Metal ion contamination in surface and ground water is a major threat as it has a direct implication on the health of terrestrial and aquatic flora and fauna. Lead (Pb2+), mercury (Hg2+), cadmium (Cd2+), nickel (Ni2+), copper (Cu2+) and cobalt (Co2+) are few of these metal ions which are classified under the high risk category. Of these, lead and mercury are of greater concern, as even nanomolar concentrations can be lethal, as they can be bio-accumulated and result in physiological as well as neurological disorders. In Asian countries like India and China, heavy metal pollution is more prevalent, as a consequence of poor governmental policies or ineffective or inadequate measures to combat this problem. In recent times, the monitoring and assessment of water pollution is a critical area of study, as it has a direct implication for its prevention and control. The major techniques used for metal ion detection are atomic absorption spectroscopy (AAS), X-ray fluorescence, ion chromatography, neutron activation, etc. Alternatively, the electrochemical, optical and electrical methods provide a platform for the fabrication of portable devices, which can facilitate the on-site analysis of samples in a rapid and cost-effective manner. This has led to a new field of research called chemical sensors or chemo sensory devices. The main aim of this study is to develop various chemosensory materials and test their response towards metal ion sensing. In this study, electroactive polymers have been synthesized for various sensor applications. The focus has been to design synthesize and test various functionalized electroactive polymers (FEAP) for the development of electrochemical, optical and chemoresistive sensors. Electroactive polymers like polyaniline, polypyrrole, polypyrrole grafted to exfoliated graphite oxide and dipyrromethene conjugated with p-(phenylene vinylene) have been synthesized and evaluated after functionalizing with metal coordinating ligands. These metal coordinating ligands were selected, in order to enhance their metal uptake capacity. Various metal ligands like imidazole, tertiary amine group, iminodiacetic acid, and dipyrromethene incorporated either in the polymer backbone or as a part of the backbone have been chosen for the metal binding. These functionalized electroactive polymers (FEAP) served as active material for metal ion sensing. The present investigation is subdivided into three sections. The first part includes design and chemical synthesis of the functionalized polymers by a series of organic reactions. The synthesis has been followed up by characterization using spectroscopic methods including NMR, FTIR, GCMS and Mass spectrometry. In the second part of the investigation, the synthesized polymer has been characterized for the changes in electronic, electric and optical properties after interaction with the selected metal ions. For this, the FEAP is allowed to interact with various metal ions and the changes in the relevant properties have been measured. This includes the study of changes in the conductivity, electronic properties like absorption or emission of the polymer, changes in the redox properties, etc. The third phase of investigation deals with the fabrication of the devices using the active FEAP. The sensor devices comprised of either films, or electrode modified with FEAP or solution of the FEAP, in combination with an appropriate technique has been used for the sensing. The major objectives are enumerated below 1. Functionalzation of polyaniline with imidazole functional group to get imidazole functionalized polyaniline (IMPANI) and study of the electronic, electrical and optical properties of the same. 2. Preparation of films of IMPANI and study of the change in conductivity of the film upon interaction with various metal ions, namely Cu2+, Co2+ and Ni2+ in their chloride form. 3. Synthesis of amine functionalized aniline monomer and chemical graft polymerization onto exfoliated graphite oxide as a substrate to synthesise the amine funtionalised polyaniline grafted to exfoliated graphite oxide (EGAMPANI). Modification of the carbon paste electrode (CPE) with EGAMPANI and study of the electrode characteristic. 4. Study of the electrode properties of EGAMPANI modified carbon paste electrode. 5. Evaluation of the EGAMPANI modified carbon paste electrode as a multi-elemental voltammetric sensor for Pb2+, Hg2+ and Cd2+ in aqueous system. 6. Functionalization of polypyrrole with iminodiacetic acid and characterization of the polymer to synthesis iminodiacetic acid functionalized polypyrrole (IDA-PPy). 7. Modification of the CPE with IDA-PPy by drop casting method and evaluation of the Pb2+ sensing properties. 8. Study of the effect of other metal ions say Hg2+, Co2+, Ni2+, Zn2+, Cu2+ and Cd2+ on the anodic stripping current of Pb2+ using EGAMPANI modified CPE. 9. Synthesis of dipyrromethene-p-(phenylene vinylene) conjugated polymer for heavy metal ion sensing. 10. Study of the changes in the optical absorption and emission properties of the polymer in THF and evaluation of the change in these optical properties upon interaction with the metal ions as analyte. The salient findings of the research work are highlighted as follows, In the first synthesis, aniline has been functionalized with imidazole group and this monomer has been chemical oxidatively polymerized to obtain imidazole functionalized polyaniline (IMPANI). The synthesized polymer possesses a nano-spherical structure, as confirmed from the morphological characterisation using scanning electron microscopy. The IMPANI has been interacted with a representative metal ion, copper (II) chloride, and the copper complexed polymer (Cu-IMPANI) has been subjected to various studies. The coordination of copper with IMPANI results in an increase of molecular weight of the polymer as a result of aggregation, as observed from dynamic light scattering measurements. Apart