Photo-induced charge transfer which occurs between molecules or different parts of a large molecule is the pivotal process related to performances of organic electronics. In particular, injection of charge carriers into conjugated polymers and dissociation of photo-generated excitons at the heterojunction between a donor and acceptor system are of great importance in determining the luminescence efficiency of organic light emitting diodes (OLEDs) and solar energy conversion efficiency of organic solar cells, respectively. However, the complex nature of organic semiconductors as well as complicated primary processes involved in the functioning of these devices have prevented us from understanding unique characteristics of these processes and thereby engineering better materials for higher performances. In this dissertation, two different types of photo-induced (or -related) charge transfer processes occurring in organic semiconductors were investigated by using single molecule spectroscopy (SMS) techniques to unravel the complexities of these processes. The carefully designed functioning capacitor-like model devices similar to OLEDs and photovoltaic cells were fabricated where isolated single nanoparticles were introduced as an active medium to mitigate the complexities of these materials. We observed that injection of positively charged carriers (holes) into poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) single nanoparticles from the carbazole hole transport layer does not occur in the absence of light. We denoted the observed hole injection in aid of light as the light-induced hole transfer mechanism (LIHT). It was revealed that the charging dynamics are highly consistent with a cooperative charging effect. In addition, the LIHT was proposed as the possible source for the formation of deep trapped hole in organic devices. Local exciton dissociation yields across a nanostructured domain between poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) single nanoparticles and either poly(9,9- dioctylfluorene - co - bis-N,N- (4 -butylphenyl)-bis-N,N-phenyl-1,4-phenylene diamine) (PFB) or poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) film in model photovoltaic devices was also investigated. A wide distribution of exciton dissociation yields was observed from each nanodomain due to the device geometry. The observed hysteresis in fluorescence voltage curve was ascribed to accumulated charges following charge separations. The dynamics of charge separation under the applied electric field was described in more detail. / text

In bacteria, nucleoid associated proteins (NAPs) represent a prominent group of global regulators that perform the tasks of genome compaction, establishing chromosomal architecture and regulation of various DNA transactions like replication, transcription, recombination and repair. HU, a basic histone like protein, is one of the most important NAPs in Eubacteria. Mycobacterium tuberculosis produces a homodimeric HU (MtbHU), which interacts with DNA non-specifically through minor groove binding. Exploration for essential genes in Mtb (H37Rv) through transposon insertion has identified HU coding gene [Rv2986c, hupB; Gene Id: 15610123; Swiss-Prot ID: P95109)] to be vital for the survival and growth of this pathogen. MtbHU contains two domains, the N-terminal domain which is considerably conserved among the HU proteins of the prokaryotic world, and a C–terminal domain consisting of Lys-Ala rich multiple repeat degenerate motifs. Sequence analysis carried out by the thesis candidate showed that MtbHU exhibits 86 to 100 percent identity within the N-term region among all the mycobacterium species and some of the members of actinobacteria, including important pathogens like M. tuberculosis, M. leprae, M. ulcerans, M. bovis, Nocardia; while C term repeat region varies relatively more. This strikingly high cross species identity establishes the MtbHU N-terminal domain (MtbHUN) as an important representative structural model for