Coordination capabilities of anthracene ligand in binuclear sandwich complexes: DFT investigation

Abstract

DFT calculations with full geometry optimization using BP86 and mPW1PW91 functionals have been carried out on binuclear hypothetical compounds of the type M2(Ant)2 (Ant = anthracene). This work investigates the possibility for such compounds to exist for the M = Ti–Ni series. The analysis of their electronic and molecular structures in relation to their electron counts allows a comprehensive rationalization of the bonding of these compounds. A very rich coordination chemistry of anthracene has been highlighted. This richness comes from the very large electronic and structural flexibility of anthracene, which is able to adapt itself to the electronic demand of metals. Each of the C6 rings of anthracenes can be coordinated in various hapticities and symmetries depending on the nature of the metal and the structure’ spin state. This flexibility favors the possibility of existence of several isomers closeness in energy. The asymmetry between the two anthracenes causes binuclear complexes to exhibit very different coordination with different oxidation states. In some cases, the M–M bonding is not privileged despite the metals’ electronic deficiency.