Figure 3
Second-level R42(8) or R44(12) hydrogen-bond motifs in (a) 1,1,3,3-tetramethylguanidinium dihydrogen orthophosphate (Criado et al., 2000), (b) 1,1,3,3-tetramethylguanidinium propionate (King et al., 2011), (c) dicyclohexylammonium 4-nitrophenylsulfinate (Brito et al., 2006) and (d) N-[2-(3-methoxyphenoxy)propyl]-m-tolylacetamidinium p-toluenesulfonate monohydrate (Blaton et al., 1995). In (d), the water molecule has been omitted and the substituted phenyl rings are shown as small spheres for clarity. The small circles in (a), (c) and (d) indicate crystallographic inversion centres. |