THEORETICAL INVESTIGATION OF THE STRUCTURE OF NON-COVALENT COMPLEXES BETWEEN FULLERENES AND LACTAMS

• Published in: Proceedings of the Indiana Academy of Science Vol. 129; no. 2; pp. 76 - 87
• Main Authors: Lieb, Shannon G, Kirsch, Joe L, Schemenauer, D, Engle, A, Brown, E, Kanter, J, Wade, J
• Format: Journal Article
• Language: English
• Published: Indiana Academy of Science 01.07.2020
• Subjects: United States
• ISSN: 0073-6767; 2380-7717

Experimental research by Kirsch et al. (2015, 2017) employed FTIR to study carbonyl frequency shifts of lactams upon the formation of a complex with fullerenes. This current, theoretical study elucidates the most probable structures of the fullerene--lactam complex. It employs the experimental results, along with theoretical values of the molecular dipole moment ([mu]), dispersion energy ([E.sub.disp]), absolute enthalpy (H), and the distance from the center of mass of a fullerene to the center of mass of the complexed lactam (cm2cm). The most probable structures of the fullerene--lactam complex were based on the consistent trend of enthalpies of complex formation. The role of [E.sub.disp] is lacking in low level DFT and HF calculations and is an important contribution to the overall most stable structure for these dipole induced dipole structures. The B3LYP/6-31G* calculations without Grimme's semi-empirical [E.sub.disp] corrections are compared to HF-D3 calculations, which include [E.sub.disp]. Our conclusions based on the HF-D3 calculations are that the parallel conformations are the most stable for the [C.sub.60] and [C.sub.70]--lactam complexes. In addition, the most stable [C.sub.70] lactam complexes place the associated lactam more favorably in the equator position on [C.sub.70].