from this, a significant finding is the decrease of the pH of the system after copper ion coordination attesting to the generation of a secondary hydrochloride ion during the coordination of the copper to the imidazole side chain. This is further confirmed by an increase in conductivity of the Cu-IMPANI compared to IMPANI, measured using the four-probe technique. The increase of conductivity due to copper coordination is one order of magnitude higher. The films which have been prepared from IMPANI and Cu-IMPANI exhibit different morphology. The Cu-IMPANI film prepared by prior co-ordination of Cu ion with IMPANI powder shows a flaky structure, which is not preferable for the conductivity measurements, as a consequence of discontinuity in the medium. To overcome this problem, IMPANI films were initially prepared and then interacted with copper ions for a desired duration, before measurement of the conductivity. This latter procedure enabled the preparation of smooth films for the development of chemoresistive sensors. In continuation of the initial study highlighted above, IMPANI films of thickness 0.02 ± 0.001 mm have been prepared using IMPANI and PANI in DMPU in the ratio of 7:3 by mass. After exposure of the films with respective metal chlorides, such as Ni2+, Co2+ and Cu2+, a change in conductivity is observed in the concentration range of 10-2 to 1 M of metal chlorides. The sensor response may be arranged in the sequence: Ni2+ > Cu2+ > Co2+ at 1M concentration. On the contrary, films prepared from PANI-EB under identical conditions do not exhibit any appreciable change in conductivity. The optimum exposure time is determined to be 10 min for a maximum change in conductivity, after exposure to the chosen metal ions. In the second system taken up for investigation, a tertiary amine containing polyaniline (AMPANI) has been grafted to exfoliated graphite oxide. The amine containing polyaniline grafted to exfoliated graphite oxide (EGAMPANI) has been characterised for structural, morphological and elemental composition. The grafting percentage has been determined to be 7 % by weight of AMPANI on the EGO surface. The synthesized EGAMPANI (5 weight %) has been used to modify carbon paste electrode (CPE) for electrochemical sensor studies. Based on the differential pulse anodic stripping voltammetric studies, the electrochemical response may be arranged in the following sequence: Pb 2+>Cd 2+>Hg 2+ The minimum detection levels obtained are 5×10-6, 5×10-7, and 1.0×10-7 M for Hg2+, Cd2+ and Pb2+ ions respectively. In the next study, an iminodiacetic acid functionalized polypyrrole (IDA-PPy) has been synthesized and characterised for its elemental and structural properties. This has been further used to modify the CPE by drop casting method and used for the specific detection of Pb2+ in acetate buffer. Various parameters governing the electrode performance such as concentration of depositing solution, pH of depositing solution, deposition potential, deposition time, and scan rate, have been optimized to achieve maximum performance and found to be 20 μl, 4.5, -1.3 V, 11 min, 8 mV s-1 respectively for the chosen parameters. Additionally, the influence of other heavy metal ions on the lead response has been studied and it is observed that Co, Cu and Cd ions are found to be interfering. Further, the response of Cd, Co, Cu, Hg, Ni and Zn on IDA-PPy functionalized electrode has been evaluated. The selectivity of IDA-PPy modified electrode for Pb2+ is observed in the concentration range of 1 × 10-7 M and below. The IDA-PPy modified CPE shows a linear correlation for Pb2+ concentration in the range from 1×10-6 to 5×10-9 M and with a lowest limit of detection (LLOD) of 9.6×10-9 M concentration. The efficacy of the electrode for lead sensing has also been evaluated with an industrial effluent sample obtained from a lead battery manufacturing unit. The fourth synthesis pertained to the development of an optical sensor for Fe2+, and Co2+ ions. For this, dipyrromethene as a metal coordinating ligand in conjugation with p-phenylenevinylene has been synthesized and tested for its structural as well as optical properties. It is observed that the polymer shows three absorptions, namely at 294 nm, 357 nm and a major absorption observed as a broad band ranging from 484 to 670 nm. The emission spectrum of the polymer excited at 357 nm shows a characteristic blue emission with a maximum intensity centered at 425 nm. The emission quenching in the presence of various metal ions have been tested and are found to be quenched in presence of Fe2+ and Co2+ ions. All the other metal ions tested namely, Cr3+, Cu2+, and Zn2+ are not found to exhibit any change in the emission spectra below the concentration of 1 × 10-4 M. The linear correlation of the emission intensity with the concentration of the Co2+ and Fe2+ ions has been determined using Stern-Volmer plot. For Co2+ the Stern-Volmer regime is observed from 1×10-4 to 9×10-4 M concentration and the quenching constant Ksv is determined to be 8.67 ×103 M-1. For Fe2+, the linearity is found to be in the regime of 1×10-5 to 9×10-5 M and the quenching constant Ksv is determined to be 7.90 × 103 M-1. In conclusion, different electroactive polymers functionalized with metal coordinating ligands have been synthesized, characterised and evaluated for metal sensing applications. Techniques like electrochemical, optical and conductivity have been used to characterise the response of these FEAP towards metal sensing. It is can be concluded that the electrochemical sensors are more reliable for sensing especially at very low concentrations of metal ions such as Pb, Cd and other techniques like optical and conductimetric are good for detecting metal ions namely Fe, Co, Ni, Cu. The selectivity towards the metal ions is a function of the metal chelating ligand and the extent of sensitivity is dependent upon the technique employed.

