Refine
Has Fulltext
- yes (113)
Is part of the Bibliography
- yes (113)
Year of publication
Document Type
- Doctoral Thesis (113) (remove)
Language
- English (113) (remove)
Keywords
- Supramolekulare Chemie (21)
- Selbstorganisation (18)
- Farbstoff (13)
- Merocyanine (10)
- Perylenbisimid (10)
- Perylenderivate (10)
- Aggregation (9)
- Fluoreszenz (9)
- Organische Chemie (9)
- perylene bisimide (9)
- Elektronentransfer (8)
- self-assembly (8)
- Squaraine (6)
- Chemische Synthese (5)
- Chromophor (5)
- Exziton (5)
- Katalyse (5)
- Nucleinsäuren (5)
- Self-assembly (5)
- supramolecular chemistry (5)
- Flüssigkristall (4)
- Ladungstransfer (4)
- Metallosupramolekulare Chemie (4)
- NMR-Spektroskopie (4)
- Naphthylisochinolinalkaloide (4)
- Perylenbisdicarboximide <Perylen-3,4:9,10-bis(dicarboximide)> (4)
- Perylene Bisimide (4)
- Polymere (4)
- Supramolekulare Struktur (4)
- Wasseroxidation (4)
- Aggregat <Chemie> (3)
- Ancistrocladaceae (3)
- Chirality (3)
- Chiralität <Chemie> (3)
- DNA (3)
- DNS (3)
- Energietransfer (3)
- Fotokatalyse (3)
- Hydrogel (3)
- Merocyanin (3)
- Quantenchemie (3)
- Ruthenium Komplexe (3)
- Selbstassemblierung (3)
- Self-Assembly (3)
- Triarylamine (3)
- Wasser (3)
- catalysis (3)
- electron transfer (3)
- energy transfer (3)
- fluorescence (3)
- metallosupramolecular chemistry (3)
- non-covalent interactions (3)
- organische Solarzelle (3)
- transient absorption (3)
- transient absorption spectroscopy (3)
- water oxidation (3)
- 10-bis(dicarboximide)> (2)
- 4:9 (2)
- Ancistrocladus (2)
- Aptamer (2)
- Aromatically annulated triquinacenes (2)
- Aromatisch anellierte Triquinacene (2)
- C-C coupling (2)
- Chiralität (2)
- Click-Chemie (2)
- Dyade (2)
- Energy Transfer (2)
- Exciton coupling (2)
- Exzitonenkopplung (2)
- FRET (2)
- Fluoreszenz-Resonanz-Energie-Transfer (2)
- Gold (2)
- Guanidinderivate (2)
- J- and H-Aggregate (2)
- J- and H-Aggregates (2)
- Liquid Crystal (2)
- Merocyanine dyes (2)
- Methyltransferase (2)
- Molekulare Erkennung (2)
- Nucleoside (2)
- Oligomere (2)
- Organic Chemistry (2)
- Organische Solarzelle (2)
- Organische Synthese (2)
- Organischer Feldeffekttransistor (2)
- Organischer Halbleiter (2)
- Oxidation (2)
- Perylenbisdicarboximide (2)
- Perylenbisdicarboximide <Perylen-3 (2)
- Perylenbisimide (2)
- Perylene bisimide (2)
- Photosensibilisator (2)
- Polycyclische Aromaten (2)
- Pyrene (2)
- RNA (2)
- RNS (2)
- Ringöffnungspolymerisation (2)
- Ruthenium complexes (2)
- Rutheniumkomplexe (2)
- SARS-CoV-2 (2)
- Scheibe-Aggregat (2)
- Selbstassoziation (2)
- Spinchemie (2)
- Strukturaufklärung (2)
- Supramolecular Chemistry (2)
- Transiente Absorption (2)
- Triarylamin (2)
- Triquinacenderivate (2)
- Wasserstoffbrückenbindung (2)
- Wirt-Gast-Beziehung (2)
- charge separation (2)
- charge transfer (2)
- cooperativity (2)
- curved hydrocarbons (2)
- cyclophane (2)
- dimer (2)
- gekrümmte Kohlenwasserstoffe (2)
- intervalence charge transfer (2)
- naphthylisoquinoline alkaloids (2)
