DF T/B۳LYP Study of the Substituent and Solvent Effects on the Reaction Enthalpies of Homolytic and Heterolytic N– H Bond Cleavage in Melato nien Derivatives

Melatonin is an animal and plant hormone, its ability to scavenge hydroxyl radicals was discovered and scave nges free radicals [۱]. The reaction between free radic als and antioxidants can follow different mechanisms (HAT, SET-PT and SPLET) [۲]. T he reaction e nthalpy of the first step of HAT, SET-PT and SPLET mechanism corresponds to the BDE, IP and PA, respectively [۳]. Understanding the role of different structural features and preparation of new comp ounds with enhanced antioxidant property i s of great interest. Melatonin stru cture (Figure ۱) represe nts the basic structure. Various substituen ts such as electron–wit hdrawing groups (EWG) and electr on–donating groups (ED G) were located i n three available positi ons on the aromatic r ing (Figure ۱). We have investig ated the substituen t effect on reaction enthalpies of homolytic (HAT mech anism) and heterolytic two–step (SPLET a nd SET–PT ) mechanisms of N–H bond cleavage for mon o–substitut ed melatonins in gas phase and water.

کلیدواژه ها:

Natural A ntioxidant ، Melatonin ، Solvent Effect ، Reaction Enthalpy ، S ubstituent