Mother nature has laid out a beautiful blueprint to capture sunlight and convert to usable form of energy. Inspired by nature, donor-acceptor systems are predominantly studied for their light harvesting applications. This dissertation explores new donor-acceptor systems by studying their photochemical properties useful in building artificial photosynthetic systems. The systems studied are divided into phthalocyanine-porphyrin-fullerene-based, perylenediimide-based, and aluminum porphyrin-based donor-acceptor systems. Further effect of solvents in determining the energy or electron transfer was studied in chapter 6. Such complex photosynthetic analogues are designed and characterized using UV-vis, fluorescence spectroscopy, differential pulse voltammetry and cyclic voltammetry. Using ultrafast transient absorption spectroscopy, the excited state properties are explored. The information obtained from the current study is critical in getting one step closer to building affordable and sustainable solar energy harvesting devices which could easily unravel the current energy demands.

This bachelor thesis covers the initial development of a synthesis of fullerene dimers using two different types of linking reactions. Different setups for [3+2] cycloadditions to fullerenes (Prato reaction) were tested, and for that purpose, an N-alkylated amino acid was synthesised. Hydroarylation of fullerene using Rh-catalysis was also studied, using both MIDA protected and unprotected boronic acids, as well as by using cycloaddition products. A range of model compounds in form of fulleropyrrolidenes were synthesised. Products were puried with HPLC and analysed with MALDI-MS and 1H NMR. A range of new compounds were synthesised and characterisation of them was begun. With MALDI-MS, indications that the fullerene dimer had formed were found. Using synthesised model compounds, by-products of the hydroarylation reaction were identied. / Denna kandidatuppsats behandlar påborjandet av syntesutvecklingen för bildandet av fullerendimerer genom användandet av två olika sorters länkningskemi. Olika förhållanden och reagens for [3+2]-cykloaddition till fullerener (Pratoreaktionen) studerades, och i samband med det syntetiserades en N-alkylerad aminosyra. Hydroarylering av fullerener med hjälp utav rodiumkatalys studerades även, genom reaktioner med både skyddade och oskyddade borsyror, inklusive fulleropyrrolidiner. Produkter har renats upp med HPLC och analyserats med MALDI-MS och 1H NMR. En uppsättning nya substanser har syntetiserts, men karaktäriseringen av dessa har inte slutförts. Genom användning av MALDI-MS har indikationer att fullerendimer bildats framkommit. Genom att använda syntetiserade modellsubstanser har biprodukter från hydroaryleringsreaktionen identierats.

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The recent availability of X-ray Free Electron Lasers (XFELs) has opened a completely new and unexplored regime for the study of light-matter interactions. The extremely bright intensities delivered by XFELs can couple many photons into the target, turning well known interactions such as photoionization and scattering into new, non-linear, complex many-body phenomena. This thesis reports theoretical investigations aiming to improve the understanding of the fundamental processes and dynamics triggered by intense X-ray pulses, with a special focus in finite systems such as molecules and clusters. Sequential multiple photoionization in atomic clusters was investigated, where previous observations were extended for higher charge states where direct photoionization is frustrated. Through a rate equation study and subsequent molecular dynamics simulations, it was found that frustrated ionization is partially responsible for the low-energy peak observed in the electron energy spectrum. The influence of plasma evaporation over the formation of the sequential low-energy peak was also investigated, identifying the effects of the system size and photon energy. Multiple channel ionization was also investigated for the case of fullerenes. This is done through a series of studies, starting from a simplified rate equation scheme, and culminating with full molecular dynamics simulations. From these results, a good insight was obtained over the origin, physical meaning, and relevant parameters that give rise to the complicated features observed in the electronic spectra. The mechanisms responsible of all these features are expected to be present in other systems, making these results quite general. Diffractive imaging of biomolecules was studied in a final step, with a particular focus on the influence of intramolecular charge transfer mechanisms. To this end a conformer of T4 Lysozyme was used, a representative enzyme with well known structure. Charge migration is found to allow for additional processes such as proton ejection, a mechanism which enables an efficient release of energy from the system. This mechanism considerably suppresses structural damage for heavy ions, improving the quality of the measured diffraction patterns.

