Browsing by Subject "Rotaxanes."
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Item Open Access pH-responsive rotaxanes and polypseudorotaxanes(Bilkent University, 2007) Tiftik, Hasan BurakIn this study, a series of mechanically interlocked molecules like polypseudorotaxanes, rotaxanes and pseudorotaxanes have been synthesized via CB6 catalyzed 1,3-dipolar cycloaddition using diazide and dialkyne monomers, which contain long dodecyl and short propyl aliphatic spacers. To reach these novel interlocked molecules, first appropriate monomeric units were designed and synthesized. These monomeric units were diazido and dialkyne functionalized, propyl and dodecyl spacers containing, diamine salts. These monomers were fully characterized by spectroscopic techniques like 1H, 13C-NMR and FT-IR and elemental analysis. After the preparation of the monomers, polypseudorotaxanes were synthesized via CB6 catalyzed 1,3-dipolar cycloaddition. The polymer formation proceeded through step-growth polymerization in the presence of CB6. The reaction was followed by 1H-NMR spectroscopy easily, because the appearance of a diagnostic peak at 6.5 ppm indicated the formation of triazole ring, which joins the monomers. The polypseudorotaxane was also characterized by spectroscopic techniques like 1H, 13C-NMR and FT-IR and matrix assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). It produced a maximum mass at around 15600 Da which corresponds to about six repeating units that is basically 12 CB6s threaded triazoles. The experimental results reveal that this polypseudorotaxane behaves as a pH-driven polymeric switch. Thus, when amine groups are protonated at an appropriate pH, CB6s are located on the triazole rings due to ion–dipole interaction, whereas at high pH they move onto the hydrophobic aliphatic spacer rather than slipping off the polypseudorotaxane. After the synthesis of the polypseudorotaxanes, a series of rotaxanes and pseudorotaxanes have also been synthesized using the already prepared dialkyne and diazide monomers. Rotaxanation was also carried out via a 1, 3-dipolar cycloaddition reaction catalyzed by CB6. Among them, a bistable CB6-based [3]rotaxane synthesized through CB6 catalyzed 1,3-dipolar cycloaddition contains two recognition sites and behaves as a reversible molecular switch. It exhibits conformational changes caused by the movement of rings under base, acid and heat stimuli from one location to the other.Item Open Access Rotaxanes and polyrotaxanes based on cucurbit[6]uril and porphyrin(Bilkent University, 2005) Cındır, NesibeItem Open Access Supramolecular chemistry of cucurbit[n]uril homologues with a ditopic guest and light emitting conjugated polymers(Bilkent University, 2011) Artar, MügeThe general objective of this thesis is to explore the ability of cucurbit[n]uril (CB[n]) (n= 6,7,8) homologues to form nano-structured supramolecular assemblies with various organic guests through self-sorting, self-assembly and recognition. In the first part of the thesis, the selectivity and recognition properties of CB[n] homologues towards a ditopic guest have been investigated. The guest was synthesized through Cu(I)-catalyzed click reaction between the salts of N,N'-bis-(2- azido-ethyl)-dodecane-1,12-diamine and propargylamine and contain two chemically and geometrically distinct recognition sites, namely, a flexible and hydrophobic dodecyl spacer and a five-membered triazole ring terminated with ammonium ions. Complex formation between the guest and CB[6], CB[7] and CB[8] in the ratios of 1:2, 1:1 and 1:1, respectively, was confirmed by 1H NMR spectroscopy and mass spectrometry. It was also revealed that CB[n] homologues have ability to self-sort and recognise the guests according to their chemical nature, size and shape. Kinetic formation of a hetero[4]pseudorotaxane via sequence-specific self-sorting was confirmed and controlled by the order of the addition. In the second part, the effect of CB[n] homologues on the dissolution and the photophysical properties of non-ionic conjugated polymers in water were investigated. A fluorene-based polymer, namely, poly[9,9-bis{6(N,N dimethylamino)hexyl}fluorene-co-2,5-thienylene (PFT) was synthesized via Suzuki coupling and characterization was performed by spectroscopic techniques including 1D and 2D NMR(Nuclear Magnetic Resonans), UV–vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS)(Matrix Assisted Laser Desorption/Ionization Mass Spectroscopy ). The interaction of CB[6], CB[7] and CB[8] with PFT have been investigated and it was observed that only CB[8] among other CB homologues forms a water-soluble inclusion complex with PFT. Furthermore, upon complex formation a considerable enhancement in the fluorescent quantum yield of PFT in water was observed. The structure of resulting PFT@CB[8] complex was characterized through 1H-NMR and selective 1DNOESY(The Nuclear Overhauser Enhancement Spectroscopy) and further investigated by imaging techniques (e.g. AFM(Atomic Force Microscopy), SEM(Scanning Electron Microscopy), TEM(Transmission Electron Microscopy) and fluorescent optical microscopy) to reveal the morphology. The results suggested that through CB[8]-assisted self-assembly of PFT polymer chains vesicle-like nanostructures formed. The sizes of nanostructures were also determined using dynamic light scattering (DLS(Dynamic Light Scattering)) measurements.