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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.
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.
Metal alkynyl complexes have been shown to be potentially useful third-order nonlinear optical switches, with large two-photon absorption cross-sections and strong changes in photon absorption properties on oxidation. By forming multinuclear complexes, switches with more then two states can be made. Chapter 1 presents an introduction to nonlinear optics and reviews some inorganic materials which have had their nonlinear optical properties measured. Chapter 2 details new synthetic routes into binuclear complexes incorporating an osmtum chloro-alkynyl metal centre. Structural, electrochemical and spectroelectrochemical studies on selected examples have been carried out. Chapter 3 details new facile synthetic routes into osmtum ammine-alkynyl and osmium bis-alkyny1 complexes. Synthesis of osmium and ruthenium binuclear and trinuclear complexes with both diethyny1 and triethyny1 bridges between the metal atoms has been explored. Structural, electrochemical, spectroelectrochemical and theoretical studies have been carried out on selected complexes. Chapter 4 reports the synthesis of a number of branched multinuclear complexes incorporating both osmium and ruthenium metal atoms. Electrochemical and spectroelectrochemical studies have been carried out on selected examples. The Z-scan technique has been used to investigate the third-order nonlinear optical properties of a number of linear and branched bimetallic complexes, showing large effects but some photo-induced instability. Chapter 5 details the formation of a number of new mononuclear and unsymmetrical binuclear iron alkynyl complexes. The electrochemical and spectroelectrochemical behaviour of the complexes exhibiting a reversible redox process has been explored. - provided by Candidate.
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."
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.
High power laser pulses can be a threat to optical sensors, including the human eye. Traditionally this threat has been alleviated by colour filters that block radiation in chosen wavelength ranges. Colour filters’ main drawback is that they block radiation regardless of it being useful or damaging, information is lost for wavelengths at which the filter is active. Protecting the entire wavelength range of a sensor would block or strongly attenuate the radiation needed for the operation of the sensor. Sol-gel glasses highly doped with optically non-linear chromophores have previously shown high optical quality in combination with efficient optical power limiting (OPL) through reverse saturable absorption (RSA). These filters transmit visible light unless the light fluence is above a certain threshold. A key design consideration of laser protection filters is linear absorption in relation to the threshold level. A high linear absorption means that the user’s view is degraded by the filter. To model the photokinetics of RSA chromophores, the five-level population model is widely used. It consists of three singlet and two triplet levels. Model parameters relevant for OPL performance include linear absorption cross-sections, two-photon absorption (2PA) cross-sections, lifetimes, quantum yields and inter-system-crossing (ISC) times. The dominant design paradigm is to have a highly absorbing and long-lived triplet state that is quickly populated by ISC during the beginning of a laser pulse. To simultaneously achieve a lower threshold and linear absorption a vast number of materials for self-activated filters were evaluated, either as bulk glasses or solutions. An f/5 setup was used to evaluate their OPL performance while several photophysical measurements were performed to gain an understanding of system behaviour. The first three series of methyltriethoxysilane (MTEOS) Sol-Gel glasses were doped with gold nanoparticles either solely, or with one of two Pt-acetylide chromophores. One with shorter conjugated ligands, the second with similar but longer conjugated ligands. Finally, a series of multi-branched fluorene chromophores were evaluated in solution. Their central moiety was either an organic benzene unit or an ISC promoter in the form of para-dibromobenzene or a platinum(II)-alkynyl unit. For the gold nanoparticle doped glasses, the lower performance Pt-acetylide with short ligands had its OPL threshold lowered at 600nm while the glasses doped with only gold nanoparticles showed no OPL at all. Secondly, the enhancement was most pronounced for very low gold nanoparticle concentrations. While gold nanoparticles alone showed good OPL performance at 532 nm, at this wavelength neither Pt-acetylide showed an obvious OPL enhancement beyond linear absorption losses from codoping with gold nanoparticles. The improved OPL performance at 600 nm was attributed to stronger 2PA, by electric field enhancement from the gold nanoparticles. The lack of detectable OPL improvement for 532 nm and for the higher performance Pt-Acetylide chromophore with long ligands were qualitatively explained by a lower sensitivity to 2PA on system performance. A degraded performance from linear absorption by excess nanoparticles in front of the focus explained the weakening of the enhancement at higher gold nanoparticle concentrations. All three fluorene chromophores, including the chromophore without a central ISC promoter, showed broadband OPL through the visible spectrum. The OPL performance of the two chromophores with ISC promoters was expected considering their transient absorption at microsecond time-scales. For the fluorene chromophore without an ISC-promoter, ultra-fast transient absorption was used to identify singlet excited state absorption as the source of the OPL performance. Both of these series of experiments demonstrate how a simplistic view of simply increasing desired photophysical parameters, e.g. effective 2PA cross-section or ISC quantum yield, do not always result in a noticeable increase in system performance. By employing numerical population models it was possible to identify which parameters had the highest impact on OPL performance. Laserpulser med hög effekt kan vara ett hot mot optiska sensorer, inklusive