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

The present paper reports the spectroscopic investigations on non-covalent interaction of fullerenes C60 and C70 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 C70 more strongly compared to C60, i.e. KC60–2 = 47,540 dm3 mol−1 and KC70–2 = 86,360 dm3 mol−1. Proton NMR studies provide very good support in favor of strong binding between C70 and 2. Estimation of solvent reorganization energy (RS) evokes that C70–2 complex is stabilized more compared to C60–2 complex as RS(C60–2) = −1.162 eV and RS(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 C60 and C70 complexes of 2 in terms of enthalpies of formation values.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The present article introduces a newly designed trihomocalix[6]arene molecule, 2. ► For the first time, fullerene-2 interaction is studied in solution. ► Binding of fullerenes with 2 is clearly demonstrated by UV–vis and NMR studies. ► 2 serves as an effective molecular receptor for both C60 and C70.