The growing incidences of orthopedic problems globally have created a huge demand for strong bioactive materials for bone tissue engineering. Over the years, studies have shown chemical, physical, and mechanical properties of biomaterials influence the cellular interactions at the material-tissue interface, which subsequently controls biological response to materials. Strong biomaterials with surface properties that actively direct cellular response hold the key for engineering the next generation orthopedic implants. With its unique properties graphene can be used to reinforce poly (ε-caprolactone) (PCL) to prepare strong and bioactive polymer nanocomposites for bone tissue regeneration. The thesis entitled ―Engineering bioactive and multifunctional graphene polymer composites for bone tissue regeneration” systematically studies the effect of different chemically functionalized and metal-graphene hybrid nanoparticles in PCL composites for bone tissue engineering. The thesis comprises of seven chapters. Chapter 1 is an outline review on the impact of graphene and graphene derived particles to prepare supporting substrates for tissue regeneration and the associated cell response to multifunctional graphene substrate. This chapter discusses how cells interact with different graphene based particles and the interplay between cells performance and multifunctional properties of graphene based substrates. Chapter 2 describes the role, if any, of the functionalization of graphene on mechanical properties, stem cell response and bacterial biofilm formation. PCL composites of graphene oxide (GO), reduced GO (RGO) and amine-functionalized GO (AGO) were prepared at different filler contents (1%, 3% and 5%). Although the addition of the nanoparticles to PCL markedly increased the storage modulus, this increase was higher for GO and AGO than with RGO. In vitro cell studies revealed that the AGO and GO particles significantly increased human mesenchymal stem cell (hMSC) proliferation. AGO was most effective in augmenting stem cell osteogenesis leading to mineralization. Bacterial studies revealed that interaction with functionalized GO induced bacterial cell death due to membrane damage which was further accentuated by amine groups in AGO. The synergistic effect of oxygen containing functional groups and amine groups on AGO-reinforced composites renders the optimal combination of improved modulus, favorable stem cell response and biofilm inhibition desired for orthopaedic applications. In Chapter 3, toward preparing strong multi-biofunctional materials, poly(ethylenimine) (PEI) conjugated graphene oxide (GO_PEI) was synthesized using poly(acrylic acid) (PAA) as spacer and incorporated in PCL at different fractions. GO_PEI significantly promoted proliferation and formation of focal adhesions in hMSCs on PCL. GO_PEI was highly potent in inducing stem cell osteogenesis leading to 90% increase in alkaline phosphatase activity and mineralization over neat PCL with 5% filler content and was 50% better than GO. Remarkably, 5% GO_PEI was as potent as soluble osteo-inductive factors. Increased adsorption of osteogenic factors due to the amine and oxygen containing functional groups on GO_PEI augment stem cell differentiation. GO_PEI was also highly efficient in imparting bactericidal activity with 85% reduction in counts of E. coli colonies compared to neat PCL at 5% filler content and was more than twice as efficient as GO. This may be attributed to the synergistic effect of the sharp edges of the particles along with the presence of the different chemical moieties. Thus, in contrast to using labile biomolecules, GO_PEI based polymer composites can be utilized to prepare bioactive resorbable biomaterials for fabricating orthopedic devices for fracture fixation and tissue engineering. Chapter 4 describes the preparation of hybrid nanoparticles of graphene sheets decorated with strontium metallic nanoparticles and its advantages in bone tissue engineering. Strontium-decorated reduced graphene oxide (RGO_Sr) nanoparticles were synthesized by facile reduction of graphene oxide and strontium nitrate. X-ray diffraction, transmission electron microscopy, and atomic force microscopy revealed that the hybrid particles were composed of RGO sheets decorated with 200 – 300 nm metallic strontium particles. Thermal gravimetric analysis further confirmed the composition of the hybrid particles as 22 wt% of strontium. Macroporous tissue scaffolds were prepared incorporating RGO_Sr particles in PCL. The PCL/RGO_Sr scaffolds were found to elute strontium ions in aqueous medium. Osteoblast proliferation and differentiation was significantly higher in the PCL scaffolds containing the RGO_Sr particles in contrast to neat PCL and PCL/RGO scaffolds. The increased biological activity can be attributed to the release of strontium ions from the hybrid nanoparticles. This study demonstrates that composites prepared using hybrid nanoparticles that elute strontium ions can be used to prepare scaffolds with osteoinductive property. These findings have important implications for designing the next generation of biomaterials for use in tissue regeneration. Chapter 5 discusses the use of hybrid graphene-silver particles (RGO_Ag) to reinforce PCL and compared with PCL/RGO and PCL/Ag composites containing RGO and silver nanoparticles (AgNPs), respectively. RGO_Ag hybrid particles were well dispersed in the PCL matrix unlike the RGO and AgNPs due to enhanced exfoliation. RGO_Ag led to 77 % increase in the modulus of PCL and provided a conductive network for electron transfer. Electrical conductivity increased four orders of magnitude from 10-11 S/cm to 10-7 S/cm at 5 wt % filler that greatly exceeded the improvements with the use of RGO and AgNP in PCL. RGO_Ag particles reinforced in PCL showed sustained release of silver ions from the PCL matrix unlike the burst release from PCL/Ag. PCL/RGO_Ag and PCL/RGO composites were non-toxic to hMSCs and supported osteogenic differentiation unlike the PCL/Ag composites which were highly toxic at ≥3% filler content. The PCL/RGO_Ag composites exhibited good antibacterial effect due to a combination of silver ion release from the AgNPs and the mechanical rupture induced by the RGO in the hybrid nanoparticles. Thus, the synergistic effect of Ag and RGO in the PCL matrix uniquely yielded a multifunctional material for use in implantable biomedical devices and tissue engineering. Chapter 6 presents investigation of potential differences in the biological response to graphene in polymer composites in the form of 2D substrates and 3D scaffolds. Results showed that osteoblast response to graphene in polymer nanocomposites is markedly altered between 2D substrates and 3D scaffold due to the roughness induced by the sharp edges of graphene at the surface in 3D but not in 2D. Osteoblast organized into aggregates in 3D scaffolds in contrast to more well spread and randomly distributed cells on 2D discs due to the macro-porous architecture of the scaffolds. Increased cell-cell contact and altered cellular morphology led to significantly higher mineralization in 3D scaffolds compared to 2D. This study demonstrates that the cellular response to nanoparticles in composites can change markedly by varying the processing route. Chapter 7 summarizes the important results and future directions of the work. This chapter provides general conclusions arising from this study, and makes suggestions for future work designed to provide a greater understanding of the in vivo response in terms of bio-distribution of the released functionalized graphene from the scaffold or substrate must be assessed with special attention on their accumulation or excretion.