the above mentioned group of pathogens. The thesis candidate has solved the X-ray crystal structure of MtbHUN, crystallized in two different forms, P2 and P21. The crystal structures in combination with computational analyses elucidate the structural details of MtbHU interaction with DNA. Moreover, the similar mode of self assembly of MtbHUN observed in two different crystal forms reveals that the same DNA binding interface of the protein can also be utilized to form higher order oligomers, that HU is known to form at higher concentrations. Though the bifunctional interface involved in both DNA binding and self assembly is not akin to a typical enzyme active site, the structural analysis identified key interacting residues involved in macromolecular interactions, allowing us to develop a rationale for inhibitor design. Further, the candidate has performed virtual screening against a vast library of compounds, and design of small molecules to target MtbHU and disrupt its binding to DNA. Various biochemical, mutational and biological studies were performed in the laboratory of our collaborator Prof. V. Nagaraja, MCBL, IISc., to investigate these aspects. After a series of iterations including design, synthesis and validation, we have identified novel candidate molecules, which bind to MtbHU, disrupt chromosomal architecture and arrest M. tuberculosis growth. Thus, the study suggests that, these molecules can serve as leads for a new class of DNA-interaction inhibitors and HU as a druggable target, more so because HU is essential to Mtb, but absent in human. Our study proposes that, targeting the nucleoid associated protein HU in Mtb can strategize design of new anti-mycobacterial therapeutics. Perturbation of MtbHU-DNA binding through the identified compounds provides the first instance of medium to small molecular inhibitors of NAP, and augurs well for the development of chemical probe(s) to perturb HU functions, and can be used as a fundamental chemical tool for the system level studies of HU-interactome. Section I: “Crystal structure of Mycobacterium tuberculosis histone like protein HU and structure based design of molecules to inhibit MtbHU-DNA interaction: Leads for a new target.” of this thesis presents an elaborate elucidation of the above mentioned work. The candidate has additionally carried out structure based computational and theoretical work to elucidate the interaction of amino acid based metal complexes which efficiently bind to DNA via minor-groove, major-groove or base intercalation interaction and display DNA cleavage activity on photo-irradiation. This understanding is crucial for the design of molecules towards Photodynamic Therapy (PDT). PDT is an emerging method of non-invasive treatment of cancer in which drugs like Photofrin show localized toxicity on photoactivation at the tumor cells leaving the healthy cells unaffected. The work carried out in our group in close collaboration with Prof. A.R. Chakravarty of Inorganic and Physical Chemistry Department elaborates the structure based design of Amino acid complexes containing single Cu (II), such as [Cu(L-trp)(dpq)(H2O)]+ , [Cu (L-arg) 2](NO3)2 , Amino acid complexes containing oxobridged diiron Fe(III), such as [{Fe(L-his)(bpy)}2(μ-O)](ClO4)2 , [{Fe(L-his)(phen)}2(μ-O)](ClO4)2 , and Complexes containing Binuclear Cu(II) coordinated organic moiety, such as [{(dpq) CuII}2(μ-dtdp)2], which bind to DNA through minor groove/major groove/base intercalation interactions. Docking analysis was performed with the X-ray crystallographic structure of DNA as receptor and the metal complexes as ligands, to study the mode of binding to DNA and to understand the possible mode of DNA cleavage (single/double strand) when activated with laser. Section II: “Structure based computational and theoretical analysis of metal coordinated complexes containing amino acids and organic moieties designed for photo induced DNA cleavage” of this thesis presents a detailed presentation of the above mentioned work.

