Reactions of melatonin and related indoles with free radicals: a computational study.

Melatonin is being increasingly promoted as a therapeutic agent for the treatment of jet lag and insomnia and has been recently suggested to act as an efficient free-radical scavenger. In the present work, its mechanisms of action for scavenging hydroxyl radicals have been investigated using semiempirical AM1 and density functional theory (DFT) computational tools. Two different reactions were proposed as follows: one involving the abstraction of an indolic hydrogen to yield a neutral radical and another involving the addition of the hydroxyl radical to the indolic moiety.

Structure and Bonding in Pentacyano(L)ferrate(II) and Pentacyano(L)ruthenate(II) Complexes (L = Pyridine, Pyrazine, and N-Methylpyrazinium): A Density Functional Study.

Density Functional Theory (DFT) at the generalized gradient approximation (GGA) level has been applied to the complexes [Fe(CN)(5)L](n-) and [Ru(CN)(5)L](n-) (L = pyridine, pyrazine, N-methylpyrazinium), as well as to [Fe(CN)(5)](3)(-) and [Ru(CN)(5)](3)(-). Full geometry optimizations have been performed in all cases. The geometrical parameters are in good agreement with available information for related systems.

Theoretical and Experimental Study of Medium Effects on the Structure and Spectroscopy of the [Fe(CN)(5)NO](2)(-) Ion.

The influence of the solvent on the structure and IR spectrum of the [Fe(CN)(5)NO](2)(-) ion is investigated by using gradient corrected density functional theory. IR spectra are also measured on different solvents and the results obtained are compared with the predicted ones. We have treated the solvent effects with a continuum model, based on the Onsager's reaction field approach; in order to mimic strong specific interactions, calculations were also performed on the complex protonated at the cyanide trans to the nitrosyl group.