The aluminium(III) complexes of hydroxyflavones in absolute methanol. Part II. Ligands containing more than one chelating site

Abstract

The complexes formed in absolute methanol between aluminium chloride and the multidentate ligands kaempferol, morin, quercetin, rutin, and 3,3',4'-trihydroxyflavone have been studied by U.V. and visible spectroscopy. The stoicheiometry of the complexes favoured at various metal to ligand ratios, and under a range of acidity conditions, has been established by the method of molar-ratios. From this data the preferred site for complex formation, in acid, neutral, and basic solution, has been established for each ligand.

DFT and1H NMR molecular spectroscopic studies on biologically anti-oxidant active paramagnetic lanthanide(III)-chrysin complexes

“…The measured energies and the extinction coefficients are comparable to this portion of the free ligand, which help us to assign that the band as a spin allowed (p-p*) transition of the ligand. The second absorption transition observed between the spectral range 200-293 nm correspond to the A ring portion (quinolic system band II) which is due to p-p*, n-p* and n-s* transitions within the quinolic ring of the chrysin molecule [5,[7][8][9]. These ligand-centered bands are accompanied by weaker transitions with lower energy extending into the visible region from 200 to 293 nm (figure 2).…”

“…Because of the presence of the hydroxyl and ketonic groups, they have strong chelating ability and bind to the metal ion in neutral solution. Several reports are available in the literature on flavonoids and their metal complexes with transition and non-transition metal ions [2][3][4][5][6][7][8][9][10][11][12][13]. It is known that polyphenolic ligands (flavonoids) play a very important role as anti-oxidants and demonstrate free radical scavenging ability [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

“…In recent years great attention has been devoted to the design and synthesis of lanthanide coordination complexes with polyphenolic ligands such as flavonoids [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Flavonoids are polyphenolic organic compounds and are most frequently found in vegetable and other vascular plants that have potential applications in various fields of medical science [15][16][17][18].…”

1H NMR, spectroscopic and molecular modeling studies on paramagnetic lanthanide(III)-quercetin complexes

“…The characteristic absorption peaks are given in [26,30] owing to the strong absorption of quercetin ligand in the visible region. The quercetin ligand shows two absorption bands in methanol, DMF and DMSO solution spectrums [14,16], band I is due to the n-s*, n-p* and p -p* transitions, whereas band II represents ring B, due to n-s* and p -p* transitions [31,32]. The explanation of the above two bands would be similar as that discussed for the analogous complexes [32].…”

Synthesis and Physicochemical Properties of the Complexes of Co(II), Ni(II), and Cu(II) with Chrysin

“…Based on these results and taking data literature data (11,12) into account, the structure of the obtained complex compounds given in Fig. 4 is proposed.…”