A Dialkyl Viologen Ionic Liquid: X-ray Crystal Structure Analysis of Bis(trifluoromethanesulfonyl)imide Salts

作者：Tahara Hironobu^*; Furue Yutaro; Suenaga Chie; Sagara Takamasa

来源：Crystal Growth & Design, 2015, 15(10): 4735-4740.

DOI：10.1021/acs.cgd.5b00645

An X-ray crystal structure of a viologen type ionic liquid compound, bis(trifluoromethanesulfonyl)imide (TFSI) salt of butyl heptyl viologen [C4VC7 center dot(TFSI)(2)], with a melting point (mp) of 52 degrees C was examined. A cis conformer of TFSI (cis-TFSI), known to be less stable than trans-TFSI, was found in the crystal in a 1:1 coexistence with trans-TFSI. In contrast, all TFSI anions found in dimethylviologen TFSI salts [C1VC1 center dot(TFSI)(2)] were of trans conformation. The lower mp of C4VC7 center dot(TFSI)(2) compared to that of C1VC1.(TFSI)(2) originates in a smaller electrostatic lattice energy and disordered structure of the side chains of C4VC7. Any charge transfer interaction causing a visible region absorption band was not observed in the solids of either C4VC7 center dot(TFSI)(2) (dihedral angle of bipyridinium phi = 37.2 degrees) or C1VC1 center dot(TFSI)(2) (phi = 9 degrees).

• 出版日期2015-10