det oskyddade ögat. Traditionellt har detta hot hanterats med färgfilter som stoppar strålning inom valda våglängdsband. Färgfilters huvudsakliga begränsning ligger i att de tar bort strålning oberoende av om den är användbar eller skadlig, att information försvinner för de våglängder filtret skyddar för. Skydd över hela det våglängdsband en sensor verkar i skulle stoppa eller kraftigt försvaga strålningen som sensorn behöver för att fungera. Sol-gel glas högdopade med optiskt icke-linjära molekyler har tidigare visat hög optisk kvalité i kombination med en effektiv optisk effektbegränsning (OPL) via omvänd blekning (RSA). Dessa filter transmitterar synligt ljus så länge ljusets fluens (pulsenergi per area [J cm-2]) inte ligger över en viss begränsningsnivå. En nyckelfaktor i designen av laserskyddsfilter är linjärabsorption kontra begränsningsnivå. Genom att öka kromoforkoncentrationen så kan begränsningsnivån sänkas till kostnad av ökad linjärabsorption. Detta betyder dock att användarens omvärldsuppfattning genom filtret riskerar att minska. För att modellera fotokinetiken av RSA-molekyler har femnivåpopulationsmodellen varit vida använd. Den består av tre singlet-nivåer och två tripletnivåer. Modellparametrar relevanta för OPL-prestanda innefattar kvantverkningsgrader, olika övergångars linjärabsorptionstvärsnitt, tvåfotonsabsorptionstvärsnitt och livstider samt halveringstider för överföring mellan singlet och triplettillstånd. Den dominanta designparadigmen är att ha ett hög- absorberande och långlivat tripletläge som snabbt populeras i början av en laserpuls. För att samtidigt uppnå en lägre begränsningsnivå och lägre linjärabsorption utvärderades ett flertal självaktiverade filter, antingen i form av glas eller i vätskelösning. En f/5-uppställning användes för att utvärdera deras OPLprestanda medan en mängd fotofysiska mätningar utfördes för att få en förståelse för deras systembeteende. De tre första serierna av MTEOS Sol-Gel glas var dopade med guldnanopartiklar antingen enbart, eller med en av två Pt(II)-acetylidmolekyler. Den första hade kortare konjugerade ligandarmar, den andra var liknande men hade längre ligandarmar. Slutligen utvärderades en serie av flerarmade flourenmolekyler i vätskelösning. Deras centrala enhet bestod antingen av en organisk bensenring eller en ISC-gynnare i form av para-dibromobensen eller en Pt(II)-acetylidenhet. Guldnanopartiklarna kunde förstärka OPL-prestandan för enbart den mindre effektiva korta Pt(II)-acetylidmolekylen på 600nm men ej 532nm. Filtren dopade med enbart guldnanopartiklar visade god prestanda på 532nm men ingen på 600nm. Alla tre fluorenmolekyler visade OPL genom det synliga spektrat, även den molekylen utan ISC-gynnare. Både dessa serier experiment demonstrerar hur ett förenklat angreppsätt med att enbart öka eftertraktade fotofysiska parametrar, t.ex. effektivt 2PA-tvärsnitt eller ISC-kvantverkningsgrad, inte alltid resulterar i märkbart ökad systemprestanda. Genom att använda numeriska populationsmodeller visas hur det är möjligt att identifiera vilka parametrar som har den största inverkan på OPL-prestanda.
The interaction of light with a nonlinear optical (NLO) material gives rise to new optical fields with altered properties (e.g. phase, frequency, amplitude, polarization, path, etc.), which are of utmost importance for photonic applications. The search for new efficient NLO materials for applications has thus been accelerated. In particular, interest in the NLO properties of organometallic systems has undergone enormous growth in the past decade. This thesis consists of a compilation of several papers relating to the experimental and density functional theory (DFT) studies of the nonlinear optical properties of metal alkynyl complexes. Paper 1 includes a brief introduction to nonlinear optical phenomena, in particular to the second-order NLO effects, and the popular experimental and quantum chemical methods for the determination of molecular first hyperpolarizability. It also includes a comprehensive review of previous semi empirical and DFT NLO calculations relating to organometallic complexes. Paper 2 deals with the benchmarking of DFT methods for first hyperpolarizabilities and excitation energies of metal alkynyls against the relevant experimental data. Papers 3-9 are combined experimental and computational (DFT) studies of dipolar (paper 3-8) and octupolar (paper 9) metal alkynyl complexes. The contribution from the calculations to each paper is as follows. In paper 3, linear optical and quadratic nonlinear optical properties of alkynyl complexes with different ligated metal centres (Ru, Ni, and Au) and with different bridges (phenylene, naphthalenylene, and anthracenylene) are calculated with DFT and time dependent DFT (TD-DFT). In paper 4, the linear optical and quadratic nonlinear optical properties of ruthenium alkynyl complexes with oligo(phenylenevinylene) bridges were calculated using DFT and the results compared with the experimental data. In paper 5, the experimentally determined linear optical properties and first hyperpolarizabilities of some ruthenium alkynyl complexes with yne/ene/azo inter-ring linkers are rationalized by DFT/TD-DFT calculations. In paper 6, the structural, linear optical, and nonlinear optical properties of ruthenium alkynyl complexes with P-P (= dppf, dppb, and dppe) and N-N (4,4'-di-tert-butyl-2,2'-bipyridine) donor co-ligands were rationalized from DFT calculations. Paper 7 consists of TD-DFT calculations undertaken on a series of bis(alkynyl) Ru complexes to rationalize the experimental linear optical data. In paper 8, the mechanism of two-dimensional NLO character in Y-shaped ruthenium alkynyl complexes is studied with the use of DFT/TD-DFT calculations. In paper 9, computational studies were undertaken to assign the key optical transitions for some octupolar compounds bearing (N-heterocyclic carbene) gold or diphenylamino substituents at the periphery.
Organometallic chemistry is based on the reactions and use of a class of compounds (R-M) that contain a covalent bond between carbon and metal. They are prepared either by direct reaction of the metal with an organic compound or by replacement of a metal from another organometallic substance. This book presents research in this field.