Chemical physics behind formation of efficient charge-separated state for complexation between PC70BM and designed diporphyrin in solution

• Supramolecular interaction between PC70BM and diporphyrin molecules is established.
• Diporphyrin having carbazole spacer exhibits large binding affinity toward PC70BM.
• Solvent dependence of charge separation is observed in present work.
• Electron transfer process is facilitated in solvent having high dielectric constant.

The present work reports supramolecular interaction of [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) with two designed diporphyrin molecules having dithiophene (1) and carbazole (2) spacer in solvent having varying polarity. Studies on complex formation reveal relatively higher binding constant for PC70BM/2 complex in all the solvent studied. Solvent dependence of charge separation and charge recombination processes in PC70BM/diporphyrin non-covalent complexes has been well established in present work. Donor–acceptor geometry and stabilization of the singlet excited state of the diporphyrin during charge recombination are considered to be the possible reasons for this behavior.

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