The investigation and control of the properties of carbon based materials such as fullerenes and nanotubes is a highly dynamic research field. Due to its unique properties, e.g. an almost nano-dimensional size, three-dimensional cage topology, hydrophobicity, rich redox- and photochemistry, large absorption cross section, C60 has a high potential as building block for molecular devices and biological applications. It can be functionalized, anchored to a surface and self-assembled into larger supramolecular entities, such as monolayers. Mass spectrometry and related techniques such as ion-molecule reactions, action spectroscopy and ion mobility have been used throughout this work to study fullerene based systems, ranging from hydrides, derivatives, non-covalent complexes and coordinated metal complexes. Simulations predicting structural, electronic and mechanical properties have been combined with the experimental results to assist in their analysis and interpretation. Using ion molecule reactions, the reactivity of gas phase C60 anions with methanol has been studied. Hydride formation by simple collisions in the gas phase with methanol as well as reversible dehydrogenation by infrared multiphoton activation has been demonstrated. C60 functionalization by 3-azido-3-deoxythymidine (AZT) has been performed and the charged product characterized both by collisional activation and action spectroscopy. Deprotonation has been shown to lead to rearrangements of the nucleoside analogue and to a subsequent charge transfer to the fullerene. To prevent unwanted rearrangements and side reactions, encapsulation of C60 is suggested, the host molecule acting as a steric barrier. C60 complexation by γ-cyclodextrins has been performed and the ions of the complexes characterized both by collisional activation and ion mobility. It has been demonstrated that, compared to deprotonated species, the sodiated C60:(γ-cyclodextrin)2 ions were highly compact structures. With only two small polar caps accessible to reagents, sodiated C60: (γ-cyclodextrin)2 complexes sterically protect the C60 core from unwanted side reactions. Finally, explorative work on C60 immobilization on silver colloids using surface enhanced Raman spectroscopy and on the characterization of C60 complexes with iron and manganese porphyrin is presented.

<p>The ability of photocatalytic nanoparticles (NPs) to produce reactive oxygen species (ROS) has inspired research into several new applications and technologies, including water purification, contaminant remediation, and self-cleaning surface coatings. As a result, NPs continue to be incorporated into a wide variety of increasingly complex products. With the increased use of NPs and nano-enabled products and their subsequent disposal, NPs will make their way into the environment. Currently, many unanswered questions remain concerning how changes to the NP surface chemistry that occur in natural waters will impact reactivity. This work seeks to investigate potential influences on photoreactivity – specifically the impact of functionalization, the influence of anions, and interactions with biological objects - so that ROS generation in natural aquatic environments may be better understood.</p><p>To this aim, titanium dioxide nanoparticles (TiO2) and fullerene nanoparticles (FNPs) were studied in terms of their reactive endpoints: ROS generation measured through the use of fluorescent or spectroscopic probe compounds, virus and bacterial inactivation, and contaminant degradation. Physical characterization of NPs included light scattering, electron microscopy and electrophoretic mobility. These systematic investigations into the effect of functionalization, sorption, and aggregation on NP aggregate structure, size, and reactivity improve our understanding of trends that impact nanoparticle reactivity.</p><p>Engineered functionalization of FNPs was shown to impact NP aggregation, ROS generation, and viral affinity. Fullerene cage derivatization can lead to a greater affinity for the aqueous phase, smaller mean aggregate size, and a more open aggregate structure, favoring greater rates of ROS production. At the same time however, fullerene derivatization also decreases the 1O2 quantum yield and may either increase or decrease the affinity for a biological surface. These results suggest that the biological impact of fullerenes will be influenced by changes in the type of surface functionalization and extent of cage derivatization, potentially increasing the ROS generation rate and facilitating closer association with biological targets.</p><p>Investigations into anion sorption onto the surface of TiO2 indicate that reactivity will be strongly influenced by the waters they are introduced into. The type and concentration of anion impacted both aggregate state and reactivity to varying degrees. Specific interactions due to inner sphere ligand exchange with phosphate and carbonate have been shown to stabilize NPs. As a result, waters containing chloride or nitrate may have little impact on inherent reactivity but will reduce NP transport via aggregation, while waters containing even low levels of phosphate and carbonate may decrease “acute” reactivity but stabilize NPs such that their lifetime in the water column is increased.</p><p>Finally, ROS delivery in a multicomponent system was studied under the paradigm of pesticide degradation. The presence of bacteria or chlorpyrifos in solution significantly decreased bulk ROS measurements, with almost no OH detected when both were present. However, the presence of bacteria had no observable impact on the rate of chlorpyrifos degradation, nor chlorpyrifos on bacterial inactivation. These results imply that investigating reactivity in simplified systems may significantly over or underestimate photocatalytic efficiency in realistic environments, depending on the surface affinity of a given target.</p><p>This dissertation demonstrates that the reactivity of a system is largely determined by NP surface chemistry. Altering the NP surface, either intentionally or incidentally, produces significant changes in reactivity and aggregate characteristics. Additionally, the photocatalytic impact of the ROS generated by a NP depends on the characteristics of potential targets as well as on the characteristics of the NP itself. These are complicating factors, and the myriad potential exposure conditions, endpoints, and environmental systems to be considered for even a single NP highlight the need for functional assays that employ environmentally relevant conditions if risk assessments for engineered NPs are to be made in a timely fashion so as not to be outpaced by, or impede, technological advances.</p> / Dissertation

