Aqueous Supramolecular Assemblies from Organic Chromophores: Emission Control, Bio-analyte Detection, and Light Harvesting

Bhaumik, Shubhra Kanti (2022) Aqueous Supramolecular Assemblies from Organic Chromophores: Emission Control, Bio-analyte Detection, and Light Harvesting. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Shubhra Kanti Bhaumik (16RS010)) 16RS010.pdf - Submitted Version Restricted to Repository staff only Download (12MB)

Abstract

The research work presented in this thesis mainly focused on developing luminescent materials based on supramolecular assemblies of small organic chromophoric molecules. We employed a series of extended α-cyanostilbene derivatives having mono/di/tetra positive charge(s) in their structures. We varied alkyl chain lengths attached to the pyridinium end(s) and thus modulated their self-assembly properties. By regulating their properties, we were able to generate multiple luminescence in aqueous media, detect biologically important polyanions and construct artificial light-harvesting systems. We also employed phenylpyridinium derivatives to fabricate stimuliresponsive room temperature phosphorescence (RTP) emissive materials. This thesis consists of five chapters. In Chapter 1, a brief overview of molecular self-assembly, particularly in aqueous media, and host-guest chemistry of cucurbit[n]urils are discussed. The design of organic chromophores, i.e., cyanostilbene derivatives and phenylpyridine derivatives are also discussed. Their synthetic procedures, characterization and instruments used to perform the works in this thesis are described in Chapter 2. In Chapter 3, the construction of multicolor luminescence in aqueous media by employing host-guest chemistry between amphiphilic cyanostilbene and cucurbit[7]uril, and by photoirradiation of amphiphilic cyanostilbene is discussed. Chapter 4 presents the detection of biologically important analytes such as heparin and DNA using cationic cyanostilbenes. Heparin binding by either multivalent interactions or by the formation of smaller assemblies/clusters on the heparin surface by di-cationic cyanostilbenes is discussed in this chapter. Moreover, the detection and binding of heparin and DNA by tetracationic cyanostilbene dimers are described. This chapter also contains the detection of heparin by donor-acceptor based cyanostilbenes. The construction of artificial light-harvesting systems in aqueous media using heparin as a biomolecular scaffold and the cationic cyanostilbene derivatives as energy donors is discussed in Chapter 5. In Chapter 6, the generation of pH-responsive RTP in aqueous media and excitation wavelength-dependent RTP in solid/crystal states employing phenylpyridine derivatives are discussed.

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