Isolation of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand: syntheses, structural descriptions and magnetic studies

Abstract

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is found to be a simple mono alkoxo-bridged Co(III) dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ(3)-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered Co(II) and Co(III) ions and 4 has both six- and five-coordinate Ni(II) centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, (1)H-NMR and ESI mass study results and is supposed to have one Ni(II) center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions.

Isolation and Characterization of Different Homometallic and Heterobimetallic Complexes of Nickel and Zinc Ions by Controlling Molar Ratios and Solvents

“…This slight decrease in χ M T observed at lower temperatures could be due to zero field splitting (ZFS) . The M vs. H plots at 5–10 K show that rate of increase of magnetization is slow.…”

“…It has been observed that ferromagnetic magnetic exchange interaction is observed when M–O–M bond angle is lower than 98° . In the complex 4 bond angles of Ni(1)–O(2)–Ni(2) and Ni(2)–O(4)–Ni(1) are 96.97 and 95.38 0 which fall well below 98 0; therefore, Ni II ions in the complex 4 exhibit ferromagnetic exchange interactions , . At 15 K, sharp increase in χ M T value indicates very strong ferromagnetic interaction and complex exhibits super‐magnetic behavior at this temperature.…”

“…On further cooling from 15 K to 6 K, the value of χ M T decreases to the 2.76 cm 3 K mol –1 . This decrease could be due to zero field splitting (ZFS) . The M vs. H plots at 5–10 K show that rate of increase of magnetization is moderate and do not reach the saturation at 5 K (Figure ).…”

Hydroxide‐Bridged Mixed‐Valence Tetranuclear Cobalt 4‐Nitrophenol Inclusion Complex Showing Single Molecule Magnet Property

“…The Co 2+ ions are in a compressed distorted octahedral environment with slightly distorted O h symmetry, in such case the ground orbital triplet 4 T 1g splits into two states 4 A 2g and 2 E g by distortion on the octahedral geometry; these were also split into six sub‐states by spin‐orbit interactions . In order to avoid over parameterization while calculating magnetic data, conventional approximate axial distortion was considered in each case.…”

Synthesis, Spectroscopy and X-ray Crystallography Structure of Pyridine 4-Carbaldehyde Semicarbazone Schiff Base Ligand

“…Schiff bases are also used as significant intermediates for synthesis of various bioactive materials [6][7][8][9]. Countless Schiff bases and their coordination complexes with outstaning antimicrobial activity, antifungal, and anticancer abilities have been reported [8][9][10][11][12][13]. The Schiff bases with pyridine ring have received more attention in literature [14][15].…”