Synthesis, ultrafast spectroscopy and theoretical modeling of Lutetium bisphthalocyanine

In dieser Arbeit wurde der Doppeldecker Komplex Lutetium Bisphthalocyanin synthetisiert um elektronische Wechselwirkungen der beiden makrozyklischen Liganden auf ultraschnellen Zeitskalen im Hinblick auf Energietransfer und Ladungstrennung zu studieren. Der Sandwichkomplex wurde basenkatalysiert mittels zyklischer Tetramerisierung unter Verwendung eines Metalltemplateffekts synthetisiert, anschließend chromatographisch abgetrennt und aufgereinigt. Die Charakterisierung beinhaltet ein und zwei dimensionale NMR Techniken, elektronische und Schwinungsspektroskopie sowie eine massenspektrometrische Analyse. Dabei stellte sich heraus, dass der dimere Komplex kaum eindeutige Signale liefert, die Rückschlüsse auf dessen Struktur erlauben. Dennoch ist es möglich den elektronischen Zustand anhand redoxsensitiver Banden zu identifizieren. Kohärente zwei-dimensionale elektronsiche Spektroskopie stellt ein wertvolles Mittel zur Untersuchung von molekulardynamischen Prozessen wie Wellenpaketen, elektronischem Energietransfer oder Ladungstrennung dar. In weiterem Verlauf wird ein multifunktioneller Aufbau beschrieben, der es ermöglicht diese Prozesse in Echtzeit zu verfolgen. Das Dimer sollte ursprünglich als biomimetrisches Modellsystem zur Untersuchung des Beitrags von elektronischen Kohärenzen zur Effizienz von Lichtsammelsystemen dienen. Es stellte sich heraus, dass jegliche Beiträge durch eine extrem schnelle Populationsdynamik ausgelöscht werden, diese aber ein neues Detail in der elektronischen Struktur des Bisphthalocyanins freigibt. Mögliche Modelle die dessen Ursprung aufklären könnten, werden im theoretischen Teil unter Zuhilfenahme quantenchemischer Rechenmethoden diskutiert. Die Dimension des behandelten Systems erfordert eine Berechnung mittels Dichtefunktionaltheorie. Das Vorhandensein verschiedenartiger elektronischer Zustände kompliziert die Simulation und schränkt die Genauigkeit der Ergebnisse stark ein. BHLYP erwies sich als geeignetstes all-round Funktional, speziell für die Berechnung von charge-transfer Anregungsenergien. Die Einbeziehung des Gegenions, lieferte eine Aufspaltung der elektronischen Zustände, die die experimentellen Beobachtungen reproduziert und deutet auf eine Asymmetrie des Dimers hin, die wahrscheinlich zu einer partiellen Ladnungstrennung führt.In this thesis a lutetium bisphthalocyanine double-decker complex is synthesized to study the interaction of the macrocyclic ligands on ultrashort timescales with special concern on the elementary processes of energy transfer and charge separation. The molecular dimer is prepared by a metal template assisted cyclic tetramerization reaction under basic condition in the bulk phase at elevated temperature following chromatographic separation and purification by recrystallization. The spectroscopic characterization includes one and two dimensional NMR, vibrational and electronic spectroscopy as well as mass spectrometry. It is found that the symmetry of the molecular structure leads to few signals in all of the aforementioned spectroscopic techniques. Despite these difficulties, it is possible to assign the electronic state by inspection of some redox sensitive marker bands. Coherent two-dimensional electronic spectroscopy (2D-ES) provides a versatile tool for investigating molecular dynamics in real time. The observable processes include nuclear wavepackets, electronic energy transfer and dissipation just as charge transfer dynamics. A multifunctional non-linear spectroscopy set-up capable of following these processes in the visible spectral range is described and applied to the synthesized phthalocyanine dimer. The work intended to focus on recently discussed importance of electronic coherences to energy transfer in biological systems by using this relatively simple model system. However, it turned out that the induced dynamics are dominated by an ultrafast initial population decay that extinguishes all possible electronic coherences but exposes a previously unseen feature in the electronic structure through asymmetric recovery of the missing low energy cross-peak. Possible scenarios to account for its emergence are tackled by quantum chemical calculations. Computation of the electronic structure is vital and an elementary step in the discussion of excited state processes. The sheer size of the considered system and different state characters make theoretical modeling cumbersome and restrict it to DFT methods. A test of various functionals marks BHLYP as most suitable for calculating charge transfer excitation energies. Association of the anionic dimer complex with the TBA counterion leads to structural asymmetry of the rings that lifts the degeneracy of states thus doubling the number of transitions and altering their character