- nicht-kovalente Wechselwirkungen (2)
- organic solar cell (2)
- organic solar cells (2)
- polymer-peptide-conjugate (2)
- redox cascade (2)
- ruthenium complexes (2)
- spin chemistry (2)
- supramolekulare Chemie (2)
- thiol-ene (2)
- triarylamine (2)
- triquinacene derivatives (2)
- "steepest descent-modest ascent" (1)
- "steilsten Abstieg - schwächste Aufstieg" (1)
- (bi)pyridine-based ligand (1)
- 2"-> (1)
- 2':6' (1)
- 5'-O-Methyldioncophylline D (1)
- A-D-A dyes (1)
- A. abbreviatus (1)
- A. likoko (1)
- Absolute Configuration (1)
- Absolute Konfiguration (1)
- Absorption (1)
- Acenes (1)
- Acetylneuraminsäure <N-> (1)
- Actinomyceten (1)
- Actinomycetes (1)
- Adsorption (1)
- Aggregate (1)
- Akzeptor <Chemie> (1)
- Alkaloid (1)
- Alkaloide (1)
- Alkoxylradikale (1)
- Alkoxylradikals (1)
- Aminosäuren (1)
- Amphiphile Verbindungen (1)
- Ancistrolikokine E3 (1)
- Anode (1)
- Anti-infectious activity (1)
- Antiausterity activity (1)
- Antimalariamittel (1)
- Antimicrobial activities (1)
- Antimicrobial proteins (1)
- Antimikrobielle Aktivitäten (1)
- Antimikrobieller Wirkstoff (1)
- Antitumor-Antibiotikum (1)
- Antitumor-antibitioc (1)
- Arene-Fluoroarene (1)
- Artificial Base Pair (1)
- Asymmetric synthesis (1)
- Asymmetrische Synthese (1)
- Atropisomere (1)
- Atropisomerie (1)
- Base pairing (1)
- Basenpaarung (1)
- Biomaterial (1)
- Bioorganic chemistry (1)
- Bioorganik (1)
- Bioorthogonal (1)
- Biradikal (1)
- Bodipy (1)
- Bola-Amphiphil (1)
- Bor-Stickstoff-Verbindungen (1)
- Borane (1)
- Boron-Nitrogen Dative Bond (1)
- CD-Spektroskopie (1)
- COVID-19 (1)
- Cage (1)
- Calix[4]aren (1)
- Carbazolderivate (1)
- Carboxylat-Rezeptor (1)
- Catalysis (1)
- Charge-transfer-Komplexe (1)
- Chemie (1)
- Chemische Bindung (1)
- Chemische Reaktion (1)
- Chemosensor (1)
- Chirality Transfer (1)
- Chlorin (1)
- Chlorinderivate (1)
- Chromophore (1)
- Circular Dichroism (1)
- Circular dichroism (1)
- Circular-Dichroismus (1)
- Computational chemistry (1)
- Computerchemie (1)
- Congo (1)
- Congolese Ancistrocladus plants (1)
- Coordination Polymer (1)
- Corannulene (1)
- Coronaviren (1)
- Covalent Organic Framework (1)
- Crosslinker (1)
- Crosslinking (1)
- Cyaninfarbstoff (1)
- Cyclic peptides (1)
- Cyclooctine (1)
- Cyclooctyne (1)
- Cyclophan (1)
- Cyclovoltammetrie (1)
- DOSY-NMR (1)
- Demethylase (1)
- Demethylierung (1)
- Demokratische Republik Kongo (1)
- Deoxyribozymes (1)
- Diamant (1)
- Diarylethen (1)
- Diarylethene (1)
- Diarylethylene (1)
- Dicarboximide (1)
- Dicarboximides (1)
- Dichtebestimmung in Theorie und Experiment (1)
- Dihydrooxazole (1)
- Dimer (1)
- Dimer-Konfiguration (1)
- Dimere (1)
- Dimeric Naphthylisoquinoline Alkaloids (1)
- Dioncophylline C (1)
- Donator <Chemie> (1)
- Donor (1)
- Donor-Akzeptor Triaden (1)
- Donor-Photosensibilisator-Akzeptor Triade (1)
- Drug Delivery System (1)
- Dyad (1)
- Dye (1)
- Dyes/pigments (1)
- Dünnschichttransistor (1)
- EPR spectroscopy (1)
- Electron Transfer (1)
- Electron density (1)
