1. SUPPLEMENTARY MATERIAL Radiation Stability of Cations in Ionic Liquids. 4. Task-Specific Antioxidant Cations for Nuclear Separations and Photolithography. Ilya A. Shkrob 1 , Timothy W. Marin 1,2 1 Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439, USA 2 Chemistry Department, Benedictine University, 5700 College Road, Lisle, IL 6053, USA List of abbreviations in the text. A - anion Ar generic aryl group ArOH 3,5-dialkyl-4-hydroxyphyenyl group B heterocycle base Bz benzyl BzPy + 1-benzylpyridinium cation BzMeIm + 1-benzyl-3-methylimidazolium cation C + cation ESI MS/MS electrospray ionization tandem mass spectrometry DFT density functional theory DIAD diisopropyl azodicarboxylate DMSO dimethylsulfoxide EPR electron paramagnetic resonance EUV extreme ultraviolet hfcc hyperfine coupling constant HOArS + Me 2 3,5-Dialkyl-4-hydroxyphenyldimethylsulfonium cation (1a,b) LH polymeric matrix MeIm N-methylimidazole MeIm + CH 2 ArOH 1-(3,5-di-tert-butyl-4-hydroxybenzyl)-3-methylimidazolium cation (2) MeImH + N-methylimidazolium cation m.p. melting point NMR nuclear magnetic resonance NTf 2 - bistriflimide anion Sac - saccharinade anion Ph phenyl Ph 2 CHPyMe + 1-Methyl-4-diphenylmethylpyridinium cation (4) Py pyridine PyH + pyridinium cation Py + CH 2 ArOH 1-(3,5-di-tert-butyl-4-hydroxybenzyl)-pyridinium cation (3) tBu tert-butyl Tf CF 3 SO 2 (triflyl) group