Transfer of Vibrational Coherence Through Incoherent Energy Transfer Process in F\"{o}rster Limi

We study transfer of coherent nuclear oscillations between an excitation energy donor and an acceptor in a simple dimeric electronic system coupled to an unstructured thermodynamic bath and some pronounced vibrational intramolecular mode. Our focus is on the non-linear optical response of such a system, i.e. we study both excited state energy transfer and the compensation of the so-called ground state bleach signal. The response function formalism enables us to investigate a heterodimer with monomers coupled strongly to the bath and by a weak resonance coupling to each other (F\"{o}rster rate limit). Our work is motivated by recent observation of various vibrational signatures in 2D coherent spectra of energy transferring systems including large structures with a fast energy diffusion. We find that the vibrational coherence can be transferred from donor to acceptor molecules provided the transfer rate is sufficiently fast. The ground state bleach signal of the acceptor molecules does not show any oscillatory signatures, and oscillations in ground state bleaching signal of the donor prevail with the amplitude which is not decreasing with the relaxation rate.Comment: 11 pages, 9 figure

Ultrafast Photo-Induced Charge Transfer Unveiled by Two-Dimensional Electronic Spectroscopy

The interaction of exciton and charge transfer (CT) states plays a central role in photo-induced CT processes in chemistry, biology and physics. In this work, we use a combination of two-dimensional electronic spectroscopy (2D-ES), pump-probe measurements and quantum chemistry to investigate the ultrafast CT dynamics in a lutetium bisphthalocyanine dimer in different oxidation states. It is found that in the anionic form, the combination of strong CT-exciton interaction and electronic asymmetry induced by a counter-ion enables CT between the two macrocycles of the complex on a 30 fs timescale. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra, and we monitor how the excited state charge density ultimately localizes on the macrocycle closest to the counter-ion within 100 fs. A comparison with the dynamics in the radical species further elucidates how CT states modulate the electronic structure and tune fs-reaction dynamics. Our experiments demonstrate the unique capability of 2D-ES in combination with other methods to decipher ultrafast CT dynamics.Comment: 14 pages, 11 figures, and Supporting informatio

Hierarchy of hybrid materials — the place of inorganics-in-organics in it, their composition and applications

Hybrid materials, or hybrids incorporating both organic and inorganic constituents, are emerging as a very potent and promising class of materials due to the diverse, but complementary nature of the properties inherent of these different classes of materials. The complementarity leads to a perfect synergy of properties of desired material and eventually an end-product. The diversity of resultant properties and materials used in the construction of hybrids, leads to a very broad range of application areas generated by engaging very different research communities. We provide here a general classification of hybrid materials, wherein organics–in-inorganics (inorganic materials modified by organic moieties) are distinguished from inorganics–in–organics (organic materials or matrices modified by inorganic constituents). In the former area, the surface functionalization of colloids is distinguished as a stand-alone sub-area. The latter area—functionalization of organic materials by inorganic additives—is the focus of the current review. Inorganic constituents, often in the form of small particles or structures, are made of minerals, clays, semiconductors, metals, carbons, and ceramics. They are shown to be incorporated into organic matrices, which can be distinguished as two classes: chemical and biological. Chemical organic matrices include coatings, vehicles and capsules assembled into: hydrogels, layer-by-layer assembly, polymer brushes, block co-polymers and other assemblies. Biological organic matrices encompass bio-molecules (lipids, polysaccharides, proteins and enzymes, and nucleic acids) as well as higher level organisms: cells, bacteria, and microorganisms. In addition to providing details of the above classification and analysis of the composition of hybrids, we also highlight some antagonistic yin-&-yang properties of organic and inorganic materials, review applications and provide an outlook to emerging trends