- Elektrochemie (1)
- Elektronendichte (1)
- Elektronendichtebestimmung (1)
- Elektronenspinresonanzspektroskopie (1)
- Energieaufnahme (1)
- Energietransfer <Mikrophysik> (1)
- Enzym (1)
- Enzyminhibitor (1)
- Epitranskriptom (1)
- Excitons (1)
- Farbstoffe (1)
- Farbstoffe/Pigmente (1)
- Festkörper-NMR (1)
- Festphasensynthese (1)
- Fluorescence (1)
- Fluoreszenzaktivierung (1)
- Fluoreszenzspektrometer (1)
- Fluoreszenzspektroskopie (1)
- Foldamers (1)
- Fulleren-Netzwerk (1)
- Fullerene (1)
- Funktionalisierung <Chemie> (1)
- Funktionelle Polymere (1)
- Galectine (1)
- Gelieren (1)
- Glucosyltransferasen (1)
- Glycoengineering (1)
- Gold Nanoparticles (1)
- Gold Nanopartikel (1)
- Grün fluoreszierendes Protein (1)
- Guanidiniocarbonylpyrrol (1)
- H-Aggregate (1)
- H-bonds (1)
- Halbleiter (1)
- Hekate (1)
- Helicene (1)
- Helicität <Chemie> (1)
- Helix- and Zick-Zack-Konformere (1)
- Helix- and Zig-Zag-Conformers (1)
- Helix-Coil-Transition (1)
- Helix-Knäuel-Umwandlung (1)
- Heterosolarzelle (1)
- Hexaarylbenzene (1)
- Hexaarylbenzole (1)
- Host-Guest Chemistry (1)
- Host-Guest-Chemistry (1)
- Hydrogen bond (1)
- Inhibitor (1)
- Intermolecular Interactions (1)
- Intermolekulare Wechselwirkungen (1)
- Intervalenzladungstransfer (1)
- Iridium-Photosensibilisator (1)
- Iridiumkomplexe (1)
- Isolation (1)
- Isolierung (1)
- Isolierung <Chemie> (1)
- J-Aggregat (1)
- J-Aggregate (1)
- J-Aggregates (1)
- J-aggregate (1)
- Jozimine A2 (1)
- Kinetic Self-assembly (1)
- Kinetik (1)
- Kohlenhydrate (1)
- Kohlenstoff (1)
- Kohn-Sham Orbitale (1)
- Kohn-Sham Orbitals (1)
- Kolloidalstabilität (1)
- Kombinatorische Synthese (1)
- Komplexierung (1)
- Konfiguration <Chemie> (1)
- Konformeren (1)
- Konglomerat (1)
- Kongo (1)
- Kooperativität (1)
- Koordinationspolymer (1)
- Koordinationspolymere (1)
- Kraftfeld (1)
- Kupplungsreaktion (1)
- Käfigverbindungen (1)
- Ladungstrennung (1)
- Lebende Polymerisation (1)
- Leitfähige Polymere (1)
- Lichtabsorption (1)
- Lichtsammelsystem (1)
- Ligand (1)
- Liquid Crystals (1)
- Living Polymerisation (1)
- Lower Critical Solution Temperature (LCST) (1)
- MRCI (1)
- Magnetfeldeffekt (1)
- Makrocyclische Verbindungen (1)
- Makrozyklus (1)
- Mechanismus (1)
- Merocyanine dye (1)
- Mesogen (1)
- Metabolismus (1)
- Metaheuristik-Suchmethoden (1)
- Metall-Ion (1)
- Metallosupramolecular chemistry (1)
- Methylierung (1)
- Michael addition (1)
- Michael-Addition (1)
- Molecular dynamics (1)
- Molecular probes (1)
- Molekül (1)
- Moleküldynamik (1)
- Moleküloptimierung (1)
- Moller-Plesset (1)
- Monoschicht (1)
- Mulliken-Hush (1)
- Multi Reference (1)
- Multireferenz (1)
- N-acetyllactosamine (1)
- NIQs (1)
- NIR chromophore (1)
- Nanodiamant (1)
- Nanopartikel (1)
- Nanoribbon (1)
- Nanosegregation (1)
- Nanostructure (1)
- Nanostrukturen (1)
- Naphthalinbisimid (1)
- Naphthochinonen (1)
- Naphthoquinones (1)
- Naphthyl Isoquinolines (1)
- Naphthylisochinoline (1)
- Naphthylisoquinolin (1)
- Naphthylisoquinoline (1)
