Photophysical insights on a new supramolecular recognition element comprising PyC60 and a bisporphyrin studied in solution

Abstract The present work reports detailed photophysical insights on supramolecular interaction between C 60 pyrrolidine tris-acid ethyl ester (PyC 60 ) and a designed diporphyrin ( 1 ) in toluene. Both UV–vis and steady state fluorescence studies indicate effective complexation between PyC 60 and 1 as revealed from the value of binding constant ( K ) of PyC 60 – 1 complex, i.e., K PyC60– 1 (UV–vis) = 7625 dm 3 ·mol −1 and K PyC60– 1 (fluorescence) = 9550 dm 3 ·mol −1 . Time-resolved fluorescence measurements evoke that the decay of photoexcited 1 in presence of PyC 60 occurs only via static quenching mechanism and the magnitude of bimolecular quenching constant value for such system is enumerated to be 9.033 × 10 11  dm 3 ·mol −1 · sec −1 . In 1,2-dichlorobenzene (DCB), PyC 60 – 1 system exhibits appreciable value of rate-constant of charge-separation ( k cs ) and quantum yield of charge-separation (ϕ CS ) than that observed in toluene. However, magnitude and order of both k cs (=5.35 × 10 7 ) and ϕ CS (= 0.085) value for the PyC 60 – 1 system estimated in DCB indicate that like toluene, there is no possibility of electron transfer in DCB. Both 1 H and 13 C NMR spectra of PyC 60 molecule show appreciable shift of functional protons and carbon moiety of parent molecule in presence of 1 , respectively. Quantum chemical calculations by ab initio method in vacuo establish the geometric structure of PyC 60 – 1 complex and predict that dispersive forces associated with π-π interaction play significant role behind non-covalent interaction between PyC 60 and 1 .