Molecular and crystal structure of 1-(8-carboxyoctyl)-1,3,5,7-tetraazaadamantan-1-ium bromide and 1-(6-bromohexyl)-1,3,5,7-tetraazaadamantan-1-ium bromide

Abstract

The molecular and crystal structures of a pair of quarternised bromide derivatives of hexamethylenetetramine have been determined. 1-(8-Carboxyoctyl)-1,3,5,7-tetraazaadamantan-1-ium bromide, 1, C₁₄H₂₇N₄O₂Br, M_r = 363.31, triclinic, P , a = 9.759(5), b = 12.699(7), c = 14.125(6) Å, α = 96.45(3), β = 99.17(3), γ = 104.74(3)° , V = 1649.7(14) ų, Z = 4, D_c = 1.463 g cm^-3, λ (MoKα ) = 0.7107 Å μ = 2.503 cm^-1, F(000) = 760, R (on F) = 0.058, R_W (on I) = 0.162 for 3625 unique reflections with [I -σ (I)]. There are two symmetry independent sets of ions, each set being linked with strong O…Br interactions to form linear arrays. The symmetry indenpendent arrays are in turn connected with C---H…O interactions to form a layer. 1-(6-Bromohexyl)-1,3,5,7-tetraazaadamantan-1-ium bromide, 2, C₁₂H₂₉N₄Br₂, M_r = 384.17, monoclinic, P2₁/n, a = 8.976(4), b = 15.743(8), c = 11.329(6) Å, β = 103.70(2)° , V = 1555.3(13) ų, Z = 4, D_c = 1.641 g cm^-3, λ (MoKα ) = 0.7107 Å μ = 5.203 cm^-1, F(000) = 776, R (on F) = 0.066, R_W (on I) = 0.168 for 1310 unique non-zero reflections with [I >>2σ (I)]. Two Br^- anions are located between two cations resulting in the formation of a cyclic centrosymmetric dimer. Each dimer is surrounded by six similar dimers and is connected to them with C---H…N hydrogen bonds to form corrugated molecular sheets. The symmetrical bond lengths of the hexamethylenetetramine skeleton are distorted by quarternisation in both 1 and 2.