Ultraslow Phase Transitions in an Anion-Anion Hydrogen-Bonded Ionic Liquid

Autor(es)

Faria, Luiz F. O. ^[1] ; Lima, Thamires A. ^[1] ; Ferreira, Fabio F. ^[2] ; Ribeiro, Mauro C. C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Lab Espect Mol, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo - Brazil

^[2] Univ Fed ABC, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry B; v. 122, n. 6, p. 1972-1980, FEB 15 2018.
• Citações Web of Science: 5

Resumo

A Raman spectroscopy study of 1-ethyl-3-methylimidazolium hydrogen sulfate, {[}C(2)C(1)im]{[}HSO4], as a function of temperature, has been performed to reveal the role played by anion-anion hydrogen bond on the phase transitions of this ionic liquid. Anion-anion hydrogen bonding implies high viscosity, good glass forming ability, and also moderate fragility of {[}C(2)C(1)im]{[}HSO4] in comparison with other ionic liquids. Heating {[}C(2)C(1)im]{[}HSO4] from the glassy phase results in cold crystallization at similar to 245 K. A solid-solid transition (crystal I -> crystal II) is barely discernible in calorimetric measurements at typical heating rates, but it is clearly revealed by Raman spectroscopy and X-ray diffraction. Raman spectroscopy indicates that crystal I has extended ({[}HSO4](-))(n) chains of hydrogen-bonded anions but crystal II has not. Raman spectra recorded at isothermal condition show the ultraslow dynamics of cold crystallization, solid-solid transition, and continuous melting of {[}C(2)C(1)im]{[}HSO4]. A brief comparison is also provided between {[}C(2)C(1)im]{[}HSO4] and {[}C(4)C(1)im]{[}HSO4], as Raman spectroscopy shows that the latter does not form the crystalline phase with extended anion-anion chains. (AU)

• Processo FAPESP: 15/05803-0 - Estrutura de líquidos iônicos em alta pressão
• Beneficiário: Luiz Felipe de Oliveira Faria
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 12/13119-3 - Espectroscopia vibracional em fases condensadas
• Beneficiário: Mauro Carlos Costa Ribeiro
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 14/15049-8 - Estudo por espectroscopia Raman da transição vítrea de líquidos iônicos em alta pressão.
• Beneficiário: Thamires Andrade Lima
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado