Metal Complexes of Phosphorus Compounds Including Indigoid Structure: Synthesis, Characterization, and Biological Study

Abstract

Interaction of hexachlorocyclodiphosph(V)azanes, (I _{a − h} ) with 5,5′ indigodisulfonic acid disodium salt (II) furnished the expected cyclodiphosph(V)azanes of the type (H ₂ L ¹ –H ₂ L ⁸ ). The coordinating behavior of H ₂ L ¹ , where H ₂ L ¹ is 1,3diphenyl-2,2,4,4-tetrachloro-2,4-di1,1′-di(5,5′ indigodisulfonic acid disodium salt)cyclodiphosph(V)azane, towards the transition metal ions Mn(II), Co(II), Ni(II), Cu(II) and Fe(III) was studied. The structures of the isolated products are proposed based on elemental analyses, molar conductance, spectral analysis (IR,¹H-NMR, and UV-Vis), as well as magnetic susceptibility measurements and thermogravimetric analysis (TGA). From the elemental analyses, 1:2 (ligand:metal) ratio is suggested, and the complexes are found to have the general formula [(M)₂(L¹)(Cl)_x.n(H₂O)]· zH₂O where M = Mn(II) and Co(II) (x = 2, n = 6, z = 1); M = Ni(II) (x = 2, n = 6, z = 1.5); M = Cu(II) (x = 2, n = 2, z = nil); M = Fe(III) (x = 4, n = 4, z = 4) and (L¹) = the deprotonated form of cyclodiphosphazane ligand. The molar conductance data show that all complexes are non-electrolytes. The spectral data and magnetic susceptibility measurements revealed that the ligand behaves as a dibasic tetradentate ligand coordinated to the metal ions through heterocyclic nitrogen and carbonyl oxygen atoms in an octahedral and square planar manner. Some ligand field parameters (Dq, B, and β), in addition to ligand field stabilization energy (LFSE), were calculated. The thermal behavior of these complexes is studied using TG technique and the different dynamic parameters are calculated applying Coats–Redfern equation. Antimicrobial activities have been studied using the agar–disc diffusion technique, and the higher antimicrobial activity has been observed for the iron (III) complex compared to the other metal complexes.

Keywords:

• Biological study
• cyclodiphosphazane
• transition metal complexes

Notes

^a 1– 5 represent cyclodiphosph(V)azane metal complexes; L¹ represent the deprotonated form of the cyclodiphosph(V)azane ligand H₂L¹.

^b Molar conductance (ohm^{− 1} cm² mol^{− 1}) of 1 × 10^{− 3} M solution in DMF at room temperature.

^c Room temperature effective magnetic moment for each metal ion.

∗The ligand field splitting energy (Dq), interelectronic repulsion parameter (B), nephelauxetic ratio (β), and ligand field stabilization energy (LFSE). The lowering in the B values compared to the free metal ion values (1120 and 1080 for Co(II) and Ni(II) ions, respectively) suggests an appreciable amount of covalent character in the metal–ligand bonds. Additionally, the β value is less than unity suggesting a largely covalent bond between the organic ligand and metal (II) ions in these complexes.