- Naphthylisoquinoline alkaloids (1)
- Natural Products (1)
- Natural products (1)
- Naturstoffe (1)
- Nicht-Fulleren Akzeptor (1)
- Non-Fullerene Acceptor (1)
- Non-linear optics (1)
- Nonlinear Optical Properties of Organic Materials (1)
- Nucleic acids (1)
- Nucleosidanaloga (1)
- Nukleinsäure (1)
- OFETs (1)
- OLC (1)
- OLED (1)
- Oligomers and Polymers (1)
- Oligonucleotide (1)
- Onbead-Enzymscreening (1)
- Optimierungsmethoden (1)
- Optimization methods (1)
- Organic Field-Effect Transistor (1)
- Organic field-effect transistor (1)
- Organic semiconductors (1)
- Organische Halbleiter (1)
- PEDOT (1)
- PNA (1)
- Pancreatic cancer (1)
- Paracyclophane (1)
- Pentacen (1)
- Peptid-Nucleinsäuren (1)
- Peptidsynthese (1)
- Perylen-Farbstoffe (1)
- Perylenbisanhydrid (1)
- Perylenbisimiden (1)
- Perylenbisimides (1)
- Perylene Bisimides (1)
- Perylentetracarbonsäurederivate (1)
- Pflanzenzelle (1)
- Pflanzenzellkulturen (1)
- Phosphoramidite (1)
- Phosphorylase (1)
- Photochemie (1)
- Photochemistry (1)
- Photochromie (1)
- Photoconductivity (1)
- Phytochemical investigations of a Congolese Ancistrocladus Liana (1)
- Phytochemie (1)
- Plant cell cultures (1)
- Polyamin (1)
- Polycarbazole (1)
- Polycyclic aromatic hydrocarbons (1)
- Polymer (1)
- Polymerhalbleiter (1)
- Polymerkomplexe (1)
- Polymerlösung (1)
- Polymorphismus (1)
- Porosität (1)
- Porous Materials (1)
- Porphyrin (1)
- Protease (1)
- Protein Corona (1)
- Proteinadsorption (1)
- Proteinen mit antimikrobieller Wirkung (1)
- Protonen-NMR-Spektroskopie (1)
- Protonenreduktion (1)
- Pyren (1)
- Pyrenderivate (1)
- Quadruplex-DNS (1)
- Quality assessment of antimalarial medicines from the Congo (1)
- Quantenchemische Rechnungen (1)
- Quantifizierung (1)
- Quantum Chemical CD Calculations (1)
- Quantum Chemical Calculations (1)
- Quantum mechanics / molecular modeling (1)
- Quasi-Newton-Verfahren (1)
- RAFT (1)
- RNA G-quadruplex (1)
- RNA labeling (1)
- RNA modifications (1)
- RNA structures (1)
- Raman (1)
- Raumfüllung (1)
- Redox-Kaskade (1)
- Redoxkaskade (1)
- Redoxreaktion (1)
- Reduction (1)
- Reticular Chemistry (1)
- Ribozym (1)
- Ribozymes (1)
- Ring closing metathesis (1)
- Ringschlussmetathese (1)
- Rotation (1)
- Ruthenium (1)
- Ruthenium-Photosensibilisator (1)
- Räumliche Anordnung (1)
- Röntgendiffraktometrie (1)
- SARS (1)
- SELEX (1)
- SERS (1)
- SIB (1)
- Second coordination sphere engineering (1)
- Self-Assembly in Water (1)
- Self-Sortierung (1)
- Sialic acids (1)
- Sialinsäuren (1)
- Solid-State NMR Spectroscopy (1)
- Sonogashira (1)
- Sonogashira-Hagihara-Reaktion (1)
- Space filling (1)
- Spectroscopy (1)
- Speicher <Informatik> (1)
- Spektroelektrochemie (1)
- Spermin (1)
- Spin flip (1)
- Spin labels (1)
- Spin-Sonde (1)
- Spin-chemistry (1)
- Squarain Farbstoffe (1)
- Squaraine Dyes (1)
- Stacking (1)
- Structural elucidation (1)
- Supercap (1)
- Superkondensator (1)
- Supramolecular Block Copolymers (1)
- Supramolecular Interaction (1)
- Supramolecular aggregates (1)
