Molecular structure and DFT calculations of aqua(5,10,15,20-tetrakis[4-(benzoyloxy)phenyl] porphyrinato)magnesium-dioxane

Abstract In this work, complex [Mg(TPBP)(H2O)], where TPBP is the 5,10,15,20-tetrakis[4-(benzoyloxy)phenyl]porphyrin ligand, was obtained unintentionally as a by-product of the reaction of the [Mg(TPBP)] complex with an excess of dioxane in dichloromethane. The crystal structure of five coordinated Mg(II) [Mg(TPBP)(H2O)] (dioxane) (1), was determined using single crystal X-ray diffraction (SCXRD) analysis and studied using Hirshfeld surfaces computational method. The metal cation is surrounded by four porphyrin nitrogen atoms and one axially bonded water molecule, forming a regular tetrahedron. In this complex, the molecular structure and the three-dimensional framework were stabilized by inter-and intramolecular O–H⋯O and C–H⋯O hydrogen bonds, and by weak C–H⋯Cg π interactions. The results of the infrared and proton nuclear magnetic resonance spectroscopies are in good agreement with the transformation of the porphyrinic Mg(II) complex [Mg(TPBP)] to the one involving a bonded water molecule. Density Functional Theory (DFT) calculations on [Mg(TPBP)(H2O)] (dioxane) (1) complex revealed its enhanced thermodynamic stabilization which is attributed to the existence of hydrogen bonding interactions and the kinetic lability will be attributed to the small difference between the energy levels.