Synthesis And Characterization Of Isoflavone Derivatives Exhibiting Liquid Crystalline Properties
| dc.contributor.author | Yam, Wan Sinn | |
| dc.date.accessioned | 2016-09-08T01:36:51Z | |
| dc.date.available | 2016-09-08T01:36:51Z | |
| dc.date.issued | 2008-07 | |
| dc.description.abstract | Six series of classical rod-like, calamitic liquid crystals had been synthesized and characterized. These liquid crystals contained 3-phenyl-4H-4-0ne-benzopyran or generally known as isoflavone within the central moiety. The syntheses of these liquid crystalline compounds involved alkylation, Friedel-Crafts acylation, cyclization and esterification reactions. CHN microanalysis, FTIR, ID and 2D-NMR spectroscopic methods were used to elucidate the structures of these compounds. The transition temperatures of the synthesized compounds and respective enthalpy values were determined by differential scanning calorimetry whilst a polarized optical microscope was used for texture observation. The first four series, each consisted of eight homoiogues, incorporated isoflavone within their central cores with either one or two flexible acyloxy or alkyloxy terminal chains in odd or even parity. The cOJqpounds thus obtained exhibited nematic (N), smectic A (SmA) and smectic C (Sme) phases. Compounds from the fifth and sixth series, on the other hand, were isoflavone derivatives bearing decyloxy chain on one end and different substutuents. R, on the other. of which R = F. CI. Br. CH), OCH3 and H. Compounds with substituents, R = F, C1 and Br are smectogenic displaying only SmA phase whilst compound with R = OCH3 was nematogenic. Compound with R = CH3 exhibited both N and SmA phases. Compound with R = H was non-mesogenic in the fifth series but the elongated derivative bearing the same substituent was mesogenic showing SmA phase in the sixth series. In order to investigate the molecular packing associated with the intermolecular attraction as well as the correlation between the thermal behaviour of these molecules with their anisotropy properties in Nand smectic phases, the X-ray diffraction studies had been carried out on representative compounds 7-n-hexyloxy-3-(4-nhexyloxyphenyl)- 4H-l-benzopyran-4-one. ALAB-OC, and 7-n-hexadecyloxy-3-( 4-nhexadecyloxyphenyI)- 4H-l-benzopyran-4-one, ALAB-oC1, from the second series, 7-nxxxi decanoyloxy-3-[ 4' -(3-methylbutyloxyphenyl)]-4H-l-benzopyran-4-one, MBPB-COOC, from the third, 7-n-decanoyloxy-3-(4'-methylphenyl)-4H-l-benzopyran-4-one, lOPB-CH3 and 7- (4" -n-decyloxybenzoyloxy )-3-( 4' -fluorophenyl)-4H-l-benzopyran-4-one, IOBB-F from fifth and sixth series, respectively. From the X-ray data, molecules of compounds ALAB-OC, were arranged in layers in SmA phase whilst the molecular tilt angles, 9 from the normal to layer within the SmC phase was approximately 150 as obtained at 11°C below the transition temperature. However, the molecular tilt angles, 9 for compounds ALAB-OC1, and MBPBCOOC, could not be determined due to a first order transition from crystal to SmC phases in these compounds. The X-ray diffiaction analyses also revealed that the molecules in compound lOPS.CH3 were intercalated in SmA phase. Molecules in compound IOBB-F were arranged in bilayers in crystal phase but monolayers were favoured in SmA phase. Single crystal X-ray diffraction analyses had also been carried out on compounds ALAB-OC" MBPB-COOC" 7-nhexyloxy- 3-[4' -(3-methylbutyloxyphenyl)]-4H-l-benzopyran-4-one, MBPB-OC, and tOPBCH; b wherein all crystals were found to be triclinic. The molecular structures of the earlier mentioned compounds were confinned for the first time by X-ray crystallography and found to conform to those as inferred from FTIR and NMR techniques. The long flexible terminal chains of these crystals were found to be fully stretched. except for compound ALAB-OC, which had a highly disordered structure. Compound IOPS-CH3 had the lowest torsion angle in any hitherto reported isoflavone derivatives. The packing of molecules of these compounds showed that they lay anti-parallel to one another and the crystal cohesion resulted from dipolar interactions between anti-parallel ether or ester groups as well as van der Waals interaction of neighbouring molecules stabilized the packing of the molecules. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/2485 | |
| dc.subject | Chemical Sciences | en_US |
| dc.subject | Synthesis And Characterization | en_US |
| dc.title | Synthesis And Characterization Of Isoflavone Derivatives Exhibiting Liquid Crystalline Properties | en_US |
| dc.type | Thesis | en_US |
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