Current fossil fuels (Coal and Petroleum) based economy is not sustainable in the long run because of its dwindling resources, and increasing concerns of climate change due to excessive carbon dioxide (CO2) emission. To mitigate CO2 emission and climate change, scientists across the world have been looking for clean and sustainable energy sources. Among them hydrogen gas (H2) could be more promising because it is the most clean fuel and can be produced from cheap source (water) which is renewable and abundant. Nevertheless, the bottleneck for hydrogen economy is lying in the cost of hydrogen production from water. Still there are no any efficient systems developed which can deliver hydrogen from water in economically viable way. Meanwhile, recent research on old molecule ammonia-borane (H3N•BH3, AB) as hydrogen source has increased the hope towards the hydrogen economy, however, catalytic recycling (or efficient regeneration) of AB from the dehydrogenated product polyborazylene (PB or BNHx) is the biggest hurdle which prevents use of AB as practical hydrogen storage material. Therefore, it is imperative to understand the dehydrogenation pathways of ammonia-borane (or related amine-boranes) which lead to polymeric or oligomeric product(s). On the other hand, methane (CH4) is abundant (mostly untamed) but cleaner fuel than its higher hydrocarbon analogs. To develop highly efficient catalytic systems to transform CH4 into methanol (gas to liquid) is of paramount importance in the field of catalysis and it could revolutionize the petrochemical industry. Therefore, to activate CH4, it is crucial to understand its binding interaction with metal center of a molecular catalyst under homogenous condition. However, these interactions are too weak and hence σ–methane complexes are very elusive. In this context, σ-H2 and σ-borane complexes bear some similarities in σ-bond coordination (and four coordinated boranes are isoelectronic with methane) could be considered as good models to study σ-methane complexes. Studying the H−H and B−H bond activation in H2 and amine-boranes, respectively, would provide fundamental insights into methane activation and its subsequent functionalization. Moreover, the proposed methanol economy by Nobel laureate George Olah seems more promising because methanol can be produced from CH4 (CO2 as well). This in turn will gradually reduce the amount of two powerful greenhouse gases from the earth’s atmosphere. Thus, efficient and economic production of methanol from CH4 and CO2 is one of most challenging problems of today in the field of catalysis and regarded as the holy grails. Furthermore, very recently formic acid (HCOOH) is envisaged as a promising reversible hydrogen storage material because it releases H2 and CO2 in the presence of a suitable and efficient catalyst or vice versa under ambient conditions. Objective of the research work: Taking the account of the above facts, the research work in this thesis is mostly confined to utilize electrophilic Ru(II)-complexes for activation of small molecules such as ammonia-borane (H3N•BH3) [and related amine-borane (Me2HN•BH3)], hydrogen (H2), methane (CH4), formic acid (HCOOH) and carbon dioxide (CO2) and investigation of their mechanistic pathways using NMR spectroscopy under homogeneous conditions. Though these molecules are small, they have huge impacts on chemical industries (energy sector and chemical synthesis: drugs/natural products) and environment [CO2 and CH4 are potent green house gases] as well. However, they are relatively inert molecules, especially CH4 and CO2, and impose very tough challenges to activate and functionalize them into useful products under ambient conditions. The partial oxidation of the strong C−H bond in CH4 for its transformation into methanol under relatively mild condition using an organometallic catalyst is considered as a holy grail in the field of catalysis which is mentioned earlier. More importantly, to develop better and highly efficient homogeneous catalytic systems for the activation of these molecules, it is imperative to understand the mechanistic pathways using well defined homogeneous metal complexes. Thus, an understanding of the interaction of these inert molecules with metal center is obligatory. In this context, discovery of a σ-complex of H2 gave remarkable insights into H−H bond activation pathways and its implications in catalytic hydrogenation reactions. Subsequently, σ-borane complexes of amine-boranes were discovered and found to be relatively more stable because of stronger M−H−B interaction and hence act as good models to study the M−H−C interaction of elusive σ-methane complex. On the other hand, HCOOH, a promising hydrogen storage material and its efficient catalytic dehydrogenation/decarboxylation and CO2 hydrogenation back to HCOOH using well defined homogeneous catalysts could lead to a sustainable energy cycle. Therefore, it is quite significant to understand the mechanistic pathways of formic acid dehydrogenation/decarboxylation and carbon dioxide reduction to formic acid for the development of next generation efficient catalysts. Chapter highlights: Keeping all these in view, we carried out thorough studies on the activation of these small molecules by electrophilic Ru(II)-complexes. This thesis provides useful insights and perspective on the detailed investigation of mechanistic pathways for the activation of small molecules such as H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2 using electrophilic Ru(II)-complexes under homogeneous conditions using NMR spectroscopy. In Chapter 1 we provide brief overview of small molecule activation using organometallic complexes. This chapter presents pertinent and latest results from literature on the significance of small molecule activation. Although there are several small molecules which need our attention, however, we have focused mainly on H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2. In Chapter 2, we present detailed investigation of mechanistic pathways of B−H bond activation of H3N•BH3 and Me2HN•BH3 using electrophilic [RuCl(dppe)2][OTf] complex using NMR spectroscopy as a model for methane activation. In these reactions, using variable temperature (VT) 1H, 31P{1H} and 11B NMR spectroscopy we detected several intermediates en route to the final products at room temperature including a σ-borane complex. On the basis of elaborative studies using NMR spectroscopy, we have established the complete mechanistic pathways for dehydrogenation of H3N•BH3/Me2HN•BH3 and formation of B−H bond activated/cleaved products along with several Ru-hydride and Ru-(dihydrogen) complexes. Keeping the B−H bond activation of amine-boranes in view as a model for methane activation, we attempted to activate methane using [RuCl(dppe)2][OTf] complex. In addition, [Ru(OTf)(dppe)2][OTf] complex having better electrophilicity than [RuCl(dppe)2][OTf], was synthesized and characterized. The [Ru(OTf)(dppe)2][OTf] complex has highly labile triflate bound to Ru-metal and therefore its reactivity studies toward H2 and CH4 were carried out where H2 activation was successfully achieved, however, no any spectroscopic evidence was found for C−H bond activation of CH4. The Chapter 3 describes the synthesis and characterization of several Ru-Me complexes such as trans-[Ru(Me)Cl(dppe)2], [Ru(Me)(dppe)2][OTf], trans-[Ru(Me)(L)(dppe)2][OTf] (L = CH3CN, tBuNC, tBuCN, H2) with an aim to trap corresponding σ-methane intermediate at low temperature. However, interestingly, we observed spontaneous but gradual methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] complex at room temperature. We thoroughly investigated mechanistic details of methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy, NOESY and DFT calculations. Furthermore, H2 activation was confirmed unambiguously by [Ru(Me)(dppe)2][OTf] and Ru-orthometalated complexes using NMR spectroscopy under ambient conditions. An effort was also made to activate methane using Ruorthometalated complex in pressurized condition of methane in a pressure stable NMR tube. Moreover, preliminary studies on protonation reaction of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy to trap σ-methane at low temperature was carried out which provided us some useful information on dynamics between proton and Ru-Me species. The Chapter 4 provides useful insights into the mechanistic pathways of dehydrogenation/decarboxylation of formic acid using [RuCl(dppe)2][OTf]. Catalytic dehydrogenation of HCOOH using [RuCl(dppe)2][OTf] was observed in presence of Hunig base (proton sponge). In addition, a complex [Ru(CF3COO)(dppe)2][OTf] was synthesized and characterized using NMR spectroscopy, and found to readily dehydrogenate HCOOH. Moreover, preliminary results on transfer hydrogenation of CO2 into formamide using [RuCl(dppe)2][OTf] as a precatalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source was confirmed using 13C NMR spectroscopy. The mechanisms were proposed for HCOOH dehydrogenation and transfer hydrogenation of CO2 based on our NMR spectroscopic studies. Furthermore, a few test reactions of transfer hydrogenation of selected alkenes such as cyclooctene, acrylonitrile, 1-hexene using [RuCl(dppe)2][OTf] as pre-catalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source showed quantitative conversion to hydrogenated products.

