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Spectroscopic Evidence for an Attractive Cation–Cation Interaction in Hydroxy‐Functionalized Ionic Liquids: A Hydrogen‐Bonded Chain‐like Trimer
Author(s) -
Niemann Thomas,
Strate Anne,
Ludwig Ralf,
Zeng Helen J.,
Menges Fabian S.,
Johnson Mark A.
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201808381
Subject(s) - cationic polymerization , trimer , chemistry , hydrogen bond , ionic bonding , tetrafluoroborate , ion , cluster (spacecraft) , pyridinium , ionic liquid , crystallography , inorganic chemistry , molecule , polymer chemistry , organic chemistry , dimer , computer science , programming language , catalysis
We address the formation of hydrogen bonded domains among the cationic constituents of the ionic liquid (IL) 1‐(3‐hydroxypropyl)pyridinium tetrafluoroborate [HPPy][BF 4 ] by means of cryogenic ion vibrational predissociation spectroscopy of cold (ca. 35 K) gas‐phase cluster ions and quantum chemistry. Specifically, analysis of the OH stretching bands reveals a chain‐like OH⋅⋅⋅OH⋅⋅⋅OH⋅⋅⋅BF 4 − binding motif involving the three cations in the cationic quinary cluster ion (HPPy + ) 3 (BF 4 − ) 2 . Calculations show that this cooperative H‐bond attraction compensates for the repulsive Coulomb forces and results in stable complexes that successfully compete with those in which the OH groups are predominantly attached to the counter anions. Our combined experimental and theoretical approach provides insight into the cooperative effects that lead to the formation of hydrogen bonded domains involving the cationic constituents of ILs.