Absorption spectrophotometric, NMR and theoretical investigations on ground state non-covalent interaction of C60 and C70 with a designed trihomocalix[6]arene in solution

Abstract The present paper reports the spectroscopic investigations on non-covalent interaction of fullerenes C 60 and C 70 with a designed trihomocalix[6]arene ( 2 ) in toluene. UV–vis studies reveal appreciable ground state interaction between fullerenes and 2 . Jobs method of continuous variation establishes 1:1 stoichiometry for fullerene– 2 complexes. Binding constant ( K ) data reveals that 2 binds C 70 more strongly compared to C 60 , i.e. K C60– 2  = 47,540 dm 3  mol −1 and K C70– 2  = 86,360 dm 3  mol −1 . Proton NMR studies provide very good support in favor of strong binding between C 70 and 2 . Estimation of solvent reorganization energy ( R S ) evokes that C 70 – 2 complex is stabilized more compared to C 60 – 2 complex as R S(C60– 2 )  = −1.162 eV and R S(C70– 2 )  = −1.244 eV. Semiempirical calculations at third parametric level of theory in vacuo evoke the single projection structures of the fullerene– 2 complexes and interpret the stability difference between C 60 and C 70 complexes of 2 in terms of enthalpies of formation values.