Spectroscopic and theoretical insights on determination of binding strength and molecular structure for the supramolecular complexes of a designed bisporphyrin with C _(60) and C _(70)

摘要

The present article examines the binding affinity of the newly designed Zn _2-bisporphyrin molecule, syn-1, towards C _(60) and C _(70) in toluene medium. The investigation is carried out by UV-vis spectrophotometric, steady state and time-resolved fluorescence spectroscopic techniques. The bisporphyrin, syn-1, serves as an effective and selective molecular tweezer for C _(70) as average value of binding constants (K) for the non-covalent complexes of syn-1 with C _(60) and C _(70) are estimated to be 1.65 × 10 ~4 and 1.05 × 10 ~5 dm ~3 · mol ~(-1), respectively. Binding of C _(70) in the cleft of syn-1 is clearly demonstrated by the quantum chemical calculations at ab initio level of theory. Molecular electrostatic potential maps demonstrate significant redistribution of charges in these supramolecules. Proton NMR studies suggest that the C _(70) moiety remains at the shallow part of the cleft of syn-1.