Nowadays we are all witnesses of a competition of facilities at different countries to study unknown regions of neutron rich nuclei. Much efforts are devoted to understand the role of neutron excess and its influence on nuclei in vicinity of closed neutron shells. One of the means to investigate nuclear structure is in beta-decay. Once a nucleus is proven to exist, its beta-decay properties, such as T1/2 and Pn (probability of beta-delayed neutron emission), which are relatively easy to measure, can provide the first hints on the nuclear structure. On the r-process site, "waiting points"(nuclei on closed neutron shells) has significant effects on the r-process dynamics and the abundance distribution. The actual side and the astrophysical conditions under which the nuclear synthesis takes place are still not certainly known - since r-process nuclei are difficult to produce and to study experimentally, input parameters for r-process calculations are mostly derived from theoretical models. As it has been seen lately, most of the theories have failed to reproduce newly measured data sets near shell closures. With new experimental data already (or shortly) available theoretical approaches can be adjusted. Since a beta-delayed neutron emission becomes strong if not dominating decaying channel for nuclei far stability, a proper neutron detector to study their properties is indispensable. To conduct the appropriate investigations, in the frame of the present thesis, in close collaboration with JINR (Dubna) a new detection system was constructed. It consists of 80 ³He-filled counters, 4π beta detector and a HPGe in order to measure simultaneously beta, gamma, neutron activity. The development of such a detection system system, currently installed at ALTO ISOL facility, was the first objective of the thesis. Then, during two experimental campaigns conducted to investigate beta decay properties of neutron rich nuclei in the neighborhood of N=50, N=82 the workability of the newly produced detection system was proven. In the vicinity of ⁷⁸Ni: half- lives and probability of beta-delayed neutron emission for ⁸º,⁸²,⁸³,⁸⁴Ga were measured. We were the first to observe the structure of ⁸¹,⁸² Ge via beta neutron gated gamma spectra. Thanks to the neutron detection channel the absolute intensities of beta decay were proposed for the first time. In the vicinity of ¹³²Sn the half lives of ¹²³Ag, ¹²⁴Ag, ¹²⁵Ag and ¹²⁷In, ¹²⁸In was measured. For the first time the beta delayed neutron emission was observed for ¹²⁶Cd, its Pn value also measured. Based on the data obtained we come to the conclusion that to figure out the relative contribution of allowed and forbidden decays more theoretical efforts should be done crossing the N=50 shell. Whereas in the vicinity of N=82 shell more experimental challenge are required.

The innovative design of flat panel volume computed tomography (CT) systems has recently led to the emergence of a wide spectrum of new applications for both diagnostic and interventional purposes, such as ultra-high resolution bone imaging, image guided interventions, dynamic CT angiography, and interventional neuroradiology. Most of these applications require low X-ray dose to limit potential harm to the patient. One of the main challenges of low dose imaging is to maintain a quantum noise limited system to achieve the highest possible signal to noise ratio (SNR) at a given dose. One potential method to achieve a quantum noise limited system is to employ a high gain detector. Current flat panel CT technology is based on indirect conversion detectors that contain a scintillator and hydrogenated amorphous silicon (a-Si:H) p-i-n photodetectors which have a gain below unity and require a specialized p-layer. In this thesis, an alternative detector to the p-i-n photodetector, which can achieve gain above unity and thus aid in achieving quantum noise limited systems is investigated for large area flat panel imaging. The proposed detector is based on amorphous selenium (a-Se). Amorphous selenium is the most highly developed photoconductor for large area direct conversion X-ray imaging and is still the only commercially available large area direct conversion flat panel X-ray detector. However, the use of a-Se for indirect conversion imaging has not been significantly explored. Amorphous selenium has field dependent mobility and conversion efficiency, which increase with increasing electric field. It is also the only large area compatible avalanche-capable material; a property that was discovered more than 30 years ago. This unique property could be leveraged to provide the gain necessary for low dose medical imaging applications. The only current commercial avalanche capable a-Se optical detector uses electron beam readout in vacuum, which is not large area compatible and makes integration with pixelated readout electronics challenging. The detector structure proposed in this research seeks to address the challenges associated with integration of an avalanche capable a-Se detector with large area X-ray imager. One important aspect in the development of a-Se avalanche detectors is reducing the dark current and preventing a-Se breakdown as the electric field across the device is increased. A high dark current reduces the dynamic range of the detector, it increases the noise level, and it can lead to crystallization of the detector due to joule heating. To overcome the dark current problem, different blocking layers that allow for integration with large area flat panel imagers were investigated. Experimental results from fabricated devices provided the basis for the choice of the most suitable blocking layer. Two device structures are proposed using the selected blocking layer, a vertical structure and a lateral structure, each having associated benefits and drawbacks. It was shown that introducing a polyimide blocking layer brought down the dark current more than four orders of magnitude at high electric fields and does not deteriorate the charge transport properties of the detectors. The polyimide blocking layer also greatly minimizes physical stress related crystallization in a-Se improving reliability. Gain above unity was observed in the vertical structure and the initiation of impact ionization was verified by performing time-of-flight experiments. Although impact ionization was not verified in the lateral structure, this device structure was found to be highly sensitive to ultraviolet light due to the absence of a top contact layer. Devices were fabricated on several different substrates, including a CMOS substrate, to demonstrate their integration compatibility with large area readout electronics. The exhibited performance of the vertical device structure demonstrates that it is a suitable alternative to the p-i-n photodetector for low dose imaging applications.

