Characterization of IR spectroscopy, APT charge, ESP maps, and AIM analysis of C20 and its C20-nAln heterofullerene analogous (n=1-5) using DFT

In this computational inspection, influences of substituted aluminum(s) on the vibrational frequency, infrared (IR) spectroscopy, atomic polar tensor (APT) charge, and electrostatic potential (ESP) map, along with atoms in molecules (AIM) analysis of C-20 fullerene and its C20-nAln derivatives (where n = 1-5) are investigated using B3LYP/6-311 + G*, B3LYP/6-311++G**, M06-2X/6-311++G**, B3PW91/6-311 + G*, and B3LYP/AUG-cc-pVTZ. IR spectroscopy emerges that exclusive of C15Al5, the other optimized structures are global minimum without imaginary frequency. Substituting C-20 to C20-nAln heterofullerenes leads to higher APT charge distribution upon surfaces of heterofullerenes than unsubstituted species. Accordingly, the highest negative and positive APT charges on carbon and aluminum atoms of C15Al5 suggest that these sites can be attacked more readily by electrophilic and nucleophilic regents, that is, may act as the Lewis acid or Lewis base centers. This species is including five alternative aluminum heteroatoms in equatorial position and can be suitable hydrogen storage. AIM analysis of the studied C20-nAln derivatives implies the highest rho(r) of 0.083 a.u., the highest negative backward difference (2)rho(r) of -0.084 and -0.085 a.u. and the highest positive G(r)/V(r) of 4.86 and 4.69 a.u. at bond critical point of C-Al bond with the strongest covalent property in the most stable C19Al1 and C17Al3 species, respectively, between studied structures.

Automated summary

The study investigates the effects of substituting aluminum on the vibrational frequency, IR spectroscopy, APT charge, and ESP map of C-20 fullerene and its derivatives. The results suggest that the highest APT charge distribution occurs on the surfaces of the substituted heterofullerenes, particularly in C15Al5. Analysis also indicates that these substituted species may act as Lewis acid or Lewis base centers. Furthermore, the AIM analysis highlights the strongest covalent property in the C-Al bond of the most stable species, C19Al1 and C17Al3.