SYNTHESIS OF COUMARIN-AZO DERIVATIVES AND THEIR POTENTIAL APPLICATIONS

Eswaran, Madiahlagan (2020) SYNTHESIS OF COUMARIN-AZO DERIVATIVES AND THEIR POTENTIAL APPLICATIONS. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Coumarin is a versatile heterocyclic compound and is widely used as an active scaffold in organic synthesis. In this study coumarin, a natural product based compound, was chemically incorporated with active moieties such as azo and long alkyl chain for various applications. In this reasearch a total of 24 compounds were synthesized comprises of 4 compounds from model study, 15 compounds from the series and 5 new novel compounds. A series of coumarin-azo bearing long alkyl chain 57a-e with different chain length have been succesfully synthesized. Coumarin-azo derivatives were prepared via Williamson etherification and followed by acid hydrolysis to obtain intermediate 55a-e. The intermediates were azotized and coupled with phenol in order to obtain azophenol derivatives 56a-e. Finally 56a-e were esterified with 8 via Steglich Esterification. All synthesized compounds were elucidated with CHN, FTIR, UV-Vis and NMR Spectroscopy. The antibacterial activity of 57a-e was evaluated against E. coli and S. aureus via Kirby Bauer disc diffusion. Based on the evaluation in disc diffusion, all the synthesized compounds 57a-e showed no inhibition activities. The synthesized compounds were also evaluated for Dye Sensitized Solar Cells (DSSCs) study. The photovoltaic open circuit voltage obtained ranged from 0.272-0.173 V as the alkyl chain length increases. However, based on the band gap calculations obtained ranged 3.70-3.48 eV indicated the synthesized compounds not suitable as dye sensitizer in DSSC. Polarizing Optical Microscopy (POM) analysis of 57a-e showed liquid crystal properties where coumarin-azo derivative 57e exhibited smectic A phase, while 57b-d exhibited nematic phase. The aromatic ring acted as mesogenic group, N=N as central linkage and alkyl chain contributed to typical rod like liquid crystal molecules. Based on the findings obtained, the synthesized compound from natural product based compound as active scaffold contributed towards the potential development in optical storage device. Keywords: Coumarin-azo, alkyl chain, liquid crystal study, antibacterial study, Dye Sensitized Solar Cell (DSSC), natural product modification

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