Ce travail de thèse est centré sur l'étude expérimentale de deux types de transformations photo-induites observées dans différents complexes métalliques (Fe, Ru, ...) à ligand nitrosyle: (i) la photo-isomérisation au cours de laquelle le ligand NO passe d'un état lié par l'azote (M-NO, état stable GS) à un état lié par l'oxygène (M-ON, état métastable MSI). C'est un processus réversible et un second état métastable, 'side-on' MSII est observable au cours du processus inverse, MSI --> 'side-on' MSII --> GS; (ii) la libération photo-induite du radical NO°. La photo-isomérisation a été étudiée dans le système [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O (sur monocristal) par la diffraction des RX, l'absorption visible statique et l'absorption UV-Vis résolue en temps. Nous avons pu mettre en évidence un processus d'absorption de photons (473 nm) en deux étapes, suivre la dynamique des transformations directes et inverses par l'évolution des paramètres de maille et des l'absorption optique visible, caractériser structuralement l'état 'side-on' MSII. La nature de l'état intermédiaire, MSII, lors du processus direct semble être différente de l'état 'side-on' mais la très faible population de cet intermédiaire n'a pas permis de trancher définitivement. Le rôle de la molécule d'eau dans la maille du complexe [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O a été testé par diffraction des RX sur les échantillons hydratées, déshydratées et réhydratées. L'effet de déshydratation sur l'évolution des paramètres de maille et sur la génération d'espèces MSII au cours de la photo-commutation inverse, MSI --> MSII --> GS, est présenté. La libération photo-induite du radical NO° a été étudiée dans une solution d'acétonitrile du complexe trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 par spectroscopies d'absorption UV-Vis et Mi-IR, statiques et résolues en temps. En observant la dynamique ultra-rapide de la photo-transformation, nous avons mis en évidence un processus d'absorption de photons (406 nm) en deux étapes. La nature de l'état intermédiaire est discuté par rapport à de récents calculs théoriques et au processus de photo-isomérisation. / This Ph. D. thesis is focused on the experimental study of two photo-induced processes observed in various [ML_5NO] complexes, where M=Fe, Ru, ..., L=CN, Cl, ... : (i) photo-isomerization, where the system goes from N-bound state (M-NO, stable GS state) to O-bound state (M-ON, metastable MSI state) and a second metastable state, 'side-on' MSII is observed during the inverse photo-transformation, MSI --> 'side-on' MSII --> GS; (ii) photo-induced release of NO° radical. The photo-isomerization is investigated in single crystals of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O compound by means of X-Ray diffraction, steady state visible and time-resolved UV-visible absorption spectroscopies. During these experiments we observed the evidence of a two-step photon absorption process (473 nm), we followed the dynamics of direct and inverse photo-switching by the evolution of lattice parameters and absorption in the visible range and we caracterised the structure of 'side-on' MSII state. The nature of MSII in the direct photo-switching, GS --> MSI, seems to be different from the 'side-on' configuration, however, we do not have a direct access to this state due to its low population. The role of water molecule in the unit cell of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O complex was tested by X-Ray diffraction studies on hydrated, dehydrated and rehydrated samples. The effect of sample dehydration on the unit cell parameters evolution and MSII species generation during the MSI --> MSII --> GS inverse photo-switching is presented. The photo-induced NO° release in trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 system in acetonitrile solution is studied by the UV-visible and mid-IR absorption spectroscopies, both steady state and time-resolved. By observing the ultra-fast dynamics of photo-transformation we evidenced a two-step photon absorption process (406 nm). The nature of intermediate state is discussed within the recent theoretical calculations and the photo-isomerization process.