Optical spin readout (OSR) in fullerene-based systems has the potential to solve the spin readout and scalability challenges in solid-state quantum information processing. While the rich variety of chemical groups that can be linked (covalently or not) to the fullerenes opens the possibility of making large and controlled arrays of qubits, optical methods can be used to measure EPR down to a single spin thanks to the large energy of optical photons compared to the microwave ones. After reviewing the state of the art of OSR, for which the diamond NV cen- ters constitute the benchmark, we undertake the study of fullerene-based species for OSR. An optically detected magnetic resonance (ODMR) setup was imple- mented in a commercial EPR spectrometer for this purpose. Each experimental chapter focuses on one of the molecular systems in question: a functionalised C₆₀ fullerene with a phosphonate group (C₆₀-phosphine), porphyrin-fullerene ar- chitectures (weakly, strongly and moderately coupled) and finally erbium-doped trimetallic nitride template (TNT) fullerenes (focusing on ErSc₂N@C₈₀). In the C₆₀-phosphine system, coherent optically detected magnetic resonance (ODMR) in the triplet state has been achieved. Since a large variety of organic and organometallic molecules can be attached to it both via the fullerene cage and the phosponate group, this result makes it a very useful template to study OSR molecules chemically linked to a qubit. In the porphyrin based structures, an intermediate coupling case in the form of a trimer-fullerene host-guest complex is found to allow detection of both the porphyrin and fullerene triplet sates by CW ODMR, which makes organo-metallic complexes a possible coupling route for a qubit to an OSR component. In the TNT fullerene, crystal field mixing makes the Er³⁺ inaccessible by ODMR. However, optical photons cause a mechanical rearrangement of the en- dohedral cluster which in turns impacts on the observed EPR. In particular, the dynamics of this process have been studied for the first time and hint to- wards diffusion kinetics at low pump power. An orientational selectivity has been discovered by using a polarised pump, and the time dynamics indicate the rearrangement of the matrix via difusion on a free volume around the fullerenes. This shows that the endohedral Er³⁺ in ErSc₂N@C₈₀ can probe the environment outside the cage.

Master of Science / Department of Physics / Matthias Kling / This thesis consists of two major parts. The first part concerns studies of the orientation dependence of the ionization of diatomic molecules in intense, femtosecond two-color laser fields. The second part is about studies on the ionization mechanisms of the C[subscript]6[subscript]0 molecule in femtosecond near-infrared and ultraviolet laser fields. In the first part, experimental and theoretical results on the asymmetric ion emission of the heteronuclear molecules CO and NO in two-color laser fields are discussed. The two-color fields, which can be tailored by a relative phase, are used to ionize and dissociate CO and NO molecules, both of which are molecules with small polarizabilities. The resulting C[superscript]+, C[superscript]2[superscript]+, N[superscript]+ and O[superscript]+ ions are detected by a velocity map imaging (VMI) setup. The photoelectrons from above-threshold ionization (ATI) of Xe are studied under such a two-color field to assign the phase. For both CO and NO we find that enhanced ionization occurs when the molecule is oriented with the electric field pointing from the C or N atom toward the O atom. This is in agreement with the molecular orbital Ammosov-Delone-Krainov (MO-ADK) theory and the Stark-corrected strong-field-approximation (SFA) calculations. The second part is devoted to the investigation of the ionization mechanism of neutral C[subscript]6[subscript]0 molecules with 30 fs laser pulses at about 800 nm and with 50 fs pulses at about 400 nm. The angular distributions of photoelectrons are measured utilizing VMI. Measurements under different intensities are carried out for the two wavelengths. In our work, thermal electron emission is highly suppressed by the use of short pulses. For near-infrared excitation, photoelectron angular distributions (PADs) that contain six lobes are observed for low energy electrons. This behavior is different from studies for longer pulses of about 120 fs [1]. Further analysis indicates that the PADs might originate from single photon ionization of a super atomic molecular orbital (SAMO), however, a detailed assignment requires further theoretical work. The PADs for the ultraviolet excitation show very similar structures to earlier results [1]. For the near-infrared excitation, we have carried out studies as a function of the chirp of the pulses and find effects on photoelectron spectra and on PADs, which are tentatively explained by sequential multiphoton ionization via “doorway” states.

