TY - THES A1 - Roos, Markus T1 - Synthesis, Photophysics and Photocatalysis of [FeFe] Complex Containing Dyads and Bimolecular Systems T1 - Synthese, Photophysik und Photokatalyse von [FeFe]-Komplex enthaltenden Dyaden und bimolekularen Systemen N2 - In the course of this work, a total of three photocatalytically active dyads for proton reduction could be synthesized together with the associated individual components. Two of them, D1 and D2, comprised a [Ru(bpy)3]2+ photosensitizer and D3 an [Ir(ppy)2bpy]+ photosensitizer. A Ppyr3-substituted propyldithiolate [FeFe] complex was used as catalyst in all systems. The absorption spectroscopic and electrochemical investigations showed that an inner-dyadic electronic coupling is effectively prevented in the dyads due to conjugation blockers within the bridging units used. The photocatalytic investigations exhibited that all dyad containing two-component systems (2CS) showed a significantly worse performance than the corresponding bimolecular three-component systems (3CS). Transient absorption spectroscopy showed that the 2CS behave very similarly to the associated multicomponent systems during photocatalysis. The electron that was intended for the intramolecular transfer from the photosensitizer unit to the catalyst unit within the dyads remains at the photosensitizer for a relatively long time, analogous to the 3CS and despite the covalently bound catalyst. It is therefore assumed that this intramolecular electron transfer is likely to be hindered as a result of the weak electronic coupling caused by the bridge units used. Instead, the system bypasses this through an intermolecular transfer to other dyad molecules in the immediate vicinity. In addition, with the help of emission quenching experiments and electrochemical investigations, it could be clearly concluded that all investigated systems proceed via the reductive quenching mechanism during photocatalysis. N2 - Im Rahmen dieser Arbeit konnten insgesamt drei photokatalytisch aktive Dyaden zur Protonenreduktion zusammen mit den zugehörigen Einzelkomponenten synthetisiert werden. Zwei von ihnen, D1 und D2, umfassten einen [Ru(bpy)3]2+-Photosensibilisator und D3 einen [Ir(ppy)2bpy]+-Photosensibilisator. Als Katalysator wurde in allen Systemen ein Ppyr3-substituierter Propyldithiolat-[FeFe]-Komplex verwendet. Die absorptionsspektroskopischen und elektrochemischen Untersuchungen zeigten, dass eine innerdyadische elektronische Kopplung aufgrund von Konjugationsblockern innerhalb der verwendeten Brückeneinheiten wirksam verhindert wird. Die photokatalytischen Untersuchungen zeigten, dass alle dyadenhaltigen Zweikomponentensysteme (2CS) eine signifikant schlechtere Leistung zeigten als die entsprechenden bimolekularen Dreikomponentensysteme (3CS). Mithilfe der transienten Absorptionsspektroskopie konnte gezeigt werden, dass sich die 2CS während der Photokatalyse sehr ähnlich wie die zugehörigen Mehrkomponentensysteme verhalten. Das Elektron, das für den intramolekularen Transfer von der Photosensibilisatoreinheit zur Katalysatoreinheit innerhalb der Dyaden vorgesehen war, verbleibt analog zu den 3CS und trotz des kovalent gebundenen Katalysators relativ lange am Photosensibilisator. Es wird daher angenommen, dass dieser intramolekulare Elektronentransfer wahrscheinlich aufgrund der schwachen elektronischen Kopplung, die durch die verwendeten Brückeneinheiten verursacht wird, behindert wird. Stattdessen umgeht das System dies durch einen intermolekularen Transfer zu anderen Dyadenmolekülen in unmittelbarer Nähe. Darüber hinaus konnte mithilfe von Emissionslöschungsexperimenten und elektrochemischen Untersuchungen eindeutig darauf geschlossen werden, dass alle untersuchten Systeme während der Photokatalyse über den reduktiven Löschmechanismus ablaufen. KW - Fotokatalyse KW - Elektronentransfer KW - proton reduction KW - [FeFe] hydrogenase mimic KW - dyad KW - ruthenium photosensitizer KW - iridium photosensitizer KW - Protonenreduktion KW - [FeFe]-Hydrogenase Imitator KW - Dyade KW - Ruthenium-Photosensibilisator KW - Iridium-Photosensibilisator Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234537 ER - TY - JOUR A1 - Lübtow, Michael M. A1 - Marciniak, Henning A1 - Schmiedel, Alexander A1 - Roos, Markus A1 - Lambert, Christoph A1 - Luxenhofer, Robert T1 - Ultra-high to ultra-low drug loaded micelles: Probing host-guest interactions by fluorescence spectroscopy JF - Chemistry - A European Journal N2 - Polymer micelles are an attractive means to solubilize water insoluble compounds such as drugs. Drug loading, formulations stability and control over drug release are crucial factors for drug‐loaded polymer micelles. The interactions between the polymeric host and the guest molecules are considered critical to control these factors but typically barely understood. Here, we compare two isomeric polymer micelles, one of which enables ultra‐high curcumin loading exceeding 50 wt.%, while the other allows a drug loading of only 25 wt.%. In the low capacity micelles, steady‐state fluorescence revealed a very unusual feature of curcumin fluorescence, a high energy emission at 510 nm. Time‐resolved fluorescence upconversion showed that the fluorescence life time of the corresponding species is too short in the high‐capacity micelles, preventing an observable emission in steady‐state. Therefore, contrary to common perception, stronger interactions between host and guest can be detrimental to the drug loading in polymer micelles. KW - curcumin KW - drug delivery KW - fluorenscence KW - poly(2-oxazine) KW - pol(2-oxazoline) KW - Polymer-drug interaction KW - upconversion Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206128 VL - 25 IS - 54 ER -