The present thesis deals with different aspects of the chemistry of oxovanadium(IV) complexes, their interaction with DNA and protein and photo-induced DNA and protein cleavage activity and photocytotoxicity. Chapter I presents a general introduction on various modes of interactions of organic compounds and transition metal complexes capable of targeting DNA leading to DNA strand scission, emphasizing particularly the photo-induced DNA cleavage activities for their potential application in PDT. The mechanistic pathways associated with the DNA cleavage are discussed. A comparison has been made on the advantages of photoactive metal complexes over organic conjugates. Objective of the present investigation is also dealt in this Chapter. Chapter II of the thesis deals with the synthesis, characterization, DNA binding and photo-induced DNA cleavage activity of ternary oxovanadium(IV) complexes of N-salicylidene-S-methyldithiocarbazate (salmdtc) and phenanthroline bases to explore the photo-induced DNA cleavage activity in UV-A light of 365 nm. Chapter III presents the synthesis, characterization, DNA binding and photo-induced DNA cleavage activity of ternary oxovanadium(IV) complexes containing N-salicylidene-L-methionate (salmet) and N-salicylidene-L-tryptophanate (saltrp) Schiff bases and phenanthroline bases. The objective of this work is to investigate the photo-induced DNA cleavage activity in near-IR light and to see the effect of pendant thiomethyl and indole moieties in the DNA cleavage reactions. Chapter IV deals with the synthesis, characterization, DNA binding, red-light induced DNA cleavage activity and photocytotoxicity of ternary oxovanadium(IV) complexes having N-salicylidene-L-arginine (sal-argH) and N-salicylidene-L-lysine (sal-lysH) Schiff bases and phenanthroline bases. The important results include the visible light-induced DNA cleavage activity and photocytotoxicity of the complexes in human cervical HeLa cancer cells. Chapter V describes the synthesis, characterization, DNA binding and photo-induced DNA and protein cleavage activity and photocytotoxicity of oxovanadium(IV) complexes containing bis(2-benzimidazolylmethyl)amine and phenanthroline bases. The significant results include DNA cleavage activity in near-IR light and photocytotoxicity of the dppz complex in non-small cell lung carcinoma/human lung adenocarcinoma A549 cells in visible light. Further, we have studied the protein cleavage activity of the complexes in UV-A light of 365 nm by using bovine serum albumin (BSA) and lysozyme. Finally, Chapter VI presents the binary oxovanadium(IV) complexes of phenanthroline bases. We have studied their synthesis, characterization, DNA binding and photo-induced DNA and protein cleavage activity and photocytotoxicity. Photocytotoxicity of dppz complex has been studied in human cervical HeLa cancer cells in visible light. Photo-induced protein cleavage activity of the complexes has been studied in UV-A light of 365 nm by using BSA and lysozyme. The references have been compiled at the end of each chapter and indicated as superscript numbers in the text. The complexes presented in this thesis are represented by bold-faced numbers. Crystallographic data of the complexes, characterized structurally by single crystal X-ray crystallography, are given in CIF format in the enclosed CD (Appendix-I). Due acknowledgements have been made wherever the work described is based on the findings of other investigators. Any omission that might have happened due to oversight or mistake is regretted.

