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

Abstract: 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 (K C60-1 ) and C70-1 (K C70-1 ) complexes which are enumerated to be 265,000dm3 mol−1 and 63,430dm3 mol−1, respectively, and selectivity in binding (K C60-1 /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 68,780dm3 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. [Copyright &y& Elsevier]