Effect of solvation on the condensed Fukui function and the generalized philicity index

Electrodonating and electroaccepting powers

By introducing an electron bath that represents the chemical environment in which a chemical species is immersed, and by making use of the second-order Taylor series expansions of the energy as a function of the number of electrons in the intervals between N - 1 and N, and N and N + 1, we show that the electrodonating (omega-) and the electroaccepting (omega+) powers may be defined as omega-/+ = (mu-/+)2/2eta-/+, where mu-/+ are the chemical potentials and eta-/+ are the chemical hardnesses, in their corresponding intervals. Approximate expressions for omega- and omega+ in terms of the ionization potential I and the electron affinity A are established by assuming that eta- = eta+ = eta = mu+ - mu-. The functions omega-/+(r) = omega-/+f -/+(r), where f -/+(r) are the directional Fukui functions, derived from a functional Taylor series for the energy functional truncated at second order, represent the local electrodonating and electroaccepting powers.

Philicity indices within the spin-polarized density-functional theory framework

The electrophilicity index is analyzed within the framework of spin-polarized density-functional theory. In this context, constrained philicities, omega(N) identical with (mu(N))(2)(2eta(NN)), are introduced in order to define the capability of a system to acquire or donate electrons in a process at constant spin number. The spin-philicity/spin-donicity indices, omega(S)(+/-) identical with (mu(S) (+/-))(2)(2eta(SS)), are examined and rationalized here as the philicity of a given system to change its spin-polarization state, as being defined through the spin potential mu(S) and spin hardness eta(SS) for a process at constant number of electrons. The local extension of these indices has been also outlined and numerical results have been discussed on the analysis of the electrophilic nature of some simple carbene systems both in the singlet and triplet states.

Reparameterized Austin Model 1 for quantitative structure–property relationships in liquid media

A reparameterization of the quantum-chemical AM1 (Austin Model 1) model has been carried out using a nonlinear optimization based on a modification of the Levenberg-Marquardt technique. The optimum numerical values for the one-electron resonance integral parameters (beta (s) and beta (p)) and core-core repulsion atomic parameters alpha were obtained for the elements H, C, N, O, Cl and Br using the statistical fit of a two-parameter QSPR equation for the boiling points of organic compounds. A substantially improved two-parameter correlation (R2=0.9685, s=13.48 K) was obtained by using the new optimized parameters. The QSPR equation employs two molecular descriptors, a bulk cohesiveness descriptor, [Formula: see text] and the area-weighted surface charge of hydrogen-bonding donor atom(s) in the molecule. The model developed shows remarkably accurate predictions of the normal boiling points for nine additional simple inorganic compounds. The new parameters were tested on the critical temperatures of 165 organic compounds. The new QSPR model obtained for this property was found to be statistically significantly better than the original model. [Figure: see text].