Scorpionate and terpyridine ligands are of importance in inorganic chemistry for their metal-binding properties. Tris-pyrazolylborate (Scorpionate) ligands that show facial binding mode and steric protection have been extensively used to synthesize complexes modeling the active site structure and biological function of various metalloproteins and as catalysts in C-H and NO activation and carbine transfer reactions. Terpyridine and modified terpyridine ligands showing meridional binding mode have been used in bioinorganic chemistry where Pt-terpyridine complexes are known to inhibit the activity of thiordoxin reductase (TrxR) besides showing interaction with G-quadruplex. The thesis work stems from our interest to use these ligand systems to design and prepare new 3-d metal-based photodynamic therapeutic (PDT) agents to explore their visible light-induced DNA cleavage activity and photocytotoxicity. Efforts have been made in this thesis work to design and synthesize Co(II) and Cu(II) complexes having scorpionate (Tpph) abd terpyridine (tpy) ligands. Ternary 3d-metal complexes having Tpph and planar phenanthroline bases have been synthesized and structurally characterized. The steric encumbrance of Tpph has led to the reduction in chemical nuclease activity along with enhanced photo-induced DNA cleavage activity, particularly of the Cu(II) and Co(II) complexes. The Co(II), Cu(II) and Zn(II) complexes of Tpph and a pyridyl ligand having a photoactive naphthalilmide moiety show molecular light-switch effect on binding to calf thymus DNA or BSA protein. The complexes do not show any chemical nuclease activity. The Cu(II) complex shows significant DNA cleavage activity in red light. The Co(II) complex displays significant photocytotoxicity in UV-A light. Ternary Cu(II) complexes of ph-tpy and heterocycylic bases are prepared and their DNA binding and cleavage activity studied. The complexes are avid binders to CT-DNA. The dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) complexes are photocleavers of DNA in visible light. A significant enhancement in cytotoxicity in HeLa cancer cells is observed on exposure of the dppz complex to light. The binary Cu(II) complexes are also prepared to reduce the dark toxicity using phenyl and pyrenyl substituted terpyridine ligands. The pyrenyl substituted complex shows DNA cleavage activity in the visible light, low dark toxicity and unprecedented photocytotoxicity in visible light. The copper(II) complexes generally show dark cellular toxicity due to the presence of reducing thiols. The present terpyridine copper(II) complex having pendant pyrenyl moiety shows significant PDT effect that is similar to that of the PDT drug Photofrin. Binary Co(II) complexes show efficient DNA cleavage activity in visible light, significant photocytotoxicity in visible light and cytosolic uptake behaviour. Considering the bio-essential nature of the cobalt and copper ions, the present study opens up new strategies for designing and developing 3d-metal-based photosensitizers for their potential applications in PDT.

The main objective of this thesis is the study of the optical and optoelectronic properties of organic semiconducting materials. At the beginning of this thesis is shown the growing interest in these materials and their practical application. The theoretical part presents the current state of knowledge of studied problematic related to optical phenomena and the transport of charge carriers in organic semiconductors, photochormic phenomena of reversible molecular switch and charge transfer in DNA biopolymeric matrix. Experimental section, which consists of selected author’s publications, includes study of the charge transport, photochromic reversible switching and the role of dopant in pi-conjugated organic polymer system. Conductive and semiconductive characteristics of the DNA biopolymer have been aslo studied. Conductive and photoconductive techniques together with measurement of the optical characteristics have been used for organic semiconductors characterization.

The 2010 Deepwater Horizon (DWH) oil spill resulted in a large release of polycyclic aromatic hydrocarbons (PAH) into the Gulf of Mexico. PAH can interact with ultraviolet radiation (UV) resulting in increased toxicity, particularly to early lifestage organisms. The goal of this research was to determine the sensitivity of fiddler crab larvae (Uca longisignalis) to photo-induced toxicity following exposure to Deepwater Horizon spill oil in support of the DWH Natural Resource Damage Assessment. Five replicate dishes each containing 20 larvae, were exposed to one of three UV treatments (10%, 50%, and 100% ambient natural sunlight) and one of five dilutions of water accommodated fractions of two naturally weathered source oils. A dose dependent effect of PAH and UV on larval mortality was observed. Mortality was markedly higher in PAH treatments that included co-exposure to more intense UV light. PAH treatments under low intensity sunlight had relatively high survival. These data demonstrate the importance of considering combined effects of non-chemical (i.e. UV exposure) and chemical stressors and the potential for photo-induced effects after exposure to PAH following the Deepwater Horizon spill.

