Ni(II) Dimers of NNO Donor Tridentate Reduced Schiff Base Ligands as Alkali Metal Ion Capturing Agents: Syntheses, Crystal Structures and Magnetic Properties

Abstract

Three trinuclear Ni(II)-Na(I) complexes, [Ni2(L1)2NaCl3(H2O)]·H2O (1), [Ni2(L2)2NaCl3(H2O)] (2), and [Ni2(L3)2NaCl3(OC4H10)] (3) have been synthesized using three different NNO donor tridentate reduced Schiff base ligands, HL1 = 2-[(3-methylamino-propylamino)-methyl]-phenol, HL2 = 2-[(3-methylamino-propylamino)-methyl]-4-chloro-phenol, and HL3 = 2-[(3-methylamino-propylamino)-methyl]-6-methoxy-phenol that had been structurally characterized. Among these complexes, 1 and 2 are isostructural in which dinuclearNi(II) units act as metalloligands to bind Na(I) ions via phenoxido and chlorido bridges. The Na(I) atom is five-coordinated, and the Ni(II) atom possesses hexacordinated distorted octahedral geometry. In contrast, in complex 3, two -OMe groups from the dinuclear Ni(II) unit also coordinate to Na(I) to make its geometry heptacordinated pentagonal bipyramidal. The magnetic measurements of complexes 1⁻3 indicate ferromagnetic interactions between dimeric Ni(II) units with J = 3.97 cm−1, 4.66 cm−1, and 5.50 cm−1 for 1⁻3, respectively, as is expected from their low phenoxido bridging angles (89.32°, 89.39°, and 87.32° for 1⁻3, respectively). The J values have been calculated by broken symmetry DFT method and found to be in good agreement with the experimental values.

Keywords

• Ni^II dimers
• sodium ion capturing
• ferromagnetic coupling
• magnetostructural correlation
• DFT calculation