Quantum chemical modeling of pyrene-4,5-dione adducts with cobalt diketonates

DFT computational modeling (B3LYP*/6-311++G(d,p)) of a series of adducts of Co-II bis-(malonate), bis-(acetylacetonate), bis-(hexafluoroacetylacetonate) and bis-(trifluoroacetylacetonate) with pyrene-4,5-dione has been performed. The results of calculations of Co-II bis-(malonate) complex point to the possibility of the occurrence of valence tautomeric (VT) rearrangements of this compound. It has been shown that methyl groups into the diketonate moiety (Co-II bis-(acetylacetonate) adduct) destabilize the high-spin state structure giving rise to the competitive process of dissociation into the initial bis-chelate complex and redox-active ligand. An adduct of Co-II bis-(hexafluoroacetylacetonate) with pyrene-4,5-dione is energy preferred to the high-spin state electromer, which obstructs the VT process. The most suitable energy parameters for the occurrence of thermally initiated valence tautomeric transformation (stability of the adduct with respect to dissociation into the components, energy preference of the low-spin electronic state and thermally achievable energy barrier to intramolecular electron transfer determining the intrinsic mechanism of VT rearrangements) are found for the adduct of pyrene-4,5-dione with Co-II bis-(trifluoroacetylacetonate). (C) 2015 Elsevier B.V. All rights reserved.