UV–Vis, fluorescence and NMR spectroscopic investigations on inclusion properties of a designed tetrahomocalix[8]arene with fullerenes C60 and C70 in solution

The present article reports the spectroscopic investigations on non-covalent interaction of fullerenes C60 and C70 with a macrocyclic receptor molecule, namely, 1,3,5,7-tetrahomo-p-tert-butylcalix[8]arene (1) in toluene. Jobs method of continuous variation reveals 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds selectively C60 compared to C70 as obtained from binding constant (K) data of C60-1 (KC60-1) and C70-1 (KC70-1) complexes which are enumerated to be 265,000 dm3 mol−1 and 63,430 dm3 mol−1, respectively, and selectivity in binding (KC60-1/KC70-1) is estimated to be 4.18 as obtained from UV–Vis study. Steady state fluorescence studies reveal quenching of fluorescence of 1 in presence of fullerenes and the K value of the C60-1 and C70-1 complexes are estimated to be 80,760 and 68,780 dm3 mol−1, respectively, with selectivity in binding (KC60-1/KC70-1) ∼1.18. 1H NMR analysis provides very good support in favor of strong binding between C60 and 1. The high value of K value for C60-1 complex indicates that 1 forms an inclusion complex with C60.

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► The present article introduces a newly designed tetrahomocalix[8]arene molecule, 1.
► For the first time, fullerene-1 non-covalent interaction is studied in solution.
► 1 serves as an effective molecular tweezers for C60 in solution.
► Binding of fullerenes with 1 is clearly demonstrated by proton NMR studies.