Mesomorphic properties of a tetraphenylporphyrin metallomesogen with a weak hydrogen bond interaction between axial ligands:: dihydroxo[5,10,15,20-tetrakis(4-n-dodecylphenyl)porphinato]silicon(IV)

A new metallomesogen, the dihydroxo[5,10,15,20-tetrakis(4-n-dodecylphenyl) porphinato]silicon( IV) complex, C12TPPSi(OH)(2), was synthesized and its mesomorphism was investigated in terms of the axial hydrogen bond interaction in the stacked columnar structure. It was found that this compound exhibits a 3D plastic lamellar mesophase with a columnar structure, and the axial hydroxyl groups are connected by a very weak hydrogen bond interaction in the column. This causes a dramatic increase of the clearing point for the mesophase, even though the stacking periodicity is far larger (c. 9 Angstrom) than that typically found for a columnar meosphase (c. 3.5 Angstrom).