Solid-state 13C NMR investigations of 4,7-dihydro-1H-tricyclopenta[def,jkl,pqr]triphenylene (sumanene) and indeno[1,2,3-cd]fluoranthene: Buckminsterfullerene moieties

Abstract

4,7-Dihydro-1H-tricyclopenta[def,jkl,pqr]triphenylene (sumanene) and indeno[1,2,3-cd]fluoranthene (indenofluoranthene) are structural moieties related to Buckminsterfullerene (C₆₀). As such, understanding their structural characteristics is of great interest because of the insight they shed upon C₆₀. Hence, solid-state NMR (ssNMR) and ab initio quantum mechanical calculations with Gaussian03 are used in order to understand and to better characterize the molecular conformation and properties of sumanene and indenofluoranthene. Sumanene has bowl shaped curvature in its natural conformation and indenofluoranthene is planar in its natural conformation, which led us to examine how altering the curvature affects the chemical shifts in relation to those of C₆₀. Using X-ray structures of both sumanene and indenofluoranthene as our starting model, we calculate the energy and chemical shielding tensors and compare these data with those collected utilizing the ¹³C ssNMR FIREMAT experiment. We define curvature of sumanene and indenofluoranthene using the π-orbital axis vector (POAV) pyramidalization angle (θ_p). We calculate the energy of varying conformations of indenofluoranthene versus their θ_p associated with each deformed conformation.