title: Structure of cyano-anion ionic liquids: X-ray scattering and simulations.
abstract: Ionic liquids with cyano anions have long been used because of their unique combination of low-melting temperatures, reduced viscosities, and increased conductivities. Recently we have shown that cyano anions in ionic liquids are particularly interesting for their potential use as electron donors to excited state photo-acceptors [B. Wu et al., J. Phys. Chem. B 119, 14790-14799 (2015)]. Here we report on bulk structural and quantum mechanical results for a series of ionic liquids based on the 1-ethyl-3-methylimidazolium cation, paired with the following five cyano anions: SeCN(-), SCN(-), N(CN)2 (-), C(CN)3 (-), and B(CN)4 (-). By combining molecular dynamics simulations, high-energy X-ray scattering measurements, and periodic boundary condition DFT calculations, we are able to obtain a comprehensive description of the liquid landscape as well as the nature of the HOMO-LUMO states for these ionic liquids in the condensed phase. Features in the structure functions for these ionic liquids are somewhat different than the commonly observed adjacency, charge-charge, and polarity peaks, especially for the bulkiest B(CN)4 (-) anion. While the other four cyano-anion ionic liquids present an anionic HOMO, the one for Im2,1 (+)/B(CN)4 (-) is cationic.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Kamal B
authors.initials: KB
authors.lastname: Dhungana
authors.affiliation: Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970 São Paulo, SP, Brazil.
authors.forename: Luiz F O
authors.initials: LF
authors.lastname: Faria
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Boning
authors.initials: B
authors.lastname: Wu
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Liang
authors.affiliation: Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970 São Paulo, SP, Brazil.
authors.forename: Mauro C C
authors.initials: MC
authors.lastname: Ribeiro
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Claudio J
authors.initials: CJ
authors.lastname: Margulis
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Edward W
authors.initials: EW
authors.lastname: Castner