Present work reports the photophysical insights on supramolecular interaction of a C₇₀ derivative, namely, [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₀ BM), with two designed diporphyrin molecules having dithiophene (1) and carbazole (2) spacer in toluene and benzonitrile. Both absorption spectrophotometric and steady state fluorescence investigations reveal efficient complexation of PC70 BM with 1 and 2  in both toluene and benzonitrile. The magnitude of average value of binding constant, viz., K_av, for the complexes of PC₇₀BM with 1 and 2 in toluene (benzonitrile) are estimated to be 2.185X10³dm³mol^-1(3.215X10³dm³mol^-1) and 10.180X10³dm³mol^-1(25.405X10³dm³mol^-1), respectively. Selectivity in binding for the complexation process of PC₇₀BM with 1 and 2 is estimated to be ~4.6 and ~7.90 as observed in toluene and benzonitrile, respectively. The complexation between PC₇₀BM and diporphyrin is well accounted by a theoretical model which takes into account the electronic subsystems of both acceptor and donor. Ab initio calculations in vacuoestablish that size selective orientation pattern of PC₇₀BM towards the cavity of diporphyrin dictates the magnitude of binding and electronic structure of the PC₇₀BM/diporphyrin complexes.