Magnetically actuable delivery vehicles

Stimuli-responsive amphiphilic superstructures comprise some of the most successful drug delivery systems in clinical use. Vesicular assemblies in particular, have long been recognized as excellent carrier systems for diagnostic and therapeutic agents due to their potential to encapsulate, transport and release various cargo upon local changes; the latter in response to the microenvironment. Structural incorporation of biocompatible, functional nanomaterials such as superparamagnetic iron oxide nanoparticles can be employed to design universal delivery systems, whose release profiles can be controlled externally by application of a magnetic field. The aim of this work is to establish a theranostic platform by incorporating hydrophobic SPIONs of controlled size and interfacial chemistry into stimuli-responsive amphiphilic superstructures and to demonstrate externally triggered release of a model compound via magnetic actuation. The synthesis of monodisperse nanocrystals and complete exchange of the native hydrophobic dispersant shell for irreversibly grafted nitrocatechol-derived anchors at maximal ligand density is exemplified and shown crucial for controlled capsule assembly. A method for efficient encapsulation of SPION into amphiphile membranes is outlined that allows for direct and quantitative co-self-assembly of bilayer forming amphiphiles with hydrophobic nanoparticles into controlled magnetosomes. The novel method allowed for controlling the vesicle size, lamellarity and the nanoparticle concentration in the membrane with retained vesicle stability. Various capsule systems comprising polymeric superamphiphiles and mixed lipid/superamphiphile blends were investigated and their magnetothermal release efficiencies using alternating magnetic field irradiation to cause local hyperthermia were compared. Mixed membrane capsules were found to combine efficient magnetothermal actuation with the high stability of purely polymeric membrane systems.Doctor of Philosophy (IGS