Dans un contexte de démarche écoresponsable et pour répondre aux exigences de biocompatibilité notamment dans les applications cosmétiques et biomédicales, nous avons développé de nouveaux hydrogels à base de polysaccharides neutres et anioniques en utilisant deux voies originales. La 1ère approche est biomimétique et a consisté à mimer un phénomène d’élaboration naturelle d’hydrogels que l’on retrouve chez certains végétaux pour lesquels une enzyme, la laccase, permet de créer des liens de réticulation par dimérisation des composés phénoliques (en l’occurrence de l’acide férulique FA) présents sur les arabinoxylanes des mucilages des graines de céréales par exemple. Notre travail a ainsi consisté à greffer de l’acide férulique via deux chimies différentes de type imidazole et carbodiimide respectivement pour des polysaccharides neutres ou anioniques. Nous avons ainsi fonctionnalisé trois polysaccharides : le pullulane ou PUL (neutre modèle), le carboxyméthylpullulane ou CMP (anionique modèle) et l’acide hyaluronique ou HA (anionique d’intérêt). Des taux de greffage compris entre 2 et 25% ont été obtenus. L’étude physicochimique en régimes dilué et semi-dilué a permis de mettre en évidence un comportement associatif lié au caractère amphiphile des polysaccharides fonctionnalisés. La réticulation en présence de laccase, suivie in situ en rhéologie, a été réalisée avec succès sur les différents systèmes envisagés avec des contrôles possibles de la cinétique, des propriétés mécaniques finales ou encore du gonflement des hydrogels en fonction du caractère neutre ou chargé des polysaccharides, du degré de substitution en acide férulique, de la concentration en polymère ou de l’activité enzymatique fixée. Les dérivés synthétisés ont globalement démontré des activités biologiques (antioxydante et cytocompatible) intéressantes. La deuxième approche repose sur la photoréticulation possible de polysaccharides (PUL, CMP et HA) fonctionnalisés par le greffage d’amine/acide gras mono ou polyinsaturé (oleylamine, acide oléique et linoléique) via la chimie des imidazoles. Si le pullulane modifié par l’acide linoléique à 2% s’est avéré non hydrosoluble en raison de son caractère neutre, tous les autres dérivés avec des taux de greffages de 3 et 10% ont démontré une bonne solubilité dans l’eau. Les études physicochimiques mettent en évidence un très fort caractère associatif de ces dérivés amphiphiles avec la formation de gels physiques en régime semi-dilué. La photoréticulation a été démontrée en rhéologie sous irradiation UV in situ en présence d’un photoamorceur de type Darocur 1173®. Les résultats préliminaires obtenus selon cette approche en photoréticulation ouvrent ainsi des perspectives intéressantes. / In the framework of an eco-responsible context and to take advantage of biocompatibility, notably in cosmetic and biomedical applications, we have developed new hydrogels based on neutral and anionic polysaccharides using two original routes. The first approach is biomimetic and consists of mimicking a natural development of hydrogels that is found in certain plants for which an enzyme, laccase, allows to create crosslinks by dimerization of phenolic compounds, in occurrence of ferulic acid (FA) present on arabinoxylans mucilage of cereal seeds for example. Thus, our work consisted in grafting ferulic acid via two different chemical ways that means imidazole and carbodiimide respectively for neutral or anionic polysaccharides. We functionalized three polysaccharides: pullulan or PUL (neutral model), carboxymethylpullulane or CMP (model anionic) and hyaluronic acid or HA (anionic of interest) with grafting rates of between 2 and 25%. The physicochemical study in diluted and semi-diluted regimes evidenced an associative behavior due to the amphiphilic character of the functionalized polysaccharides. The crosslinking in the presence of laccase, followed in situ thanks to rheology, has been successfully performed on the various envisaged systems with possible controls of kinetics, the final mechanical properties or the swelling of the hydrogels as a function of the neutral or charged nature of the polysaccharides, the degree of substitution in FA, the polymer concentration or the enzymatic activity. The synthesized derivatives have generally demonstrated interesting biological activities (antioxidant and cytocompatibility). The second approach is based on the possible photocrosslinking of polysaccharides (PUL, CMP and HA) functionalized by the grafting of mono or polyunsaturated fatty amine/acid (oleylamine, oleic acid and linoleic acid) via imidazole chemistry. If pullulan grafted with 2% of linoleic acid was found to be water-insoluble due to its neutral character, all other derivatives (i.e. anionic ones) with grafting rates of 3 and 10% showed good solubility in water. The physicochemical studies show a very strong associative character of these amphiphilic derivatives with the formation of physical gels in semi-diluted regime. Photocrosslinking has been demonstrated in situ thanks to rheology/UV irradiation in the presence of a Darocur 1173® photoinitiator. The preliminary results according to this photocrosslinking approach thus open interesting perspectives.

