Coordination chemistry of Zn2+ with Sal(ph)en ligands: Tetrahedral coordination or penta‐coordination? a DFT analysis

Abstract

In this article, the Lewis acidic character within a series of Zn‐Sal(ph)en complexes is reviewed and revisited. Besides traditional analyses found in the literature, conceptual density functional theory descriptors are used to assess this acidic character. Using these tools, we highlight how the nature of the bridging diamine linker in the Schiff base ligand controls this feature mainly responsible of the coordination geometry of these complexes. This Lewis acidic behavior is addressed first by application of the usual dual descriptor to a prototypical complex, namely ZnCl42−. However, the usual dual descriptor exhibits significant weaknesses to retrieve the electrophilic part on the metal cation of Zn‐sal(ph)en complexes. The inclusion of the densities of the electronic excited states through the so‐called state‐specific dual descriptor allows us to recover successfully the appropriate reactivity of these chosen complexes with different diamine bridges in flexible to semirigid, and then to rigid ranges. The coordination of the Zn2+ is shown to be dictated by the geometry of the sal(ph)en ligand. © 2018 Wiley Periodicals, Inc.