Cubic self-assembled porphyrin-based metallocomplexes Fe8Por6 are ideal hosts for encapsulation of large aromatic compounds such as coronenes and fullerenes. The host and guest interact through pi-pi stacking and van der Waals forces. An attractive feature of these host cages is the variability and versatility of the porphyrins that make up its “walls”. For example, Zn(II) porphyrins could coordinate to encapsulated guests at its axial positions. Thus, Zn-porphyrin cubes bear specific binding sites for increased host-guest binding beyond pi-pi stacking. Modelling studies indicate that 2,4,6,8-tetracyanoazulene (TCNA) is a guest that can simultaneously bind to opposite end of the molecular box. In this work we present initial steps toward the synthesis of TCNA. The general approach is to synthesize 6-methylazulene, convert to 6-cyanoazulene, and then TCNA. 4-Picoline has been coupled with chlorodinitrobenzene to produce the corresponding Zincke salt in 94% yield. The pyridinium ring is the opened with dimethylamine to give 1-aminium-3-methyl-5-(dimethylamino)-N,N-dimethyl-2,4-pentadiene chloride in 23% yield. Reaction with lithium cyclopentadienide should give the desired 6-methylazulene.

Synthesis of tetracyanoazulene as a guest for self-assembled Zn-porphyrin supramolecular cubes

253rd National Meeting (2017)

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