Electronic and vibrational polarizabilities of the twenty naturally occurring amino acids

International audienc

Electronic properties of neuroleptics: ionization energies of benzodiazepines

International audienceVertical ionization energies (VIEs) of medazepam, nordazepam and their molecular subunits have been calculated using the electron propagator method in the P3/CEP-31G* approximation. Vertical electron affinities (VEAs) have been obtained with a ∆SCF procedure at the DFT-B3LYP/6-31+G* level of theory. Excellent correlations have been achieved between IE and IE, allowing reliable assignment of the ionization processes. Our proposed assignment differs in many instances from that previously reported in the literature. The electronic structure of the frontier Dyson orbitals shows that the IE and EA values of the benzodiazepines can be modulated by substitution at the benzene rings. Hardness values, evaluated as (IE − EA)/2, follow the trend of the experimental singlet transition energies. Medazepam is a less hard (i.e., less stable) compound than nordazepam

Intramolecular hydrogen bonding in 8-hydroxyquinoline and 8-hydroxyquinoline-N-oxide. UV photoelectron spectra and MO calculations

The electronic structure of the intramolecularly hydrogen bonded compounds 8-hydroxyquinoline (2) and 8-hydroxyquinoline-N-oxide (5) is studied by means of gas-phase UV photoelectron spectroscopy and ab initio DZ pseudopotential calculations.It was found that the lone-pair ionization of the proton-acceptor atom is shifted to higher ioinization energy (0.6-0.7 and 0.8-0.9) eV in 2 and 5, respectively) relative to the corresponding non-hydrogen bonded methoxy compound. The observed shift parallels the neutral ground state hydrogen bond energy of 2 and 5. A first order perturbative treatment, applied to correct the Koopman's lEs, shows that the experimental IE shift mainly originates from differential repolarization contributions since electron correlation corrections contribute almost equally to the energy of both the chelate and non-chelate structure