Magnetic Properties of End-to-End Azide-Bridged Tetranuclear Mixed-Valence Cobalt(III)/Cobalt(II) Complexes with Reduced Schiff Base Blocking Ligands and DFT Study

Abstract

Two tetranuclear mixed-valence cobalt(III/II) complexes having the general formula [(μ1,3-N3){CoII(Ln)(μ-O2CC6H4NO2)CoIII(N3)}2]PF6 (where H2L1 and H2L2 are two reduced Schiff base ligands) have been synthesized and characterized. The structures of both complexes show cobalt(II) and cobalt(III) centers with a distorted octahedral geometry with cobalt(III) and cobalt(II) centers located at the inner N2O2 and outer O4 cavities of the reduced Schiff base ligands, respectively. The oxidation states of both cobalt centers have been confirmed by bond valence sum (BVS) calculations. The magnetic properties show that both compounds behave as cobalt(II) dimers connected through an end-to-end azido bridging ligand and show moderate antiferromagnetic Co(II)–Co(II) couplings of −11.0 and −14.4 cm–1 for 1 and 2, respectively, as also corroborated by DFT calculations, Jtheo = −13.07 cm–1 for 1 and −12.49 cm–1 for 2. The calculated spin densities of both complexes at the cobalt(II) centers are −2.75 and +2.75, respectively, clearly supporting that they are the magnetic centers.

An insight into the non-covalent interactions in the solid state structures of dinuclear cobalt(ii) complexes with N,O-donor ligands: application of the complexes in the fabrication of Schottky devices

“…[21][22][23][24][25] The unusual physical properties of several di-and polynuclear complexes with salen-type Schiff base ligands and their reduced analogues and their ability to mimic the biological functions of different metalloproteins have attracted the interest of coordination chemists to synthesize, characterize and explore new complexes in salen and reduced salen families. [26][27][28][29] Additionally, multi-metallic complexes containing paramagnetic metal centers are important for their interesting magnetic properties and applications as magnetic materials. [30][31][32][33][34] Another leading area of modern research is the study of the opto-electronic properties of these complexes.…”

Synthesis, Structures and Magnetic Properties of CuII and CoII Compounds Based on Asymmetric 5‐(1H‐Imidazole‐1‐yl)‐3‐pyridine Carboxylic Acid

“…This topology hasn't also been reported previously. Tetranuclear Co II compounds with cubane, dicubanelike [18,19] and planar-type structures [55,56] have attracted considerable attention, and such compounds frequently show unique properties, in which the tetranuclear Co II compounds with planar-type structures are very rare. To the best of our knowledge, the planar-type tetra nuclear Co II clusters with SO 4 2bridge as in 4 hasn't been reported.…”

“…Crystals were obtained by slowly cooling the reactor to room temperature at a rate of 5°C/h, bulk pink crystals were collected by filtration and washed with water, yield: 65 % (based on Himpc). Elemental analysis calculated for C 18…”

“…[13][14][15][16] Among them, the exchange-coupled molecular magnetic Co II -compounds are extraordinary interesting as the systems exhibiting strong orbital contributions to the magnetic moments and thus strong magnetic anisotropy. [17][18][19] On the other hand, another important consideration in designing such materials is the nature of ligands, functional groups, donor atoms, and so on. [20][21][22][23][24] Despite the fact that various organic ligands have been studied as potential linker, the effective and facile method for the design of interesting magnetic compounds is still the appropriate choice of well-designed organic ligands as bridges or building block.…”

“…Furthermore, as the basic spin carriers, the Cu II and Co II compounds have attracted immense attention as the desired candidates for exploiting advanced molecule‐based magnetic materials, further for comprehending the basal principle of magnetic interaction as well as the relationship between structure and magnetism in molecular system . Among them, the exchange‐coupled molecular magnetic Co II ‐compounds are extraordinary interesting as the systems exhibiting strong orbital contributions to the magnetic moments and thus strong magnetic anisotropy …”