RADICALS AS HYDROGEN-BOND ACCEPTORS

The ability of carbon radicals to act as hydrogen bond accepters has b een evaluated using ab initio theoretical methods. A hybrid Hartree-Fo ck Density Functional Theory based method (B3LYP), Moller-Plesset at t he second perturbation order (MP2), and Quadratic CI methods that incl ude single and double excitation (QCISD), have been used. The complexe s formed by four radicals CH3(d), C2H4(t). (CH3)(2)C(t) and (CH3)(3)C( d)] with four standard hydrogen bond donors [FH, H2O, HCN and H3N] hav e been studied and their geometry, interaction energy, and electronic properties, within the Atoms in Molecules (AIM) methodology framework have been analyzed. The energy and geometry results show that the stud ied radicals are poor hydrogen bond (HB) accepters and the strength of the HBs qualitatively correlates with the molecular electrostatic pot ential (MEP) minimum of the isolated radicals. The atomic partition of different properties using the AIM methodology indicates that HBs com plexes involving radicals behave differently to other HBs formed betwe en neutral molecules.