Molecular selectivity of indenopyridines for fullerenes: A comparative study

Selectivity of [60]-Fullerene (C60) over its [70]-analogue (C70) is ably established for N-containing polynuclear aromatic planar indenopyridines (I) in organic media for the first time. The present work envisages the chemical physics behind non-covalent interaction between [70]-fullerene (C70) and indenopyridines (I: I1, I3 and I4) in toluene alongwith a comparative analysis of previously studied interaction of C60 (Pal et al., 2019) via formation of multiple absorption isosbestic points and isoemissive point in UV–Vis and steady state fluorescence studies respectively, stable ground state equilibrium between C70 and I is recognized and is purely non-covalent in nature. All three indenopyridines showed high formation constant (∼105) with [70]-fullerene though the selectivity of binding favours [60]-fullerene. Experimental findings are well supported within vacuo DFT based computation. Loss of planarity of indenopyridines in the optimized adducts, FMO features, electrochemical indices and finally TD-DFT calculation validates the strong complexation. Taut wrapping of C70 by indenopyridines is most conspicuous for I4 among others as that of C60.