- Supramolecular electronics (1)
- Supramolekulare Aggregate (1)
- Synthese (1)
- Synthesediamant (1)
- Synthetischer Farbstoff (1)
- TD-DFT (1)
- Tabusuche (1)
- Targeting (1)
- Taxol (1)
- Terpyridinderivate <2 (1)
- Terrylenbisimid (1)
- Terrylenderivate (1)
- Terrylene bisimide (1)
- Theoretical Chemistry (1)
- Theoretische Charakterisierung (1)
- Theoretische Chemie (1)
- Theorie (1)
- Thermodynamics (1)
- Thiophen (1)
- Tiplet emiters (1)
- Tiplett Emitter (1)
- Total Synthesis (1)
- Totalsynthese (1)
- Triad (1)
- Triplett (1)
- Two-photon absorption (1)
- UV-VIS-Spektroskopie (1)
- UV/Vis-Absorption (1)
- Vergleich (1)
- Vesikel (1)
- Wasserlösliche Polymere (1)
- Wasseroxidationsreaktion (1)
- Wasserspaltung (1)
- Wasserstoffbrücken (1)
- Water (1)
- Water Oxidation (1)
- Wirkmechanismus (1)
- Wirkstoff-Träger-System (1)
- Wirt-Gast-Komplex-Chemie (1)
- X-Ray Diffraction (1)
- XNA (1)
- Xanthin (1)
- Zelladhäsion (1)
- Zellkultur (1)
- Zinc Chlorin (1)
- Zink (1)
- Zinkchlorine (1)
- Zweidimensionale NMR-Spektroskopie (1)
- Zweiphotonenabsorption (1)
- [FeFe] hydrogenase mimic (1)
- [FeFe]-Hydrogenase Imitator (1)
- acceptor (1)
- aggregation (1)
- alkaloids-Quinoid (1)
- amodiaquine (1)
- angeregte Zustände (1)
- artemether - lumefantrine (1)
- atropisomer (1)
- biradical (1)
- bola-amphiphile (1)
- boranes (1)
- calix[4]arene (1)
- capillary zone electrophoresis (1)
- carbohydrate chemistry (1)
- carboxylate receptor (1)
- charge recombination (1)
- charge-separated state (1)
- chirality (1)
- chlorin (1)
- complexation (1)
- computational chemistry (1)
- conformational search (1)
- cooperative (1)
- coordination polymer (1)
- cyclic trimer (1)
- cyclic voltammetry (1)
- cyclische Trimere (1)
- diamond (1)
- dicarboximide (1)
- dimerer Naphthylisochinolin-Alkaloide (1)
- dipolar aggregation (1)
- domain shift (1)
- donor-acceptor dyads (1)
- donor-acceptor triads (1)
- donor-photosensibilisator-acceptor triad (1)
- dyad (1)
- dyads (1)
- dye (1)
- dyes (1)
- dyes/pigments (1)
- electron density (1)
- enzyme engineering (1)
- excited states (1)
- exciton coupling (1)
- exciton dynamics (1)
- excitonic chirality (1)
- experimental and theoretical determination of electron density (1)
- folda-dimer (1)
- force field (1)
- fullerene network (1)
- functional dyes (1)
- galectin-1 (1)
- global minimum (1)
- gold (1)
- guanidiniocarbonyl pyrrole (1)
- halbleitende Polymere (1)
- hexaarylbenzenes (1)
- host-guest (1)
- host-guest chemistry (1)
- hydrogel (1)
- hydrogen bond (1)
- impurity profiling (1)
- inherent chirality (1)
- inhibitor (1)
- intervalence charge-transfer (1)
- iridium complex (1)
- iridium photosensitizer (1)
- isotropic hyper fine coupling (1)
- ladungsgetrennte Zustände (1)
- light harvesting (1)
- liquid crystal (1)
- macrocycle (1)
- macrocycles (1)
- magnetic field effect (1)
- mechanism (1)
- merocyanine dye (1)
- merocyanines (1)
- metabolism (1)
- metaheuristic methods (1)
- metal-ion-ligand coordination (1)