Nesta tese foram perseguidos novos avanços no campo das tetrapiridilporfirazinas supramoleculares polimetaladas, visando explorar a maior capacidade de conjugação eletrônica esperada para essa classe de compostos, e seus reflexos nas propriedades eletrônicas e eletroquímicas. Foram apresentadas novas rotas sintéticas para obtenção de tetra(3,4-piridil)porfirazinas centrometaladas coordenadas a complexos polipiridínicos de rutênio, MTRPyPz (M = Cu, Co). As propriedades espectroscópicas e eletroquímicas foram investigadas com o auxílio de técnicas de espectroscopia UV-Vis, Raman ressonante, voltametria cíclica, espectroeletroquímica e espectrometria de massas. Foram desenvolvidas aplicações em dispositivos amperométricos para determinação eletrocatalítica de substratos importantes nas indústrias, como nitrito, sulfito e ácido ascórbico. Os estudos também abrangeram a formação de compósitos das porfirazinas tetrarrutenadas com fullereno. Os nanomateriais híbridos apresentaram uma alta eficiência nos processos eletrocatalíticos com menor sobrepotencial no eletrodo, abrindo perspectivas interessantes de utilização em dispositivos moleculares / Research in supramolecular polymetallic tetrapyridylporphyrazines has been pursued in this Thesis, aiming the exploitation of the favorable electronic delocalization associated with conjugated aromatic rings, and its influence on the electronic and electrochemical properties. New synthetic routes have been developed for the preparation of tetra(3,4-pyridyl)porphyrazines containing Cu(II) and Co(II) ions in the center, and four chlorobis(2,2´bipyridine)ruthenium(II) complexes attached to the peripheral pyridyl groups. Their spectroscopic and electrochemical behaviors were investigated by means of UV-Vis and resonance Raman spectroscopy, cyclic voltammetry, spectroelectrochemistry and mass spectrometry. Applications in amperometric devices for determination of nitrite, sulfite and ascorbic acid were successfully developed. The thesis also focused on nanocomposites generated from the polymetallic porphyrazines and fullerene (C60). Such hybrid nanomaterials exhibited enhanced electrocatalytic activity associates with a significant decrease of overpotential, opening exciting perspectives of use in molecular devices

Nesta tese foram perseguidos novos avanços no campo das tetrapiridilporfirazinas supramoleculares polimetaladas, visando explorar a maior capacidade de conjugação eletrônica esperada para essa classe de compostos, e seus reflexos nas propriedades eletrônicas e eletroquímicas. Foram apresentadas novas rotas sintéticas para obtenção de tetra(3,4-piridil)porfirazinas centrometaladas coordenadas a complexos polipiridínicos de rutênio, MTRPyPz (M = Cu, Co). As propriedades espectroscópicas e eletroquímicas foram investigadas com o auxílio de técnicas de espectroscopia UV-Vis, Raman ressonante, voltametria cíclica, espectroeletroquímica e espectrometria de massas. Foram desenvolvidas aplicações em dispositivos amperométricos para determinação eletrocatalítica de substratos importantes nas indústrias, como nitrito, sulfito e ácido ascórbico. Os estudos também abrangeram a formação de compósitos das porfirazinas tetrarrutenadas com fullereno. Os nanomateriais híbridos apresentaram uma alta eficiência nos processos eletrocatalíticos com menor sobrepotencial no eletrodo, abrindo perspectivas interessantes de utilização em dispositivos moleculares / Research in supramolecular polymetallic tetrapyridylporphyrazines has been pursued in this Thesis, aiming the exploitation of the favorable electronic delocalization associated with conjugated aromatic rings, and its influence on the electronic and electrochemical properties. New synthetic routes have been developed for the preparation of tetra(3,4-pyridyl)porphyrazines containing Cu(II) and Co(II) ions in the center, and four chlorobis(2,2´bipyridine)ruthenium(II) complexes attached to the peripheral pyridyl groups. Their spectroscopic and electrochemical behaviors were investigated by means of UV-Vis and resonance Raman spectroscopy, cyclic voltammetry, spectroelectrochemistry and mass spectrometry. Applications in amperometric devices for determination of nitrite, sulfite and ascorbic acid were successfully developed. The thesis also focused on nanocomposites generated from the polymetallic porphyrazines and fullerene (C60). Such hybrid nanomaterials exhibited enhanced electrocatalytic activity associates with a significant decrease of overpotential, opening exciting perspectives of use in molecular devices