Synthesis and mesogenic properties of porphyrin octaesters

A new and efficient method of preparing 3,4-pyrrolediacetic esters 3 is rep orted, together with their conversion, according to the Lindsey procedure, to a series of octa- and dodeca-substituted porphyrins. This procedure, whi ch consists of a palladium-catalysed oxidative alkoxycarbonylation of N-sub stituted dipropargylamine derivatives 1, works nicely for n-alkyl alcohols in the range C-1 to C-14. The thermotropic behaviour of this series of porp hyrins (28 compounds) has been investigated using polarization microscopy, DSC, X-ray diffraction, and miscibility tests. The planarity of the macrocy clic core constitutes the major structural requirement for mesophase format ion. The mesophase temperature range is controlled by the length of the sid e chains through the melting point and by the strength of pi-pi interaction s among the cores through the clearing point. The same set of rules governi ng porphyrin packing in the solid state can be employed to predict mesophas e formation and organization in porphyrin octaesters.