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18-crown-6-sodium cholate complex: thermochemistry, structure and stability

Mihelj, Tea; Tomašić, Vlasta; Biliškov, Nikola (2014) 18-crown-6-sodium cholate complex: thermochemistry, structure and stability. Langmuir, 30 (21). pp. 6274-6285. ISSN 0743-7463

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Abstract

18-crown-6, one of the most relevant crown ethers, and sodium cholate, steroidal surfactant classified as natural bile salt, are components of novel, synthesized coordination complex ; 18-crown-6-sodium cholate (18C6•NaCh). Like crown ethers, bile salts act as building blocks in supramolecular chemistry in order to design new functionalized materials with a desired structure and properties. In order to obtain thermal behavior of this 1:1 coordination complex, thermogravimetry and differential thermal analysis were used, as well as microscopic observations and differential scanning calorimetry. Temperature dependent infrared spectroscopy (IR) gave a detailed view into phase transitions. The structures during thermal treatment were observed with powder X-ray diffraction, and molecular models of the phases are made. Hard, glassy, colorless compound 18C6•NaCh goes through crystalline – crystalline polymorphic phase transitions at higher temperatures. The room temperature phase is indexed to a triclinic lattice, while in the high temperature phases molecules take randomly one of the two different configurations in the unit cell, resulting in the 2-fold symmetry. The formation of cholesteric liquid crystalline phase occurs simultaneously with partial decomposition, followed by the isotropisation with simultaneous and complete decomposition at much higher temperature, as obtained by IR. The results provide valuable information about the relationship between molecular structure, thermal properties, and stability of the complex, indicating the importance of an appropriate choice of cation, amphiphilic, and crown ether unit in order to synthesize compounds with desired behavior.

Item Type: Article
Uncontrolled Keywords: 18-crown-6; sodium cholate; structure; NMR; thermal behavior; IR spectroscopy
Subjects: NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Chemistry > Physical Chemistry
Divisions: Division of Materials Chemistry
Division of Physical Chemistry
Projects:
Project titleProject leaderProject codeProject type
Metal hydrides in clean energy systems (Metalni hidridi u čistim energetskim sustavima)-Antun Drašner098-0982904-2941MZOS
Surfactants, processes in solutions and at interfaces (Površinski aktivne tvari, procesi u otopinama i na međupovršinama)-Maja Dutour Sikirić098-0982915-2949MZOS
Depositing User: Tea Mihelj
Date Deposited: 01 Dec 2015 14:59
Last Modified: 01 Dec 2015 14:59
URI: http://fulir.irb.hr/id/eprint/2340
DOI: 10.1021/la501155s

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