A computational assessment of the O-H•••O intramolecular hydrogen-bonding in substituted phenalenes: diverse degrees of covalence

The present article demonstrates a quantum chemical approach based on the Quantum Theory of Atoms-In-Molecules (QTAIM) to assess the O-H center dot center dot center dot O intramolecular hydrogen-bonding (IMHB) interactions in a series of phenalene derivatives, namely, 9-hydroxy-2,4-dihydro-1H-phenalen-1-one (9HP1O), 2-hydroxy-9,9a-dihydro-1H-phenalen-1-one (2HP1O), and 3-hydroxy-1H-phenalen-2(4H)-one (3HP2O). The topological parameters and IMHB energies have been calculated based on density functional theory (using B3LYP and CAM-B3LYP hybrid functionals, and M06-2X and LC-omega PBE functionals) and Moller-Plesset perturbation theory (MP2) approaches. The calculated geometrical and topological parameters along with the IMHB energies show the different degrees of covalence in the IMHB interactions in the studied molecular structures, and thus reveal the inequivalence of substitution pair positions in the studied phenalene derivatives. The results derived from QTAIM analyses of the studied molecules are further corroborated from noncovalent interaction analysis including a visual portrayal of the noncovalent interactions. [GRAPHICS] .