Designing Eu-β-diketonate complexes as a support of ionic liquid crystals (ILCs) with additional luminescent properties

Ignacio Sánchez, Cristián Cuerva, Gonçalo Marcelo, Elisabete Oliveira, Hugo M. Santos, José A. Campo, Carlos Lodeiro, Mercedes Cano

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Here we describe the preparation, characterisation, liquid crystal properties and photophysical studies of new potassium salts of tetrakis(β-diketonate)europium(III) complexes based on long-chained symmetrical and unsymmetrically substituted 1,3-dialkyloxyphenyl-β-diketones ligands, K[Eu(OOR(n)R(m))4] (R(n) = OC6H4OCnH2n+1; R(m) = OC6H4OCmH2m+1; n = m = 8, 10, 12, 14, 16; n = 4, 8, m = 12, 16; n = 12, m = 16). All compounds exhibit mesomorphic and luminescence behaviour, regardless the presence of symmetrical or unsymmetrical ligands. It has been shown that the shortest molecular lengths, established by the summation of the two alkyl chains at the substituents of the β-diketonate ligand, give rise to more effective mesophase transition temperatures, while the asymmetry favours higher clearing temperatures. Related to the ionic salts based on long-chained pirazolium cations [H2pzR(n)]+ (R(n) = OC6H4OCnH2n+1; n = 4, 6, 8, 10, 12, 14, 16, 18) and tetrakis(1,3-bis(methoxyphenyl)propane-1,3-dionate)europium(III) as anion, they have also been studied and proved to be luminescent materials. By contrast, none of them was found to be mesomorphic. Therefore, the strategically increased chain length at the cation did not show to be effective for achieving liquid crystal properties. Integration of one of these luminescent europium complexes onto a polymeric PMMA matrix was positively evaluated towards its use as a temperature sensor and fluoride or cyanide ion sensor.

Original languageEnglish
Pages (from-to)395-405
Number of pages11
JournalDyes and Pigments
Volume159
DOIs
Publication statusPublished - 1 Dec 2018

Keywords

  • Ionic liquids
  • Liquid crystals
  • Liquid crystalline

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