Effect of methyl­ene versus ethyl­ene linkers on structural properties of tert-butyl and mesityl bis­(imidazolium) bromide salts

The crystal structures of ligand precursor bis­(imidazolium) salts 1,1′-methyl­enebis(3-tert-butyl­imidazolium) dibromide monohydrate, C(15)H(26)N(4) (+)·2Br(−)·H(2)O or [( tBu)NHC(2)Me][Br](2)·H(2)O, 1,1′-(ethane-1,2-di­yl)bis­(3-tert-butyl­imidazolium) dibromide dihydrate, C(16)H(28)N(4) (+)·2Br(−)·2H(2)O or [( tBu)NHC(2)Et][Br](2)·2H(2)O, 1,1′-methyl­enebis[3-(2,4,6-tri­methyl­phen­yl)imidazolium] dibromide dihydrate, C(25)H(30)N(4) (2+)·2Br(−)·2H(2)O or [(Mes)NHC(2)Me][Br](2)·2H(2)O, and 1,1′-(ethane-1,2-di­yl)bis­[3-(2,4,6-tri­methyl­phen­yl)imidazolium] dibromide tetra­hydrate, C(26)H(32)N(4) (2+)·2Br(−)·4H(2)O or [(Mes)NHC(2)Et][Br](2)·4H(2)O, are reported. At 293 K, [( tBu)NHC(2)Me][Br](2)·H(2)O crystallizes in the P2(1)/c space group, while [( tBu)NHC(2)Et][Br](2)·2H(2)O crystallizes in the P2(1)/n space group at 100 K. At 112 K, [(Mes)NHC(2)Me][Br](2)·2H(2)O crystallizes in the ortho­rhom­bic space group Pccn while [(Mes)NHC(2)Et][Br](2)·4H(2)O crystallizes in the P2(1)/c space group at 100 K. Bond distances and angles within the imidazolium rings are generally comparable among the four structures. All four bis­(imidazolium) salts co-crystallize with one to four mol­ecules of water.