The synthesis of novel porphyrin macrocycles for their use as potential non-linear optical materials
The potential organic molecular compounds exhibit for the use as nonlinear optical materials, has received a lot of attention recently. Aromatic compounds containing extensive delocalised π-electronic systems are of particular interest. Porphyrins and metalloporphyrins contain an extensive delocalised 7t-electron system and are amongst those compounds of interest. The ability to manipulate the porphyrins peripheral substitution pattern has led to the synthesis of a range of novel porphyrin macrocycles. A series of meso- substituted porphyrin macrocycles ha been synthesised and the non-linear optical properties of these compounds screened. The synthesis of a series of symmetrical meso- substituted porphyrins was achieved by the reactions of various aldehydes with pyrrole or a dipyrromethane. The synthesis of a series of unsymmetrical porphyrins was achieved by the mixed condensation of two benzaldehydes and pyrrole and also by reactions at the periphery of the symmetrical porphyrins. The Reverse Saturable Absorption properties of the synthesised porphyrins was tested and was exhibited by a number of these compounds. The RSA properties of the compounds were enhanced on the introduction of an unsymmetrical nature to the macrocycle. Also, the effect is enhanced when the ethynyl moiety was introduced to the porphyrins periphery. This is due to the greater overlap between the macrocycle and the peripheral substituents.