Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties

Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties

Bibliographic Details
Main Author: Jonathan, Tietz I.
Language:English
Published: Kent State University / OhioLINK 2012
Subjects:
Chemistry
Materials Science
Organic Chemistry
thienothiophene
liquid crystals
smectic
trifluoroborates
2-alkoxythiophene
synthetic organic chemistry
thieno[3,2-b]thiophene
thieno[2,3-b]thiophene
thiophen-2(5H)-one
alkoxythienothiophene
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=kent1343074444
id ndltd-OhioLink-oai-etd.ohiolink.edu-kent1343074444
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Chemistry
Materials Science
Organic Chemistry
thienothiophene
liquid crystals
smectic
trifluoroborates
2-alkoxythiophene
synthetic organic chemistry
thieno[3,2-b]thiophene
thieno[2,3-b]thiophene
thiophen-2(5H)-one
alkoxythienothiophene
spellingShingle Chemistry
Materials Science
Organic Chemistry
thienothiophene
liquid crystals
smectic
trifluoroborates
2-alkoxythiophene
synthetic organic chemistry
thieno[3,2-b]thiophene
thieno[2,3-b]thiophene
thiophen-2(5H)-one
alkoxythienothiophene
Jonathan, Tietz I.
Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
author Jonathan, Tietz I.
author_facet Jonathan, Tietz I.
author_sort Jonathan, Tietz I.
title Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
title_short Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
title_full Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
title_fullStr Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
title_full_unstemmed Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties
title_sort thienothiophene-based liquid crystals: synthesis and comparative evaluation of mesophase properties
publisher Kent State University / OhioLINK
publishDate 2012
url http://rave.ohiolink.edu/etdc/view?acc_num=kent1343074444
work_keys_str_mv AT jonathantietzi thienothiophenebasedliquidcrystalssynthesisandcomparativeevaluationofmesophaseproperties
_version_ 1719422818582528000
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-kent13430744442021-08-03T05:38:02Z Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties Jonathan, Tietz I. Chemistry Materials Science Organic Chemistry thienothiophene liquid crystals smectic trifluoroborates 2-alkoxythiophene synthetic organic chemistry thieno[3,2-b]thiophene thieno[2,3-b]thiophene thiophen-2(5H)-one alkoxythienothiophene <p>Sulfur-based heteroaromatic cores often impart advantageous properties to liquid crystals (LCs). One little-investigated sulfur-based heterocyclic family is thienothiophene; recently, thienothiophene-based materials have attracted exponentially growing attention in a variety of materials applications. However, thienothiophenes have largely escaped the notice of the LC community. In this thesis, we present an initial exploration into the effect of the thienothiophene core on the mesomorphic properties of LCs. Thus, we have synthesized several families of target LCs: alkyl 5-(4-alkoxyphenyl)thieno[3,2-<i>b</i>]thiophene-2-carboxylate esters (<b>I</b>), alkyl 5-(4-alkoxyphenyl)thieno[2,3-<i>b</i>]thiophene-2-carboxylate esters (<b>II</b>), and two alkoxythienothiophene-based LCs (4-(alkoxycarbonyl)phenyl 5-(alkoxy)thieno[3,2-<i>b</i>]thiophene-2-carboxylate (<b>III</b>) and 4-(alkoxy)phenyl 5-(alkoxy)thieno[3,2-<i>b</i>]thiophene-2-carboxylate (<b>IV</b>)).</p><p>In the synthesis of <b>I</b>, we elaborated a series of alkyl 2-mercaptoacetates to alkyl thieno[3,2-<i>b</i>]thiophene esters in an efficient and operationally facile tandem nucleophilic substitution and aldol reaction. These thienothiophene esters were regioselectively halogenated at the α-position and submitted to Pd(0)-catalyzed Suzuki-Miyaura cross-coupling with a series of potassium 4-alkoxyphenyltrifluoroborate salts to yield the target LCs. This synthesis was efficient and marks the first use of the trifluoroborate variant of Suzuki-Miyaura coupling in the LC field. Family <b>II</b> was prepared in an analogous manner.</p><p>For the synthesis of <b>III</b> and <b>IV</b> we developed a strategically novel and facile route to 2-alkoxythiophenes by mild oxidation and Mitsunobu etherification of a series of easily prepared thiophen-2-yltrifluoroborate salts. With these materials in hand, 4-bromo-2-octyloxythiophene was regioselectively formylated by LDA-mediated deprotonation and attack by <i>N</i>-formylpiperidine. The resulting 3-bromo-5-octyloxythiophene-2-carbaldehyde was submitted to similar ring-closing conditions with a mercaptoacetate as in <b>I</b> and <b>II</b> to yield the first long-chain 2-alkoxythieno[3,2-<i>b</i>]thiophene. This ester was then hydrolyzed and submitted to Steglich esterification to give targets <b>III</b> and <b>IV</b>.</p><p>Most thieno[3,2-<i>b</i>]- and [2,3-<i>b</i>]thiophene-based materials presented in this study were found to exhibit the smectic C (SmC) mesophase. Notably, thienothiophene-based materials gave rise to much wider mesophases than their phenyl analogues. We found that thieno[2,3-<i>b</i>]thiophene, while less often exploited in the design of materials, gave markedly wider SmC mesophases in LCs than their thieno[3,2-<i>b</i>]thiophene analogues. When we incorporated a chiral tail into these molecules, however, the influence of the core on LC properties was destroyed and no significant difference was seen between thieno[2,3-<i>b</i>]- and thieno[3,2-<i>b</i>]thiophene-based LCs. Alkoxythieno[3,2-<i>b</i>]thiophene cores, which are unprecedented in materials applications, gave rise to wider and more diverse mesophases than their phenyl analogues. One target, 4-(octyloxy)phenyl 5-(octyloxy)thieno[3,2-<i>b</i>]thiophene-2-carboxylate, exhibited SmC and N phases both, making it the first nematic material we have reported based on thieno[3,2-<i>b</i>]thiophene.</p><p>In this thesis we present in detail the synthesis of the above materials, a contextual discussion of the literature, and the results of mesophase evaluation of these novel liquid crystals.</p> 2012-07-24 English text Kent State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=kent1343074444 http://rave.ohiolink.edu/etdc/view?acc_num=kent1343074444 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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