Hydrogen-bonded supramolecular architectures based on tris(hydranilato)metallate(III) (M = Fe, Cr) metallotectons

Here we report on the synthesis and characterization of two isostructural mononuclear complexes of formula [(Ph)4P]3[M(H2An)3]·6H2O (M = Fe(III) (1) or Cr(III) (2); H2An = H2C6O42– = dianion of 3,6-dihydroxy-1,4-benzoquinone (DHBQ)) as suitable metallotectons for the preparation of H-bonded supramolecular architectures. The crystal structure of 1 consists of homoleptic tris-chelated octahedral complex anions [Fe(H2An)3]3– surrounded by crystallization water molecules and (Ph)4P+ cations. The metal complexes are involved in an extensive network of moderately strong hydrogen bonds (HBs) between the peripheral oxygen atoms of the ligand and crystallization water molecules. These interactions are responsible for the formation of supramolecular layers that run parallel to the a crystallographic axis, showing an unprecedented H-bonded 2D architecture in the family of the anilato-based H-bonded networks. The supramolecular interactions present in the structure were investigated analyzing the properties of the Hirshfeld surface (HS), which points out the crucial role of the HBs in the construction of the overall supramolecular architecture, whereas the electronic properties of the metal complex were studied by means of DFT calculations. The magnetic susceptibility measurements reveal the expected paramagnetism of the two compounds with quasi-isolated spin centers.