Reactivity and a Charge-Transfer Model Analysis in Aminopolycarboxylic-Metal Complexes.

In the present work, we have calculated several density functional theory (DFT) reactivity descriptors for the aminopolycarboxylate (APC) acids at the B3LYP/6311++G (d,p) levels of theory, aiming to analyze their reactivity. Reactivity descriptors such as ionization energy, molecular hardness, electrophilicity, and condensed Fukui function local indices have been determined to predict the reactivity of APCs. The influence of the solvent was taken into account by employing the CPCM model. The results indicate that the solvation slightly modifies the tendency of the reactivity of the APCs studied. On the other hand, we applied a global and local charge-transfer partitioning model, which introduces two charge-transfer channels [one for accepting electrons (electrophilic) and another for donating one (nucleophilic)] to the complexation reaction of a set of APC acids with transition metals (Mn, Co, and Ni targets enlarged by Fe, Cu, and Zn). The correlation between the charges obtained for the interaction between APC acids and transition metal stability constants provides support for their interpretation as measures of the electrophilicity and nucleophilicity of a chemical species and, at the same time, allows one to describe the donation and back-donation processes in terms of the DFT of chemical reactivity. Also, the application of dual descriptors for these acids provides valuable information concerning the atoms in the reactants playing the most important roles in the reaction, thus helping to improve our understanding of the reaction under study.

Combined QTAIM and ETS-NOCV investigation of the interactions in ClnM[PhB(NtBu)2] complexes with M = Si & Ge (n = 0), As & Sb (n = 1), Te & Po (n = 2).

In this work, the nature of the chemical interactions between the metalloid atom (M = Si, Ge, As, Sb, Te, Po) and the nitrogen atoms in the bora-amidinate (bam) complexes (ClnM[PhB(NtBu)2]) are investigated, mainly via density-based indices. The descriptors used are derived using the quantum theory of atoms in molecules and natural orbitals for chemical valence approaches. It is shown that the strongest interaction is achieved with silicon. Indeed, it is generally the lightest metalloid in a particular group of the periodic table (i.e., Si, As, and Te for groups 14-16, respectively) that exhibits the strongest bond in the bam complex. This suggests that the atomic radius of the metalloid is a useful parameter for predicting the bonding strength. Extended transition state (ETS) decomposition results indicate that the interactions are more electrostatic than due to orbital interactions.