In examples of two large naphthalene- and triphenylene-centred hexaynes exhibiting only the nematic discotic (ND) type of mesophase, a new kind of phase induction was observed. These disc-shaped nematogens were doped with numerous dipolar carbocyclic compounds leading to the induction of two types of columnar mesophase (i.e. Droand Dho). The phase behaviour of these binary systems, depending on the structure of the dopant applied, was studied by polarizing microscopy.