Ionic liquids of an N-allcylethylenediamine-silver(I) complex cation (alkyl = hexyl, 2-ethylhexyl, and octyl) or a protic N-alkylethylenediaminium cation (alkyl = butyl, hexyl, 2-ethylhexyl, octyl, decyl, and dodecyl) with a bis(trifluoromethanesulfonyl)amide counter anion (Ag-ILs and PILs, respectively) were prepared and their physicochemical properties were investigated. The trend of solidification decreased in the order octyl >> hexyl > 2-ethylhexyl for the Ag-ILs, and butyl > dodecyl > decyl > octyl > hexyl >> 2-ethylhexyl for the PILs. The diffusion coefficients of the cations indicated stronger intermolecular interactions in PILs than in the Ag-ILs because of hydrogen-bonding networks, and it has been revealed that the intermolecular interactions increase in the order, hexyl < octyl < 2-ethylhexyl for the Ag-ILs, and hexyl approximate to 2-ethylhexyl < butyl approximate to octyl < decyl approximate to dodecyl for the PILs. The ionicity of the PILs was nearly independent (0.38-0.43) of the lengths of the alkyl chain. The octyl Ag-IL provided uniform silver(0) nanoparticles upon reaction with aqueous NaBH4 solution, whereas the 2-ethylhexyl and hexyl complexes did not form silver(0) sols. This difference can be attributed to the ordering of the nanostructures in the Ag-ILs. (C) 2011 Elsevier Inc. All rights reserved.