Amine groups physiologically play an important role in regulating the growth behavior of cells and they have technological advantages for the conjugation of biomolecules. In this work, we present a method to deposit a copolymerized coating of dopamine and hexamethylendiamine (HD) (PDAM/HD) rich in amine groups onto a target substrate. This method only consists of a simple dip-coating step of the substrate in an aqueous solution consisting of dopamine and HD. Using the technique of PDAM/HD coating, a high density of amine groups of about 30 nmol cm⁻² was obtained on the target substrate surface. The PDAM/HD coating showed a high cross-linking degree that is robust enough to resist hydrolysis and swelling. As a vascular stent coating, the PDAM/HD presented good adhesion strength to the substrate and resistance to the deformation behavior of compression and expansion of a stent. Meanwhile, the PDAM/HD coating exhibited good biocompatibility and attenuated the tissue response compared with 316L stainless steel (SS). The primary amine groups of the PDAM/HD coating could be used to effectively immobilize biomolecules containing carboxylic groups such as heparin. These data suggested the promising potential of this PDAM/HD coating for application in the surface modification of biomedical devices.

Organische Halbleiter werden für viele elektronische Bauteile und Anwendungen wie organische Solarzellen, organische Leuchtdioden und thermoelektrische Generatoren benötigt. Während die Leistung organischer p-Halbleiter in letzter Zeit bereits stark verbessert wurde, hinkt die Entwicklung von guten organischen n-Halbleitern hinterher und konnte bisher nur eingeschränkt vom Innovationsschub profitieren. Um die Effizienten dieser Bauteile weiter zu verbessern werden neue Hochleistungsmaterialien, vor allem im Bereich der n-Halbleiter benötigt. Ein wichtiges Kriterium ist dabei ein genügend tief liegendes LUMO-Energieniveau, welches luftstabile Radikalanionen ermöglicht. In dieser Arbeit werden daher verschiedene konjugierte Materialien auf Basis von Naphthalindiimiden (NDI) synthetisiert und charakterisiert. Anhand von niedermolekularen Modellverbindungen werden zunächst die Einflüsse verschiedener Kernsubstituenten auf die elektronische Struktur, Effizienz der Radikalanionenbildung und Luftstabilität der reduzierten Spezies untersucht. Gemischt mit einer kovalent an NDI angebundenen tertiären Amin Seitenkette wird photoinduziert ein intermolekularer Dotierungsprozess beobachtet, welcher mit abnehmendem Donorcharakter der Kernsubstituenten, bzw. mit sinkendem HOMO zunimmt. Das elektronenärmste NDI-Derivat mit zwei Cyano-Gruppen zeigt dabei die höchste Radikalanionen-Ausbeute und liefert Radikalanionen, die an Luft stabil sind. Dieses System wurde auf polymere Strukturen übertragen und NDI-Polymere mit niedrigen HOMO- und LUMO-Energieniveaus synthetisiert. Als Comonomer wird 1,4-Phenylen mit nur schwach elektronenschiebendem Charakter mit dem klassischen elektronenreichen Bithiophen verglichen. Die resultierenden Copolymere, jeweils mit und ohne Cyanosubstituenten wurden eingehend charakterisiert. Auch hier können luftstabile Radikalanionen in hohen Ausbeuten generiert werden. Diese Arbeit liefert ein grundlegenderes Verständnis der energetischen und strukturellen Voraussetzungen für Elektronentransferprozesse zwischen tertiären Aminen und elektronenarmen NDI-Derivaten unterschiedlicher Energieniveaus. Sie führt zu einem rationaleren Design von konjugierten Materialien mit selbstdotierenden Eigenschaften, um beispielsweise Radikalanionenkonzentration und Leitfähigkeit von organischen n-Halbleitern zu kontrollieren.:BIBLIOGRAPHISCHE BESCHREIBUNG UND REFERAT 5 I. ABKÜRZUNGSVERZEICHNIS VIII 1. EINLEITUNG 11 1.1 Organische Elektronik 12 1.1.1 Organische Thermoelektrika 14 1.1.2 Organische n Halbleiter auf Rylen Basis 18 1.2 C-C-Kupplungsreaktionen 25 1.2.1 Stille-Kupplung 27 1.2.2 Direkte C-H-Arylierungsreaktion 29 1.3 Dotierung organischer n Halbleiter 31 1.3.1 Selbstdotierung organischer Halbleiter mit Aminen 35 2. AUFGABENSTELLUNG 38 3. ERGEBNISSE UND DISKUSSION 40 3.1 PNDIT2 mit Aminoseitenketten 40 3.1.1 Synthese der Monomere 40 3.1.2 Polymerisation zu DMAP PNDIT2 41 3.1.3 Selbstdotierung von DMAP PNDIT2 42 3.2 DMAP NDI X2-Modellverbindungen 46 3.2.1 Synthesen von DMAP NDI X2 46 3.2.2 Untersuchung der Selbstdotierung von DMAP NDI X2 50 3.3 Kernsubstituierte Alkyl-NDI X2Y2 Modellverbindungen 53 3.3.1 Synthesen von NDI X2Y2 53 3.3.2 Elektronische Charakterisierungen 55 3.3.3 Untersuchung der intermolekularen Dotierung 62 3.3.4 Variation der Alkylseitenketten von Amino NDI und NDI CN2 74 3.4 NDI Copolymere 84 3.4.1 NDI Bipyridin 84 3.4.2 Synthese elektronenarmer NDI Polymere 94 3.4.3 Thermische Charakterisierung der NDI Polymere 99 3.4.4 Elektronische Charakterisierungen der NDI Polymere 101 3.4.5 Intermolekulare Dotierung der NDI Polymere 104 3.4.6 