Synthesis, characterization and ferromagnetic behavior of [Co^III(en)₂(RC₆H₄NH₂)I]I₂.H₂O complexes

Abstract

Mixed ligand cobalt(III) complexes containing aryl amine (RC₆H₄NH₂) ligand have been synthesized using a modified route developed in this study. A wide range of complexes, [Co^III(en)₂(L)I]I₂.H₂O, (where L = RC₆H₄NH₂; R = <i style="">m</i>-OMe, <i style="">p</i>-F, H, <i style="">m</i>-Me, <i style="">p</i>-Me, <i style="">p</i>-OEt and <i style="">p</i>-OMe) show promising reactivities and physical properties due to the presence of electron donor/acceptor groups in the aryl ligand. The complexes have been characterized by elemental analysis, FT-IR, UV-vis and powder X-ray diffraction patterns. FT-IR ν(M-X) and UV-vis spectral data are compatible with <i style="">trans-</i>form of the complexes. Magnetic studies yield magnetic remanence <i style="">M_r</i> = 7.071 ´ 10^-3 – 3.069 ´ 10^-5 emu/g and intrinsic coercivity, -<i style="">H_ci</i> = 141-1156 Oe. Linear regression plot of <i style="">M_r</i> versus σ yields negative slope, implying that electron withdrawing group in RC₆H₄NH₂(σ > 0) enhances ferromagnetic character while the electron donating groups (σ < 0) reduce ferromagnetism. The study provides evidence that substitution at the aryl ligand, remote from the Co(III) center, effectively displays and imparts characteristic ferromagnetic properties. Cobalt(III) complexes containing RC₆H₄NH₂ligand illustrate a simple molecular fabrication technique, which can be suitably integrated into a system, to have some control on the behavior of metal complexes. A modified ferromagnetic character due to charge build up on the metal centre by ligating nitrogen atom, which in turn makes the molecule into a centre of systematic variation in magnetization, has been observed.