Oxorhenium(V) Complexes Derived from 8,17-Dimethyl-6,15-Dioxo- 5,7,14,16-Tetrahydrodibenzo[a,h][14] Annulene-2,11-Dicarboxylic Acid and their Pyrolytical Products

Abstract

A new series of oxorhenium(V) complexes were prepared by reaction of 8,17-dimethyl-6,15-dioxo-5,7,14,16-tetrahydrodibenzo[a,h][14] annulene-2,11-dicarboxylic acid(H4L), alone or with addition of PPh3 or NaSCN, with H2[ReOCl5]. Mononuclear complexes, [ReO(H4L)Cl]Cl2, [ReO(H4L)(PPh3)]Cl3, and [ReO(H4L)- (SCN)]Cl2 were obtained in 6 N HCl, while the binuclear complex, [Re2O3(H4L)2]Cl4 was obtained in 2 N HCl. Thermal studies on these complexes showed the possibility of obtaining new complexes pyrolytically, where the complexes decompose through several isolable as well as nonisolable, intermediates during heating. [Re2O3(H2L)2], [ReO(H2L)Cl], [ReO(H2L)(PPh3)]Cl, and [ReO(H2L)(SCN)], were synthesized pyrolytically in the solid state from the respective precursor rhenium complexes. All of the prepared complexes and their thermal products have octahedral configurations. The ligand (H4L) behaves either as a neutral tetradentate or dianionic tetradentate ligand towards the oxorhenium ions in these complexes. The carboxylate groups are not coordinated to oxorhenium ions, which was checked by the acidity test and/or addition of metal ions such as Cu(II) and Ni(II), where a variety of new complexes coordinated via carboxylate groups were obtained. The screening of antibacterial and antifungal activities on the free ligand and all complexes, showed higher antifungal activities against Alternaria alternata than against Aspergillus fumigatus. The structures of all complexes and the corresponding thermal products were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, 1H-NMR and TG-DSC measurements as well as by mass spectrometry.