Magnetically actuable delivery vehicles

Supramolekulare Kapseln aus reiz-empfindlichen Trägermaterialien, stellen einige der erfolgreichsten klinischen Auslieferungssysteme für therapeutische Wirkstoffe dar. Vesikel werden seit jeher aufgrund ihres Potentials zur Einkapselung und zur umweltbedingten Freisetzung von therapeutischen und diagnostischen Agenzien als exzellente Trägersysteme geschätzt. Die strukturelle Einbindung von biokompatiblen, funktionellen Nanomaterialen wie etwa superparamagnetischen Eisenoxid-Nanopartikeln kann dazu verwendet werden, universelle Auslieferungssysteme zu kreieren, dessen Freisetzungsprofil durch Anlegen eines selektiven äußeren Reizes, beispielsweise eines magnetischen Feldes, gesteuert werden kann. Das Ziel dieser Arbeit ist die Entwicklung einer solchen theranostischen Platform sowie die Demonstration einer extern kontollierten Freisetzung einer Modellsubstanz durch magnetische Anregung. Die Synthese von monodispersen Nanokristallen und der vollständige Austausch der ursprünglichen Ligandenschale ist essentiell für die kontrollierte Herstellung der Kapseln und wird gezeigt. Es wurde eine wirkungsvolle Methode zur Einbettung von magnetischen Nanopartikeln entwickelt, die zur direkten und quantitativen Selborganisation von hydrophoben Eisenoxid-Kristallen und membranformenden Amphiphilen in kontollierte Magnetosome führt. Das neue Verfahren erlaubt die Steuerung der Vesikelgröße, Lamellarität und der Nanopartikelkonzentration in der Membran bei gleichbleibender Vesikelstabilität. Unterschiedliche Trägersysteme aus makromolekularen Superamphiphilen und gemischten Diblock Copolymer-Lipid Systemen wurden hergestellt und untersucht. Die Wirksamkeit der verschiedenen neuen Kapselsysteme bezüglich induzierter Freigabe durch magnetische Wechselfeld Anregung wurde verglichen. Es wird gezeigt, dass gemischte Membrankapseln eine effiziente magneto-thermische Freisetzung ermöglichen und diese mit der hohen Stabilität der ursprünglich untersuchten reinen Polymerkapseln kombinieren.Stimuli-responsive amphiphilic superstructures comprise some of the most successful drug delivery systems in clinical use. Vesicular assemblies in particular, have long been recognized as excellent carrier systems for diagnostic and therapeutic agents due to their potential to encapsulate, transport and release various cargo upon local changes; the latter in response to the microenvironment. Structural incorporation of biocompatible, functional nanomaterials such as superparamagnetic iron oxide nanoparticles can be employed to design universal delivery systems, whose release profiles can be controlled externally by application of a magnetic field. The aim of this work is to establish a theranostic platform by incorporating hydrophobic SPIONs of controlled size and interfacial chemistry into stimuli-responsive amphiphilic superstructures and to demonstrate externally triggered release of a model compound via magnetic actuation. The synthesis of monodisperse nanocrystals and complete exchange of the native hydrophobic dispersant shell for irreversibly grafted nitrocatechol-derived anchors at maximal ligand density is exemplified and shown crucial for controlled capsule assembly. A method for efficient encapsulation of SPION into amphiphile membranes is outlined that allows for direct and quantitative co-self-assembly of bilayer forming amphiphiles with hydrophobic nanoparticles into controlled magnetosomes. The novel method allowed for controlling the vesicle size, lamellarity and the nanoparticle concentration in the membrane with retained vesicle stability. Various capsule systems comprising polymeric superamphiphiles and mixed lipid/superamphiphile blends were investigated and their magnetothermal release efficiencies using alternating magnetic field irradiation to cause local hyperthermia were compared. Mixed membrane capsules were found to combine efficient magnetothermal actuation with the high stability of purely polymeric membrane systems.by Oliver Bixner, Mag.Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZusammenfassung in deutscher SpracheUniversität für Bodenkultur, Dissertation, 2016OeBB(VLID)193165

Triggered release from thermoresponsive polymersomes with superparamagnetic membranes

Magnetic polymersomes were prepared by self-assembly of the amphiphilic block copolymer poly(isoprene-b-N-isopropylacrylamide) with monodisperse hydrophobic superparamagnetic iron oxide nanoparticles (SPION). The specifically designed thermoresponsive block copolymer allowed for efficient incorporation of the hydrophobic nanoparticles in the membrane core and encapsulation of the water soluble dye calcein in the lumen of the vesicles. Magnetic heating of the embedded SPIONs led to increased bilayer permeability through dehydration of the thermoresponsive PNIPAM block. The entrapped calcein could therefore be released in controlled doses solely through exposure to pulses of an alternating magnetic field. This hybrid SPION-polymersome system demonstrates a possible direction for release applications that merges rational polymersome design with addressed external magnetic field-triggered release through embedded nanomaterials.Published versio

Fluorescent Magnetopolymersomes: A Theranostic Platform to Track Intracellular Delivery

We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent and magnetic vesicles is described. Cell uptake of the densely PEGylated polymer vesicles could be altered by surface modifications that vary surface charge and accessibility of the membrane active species. Cell uptake and cytotoxicity were evaluated by confocal microscopy, transmission electron microscopy, iron content and metabolic assays, utilizing multimodal tracking of membrane fluorophores and nanoparticles. Cationic functionalization of vesicles promoted endocytotic uptake. In particular, incorporation of cationic lipids in the polymersome membrane yielded tremendously increased uptake of polymersomes and magnetopolymersomes without increase in cytotoxicity. Ultrastructure investigations showed that cationic magnetopolymersomes disintegrated upon hydrolysis, including the dissolution of incorporated iron oxide nanoparticles. The presented platform could find future use in theranostic multimodal imaging in vivo and magnetically triggered delivery by incorporation of thermorepsonsive amphiphiles that can break the membrane integrity upon magnetic heating via the embedded superparamagnetic nanoparticles