complexes. A series of linear and branched ruthenium alkynyl complexes was made. Electrochemical and linear optical properties were examined.
Organometallic complexes have proven to have significant nonlinear optical (NLO) properties. They possess great design flexibility; the metal, oxidation state, ligand environment and geometry can all be varied, they may be strong oxidizing or reducing agents, and they are often able to undergo facile NLO switching. Metal alkynyl complexes form an important group of organometallic complexes that have high potential in NLO material applications. The focus of the current study is to establish structure-property relationship for ruthenium alkynyl complexes incorporating chiral R,R-Chiraphos co-ligands, and to compare the behavior of these complexes to those of analogous complexes containing the archetypical co-ligand 1,2-bis(diphenylphosphino)ethane (dppe), one of the most widely-employed diphosphine ligands in this field. Chapter 1 presents an introduction to nonlinear optics and reviews organic, inorganic and organometallic compounds for which nonlinear optical responses have been measured. Chapter 2 covers the synthesis of linear ruthenium alkynyl complexes incorporating R,R-Chiraphos. Their crystal structures, electrochemical and spectroelectrochemical properties, circular dichroism responses, and linear and quadratic nonlinear optical properties are reported. Chapter 3 reports the synthesis of ruthenium alkynyl dendrimers incorporating R,R-Chiraphos. The crystal structures, electrochemical properties, linear optical properties and circular dichroism responses of selected examples have been carried out.
This book assembles both theory and application in this field, to interest experimentalists and theoreticians alike. Part 1 is concerned with the theory and computing of non-linear optical (NLO) properties while Part 2 reviews the latest developments in experimentation. This book will be invaluable to researchers and students in academia and industry, particularlrly to anyone involved in materials science, theoretical and computational chemistry, chemical physics, and molecular physics.