Elektrische Leitfähigkeiten der NDI Polymere 109 4. ZUSAMMENFASSUNG 112 5. AUSBLICK 120 6. EXPERIMENTALTEIL 122 6.1 Methoden und Geräte 122 6.1.1 Magnetische Kernresonanzspektroskopie (NMR) 122 6.1.2 Optische Charakterisierung (UV Vis) 122 6.1.3 UV Bestrahlung 122 6.1.4 Cyclovoltammetrie (CV) 123 6.1.5 Elektronenspinresonanz-Spektroskopie (EPR) 123 6.1.6 Differential-Scanning-Calorimetry (DSC) 123 6.1.7 Thermogravimetrische Analyse (TGA) 124 6.1.8 Gelpermeationschromatographie (GPC) 124 6.1.9 Röntgenweitwinkelstreuung (GIWAXS) 124 6.1.10 Massenspektrometrie (MS) 125 6.1.11 Elektrische Leitfähigkeit 125 6.1.12 Kommerzielle Chemikalien und Ausgangsstoffe 126 6.2 Synthesen 127 7. ANHANG 163 8. LITERATURVERZEICHNIS 175 II. SELBSTSTÄNDIGKEITSERKLÄRUNG 189 III. DANKSAGUNG 191 IV. LEBENSLAUF 192 Ausbildung und beruflicher Werdegang 192 Auszeichnungen 192 V. LISTE DER PUBLIKATIONEN UND VORTRÄGE 193

Diese Arbeit beschäftigt sich mit der Synthese neuer photoreaktiver Polymere, die bei Bestrahlung mit Licht (Hg-Dampflampe, fs-gepulster Ti:Sa-Laser) definierte Reaktionen durchlaufen. Mittels kontrolliert-radikalischer Polymerisation und anschließender polymeranaloger Reaktion wurden verschiedene Azobenzen-Derivate, Arylazosulfonat-Derivate und photolabil geschützte Aminogruppen (Nitroveratryloxycarbonyl, Nvoc) in Methacrylat-Polymere eingeführt. Diese Strukturen wurden ausführlich hinsichtlich ihrer Struktur und vor allem ihrer photochemischen Eigenschaften (Extinktionskoeffizienten, Zerfallskinetik) untersucht. Dünne Schichten (d<30nm) der so hergestellten Materialien wurden bei der Entwicklung einer neuen photolithographischen Methode, der plasmonischen Nanolithographie, eingesetzt.:INHALTSVERZEICHNIS ABBILDUNGSVERZEICHNIS TABELLENVERZEICHNIS ABKÜRZUNGS- UND SYMBOLVERZEICHNIS 1 EINLEITUNG UND ZIELSTELLUNG 2 THEORETISCHE GRUNDLAGEN 2.1 PHOTOREAKTIVE POLYMERE 2.1.1 Azobenzenhaltige Polymere und deren Anwendungen 2.1.2 Arylazosulfonathaltige Polymere und deren Anwendungen 2.1.3 Photolabil geschützte Amine in Polymeren und zur Oberflächenstrukturierung 2.2 NICHT-LINEAR OPTISCHE EFFEKTE - FREQUENZVERDOPPLUNG 2.3 OBERFLÄCHENPLASMONENRESONANZ UND SHG AN METALLISCHEN NANOPARTIKELN 2.4 PHOTOCHEMISCHE STRUKTURIERUNG DÜNNER SCHICHTEN 2.5 NANOLITHOGRAPHISCHE STRUKTURIERUNG MITTELS PLASMONISCHER EFFEKTE AN METALLNANOSTRUKTUREN 3 ERGEBNISSE UND DISKUSSION 3.1 AZOBENZENHALTIGE POLYMERE 3.1.1 Synthese niedermolekularer Azobenzen-Derivate 3.1.2 Anbindung an Polymermatrix 3.1.3 Photochemische matrixabhängige Untersuchung der Isomerisationskinetik 3.1.4 Bestrahlung in dünnen Schichten mit gepulstem Femtosekunden-Laser 3.2 ARYLAZOSULFONATHALTIGE POLYMERE 3.2.1 Kontrolliert-radikalische Polymerisation von Arylazosulfonat-Monomeren 3.2.1.1 Synthese der arylazosulfonathaltigen Monomere 3.2.1.2 RAFT-Polymerisation von (AS-Mon2) 3.2.2 Polymeranaloge Einführung von Arylazosulfonateinheiten 3.2.3 Präparation und Bestrahlung dünner Schichten 3.3 PHOTOLABIL GESCHÜTZTE AMINOPOLYMERE 3.3.1 Synthese von statistischen Nvoc-geschützten Aminocopolymeren 3.3.1.1 Anbindung des Nvoc-geschützten Amins über Esterbindung 3.3.1.2 Anbindung des Nvoc-geschützten Amins über Reaktion mit Nvoc-Cl 3.3.2 Nvoc-haltige Diblockcopolymere 3.3.2.1 Synthese von P(MMA-co-GMA)-b-P(MMA-co-NvocCMS) 3.3.2.2 Synthese von P(MMA-co-MAA)-b-P(MMA-co-NvocAEMA) 3.3.3 Präparation dünner Schichten der (Block-)Copolymere 3.3.4 Bestrahlung mit gepulstem Femtosekunden-Laser 4 ZUSAMMENFASSUNG UND AUSBLICK 5 EXPERIMENTALTEIL 5.1 ANALYTISCHE METHODEN 5.2 AUFBAU FÜR DIE FS-LASER-BESTRAHLUNG 5.3 VERWENDETE CHEMIKALIEN 5.4 SYNTHESEN 5.4.1 Azobenzen-Derivate 5.4.1.1 Niedermolekulare Verbindungen 5.4.1.2 Polymerisationen und polymeranaloge Reaktionen 5.4.2 Arylazosulfonate 5.4.2.1 Niedermolekulare Verbindungen 5.4.2.2 Freie radikalische Polymerisation 5.4.2.3 RAFT-Polymerisationenen 5.4.2.4 Polymeranaloge Reaktion 5.4.3 Nvoc-geschützte (Block-)Copolymere 5.4.3.1 Niedermolekulare Verbindungen 5.4.3.2 Polymerisationen 5.4.3.3 Polymeranaloge Reaktionen 5.5 WAFERREINIGUNG UND PRÄPARATION DÜNNER SCHICHTEN LITERATURVERZEICHNIS DANKSAGUNG VERSICHERUNG

Gegenstand dieser Arbeit war die Untersuchung verschiedener Systeme Chlorosilan / Amin bezüglich deren elektronischer Struktur, Molekülstruktur und Reaktivität. Einen Schwerpunkt bildete dabei die Untersuchung der LEWIS-BASE-katalysierten Disproportionierung unterschiedlich chlorierter Disilane mit elektronenreichen Alkenen, wie Tetrakis-(dimethylamino)-ethylen (TDAE) oder N,N,N’,N’-Tetramethyl-1,4-phenylendiamin (TPDA). Die Alkene sollten auf mögliche Elektronenübertragungsreaktionen, aber auch Chelatbildung mit den eingesetzten Disilanen bzw. intermediär gebildeten Silylenen getestet werden. Ein weiterer Schwerpunkt lag bei der Synthese und Charakterisierung neuer hetero- und homocyclischer Oligosilane. Die erhaltenen Cyclooligosilane wurden auf ihre Donorwirkung gegenüber elektronendefizienten π-Alkenen und eine damit verbundene Charge-Transfer-Komplexbildung untersucht. In die Auswertung wurden auch ab-initio-Berechnungen einbezogen, die mit den experimentellen Ergebnissen (u.a. NMR, IR, Röntgeneinkristallstrukturanalyse) vergleichend diskutiert wurden.

