Theoretical Study on Electronic Gain-and-loss Properties of TEMPO and Its Derivates in Charge/Discharge Processes

Theoretical study on the electronic structures and related properties of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and its cationic lipid derivates in the charge/discharge processes has been carried out using the density functional theory (DFT) at the (U)B3LYP/6-31G(d,p) or 6-31+G(d,p) level. The changes and regularities of geometric and electronic properties of these compounds in the charge/discharge processes were revealed in detail. The computational results show that the substitute group plays a very important role in the electronic structures and related properties of TEMPOs during the charge/discharge processes. It is very interesting to find that after getting an electron, TEMPO is more stable in singlet state but the lipid is more stable in triplet state. For TEMPO, both the charge and the discharge processes greatly influence the electronic properties of N and O atoms of the radical part. For the cationic lipid, the discharge process mainly influences the pyridinium head and the charge process mainly influences the free radical head. Moreover, the solvent effect plays an important role in sonic bond lengths and the charge population of the free radical head. In addition, the UV-Vis absorption spectra of TEMPO and the lipid were calculated and simulated using TDDFT at the 6-31G(d,p) or 6-31+G(d,p) level, in satisfying agreement with the experimental ones.