Discrimination between O-H…N and O-H…O=C Complexes of 3-Methyl-4-pyrimidone and Methanol. A Matrix-isolation FT-IR and Theoretical DFT/B3LYP Investigation

FT-IR matrix-isolated spectra for 3-methyl-4-pyrimidone and its H-bonded complexes with methanol in Ar were studied with the aim of discriminating between O-H…N and O-H…O=C complexes. Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of the 3-methyl-4-pyrimidone molecule with proton donors. The observed frequency decrease of the ν(C=O) mode of 3-methyl-4-pyrimidone and the appearance of a broad ν(OH…O) band in the spectrum of the complex with methanol suggest that H-bonding with methanol occurs at the carbonyl group. Computed binding energies of the hydrogen-bonded complexes (ΔEc) and computed intermolecular distances (r(O…H)) confirm that the O-H…O=C complex is preferred with methanol. However, for H-bonding with stronger acids such as HCl, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone.Keywords: Matrix-isolation, 3-methyl-4-pyrimidone, methanol, FT-IR spectroscopy, DFT/B3LYP calculation

Interaction between Temozolomide and Water: Preferred Binding Sites

Computational methods are used to predict the most favorable site of temozolomide towards attack by a water molecule. The energetics of the various complexes are presented as well as their geometries, including perturbations of each subunit caused by the presence of the other. Molecular electrostatic potential and Natural Bond Orbital (NBO) data are used to understand the interactions which conclude the terminal amide group is the preferred attack site where water can act as simultaneous proton donor and acceptor. Other potential proton acceptor N atoms within the aromatic ring structure represent weaker binding sites. Some of the less strongly bound structures include a CH⋯O H-bond