Electric field response of molecular reactivity descriptors: a case study

Extending conceptual DFT to include external variables: the influence of magnetic fields

An extension of conceptual DFT to include the influence of an external magnetic field is proposed in the context of a program set up to cope with the ever increasing variability of reaction conditions and concomitant reactivity.

Extending conceptual DFT to include additional variables: oriented external electric field

The extension of the E = E[N, v] functional for exploring chemical reactivity in a conceptual DFT context to include external electric fields is discussed. Concentrating on the case of a homogeneous field the corresponding response functions are identified and integrated, together with the conventional response functions such as permanent dipole moment and polarizability, in an extended response function tree associated with the E = E[N, v, ε] functional. In a case study on the dihalogens F2, Cl2, Br2, I2 the sensitivity of condensed atomic charges (∂q/∂ε) is linked to the polarizability of the halogen atoms. The non-integrated (∂ρ(r)/∂ε) response function, directly related to the field induced density change, is at the basis of these features. It reveals symmetry breaking for a perpendicular field, not detectable in its atom condensed counterpart, and accounts for the induced dipole moment directly related to the molecular polarizability. The much higher sensitivity of the electronic chemical potential/electronegativity as compared to the chemical hardness is highlighted. The response of the condensed Fukui functions to a parallel electric field increases when going down in the periodic table and is interpreted in terms of the extension of the outer contours in the non-condensed Fukui function. In the case of a perpendicular field the (∂f(r)/∂ε) response function hints at stereoselectivity with a preferential side of attack which is not retrieved in its condensed form. In an application the nucleophilic attack on the carbonyl group in H2CO is discussed. Similar to the dihalogens, stereoselectivity is displayed in the Fukui function for nucleophilic attack (f+) in the case of a perpendicular electric field, and opposite to the one that would arise based on the induced density. Disentangling the expression for the evolution of the Fukui function in the presence of an electric field reveals that this difference can be traced back to local differences in the polarization or induced density between the anionic and the neutral system. This difference may be exploited, e.g. for an appropriately substituted H2CO, to generate enantioselectivity.

DFT-based reactivity and QSPR studies of platinum (IV) anticancer drugs

In the present work the influence of different axial ligands on reactivity of some selected Pt(IV) complexes with anticancer activities are investigated in both gas and solvent phases using Density Functional Theory (DFT) calculations. Calculated geometries of the complexes are in good agreement with their available X-ray data. The reactivity descriptors such as hardness, chemical potential and electrophilicity are calculated to measure stability and reactive nature of the complexes. It has been interesting to observe that the increase in the number of carbon chain of carboxylato axial ligand has no influence on reactivity of Pt(IV) complexes. Multiple linear regression analyses are performed to build Quantitative Structure Property Relationship (QSPR) models using DFT and molecular mechanics (MM+) based descriptors in gas and solvent phases. Chemical potential is found to be the most significant single descriptor to measure reduction potential of Pt(IV) complexes giving 87% correlation with experimental data. While gas phase derived descriptors are not statistically significant, inclusion of solvent medium increases the correlation of each descriptor with reduction potential and hydrophobicity of the complexes.

Antioxidant properties can be tuned in the presence of an external electric field: accurate computation of O–H BDE with range-separated density functionals

The effect of external electric field on the antioxidant properties of gallic and caffeic acids is studied. The performance of range-separated functionals in reproducing the O–H BDE is tested in the presence of an external electric field.

Applicability of optimal functional tuning in density functional calculations of ionization potentials and electron affinities of adenine–thymine nucleobase pairs and clusters

Successful application of optimally tuned long-range corrected functionals for calculation of vertical ionization potentials and electron affinities of various adenine–thymine nucleobase pairs and clusters is demonstrated.