- metallosupramolecular π-amphiphiles (1)
- mode of action (1)
- molecular recognition (1)
- molekulare Erkennung (1)
- multichromophoric arrays (1)
- n-type semiconductors (1)
- nanomaterials (1)
- naphthalene diimide (1)
- near infrared chirality (1)
- neutral polyradical (1)
- neutrales Polyradikal (1)
- non-fullerene acceptor (1)
- nucleic acid (1)
- null-aggregate (1)
- oligo(phenylene ethynylene) (OPE) (1)
- oligothiophenes (1)
- on surface self-assembly (1)
- onbead enzym screening (1)
- optical properties (1)
- optische Eigenschaften (1)
- organic photovoltaics (1)
- organic semiconductor (1)
- organic transistor (1)
- organische Photovoltaik (1)
- organische Solarzellen (1)
- organischer Feldeffekttransistor (1)
- organischer Transitor (1)
- organogelator (1)
- pentacene (1)
- perylene bisimide dimers (1)
- perylene dyes (1)
- photocatalysis (1)
- photoinduced electron transfer (1)
- photoinduzierter Elektronentransfer (1)
- photophysics (1)
- pi-pi Wechselwirkungen (1)
- pi-pi- stacking (1)
- polar solution (1)
- polare Lösung (1)
- poly(2-oxazoline)s (1)
- polyamine (1)
- polycarbazole (1)
- polyglycidol (1)
- protease (1)
- protein adsorption (1)
- protein crystallography (1)
- protein-ligand-interaction (1)
- proton reduction (1)
- quantenchemische Berechnungen (1)
- quaterrylene bisimide (1)
- quercetin (1)
- radical ion pair (1)
- resveratrol (1)
- ring opening polymerisation (1)
- ring-opening polymerization (1)
- rotation (1)
- ruthenium photosensitizer (1)
- seco-NIQs-Naphthylisoindolinone (1)
- selbst organisierende Monolagen (SAM) (1)
- selbstaggregierten (1)
- self-assembled monolayer (SAM) (1)
- self-sorting (1)
- semiconducting polymers (1)
- short-range JCT-coupling (1)
- solid-state emitter (1)
- spacer-controlled self-assembly (1)
- spectroscopy (1)
- spermine (1)
- spin relaxation (1)
- structural elucidation (1)
- structural restriction (1)
- substandard and falsified medicines from the Congo (1)
- sucrose phosphorylase (1)
- supramolecular (1)
- supramolekular (1)
- supramolekularen Elektronik (1)
- theoretical characterisation (1)
- theoretical investigations (1)
- theoretische Untersuchungen (1)
- thin film transistor (1)
- topological analysis (1)
- topologische Analyse (1)
- transiente Absorption (1)
- transiente Absorptionsspektroskopie (1)
- triaryalmine (1)
- triplet (1)
- vesicle (1)
- water oxidation reation (1)
- xanthine (1)
- zyklische Peptide (1)
Institute
- Institut für Organische Chemie (113) (remove)
Sonstige beteiligte Institutionen
Dipolar merocyanines are very attractive supramolecular building blocks, as they combine interesting functional properties with strong, directional intermolecular interactions. The pyridine dioxocyano-pyridine (PYOP) chromophore (Chapter 2.2), used in this thesis, stands out because of its exceptionally high ground state dipole moment (g ~ 17 D), in combination with the option to retain good solubility also in unpolar solvents, by decoration with solubilizing groups.