Der Gegenstand der vorliegenden Arbeit ist die Untersuchung von photoinduzierten Energietransferprozessen (EET) und Elektronentransferprozessen (ET) in Modellsystemen, die als potentiell geeignet für eine Nutzung in der artifiziellen Photosynthese angesehen werden. Den beiden wesentlichen Zugängen zur Architektur artifizieller Photosynthese-Systeme entsprechend wurden vergleichend kovalente und sich selbst organisierende Systeme untersucht. In beiden Zugängen wurden ähnliche chemische Komponenten als optisch aktive Moleküle eingesetzt, insbesondere Phthalocyanine mit einem Silizium-Zentralatom (SiPc). Durch eine Kombination von stationären und zeitaufgelösten optisch-spektroskopischen Methoden konnten die lichtinduzierten ET- und EET-Prozesse identifiziert und quantifiziert werden. Im ersten Teil der Arbeit wurden mehrere kovalent gebundene Triaden und eine Pentade untersucht. In allen Systemen finden sehr effiziente ET und EET Prozesse statt. Es wurde gezeigt, dass das Lösungsmittel großen Einfluss auf die photophysikalischen Eigenschaften der Systeme ausübt. Die Lebensdauer des ladungsseparierten Zustandes variiert von 1,7 ns in Toluol bis 30 ps in DMF. Im zweiten Teil der Arbeit wurde erstmals gezeigt, dass sich in wässriger Lösung ein supramolekularer Komplex, bestehend aus einem Beta-Cyklodextrin (CD), einem konjugierten Subphthylocyanin (SubPc), einem Porphyrin (Por) und einem SiPc bilden kann. Letzteres wurde über unterschiedliche Ketten an zwei CDs kovalent gebunden. Die Selbstorganisation wird über hydrophobe Wechselwirkungen vermittelt und die Bildung der Komplexe ist sehr effizient. Nach selektiver Anregung von SubPc finden sequenzielle ET- und EET-Prozesse von SubPc zu SiPc statt. Das Por spielt die Rolle einer energetischen und elektronischen Brücke und ermöglicht die ET und EET-Prozesse von SubPc zu SiPc. Die Ladungsrekombination in den Grundzustand geschieht innerhalb von 1,7 ns. / The main objective of the present thesis was to conduct investigations of photo-induced electron transfer (ET) and excitation energy transfer (EET) processes in model compounds that are considered potentially appropriate for use in artificial photosynthesis. Two approaches have been used to construct the artificial photosynthetic systems, namely covalent and supramolecular approach. In both systems similar optically active molecules have been employed, particularly silicon-based phthalocyanines (SiPc). A comparative study between the covalently-linked and self-assembled systems had been conducted. For these purposes, thorough spectroscopic measurements in the UV/Vis range had been performed on these conjugates. A combination of steady-state and time-resolved experiments allowed an identification and quantification of the photo-induced ET and EET processes. In the first part of the work several covalently bound triads and a pentad bearing a central SiPc unit were studied. In all systems highly efficient ET and EET processes take place. It was found that the solvent exerts great influence on the photophysical properties of the systems. The lifetime of the charge-separated state varied from 1.7 ns (toluene) down to 30 ps (DMF). In the second part of the thesis, for the first time the formation of ternary supramolecular complexes consisting of a beta-cyclodextrin (CD), a conjugated subphthalocyanine (SubPc), a porphyrin (Por) and a series of SiPcs substituted axially with two CDs via different spacers was shown. These components are held in water by host-guest interactions and the formation of these host-guest complexes was found to be very efficient. Upon excitation of the SubPc-part of the complex sequential ET and EET processes from SubPc to SiPc take place. The Por dye acts as a transfer bridge enabling these processes. The probability of ET is controlled by the linker between CD and SiPc. Charge recombination to the ground state occurs within 1.7 ns.