Chemical Physics Behind Tetraphenylporphyrin-PC70BM Interaction in Solution: Charge Transfer, Non-Covalent Binding and Photoactive Properties

The interaction between [6,6] -Phenyl -C71 -butyric acid methyl ester (PC70BM) and 5,10,15,20-Tetraphenylporphyrin, i.e., H2TPP, is studied in solution. UV-Vis study reveals formation of charge transfer (CT) absorption band for the H2TPP-PC70BM complex and the CT transition energy (h nu CT) is estimated to be 1.635 eV. Quenching of fluorescence of H2TPP in presence of PC70BM is employed successfully to determine the value of the binding constant of the H2TPP-PC70BM complex as 25,290 dm3 & sdot;mol- 1. DFT calculations generate stereoscopic structure of the H2TPP-PC70BM complex and the estimated HOMO-LUMO energy gap, i.e., 1.7827 eV, correlates excellently well with the reported value of h nu CT.