The reliable binding motif of anti-parallel -stacking due to dipole-dipole interactions has allowed the design of molecular building blocks that form assemblies of predictable geometry. The intense unstructured charge transfer UV/Vis absorption band (eg ~ 10.7 D) is a result of the dominant contribution of the zwitterionic resonance structure which brings the PYOP chromophore just beyond the cyanine limit in solvents of low polarity (c2 = 0.60, 1,4 dioxane). The high sensitivity of the S0 – S1 UV/Vis absorption band to the environment manifests itself in a pronounced negative solvatochromism and strong H-type exciton coupling within -stacked PYOP assemblies. In accordance with the classical molecular exciton theory, an increasing hypsochromic shift of the dominant absorption band of these H aggregates can be observed as the stack size increases up to about six chromophores, where it levels out at about max ~ 440 nm (CHCl3). This allows a uniquely simple estimation of the number of interacting chromophores within the self-assembled structure from a single UV/Vis absorption spectrum of an aggregate.
The defined and well investigated PYOP dimer formation was employed in this thesis to probe the applicability and limitations of concentration-, temperature-, and solvent-dependent self-assembly studies (Chapter 3). Straightforward theoretical models to evaluate datasets of concentration-, temperature-, and solvent-dependent UV/Vis absorption by nonlinear regression analysis were derived for the case of dimer formation (Chapter 2.1). Although the dimer model is well known and widely applied in literature, this detailed derivation is helpful to understand assumptions and potential problems of the different approaches for the determination of thermodynamic parameters. This helps to decide on the most appropriate method to analyse a system of interest. In this regard it should be noted that covering a large portion of the self-assembly process with the experimental data is a prerequisite for the accuracy of the analysis. Additionally, many of the insights can also be transferred to other self-assembly systems like supramolecular polymerization or host-guest interactions.
The concentration-dependent analysis is the most straightforward method to investigate self-assembly equilibria. No additional assumptions, besides mass balance and mass action law, are required. Since it includes the least number of parameters (only K, if M/D are known), it is the most, or even only, reliable method, to elucidate the self-assembly mechanism of an unknown system by model comparison. To cover a large concentration range, however, the compound must be soluble enough and generally sample amounts at least in the low mg scale must be available.
The temperature-dependent analysis has the advantage that all thermodynamic parameters G0, H0 and S0 can be obtained from a single sample in one automated measurement. However, the accessible temperature-range is experimentally often quite limited and dependent on the solvent. For systems which do not show the transition from monomer to aggregate in a narrow temperature range, as given for, e.g., cooperative aggregation or processes with a high entropy contribution, often not the entire self-assembly process can be monitored. Furthermore, the assumptions of temperature-independent extinction coefficients of the individual species as well as temperature-independent H0 and S0 must be met. Monte Carlo simulations of data sets demonstrated that even minor changes in experimental data can significantly impact the optimized values for H0 and S0. This is due to the redundancy of these two parameters within the model framework and even small thermochromic effects can significantly influence the results. The G0 value, calculated from H0 and S0, is, however, still rather reliable.
Solvent-dependent studies can often cover the entire self-assembly process from monomeric (agg = 0) to the fully aggregated state (agg = 1). However, for dyes with strong solvatochromic effects, such as the dipolar merocyanines investigated in this thesis, the results are affected. Also, the assumption of a linear relation of the binding energy G0 and the fraction of denaturating solvent f, which is based on linear free energy relationships between G0 and the solvent polarity, can lead to errors. Especially when specific solvent effects are involved.
For the evaluation of experimental data by nonlinear regression, general data analysis software can be used, where user-defined fit models and known parameters can be implemented as desired. Alternatively, multiple specialized programs for analysing self-assembly data are available online. While the latter programs are usually more user-friendly, they have the disadvantage of being a “black box” where only pre-implemented models can be used without the option for the user to adapt models or parameters for a specific system.
In Chapter 3 comprehensive UV/Vis absorption datasets are presented for the dimerization of merocyanine derivative 1 in 1,4-dioxane, which allowed for the first time a direct comparison of the results derived from concentration-, temperature-, and solvent-dependent self-assembly studies.
The results for the binding constant K and corresponding G0 from the concentration- and temperature-dependent analysis were in very good agreement, also in comparison to the results from ITC. For the temperature-dependent analysis, though, multiple datasets of samples with different concentration had to be evaluated simultaneously to cover a meaningful part of the self-assembly process. Furthermore, a significant dependence of the optimized parameters H0 and S0 on the wavelength chosen for the analysis was observed. This can be rationalized by the small thermochromic shifts of both the monomer and the dimer UV/Vis absorption band. The results from the solvent-dependent evaluation showed the largest deviation, as expected for the highly solvatochromic merocyanine dye.
