Supramolecular chemistry of cucurbit[n]uril homologues with a ditopic guest and light emitting conjugated polymers

Abstract

The 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.