Novel zirconium (IV) and hafnium (IV) phthalocyanines with dibenzoylmethane as out-of-plane ligand: Synthesis, X-ray structure and fluorescent properties

Novel phthalocyanine complexes of zirconium (IV) and hafnium (IV) containing dibenzoylmethane groups as out-of-plane ligands were synthesized and characterized by elemental analyses, GALDI mass spectrometry, IR, 1H NMR, UV–vis and fluorescence spectroscopy. The structures of the complexes were determined by single-crystal X-Ray diffraction. The synthesized compounds are isomorphous, with their central atoms exhibiting (ZrN4O4 and HfN4O4) square-antiprism coordination geometry, which consists of four nitrogen atoms from the phthalocyanine macrocycle and four oxygen atoms from the two bidentate dibenzoylmethane ligands. GALDI mass spectrometry studies have shown that hafnium phthalocyanine forms adducts with masses higher than the mass of the molecular ion, indicating a high ability of this complex to self-associate in the gas phase. The spectral-luminescent properties of the compounds in different solvents were studied. The splitting of the Q-band observed in the absorption spectra is related to the lowering of complexes symmetry due to the incorporation of two rigid ligands to the central metal atom of the macrocycle. Study of the absorption spectra of phthalocyanines over a wide concentration range does not reveal any indications for the formation of aggregates. Fluorescence quantum yield values of the complexes were determined by a comparative method in toluene and DMSO.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Phthalocyanine complexes of zirconium (IV) and hafnium (IV) with dibenzoylmethane as an out-of-plane ligand. ► Phthalocyanine complexes crystallize in a monoclinic crystal system P21/c with similar cell parameters. ► The absorption spectra showed that the complexes are non-aggregated.