However, even here by evaluation at 491 and 549 nm the deviation for G0 was only 2.5 kJ mol1 (9%) with respect to the results from the concentration-dependent analysis (G0 = 29.1 kJ mol1). Thus, despite the strong solvatochromism of the dipolar chromophore, it can still be considered a reliable method for estimating the binding strength. Furthermore, multiple repetitions of the concentration-, temperature-, and solvent-dependent studies provided insight into the reproducibility of the results and possible sources of experimental errors. In all cases, the deviations of the results were small (G0 < 0.4 kJ mol1) and within the same range as the fit error from the nonlinear regression analysis.
The insights from these studies were an important basis for the in-depth investigation of a more complex supramolecular system in Chapter 4, as a single method is often not enough to capture the full picture of a more complicated self-assembly process. To elucidate the anti-cooperative self-assembly of the chiral merocyanine 2, a combination of multiple techniques had to be applied.
Solvent-dependent UV/Vis absorption studies in CH2Cl2/MCH mixtures showed the step-wise assembly of the merocyanine monomer (max(M) = 549 nm, CH2Cl2) to first a dimer (max(D) = 498 nm, CH2Cl2/MCH 15:85) by dipole-dipole interactions, and then a -stacked higher aggregate (max(H) = 477 nm, MCH), with pronounced H-type coupling.
The thermodynamic evaluation of this data, however, suffered from the severe solvatochromism, especially of the monomeric species (max(M, CH2Cl2) = 549 nm, max(M, MCH) = 596 nm). Therefore, concentration-dependent studies were performed at three different temperatures (298, 323, 353 K) to elucidate the self-assembly mechanism and determine reliable thermodynamic parameters. The studies at elevated temperatures were hereby necessary, to obtain experimental data over a larger agg--range. Due to the pronounced difference in the thermodynamic driving force for dimerization and higher aggregate formation (KD/K5 = 6500) a concentration range exists in MCH where almost exclusively the dimer species of 2 is present, before further self-assembly by dispersion interactions occurs. Therefore, the data could be evaluated independently for the two self-assembly steps. The self-assembly of dimers into the higher aggregate could not be described by the isodesmic model but was fitted satisfactorily to a pentamer model. This rather small size of about ten -stacked PYOP chromophores was, furthermore, consistently indicated by AFM, VPO and DOSY NMR measurements. Based on 1D and 2D NMR data as well as the strong bisignate CD signal of the higher aggregate in combination with TD-DFT calculations, a P-helical stack is proposed as its structure. The small size can be rationalized by the anti-cooperative self-assembly mechanism and the sterical demand of the solubilizing trialkoxyphenyl and the chiral tetralin substituents. Additionally, the aliphatic shell formed by the solubilizing chains around the polar chromophore stack, can account for the exceptionally high solubility of 2 in MCH (> 15 mg mL1). These combined studies of the self-assembly process enabled the identification of suitable conditions for the investigation of fluorescence properties of the individual aggregate species. Aggregation-induced emission enhancement was observed for the almost non-emissive monomer (Fl(M) = 0.23%), which can be rationalized by the increasing rigidification within the dimer (Fl(D) = 2.3%) and the higher aggregate (Fl(H) = 4.5%). The helical chirality of the PYOP decamer stack, furthermore, gave rise to a strong CPL signal with a large glum value of 0.011.
The important conclusion of this thesis is that the temperature- and solvent-dependent analyses are valid alternatives to the classical concentration-dependent analysis to determine thermodynamic parameters of self-assembly equilibria. Although, for a specific supramolecular system, one approach might be favourable over the others for a variety of reasons. The experimental limitations often demand a combination of techniques to fully elucidate a self-assembly process and to gain insights in the aggregate structure. The anti-cooperative merocyanine self-assembly, which was described here for the first time for the PYOP merocyanine 2, is no exception. Besides the interest in the merocyanine assemblies from a structural and functional point of view, the insights gained from the presented studies can also be transferred to other self-assembly systems and be a guide to find the most appropriate analysis technique.