Self-assembly processes were used to construct supramolecular architectures based on metal-ligand interactions. The structures formed strongly depend on the used metal ion, the ligand type, the chosen counter ion and solvent as well as on the experimental conditions. The focus of the studies was the design of multifunctional N-donor ligands and the characterization of their complexing and structural properties. This work was divided into three distinct main parts: The bis(2-pyridylimine), the bis(2-hydroxyaryl) imine and the tripodal imine / amine ligand approach. In the first part a series of bis(2-pyridylimine) derivatives having different linking elements were employed as building blocks for novel supramolecular architectures. Reaction of individual d-block metal salts with these ligands has led to the isolation of coordination polymers, a metallamacrocycle, double-stranded helicates, triple-stranded helicates as well as of circular meso-helicates. The nature of the spacer in the Schiff base ligands, the noncovalent weak interactions, such as hydrogen bond, face-to-face π-π and edge-to-face CH-π interactions, are all important factors influencing the architecture of the final products. Topological control of the assembly process of the hexanuclear meso-helicates is clearly associated with the bidentate coordination of the sulfate anion which directs the formation of a double- rather than a triple-stranded helicate around the octahedrally coordinated Cu(II). Surprisingly, the variation of the linker function in the ligands, which significantly changes the linking angle of the pyridylimine strands, has only a little influence of the resulting structure. Also the use of a mixture of ligands does not influence the meso-helicate topology; the result is the symmetrically mixed meso-helicate. The new iron(II) triple helicate [Fe2(L5)3](PF6)4 14 {L5 = bis[4-(2-pyridylmethyleneimino)phenyl]-1,1-cyclohexane} in its chloride form binds strongly to DNA as confirmed by induced circular dichroism signals in both the metal-to-ligand charge transfer (MLCT) and in-ligand bands of the helicate. The induced CD spectrum gives some evidence that [Fe2(L5)3]4+ interacts with the DNA in a single binding mode, which is consistent with major groove binding. The cytotoxicity of the new iron(II) triple helicate 14 was evaluated on human lung cancer A549 cells and compared with that of cisplatin and that of the previously reported iron(II) triple helicate [Fe2(L1)3]4+{L1 = bis[4-(2-pyridylmethyleneimino)phenyl]methane}. The first results show some distinguishing features for 14 obviously caused by the existing structural differences of the complexes. In the second part of the thesis, novel uranyl complexes of the bis(2-hydroxyaryl) imine ligands have been synthesized and characterized. 1D coordination polymers and mononuclear structures were formed. In all complexes a distorted hexagonal bipyramidal coordination geometry around the uranyl centre is observed. The imine nitrogen atoms of the ligands do not bind to the metal centre but interact strongly with the hydroxy group via H-bonding. DFT calculations made with L8 ( α,α’-Bis(salicylimino)-m-xylene) are in good agreement with the X-ray crystal structure data. Liquid-liquid extraction studies involving selected ligands and Eu(III) or U(VI) indicate remarkably high selectivity for U(VI) over Eu(III) at weak acidic pH conditions. We believe that the study made opens up new possibilities for uranyl ion extraction which could be interesting in view of the treatment of nuclear waste. In the third part of the thesis, a series of multifunctional tripodal ligands with different N-donor centres were used for U(VI) and lanthanide, Nd(III), Eu(III) and Yb(III), binding and extraction. Reaction of these metal ions with selected tripodal ligands afforded complexes which were characterized by ESI mass spectroscopy. The complex composition was found to be 1:1 in all cases. The extraction behaviour of the tripodal ligands towards Eu(III) and U(VI) was studied both in the absence and presence of octanoic acid as co-ligand using the extraction system Eu(NO3)3 or UO2(NO3)2–buffer–H2O/ ligand–CHCl3. These separation systems show a remarkably high selectivity for U(VI) over Eu(III). It is interesting to note that the addition of the octanoic acid to the extraction system leads to high synergistic effects. A series of Eu(III) extraction experiments were done to clarify the composition of the extracted complexes. The results clearly point to the formation of various species with changing composition.

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